Fix more missing Blender descriptions leading to crashes #6420

assign_class - avoid empty geometries and assigning shape reprs to structural items
assign_class - replace object with empty if no representation was added
2026-08-06 07:51:47 +00:00 · 2025-04-15 19:43:38 +05:00 · 2025-04-15 19:43:38 +05:00 · 2025-04-15 19:43:38 +05:00 · 2025-04-14 18:59:47 +05:00 · 2025-04-14 17:49:17 +05:00
593 changed files with 29888 additions and 10128 deletions
@@ -1,20 +0,0 @@
---
-name: Bug report
-about: Create a report to help us improve
-title: ''
-labels: ''
-assignees: ''
-
---
-
-Replace this text describing what problem occurred and what you expected to happen instead.
-
-1. To reproduce this, open file '...'
-2. Click on '....'
-3. See error
-
-**Attachments**
-If applicable, add screenshots to help explain your problem. Please also drag-drop any files necessary to show the error (rename the file extension from .ifc to .txt to upload). Private files can be uploaded to https://ifcopenshell.org/upload.html - only viewed by core developers and will be deleted afterwards.
-
-**Debug information**
-If this is in Bonsai, paste the output from the Copy Debug Information option in Bonsai. It can be found under Quality and Coordination -> Quality Control -> Debug. If this is a general software issue, if relevant include details about IfcOpenShell version, operating system, Python version, etc.
@@ -0,0 +1,23 @@
+name: Bug Report
+description: Crashes, error messages, and broken features
+type: bug
+body:
+- type: textarea
+  attributes:
+    label: Bug Description
+    placeholder: |
+      Describe what problem occurred and what you expected to happen instead.
+  
+      1. To reproduce this, open file '...'
+      2. Click on '....'
+      3. See error
+- type: textarea
+  attributes:
+    label: Attachments
+    description: "Private files can be uploaded to https://ifcopenshell.org/upload.html - only viewed by core developers and will be deleted afterwards. Please submit your report first then upload private files afterwards."
+    placeholder: "If applicable, add screenshots to help explain your problem. Please also drag-drop any files necessary to show the error (rename the file extension from .ifc to .txt to upload)."
+- type: textarea
+  attributes:
+    label: Debug and Error Output
+    description: "If this is in Bonsai, paste the output from the Copy Debug Information option in Bonsai. It can be found under Quality and Coordination -> Quality Control -> Debug. If this is a general software issue, if relevant include details about IfcOpenShell version, operating system, Python version, etc."
+    render: yes
@@ -0,0 +1,8 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Community Forums
+    url: https://community.osarch.org/
+    about: Have a question? Want to discuss an idea? Try the OSArch forums instead.
+  - name: Live Chat
+    url: https://osarch.org/chat
+    about: Have a really confusing issue? Want real-time support?
@@ -1,10 +0,0 @@
---
-name: Feature request
-about: Suggest an idea for this project
-title: ''
-labels: ''
-assignees: ''
-
---
-
-Replace this text and describe a feature you'd like us to add. If it's not obvious, explain why this feature is awesome. Note that feature requests must be specific and measurable.
@@ -0,0 +1,8 @@
+name: Feature Request
+description: Suggest a new feature or improvement
+type: Feature
+body:
+- type: textarea
+  attributes:
+    label: Feature Description
+    placeholder: "Describe a feature you'd like us to add, or a change to the user interface, design, or workflow for usability. If it's not obvious, explain why this feature is awesome. Note that feature requests must be specific and measurable."
@@ -104,7 +104,7 @@ jobs:
          # Ensure Bonsai and ifcsverchok enable/disable works before uploading to extensions repo.

          # Download Blender.
-          wget -q -O blender.tar.xz https://ftp.nluug.nl/pub/graphics/blender/release/Blender4.3/blender-4.3.0-linux-x64.tar.xz
+          wget -q -O blender.tar.xz https://download.blender.org/release/Blender4.4/blender-4.4.0-linux-x64.tar.xz
          tar -xf blender.tar.xz

          # Setup Blender.
@@ -9,7 +9,7 @@ on:
 jobs:

  activate:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
    if: |
      github.repository == 'IfcOpenShell/IfcOpenShell' &&
      !startsWith(github.event.head_commit.message, 'Release ') &&
@@ -18,7 +18,7 @@ jobs:
    - run: echo ok go

  build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
    needs: activate
    steps:
    - uses: actions/checkout@v2
@@ -35,7 +35,7 @@ jobs:

    -
      name: ccache
-      uses: hendrikmuhs/ccache-action@v1
+      uses: hendrikmuhs/ccache-action@v1.2

    - 
      name: Build ifcopenshell
@@ -75,7 +75,7 @@ jobs:
        make package
      working-directory: build
    - name: Upload 
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
      with:
        # Artifact name
        name: ifcos-artifacts
@@ -83,7 +83,7 @@ jobs:
        path: build/assets/Ifc*

  deliver:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
    needs: build
    name: Docker Build, Tag, Push

@@ -118,6 +118,6 @@ jobs:
        repository: aecgeeks/ifcopenshell
        # Since the dispatch is set to `tag`, `github.ref_name` should evaluate to the pushed tag
        # On a workflow dispatch, `ref_name` will take on the value from the dispatch payload
-        tags: aecgeeks/ifcopenshell:${{ github.ref_name }}${{ github.ref_name == github.event.repository.default_branch && ',aecgeeks/ifcopenshell:latest' }}
+        tags: aecgeeks/ifcopenshell:${{ github.ref_name }}${{ github.ref_name == github.event.repository.default_branch && ',aecgeeks/ifcopenshell:22.04' }}
        file: ./Dockerfile
        push: true
@@ -9,6 +9,8 @@ on:
    paths:
      - 'src/pyodide/**'
      - '.github/workflows/publish-pyodide-demo-app.yml'
+    branches:
+      - v0.8.0

 jobs:
  activate:
@@ -4,6 +4,7 @@ on:
  push:
    tags:
      - 'v[0-9].[0-9].[0-9]*'
+  workflow_dispatch:

 jobs:
  activate:
@@ -91,7 +91,7 @@ src/bonsai/drawings
 src/bonsai/layouts

 # ifcopenshell swig and compiled files
-src/ifcopenshell-python/ifcopenshell/_ifcopenshell_wrapper.so
+src/ifcopenshell-python/ifcopenshell/_ifcopenshell_wrapper*.so
 src/ifcopenshell-python/ifcopenshell/ifcopenshell_wrapper.py

 # apple
@@ -46,6 +46,7 @@ VERSION_MINOR:=$(shell cat '../../VERSION' | cut -d '.' -f 2)
 VERSION_PATCH:=$(shell cat '../../VERSION' | cut -d '.' -f 3)
 VERSION_DATE:=$(shell date '+%y%m%d')
 LAST_COMMIT_HASH:=$(shell git rev-parse HEAD)
+LAST_COMMIT_DATE:=$(shell git show -s --format=%cI)
 PYVERSION:=py310
 PYPI_IMP:=cp

@@ -254,6 +255,7 @@ ifeq ($(IS_STABLE), TRUE)
 else
 	$(SED) "s/0.0.0/$(VERSION)-alpha$(VERSION_DATE)/" build/bonsai/blender_manifest.toml
 	$(SED) "s/8888888/$(LAST_COMMIT_HASH)/" build/bonsai/__init__.py
+	$(SED) "s/9999999/$(LAST_COMMIT_DATE)/" build/bonsai/__init__.py
 	$(SED) 's/version = "0.0.0"/version = "$(VERSION)-alpha$(VERSION_DATE)"/' build/pyproject.toml
 endif

@@ -40,6 +40,7 @@ from typing import Union, Any, Generator


 last_commit_hash = "8888888"
+last_commit_date = "9999999"


 def get_last_commit_hash() -> Union[str, None]:
@@ -51,6 +52,12 @@ def get_last_commit_hash() -> Union[str, None]:
    return last_commit_hash[:7]


+def get_last_commit_date() -> Union[str, None]:
+    if last_commit_date == str(9_999999):
+        return None
+    return last_commit_date
+
+
 # Accessed from bonsai extension:
 bbim_semver: dict[str, Any] = {}

@@ -96,6 +103,7 @@ def get_debug_info():
        "blender_version": bpy.app.version_string,
        "bonsai_version": bbim_version,
        "bonsai_commit_hash": get_last_commit_hash(),
+        "bonsai_commit_date": get_last_commit_date(),
        "last_actions": last_actions,
        "last_error": last_error,
    }
@@ -218,6 +226,7 @@ if IN_BLENDER:
        path = Path(__file__).resolve().parent
        repo = git.Repo(str(path), search_parent_directories=True)
        last_commit_hash = repo.head.object.hexsha
+        last_commit_date = repo.head.object.committed_datetime.isoformat()
    except:
        pass

@@ -20,6 +20,7 @@ import os
 import bpy
 import bpy.utils.previews
 import importlib
+from bpy_extras.io_utils import ImportHelper, ExportHelper
 from . import handler, ui, prop, operator
 from typing import Callable, Union

@@ -83,6 +84,7 @@ modules = {
    "covering": None,
    "web": None,
    "light": None,
+    "alignment": None,
    # Uncomment this line to enable loading of the demo module. Happy hacking!
    # The name "demo" must correlate to a folder name in `bim/module/`.
    # "demo": None,
@@ -220,7 +222,12 @@ def on_register(scene):

 def register():
    for cls in classes:
+        # Prevent crashes in Blender 4.4.0, see #6420.
+        if issubclass(cls, (ImportHelper, ExportHelper)):
+            assert getattr(cls, "bl_description", "") or cls.__doc__, cls
+
        bpy.utils.register_class(cls)
+
    bpy.app.handlers.depsgraph_update_post.append(on_register)
    bpy.app.handlers.undo_post.append(handler.undo_post)
    bpy.app.handlers.redo_post.append(handler.redo_post)
@@ -1,7 +1,7 @@
 ISO-10303-21;
 HEADER;
 FILE_DESCRIPTION(('ViewDefinition[DesignTransferView]'),'2;1');
-FILE_NAME('/dev/null','2024-03-03T16:03:58+11:00',(),(),'IfcOpenShell v0.7.0-eaa2aa05a','IfcOpenShell v0.7.0-eaa2aa05a','Nobody');
+FILE_NAME('/dev/null','2025-03-27T17:30:27+05:00',(''),(''),'IfcOpenShell 0.0.0','IfcOpenShell 0.0.0','Nobody');
 FILE_SCHEMA(('IFC4'));
 ENDSEC;
 DATA;
@@ -29,7 +29,7 @@ DATA;
 #22=IFCMATERIALLAYERSET((#24),$,$);
 #23=IFCRELASSOCIATESMATERIAL('0khP_Smdj12f2JrOTRbRKj',$,$,$,(#21),#22);
 #24=IFCMATERIALLAYER(#20,0.05,$,$,$,$,$);
-#25=IFCRELDECLARES('31JriXdev6BP2sC9lcxdC1',$,$,$,#2,(#26,#48,#72,#59,#92,#30,#96,#63,#21,#54,#87,#210,#153,#34,#67,#38,#82,#77,#42));
+#25=IFCRELDECLARES('31JriXdev6BP2sC9lcxdC1',$,$,$,#2,(#59,#92,#38,#82,#30,#96,#77,#63,#42,#54,#87,#153,#34,#21,#67,#210,#26,#48,#72));
 #26=IFCWALLTYPE('3R5onkTtX1IxdCMPoThRaw',$,'WAL100',$,$,$,$,$,$,.NOTDEFINED.);
 #27=IFCMATERIALLAYERSET((#29),$,$);
 #28=IFCRELASSOCIATESMATERIAL('0$mXRPCT16nP6Q70XFNvZv',$,$,$,(#26),#27);
@@ -28,11 +28,13 @@ DATA;
 #21=IFCSIMPLEPROPERTYTEMPLATE('1UDakJ5_f7kBhggNSW4$h5',$,'SymbolsPath','Default symbols SVG',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #22=IFCSIMPLEPROPERTYTEMPLATE('0d53LEtgLDQxnv__NfgH7i',$,'PatternsPath','Default patterns SVG',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #23=IFCSIMPLEPROPERTYTEMPLATE('26qFNMv7nCHgU6Jd7Anga5',$,'ShadingStylesPath','Default shading styles',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
-#24=IFCPROPERTYSETTEMPLATE('0I9merLinF5Ap$aZwaclgm',$,'BBIM_Dimension','',.PSET_TYPEDRIVENOVERRIDE.,'IfcAnnotation/DIMENSION,IfcTypeProduct',(#25,#26,#27,#28));
+#24=IFCPROPERTYSETTEMPLATE('0I9merLinF5Ap$aZwaclgm',$,'BBIM_Dimension','',.PSET_TYPEDRIVENOVERRIDE.,'IfcAnnotation/DIMENSION,IfcAnnotation/RADIUS,IfcAnnotation/DIAMETER,IfcTypeProduct',(#25,#26,#27,#28,#30));
 #25=IFCSIMPLEPROPERTYTEMPLATE('1rL2AbQsXD8RbpoWH5pYOV',$,'ShowDescriptionOnly','Hide the measurement values and show only annotation description',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
 #26=IFCSIMPLEPROPERTYTEMPLATE('0SVyOfB0rC2xNfdRYf3XvY',$,'SuppressZeroInches','Suppress 0 inch values in dimension annotation text (for example: 12'' - 0" -> 12'')',.P_SINGLEVALUE.,'IfcBoolean',$,$,$,$,$,.READWRITE.);
 #27=IFCSIMPLEPROPERTYTEMPLATE('2bUmj458PBqPAtUoI3MXsb',$,'TextPrefix','Text to add before annotation measurement value',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #28=IFCSIMPLEPROPERTYTEMPLATE('0bnzttUb9BPuN597uNTXOE',$,'TextSuffix','Text to add after annotation measurement value',.P_SINGLEVALUE.,'IfcLabel',$,$,$,$,$,.READWRITE.);
 #29=IFCSIMPLEPROPERTYTEMPLATE('2pJmUDpB50VBdCOib1zcJJ',$,'Newline_At','',.P_SINGLEVALUE.,'IfcInteger',$,$,$,$,$,.READWRITE.);
+#30=IFCSIMPLEPROPERTYTEMPLATE('2TJn72t_v2cvBUG916Dpev',$,'CustomUnit','Dimension''s custom unit',.P_ENUMERATEDVALUE.,'IfcText',$,#31,$,$,$,.READWRITE.);
+#31=IFCPROPERTYENUMERATION('CustomUnit',(IFCTEXT('Feet and Inches - Fractional'),IFCTEXT('Feet - Decimal'),IFCTEXT('Inches - Fractional'),IFCTEXT('Inches - Decimal'),IFCTEXT('Meters'),IFCTEXT('Decimeters'),IFCTEXT('Centimeters'),IFCTEXT('Millimeters')),$);
 ENDSEC;
 END-ISO-10303-21;
@@ -0,0 +1 @@
+../../libraries/IFC2X3 Demo Library.ifc
@@ -0,0 +1 @@
+../../libraries/IFC4 Demo Library.ifc
@@ -0,0 +1 @@
+../../libraries/IFC4X3 Demo Library.ifc
@@ -47,7 +47,6 @@ class IfcExporter:
        self.set_header()
        IfcStore.update_cache()
        self.sync_all_objects()
-        self.sync_edited_objects()
        tool.Project.save_linked_models_to_ifc()
        extension = self.ifc_export_settings.output_file.split(".")[-1].lower()
        if extension == "ifczip":
@@ -101,43 +100,14 @@ class IfcExporter:
                result = self.sync_object_placement(obj)
                if result:
                    results.append(result)
-                result = self.sync_object_material(obj)
-                # TODO: sync_object_material always returns None
-                # so it's never really appended
                if result:
                    results.append(result)
            except ReferenceError:
                pass  # The object is likely deleted
        return results

-    def sync_edited_objects(self) -> list[ifcopenshell.entity_instance]:
-        results: list[ifcopenshell.entity_instance] = []
-        for obj in IfcStore.edited_objs.copy():
-            if not obj:
-                continue
-            if not tool.Blender.is_valid_data_block(obj):
-                continue
-            element = tool.Ifc.get_entity(obj)
-            if element:
-                results.append(element)
-            bpy.ops.bim.update_representation(obj=obj.name)
-        IfcStore.edited_objs.clear()
-        return results
-
-    def sync_object_material(self, obj: bpy.types.Object) -> None:
-        if not obj.data or not isinstance(obj.data, bpy.types.Mesh):
-            return
-        if not self.has_changed_materials(obj):
-            return
-        bpy.ops.bim.update_representation(obj=obj.name)
-
-    def has_changed_materials(self, obj: bpy.types.Object) -> bool:
-        mprops = tool.Geometry.get_mesh_props(obj.data)
-        checksum = mprops.material_checksum
-        return checksum != tool.Geometry.get_material_checksum(obj)
-
    def sync_object_placement(self, obj: bpy.types.Object) -> Union[ifcopenshell.entity_instance, None]:
-        element = self.file.by_id(obj.BIMObjectProperties.ifc_definition_id)
+        element = self.file.by_id(tool.Blender.get_object_bim_props(obj).ifc_definition_id)
        if tool.Geometry.is_scaled(obj):
            bpy.ops.bim.update_representation(obj=obj.name)
            # update_representation might not apply scale if the object has openings
@@ -24,17 +24,15 @@ import ifcopenshell.util.unit
 import ifcopenshell.api.owner.settings
 import bonsai.bim
 import bonsai.tool as tool
-import bonsai.core.owner as core_owner
 from bpy.app.handlers import persistent
 from bonsai.bim.ifc import IfcStore
-from bonsai.bim.module.owner.prop import get_user_person, get_user_organisation
 from bonsai.bim.module.model.data import AuthoringData
 from bonsai.bim.module.aggregate.decorator import AggregateDecorator
 from bonsai.bim.module.georeference.decorator import GeoreferenceDecorator
 from bonsai.bim.module.model.decorator import WallAxisDecorator, SlabDirectionDecorator
 from bonsai.bim.module.nest.decorator import NestDecorator
 from mathutils import Vector
-from math import cos, degrees
+from math import cos
 from typing import Union, Callable


@@ -55,23 +53,24 @@ def name_callback(obj: Union[bpy.types.Object, bpy.types.Material], data: str) -
        return

    if isinstance(obj, bpy.types.Material):
-        props = obj.BIMStyleProperties
+        props = tool.Style.get_material_style_props(obj)
        if ifc_definition_id := props.ifc_definition_id:
            if props.is_renaming:
-                props.is_renmaing = False
+                props.is_renaming = False
                return
            tool.Ifc.get().by_id(ifc_definition_id).Name = obj.name
            refresh_ui_data()
        return

-    if not obj.BIMObjectProperties.ifc_definition_id:
+    props = tool.Blender.get_object_bim_props(obj)
+    if not props.ifc_definition_id:
        return

-    if obj.BIMObjectProperties.is_renaming:
-        obj.BIMObjectProperties.is_renaming = False
+    if props.is_renaming:
+        props.is_renaming = False
        return

-    element = tool.Ifc.get().by_id(obj.BIMObjectProperties.ifc_definition_id)
+    element = tool.Ifc.get().by_id(props.ifc_definition_id)
    if "/" in obj.name:
        object_name = obj.name
        element_name = obj.name.split("/", 1)[1]
@@ -87,8 +86,8 @@ def name_callback(obj: Union[bpy.types.Object, bpy.types.Material], data: str) -
    if not element.is_a("IfcRoot"):
        return
    element.Name = element_name
-    if obj.BIMObjectProperties.collection:
-        obj.BIMObjectProperties.collection.name = object_name
+    if props.collection:
+        props.collection.name = object_name
    refresh_ui_data()


@@ -288,7 +287,7 @@ def get_user(ifc: ifcopenshell.file) -> Union[ifcopenshell.entity_instance, None
 def viewport_shading_changed_callback(area: bpy.types.Area) -> None:
    shading = area.spaces.active.shading.type
    if shading == "RENDERED":
-        bpy.context.scene.BIMStylesProperties.active_style_type = "External"
+        tool.Style.get_style_props().active_style_type = "External"


 def subscribe_to_viewport_shading_changes():
@@ -348,8 +347,8 @@ def load_post(scene):

    # Bonsai overlays
    georeference_props = tool.Georeference.get_georeference_props()
-    aggregate_props = bpy.context.scene.BIMAggregateProperties
-    nest_props = bpy.context.scene.BIMNestProperties
+    aggregate_props = tool.Aggregate.get_aggregate_props()
+    nest_props = tool.Nest.get_nest_props()
    model_props = tool.Model.get_model_props()
    if georeference_props.should_visualise:
        GeoreferenceDecorator.install(bpy.context)
@@ -362,7 +361,7 @@ def load_post(scene):
    if model_props.show_slab_direction:
        SlabDirectionDecorator.install(bpy.context)

-    if scene := bpy.context.scene:
+    if preferences.should_use_snap and (scene := bpy.context.scene):
        # Snapping is off by default in Blender, but in BIM, it's more useful to be on
        scene.tool_settings.use_snap = True
        # Match default Bonsai snaps
@@ -76,8 +76,8 @@ def draw_attribute(
    elif value_name == "filepath_value":
        attribute.filepath_value.layout_file_select(layout, filter_glob=attribute.filter_glob, text=attribute.name)
    elif attribute.name in ("ScheduleDuration", "ActualDuration", "FreeFloat", "TotalFloat"):
-        propis = bpy.context.scene.BIMWorkScheduleProperties
-        for item in propis.durations_attributes:
+        props = tool.Sequence.get_work_schedule_props()
+        for item in props.durations_attributes:
            if item.name == attribute.name:
                duration_props = item
                layout.label(text=attribute.name)
@@ -293,7 +293,10 @@ def prop_with_search(
    should_click_ok: bool = False,
    original_operator_path: Optional[str] = None,
    **kwargs: Any,
-):
+) -> bpy.types.UILayout:
+    """
+    :return: Added row.
+    """
    # kwargs are layout.prop arguments (text, icon, etc.)
    row = layout.row(align=True)
    row.prop(data, prop_name, **kwargs)
@@ -307,6 +310,7 @@ def prop_with_search(
            op.original_operator_path = original_operator_path or ""
    except TypeError:  # Prop is not iterable
        pass
+    return row


 def get_enum_items(
@@ -33,7 +33,7 @@ import bonsai.bim.handler
 import bonsai.tool as tool
 from pathlib import Path
 from bonsai.tool.brick import BrickStore
-from typing import Set, Union, Optional, TypedDict, Callable, NotRequired, cast
+from typing import Set, Union, Optional, TypedDict, Callable, NotRequired


 IFC_CONNECTED_TYPE = Union[bpy.types.Material, bpy.types.Object]
@@ -106,10 +106,7 @@ class IfcStore:
    def get_file():
        if IfcStore.file is None:
            props = tool.Blender.get_bim_props()
-            IfcStore.path = props.ifc_file
-            # Interpret relative paths as relative to .blend file.
-            if IfcStore.path and not os.path.isabs(IfcStore.path):
-                IfcStore.path = os.path.abspath(os.path.join(bpy.path.abspath("//"), IfcStore.path))
+            IfcStore.set_path(props.ifc_file)
            if IfcStore.path:
                try:
                    IfcStore.load_file(IfcStore.path)
@@ -117,6 +114,13 @@ class IfcStore:
                    print(f"Failed to load file {IfcStore.path}. Error details: {e}")
        return IfcStore.file

+    @staticmethod
+    def set_path(value):
+        IfcStore.path = value
+        # Interpret relative paths as relative to .blend file.
+        if IfcStore.path and not os.path.isabs(IfcStore.path):
+            IfcStore.path = os.path.abspath(os.path.join(bpy.path.abspath("//"), IfcStore.path))
+
    @staticmethod
    def get_cache():
        if IfcStore.cache is None and IfcStore.path:
@@ -265,9 +269,11 @@ class IfcStore:
            IfcStore.guid_map[global_id] = obj

        if element.is_a("IfcSurfaceStyle"):
-            obj.BIMStyleProperties.ifc_definition_id = element.id()
+            props = tool.Style.get_material_style_props(obj)
+            props.ifc_definition_id = element.id()
        else:
-            obj.BIMObjectProperties.ifc_definition_id = element.id()
+            props = tool.Blender.get_object_bim_props(obj)
+            props.ifc_definition_id = element.id()

        tool.Ifc.setup_listeners(obj)

@@ -405,9 +411,11 @@ class IfcStore:
    @staticmethod
    def purge_blender_ifc_data(obj: IFC_CONNECTED_TYPE) -> None:
        if isinstance(obj, bpy.types.Material):
-            obj.BIMStyleProperties.ifc_definition_id = 0
+            props = tool.Style.get_material_style_props(obj)
+            props.ifc_definition_id = 0
        else:  # bpy.types.Object
-            obj.BIMObjectProperties.ifc_definition_id = 0
+            props = tool.Blender.get_object_bim_props(obj)
+            props.ifc_definition_id = 0

    @staticmethod
    def execute_ifc_operator(
@@ -20,6 +20,7 @@ from __future__ import annotations
 import bpy
 import time
 import json
+import ifcpatch
 import logging
 import traceback
 import mathutils
@@ -38,6 +39,7 @@ import bonsai.tool as tool
 from bonsai.bim.ifc import IfcStore, IFC_CONNECTED_TYPE
 from bonsai.tool.loader import OBJECT_DATA_TYPE
 from typing import Dict, Union, Optional, Any, Literal
+from ifcopenshell.util.shape import MatrixType


 class MaterialCreator:
@@ -85,7 +87,7 @@ class MaterialCreator:

    def load_existing_materials(self) -> None:
        for material in bpy.data.materials:
-            if ifc_definition_id := material.BIMStyleProperties.ifc_definition_id:
+            if ifc_definition_id := tool.Blender.get_ifc_definition_id(material):
                self.styles[ifc_definition_id] = material

    def parse_element_type_material_styles(self, element: ifcopenshell.entity_instance) -> None:
@@ -298,6 +300,20 @@ class IfcImporter:
        bpy.context.window_manager.progress_end()

    def process_context_filter(self) -> None:
+        contexts = self.file.by_type("IfcGeometricRepresentationContext")
+        if len(contexts) > 100:  # Probably something strange happening. Encountered from Revizto.
+            print("Warning! Excessive contexts were found and merged where applicable.")
+            uniques = {}
+            i = 0
+            for element in contexts:
+                data = "-".join([str(a) for a in element])
+                if unique := uniques.get(data, None):
+                    ifcopenshell.util.element.replace_element(element, unique)
+                    self.file.remove(element)
+                    i += 1
+                else:
+                    uniques[data] = element
+            print(f"Replaced {i} IfcGeometricRepresentationContext")
        tool.Loader.settings.contexts = ifcopenshell.util.representation.get_prioritised_contexts(self.file)
        tool.Loader.settings.context_settings = tool.Loader.create_settings()
        tool.Loader.settings.gross_context_settings = tool.Loader.create_settings(is_gross=True)
@@ -479,14 +495,16 @@ class IfcImporter:
            if grid.WAxes:
                self.create_grid_axes(grid.WAxes, grid_obj, grid_placement)

-    def create_grid_axes(self, axes, grid_obj, grid_placement):
+    def create_grid_axes(
+        self, axes: list[ifcopenshell.entity_instance], grid_obj: bpy.types.Object, grid_placement: MatrixType
+    ) -> None:
        for axis in axes:
            shape = tool.Loader.create_generic_shape(axis.AxisCurve)
            mesh = self.create_mesh(axis, shape)
            obj = bpy.data.objects.new(tool.Loader.get_name(axis), mesh)
            obj.show_in_front = True
            self.link_element(axis, obj)
-            self.set_matrix_world(obj, tool.Loader.apply_blender_offset_to_matrix_world(obj, grid_placement.copy()))
+            self.set_matrix_world(obj, tool.Loader.apply_blender_offset_to_matrix_world(obj, grid_placement))

    def create_element_types(self):
        for element_type in self.element_types:
@@ -511,8 +529,9 @@ class IfcImporter:
                        pass
                    elif shape:
                        mesh = self.create_mesh(element, shape)
-                        tool.Loader.link_mesh(shape, mesh)
-                        self.meshes[mesh_name] = mesh
+                        if mesh is not None:
+                            tool.Loader.link_mesh(shape, mesh)
+                            self.meshes[mesh_name] = mesh
                    else:
                        self.ifc_import_settings.logger.error("Failed to generate shape for %s", element)
                break
@@ -698,9 +717,15 @@ class IfcImporter:
    def create_structural_point_connections(self):
        for product in self.file.by_type("IfcStructuralPointConnection"):
            # TODO: make this based off ifcopenshell. See #1409
-            representation: ifcopenshell.entity_instance = next(
-                rep for rep in product.Representation.Representations if rep.RepresentationType == "Vertex"
-            )
+
+            representation = tool.Structural.get_vertex_representation(product)
+            if not representation:
+                print(
+                    "WARNING. Skipping invalid IfcStructuralPointConnection - "
+                    f"element has no valid representation:\n{product}."
+                )
+                continue
+
            mesh = tool.Loader.create_structural_point_connection_mesh(representation)
            if mesh is None:
                continue
@@ -742,12 +767,9 @@ class IfcImporter:
    def create_pointclouds(self, products: set[ifcopenshell.entity_instance]) -> set[ifcopenshell.entity_instance]:
        result = set()
        for product in products:
-            representation = self.get_pointcloud_representation(product)
-            if representation is not None:
-                pointcloud = self.create_pointcloud(product, representation)
-                if pointcloud is not None:
+            if representation := self.get_pointcloud_representation(product):
+                if pointcloud := self.create_pointcloud(product, representation):
                    result.add(pointcloud)
-
        return result

    def create_pointcloud(
@@ -795,8 +817,9 @@ class IfcImporter:
            materials_updated = bool(mesh)
            if mesh is None:
                mesh = self.create_mesh(element, shape)
-                tool.Loader.link_mesh(shape, mesh)
-                self.meshes[mesh_name] = mesh
+                if mesh is not None:
+                    tool.Loader.link_mesh(shape, mesh)
+                    self.meshes[mesh_name] = mesh
        else:
            mesh = None

@@ -807,11 +830,10 @@ class IfcImporter:
            if element.is_a(ifcclass):
                obj.display_type = "WIRE"

-        if shape:
+        if shape and mesh:
            # We use numpy here because Blender mathutils.Matrix is not accurate enough
-            mat = np.array(shape.transformation.matrix).reshape((4, 4), order="F")
+            mat = ifcopenshell.util.shape.get_shape_matrix(shape)
            self.set_matrix_world(obj, tool.Loader.apply_blender_offset_to_matrix_world(obj, mat))
-            assert mesh  # Type checker.
            if not materials_updated:
                self.material_creator.create(element, obj, mesh, tool.Geometry.does_shape_has_openings(shape))
        elif mesh:  # When does this occur?
@@ -933,7 +955,8 @@ class IfcImporter:
        self.project = {"ifc": project}
        obj = tool.Ifc.get_object(project)
        if obj:
-            self.project["blender"] = obj.BIMObjectProperties.collection
+            props = tool.Blender.get_object_bim_props(obj)
+            self.project["blender"] = props.collection
            self.has_existing_project = True
            return
        self.project["blender"] = bpy.data.collections.new(
@@ -943,10 +966,16 @@ class IfcImporter:
        obj.hide_select = True
        self.project["blender"].objects.link(obj)
        self.project["blender"].BIMCollectionProperties.obj = obj
-        obj.BIMObjectProperties.collection = self.collections[project.GlobalId] = self.project["blender"]
+        props = tool.Blender.get_object_bim_props(obj)
+        props.collection = self.collections[project.GlobalId] = self.project["blender"]

    def create_styles(self) -> None:
-        for style in self.file.by_type("IfcSurfaceStyle"):
+        styles = self.file.by_type("IfcSurfaceStyle")
+        if len(styles) > self.ifc_import_settings.style_limit:  # Probably something strange happening
+            print("Warning! Excessive styles were found and merged where applicable.")
+            ifcpatch.execute({"file": self.file, "recipe": "MergeStyles", "arguments": []})
+            styles = self.file.by_type("IfcSurfaceStyle")
+        for style in styles:
            self.create_style(style)

    def create_style(self, style: ifcopenshell.entity_instance) -> None:
@@ -959,10 +988,11 @@ class IfcImporter:
        self.material_creator.styles[style.id()] = blender_material

        style_elements = tool.Style.get_style_elements(blender_material)
+        props = tool.Style.get_material_style_props(blender_material)
        if tool.Style.has_blender_external_style(style_elements):
-            blender_material.BIMStyleProperties.active_style_type = "External"
+            props.active_style_type = "External"
        else:
-            blender_material.BIMStyleProperties.active_style_type = "Shading"
+            props.active_style_type = "Shading"

    def place_objects_in_collections(self) -> None:
        for ifc_definition_id, obj in self.added_data.items():
@@ -1027,7 +1057,7 @@ class IfcImporter:
        element: ifcopenshell.entity_instance,
        shape: Union[ifcopenshell.geom.ShapeElementType, ifcopenshell.geom.ShapeType],
        cartesian_point_offset: Union[npt.NDArray[np.float64], Literal[False]] = None,
-    ) -> bpy.types.Mesh:
+    ) -> Union[bpy.types.Mesh, None]:
        try:
            if hasattr(shape, "geometry"):
                # shape is ShapeElementType
@@ -1068,7 +1098,10 @@ class IfcImporter:
                verts=verts,
                load_indexed_maps=self.ifc_import_settings.load_indexed_maps,
            )
-            return tool.Loader.slice_layerset_mesh(element, mesh)
+            # E.g. `create_mesh` is also used for IfcRelSpaceBoundary.
+            if element.is_a("IfcObjectDefinition"):
+                return tool.Loader.slice_layerset_mesh(element, mesh)
+            return mesh
        except:
            self.ifc_import_settings.logger.error("Could not create mesh for %s", element)
            import traceback
@@ -1125,6 +1158,7 @@ class IfcImportSettings:
        self.deflection_tolerance = 0.001
        self.angular_tolerance = 0.5
        self.void_limit = 30
+        self.style_limit = 300
        # Locations greater than 1km are not considered "small sites" according to the georeferencing guide
        # Users can configure this if they have to handle larger sites but beware of surveying precision
        self.distance_limit = 1000
@@ -1145,7 +1179,7 @@ class IfcImportSettings:

    @staticmethod
    def factory(context=None, input_file=None, logger=None):
-        scene_diff = bpy.context.scene.DiffProperties
+        scene_diff = tool.Blender.get_diff_props()
        props = tool.Project.get_project_props()
        settings = IfcImportSettings()
        settings.input_file = input_file
@@ -1162,6 +1196,7 @@ class IfcImportSettings:
        settings.deflection_tolerance = props.deflection_tolerance
        settings.angular_tolerance = props.angular_tolerance
        settings.void_limit = props.void_limit
+        settings.style_limit = props.style_limit
        settings.distance_limit = props.distance_limit
        settings.false_origin_mode = props.false_origin_mode
        try:
@@ -20,6 +20,7 @@ import blf
 import bpy
 import gpu
 import ifcopenshell
+import ifcopenshell.util.element
 import bonsai.tool as tool
 from bpy.types import SpaceView3D
 from bpy_extras import view3d_utils
@@ -131,6 +132,9 @@ class AggregateDecorator:
        return shader

    def draw_custom_batch(self, coords, color):
+        indices = None
+        if not tool.Blender.validate_shader_batch_data(coords, indices):
+            return
        shader = self.dotted_line_shader()

        arc_lengths = [0]
@@ -141,6 +145,7 @@ class AggregateDecorator:
            shader,
            "LINE_STRIP",
            {"position": coords, "arcLength": arc_lengths},
+            indices=indices,
        )

        matrix = bpy.context.region_data.perspective_matrix
@@ -150,13 +155,16 @@ class AggregateDecorator:
        batch.draw(shader)

    def draw_batch(self, shader_type, content_pos, color, indices=None):
+        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
+            return
        shader = self.line_shader if shader_type == "LINES" else self.shader
        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
        shader.uniform_float("color", color)
        batch.draw(shader)

    def draw_aggregate(self, context):
-        if context.scene.BIMAggregateProperties.in_aggregate_mode:
+        props = tool.Aggregate.get_aggregate_props()
+        if props.in_aggregate_mode:
            return
        self.addon_prefs = tool.Blender.get_addon_preferences()
        decorator_color_special = self.addon_prefs.decorator_color_special
@@ -204,7 +212,7 @@ class AggregateDecorator:
            self.draw_batch("LINES", line_y, color, [(0, 1)])
            line_z = (location - Vector((0.0, 0.0, size)), location + Vector((0.0, 0.0, size)))
            self.draw_batch("LINES", line_z, color, [(0, 1)])
-            if context.scene.BIMAggregateProperties.in_aggregate_mode:
+            if props.in_aggregate_mode:
                return
            parts = ifcopenshell.util.element.get_parts(tool.Ifc.get_entity(aggregate))
            parts_objs = [tool.Ifc.get_object(p) for p in parts]
@@ -243,6 +251,8 @@ class AggregateModeDecorator:
        cls.is_installed = False

    def draw_batch(self, shader_type, content_pos, color, indices=None):
+        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
+            return
        shader = self.line_shader if shader_type == "LINES" else self.shader
        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
        shader.uniform_float("color", color)
@@ -253,7 +263,7 @@ class AggregateModeDecorator:
            return
        region = context.region
        rv3d = region.data
-        props = context.scene.BIMAggregateProperties
+        props = tool.Aggregate.get_aggregate_props()

        aggregate_obj = props.editing_aggregate
        if not aggregate_obj:
@@ -284,7 +294,7 @@ class AggregateModeDecorator:
    def draw_aggregate_empty(self, context):
        if context.mode == "EDIT_MESH":
            return
-        props = context.scene.BIMAggregateProperties
+        props = tool.Aggregate.get_aggregate_props()
        aggregate_obj = props.editing_aggregate
        if not aggregate_obj:
            return
@@ -23,6 +23,7 @@ import ifcopenshell.util.element
 import bonsai.tool as tool
 import bonsai.core.aggregate as core
 import bonsai.core.spatial
+from typing import TYPE_CHECKING


 class BIM_OT_aggregate_assign_object(bpy.types.Operator, tool.Ifc.Operator):
@@ -30,23 +31,30 @@ class BIM_OT_aggregate_assign_object(bpy.types.Operator, tool.Ifc.Operator):
    bl_label = "Assign Object To Aggregation"
    bl_description = (
        "Assign object as an aggregate to the selected IFC elements.\n\n"
-        "If called from Bonsai UI, then either 'Relating Whole' or 'Related Part' must be provided.\n"
+        "If called from Object Aggregates UI, then either 'Relating Whole' or 'Related Part' must be provided.\n"
        "If called directly, active object will be considered a relating whole"
    )
    bl_options = {"REGISTER", "UNDO"}
    relating_object: bpy.props.IntProperty()
    related_object: bpy.props.IntProperty()

+    if TYPE_CHECKING:
+        relating_object: int
+        related_object: int
+
    def _execute(self, context):
        relating_obj = None
        if self.relating_object:
            relating_obj = tool.Ifc.get_object(tool.Ifc.get().by_id(self.relating_object))
+            assert relating_obj
        elif self.related_object:
            aggregate = ifcopenshell.util.element.get_aggregate(tool.Ifc.get().by_id(self.related_object))
            if aggregate:
                relating_obj = tool.Ifc.get_object(aggregate)
-        elif context.active_object:
+                assert relating_obj
+        else:
            relating_obj = context.active_object
+
        if not relating_obj:
            self.report({"ERROR"}, "No relating object is provided.")
            return
@@ -66,7 +74,7 @@ class BIM_OT_aggregate_assign_object(bpy.types.Operator, tool.Ifc.Operator):
                    relating_obj=relating_obj,
                    related_obj=obj,
                )
-                props = context.scene.BIMAggregateProperties
+                props = tool.Aggregate.get_aggregate_props()
                if relating_obj == props.editing_aggregate and props.in_aggregate_mode:
                    new_editing_obj = props.editing_objects.add()
                    new_editing_obj.obj = obj
@@ -182,7 +190,7 @@ class BIM_OT_add_aggregate(bpy.types.Operator, tool.Ifc.Operator):
                )
            core.assign_object(tool.Ifc, tool.Aggregate, tool.Collector, relating_obj=aggregate, related_obj=obj)

-    def create_aggregate(self, context, ifc_class, aggregate_name):
+    def create_aggregate(self, context: bpy.types.Context, ifc_class: str, aggregate_name: str) -> bpy.types.Object:
        aggregate = bpy.data.objects.new(aggregate_name, None)
        aggregate.location = context.scene.cursor.location
        bpy.ops.bim.assign_class(obj=aggregate.name, ifc_class=ifc_class)
@@ -388,7 +396,7 @@ class BIM_OT_toggle_aggregate_mode_local_view(bpy.types.Operator):
    bl_options = {"REGISTER", "UNDO"}

    def execute(self, context):
-        props = context.scene.BIMAggregateProperties
+        props = tool.Aggregate.get_aggregate_props()
        objs = [o.obj for o in props.editing_objects]
        if props.in_aggregate_mode:
            if context.space_data.local_view:
@@ -33,6 +33,7 @@ from bpy.props import (
    CollectionProperty,
 )
 from bonsai.bim.module.aggregate.decorator import AggregateDecorator, AggregateModeDecorator
+from typing import TYPE_CHECKING, Union


 def can_aggregate(relating_obj: bpy.types.Object, related_obj: bpy.types.Object) -> bool:
@@ -98,10 +99,21 @@ class BIMObjectAggregateProperties(PropertyGroup):
        poll=poll_related_object,
    )

+    if TYPE_CHECKING:
+        is_editing: bool
+        relating_object: Union[bpy.types.Object, None]
+        related_object: Union[bpy.types.Object, None]
+

 class Objects(bpy.types.PropertyGroup):
    obj: PointerProperty(type=bpy.types.Object)
    previous_display_type: bpy.props.StringProperty(default="TEXTURED")
+    previous_hide_select: bpy.props.BoolProperty(default=False)
+
+    if TYPE_CHECKING:
+        obj: Union[bpy.types.Object, None]
+        previous_display_type: str
+        previous_hide_select: bool


 class BIMAggregateProperties(PropertyGroup):
@@ -114,3 +126,10 @@ class BIMAggregateProperties(PropertyGroup):
        default=False,
        update=update_aggregate_decorator,
    )
+
+    if TYPE_CHECKING:
+        in_aggregate_mode: bool
+        editing_aggregate: Union[bpy.types.Object, None]
+        editing_objects: bpy.types.bpy_prop_collection_idprop[Objects]
+        not_editing_objects: bpy.types.bpy_prop_collection_idprop[Objects]
+        aggregate_decorator: bool
@@ -34,9 +34,9 @@ class BIM_PT_aggregate(Panel):

    @classmethod
    def poll(cls, context):
-        if not context.active_object:
+        if not (obj := context.active_object):
            return False
-        props = context.active_object.BIMObjectProperties
+        props = tool.Blender.get_object_bim_props(obj)
        if not props.ifc_definition_id:
            return False
        if not tool.Ifc.get_object_by_identifier(props.ifc_definition_id):
@@ -49,11 +49,13 @@ class BIM_PT_aggregate(Panel):
        layout = self.layout
        row = layout.row()
        row.label(text="Aggregate Decorator")
-        row.prop(context.scene.BIMAggregateProperties, "aggregate_decorator", icon="HIDE_OFF", text="")
+        props = tool.Aggregate.get_aggregate_props()
+        row.prop(props, "aggregate_decorator", icon="HIDE_OFF", text="")
        if not AggregateData.is_loaded:
            AggregateData.load()

-        props = context.active_object.BIMObjectAggregateProperties
+        assert (obj := context.active_object)
+        props = tool.Aggregate.get_object_aggregate_props(obj)

        if props.is_editing:
            row = layout.row()
@@ -66,9 +68,9 @@ class BIM_PT_aggregate(Panel):
                col.enabled = False
            op = col.operator("bim.aggregate_assign_object", icon="CHECKMARK")
            if props.relating_object:
-                op.relating_object = props.relating_object.BIMObjectProperties.ifc_definition_id
+                op.relating_object = tool.Blender.get_object_bim_props(props.relating_object).ifc_definition_id
            elif props.related_object:
-                op.related_object = props.related_object.BIMObjectProperties.ifc_definition_id
+                op.related_object = tool.Blender.get_object_bim_props(props.related_object).ifc_definition_id
            row.operator("bim.disable_editing_aggregate", icon="CANCEL", text="")
            return
        else:
@@ -115,9 +117,9 @@ class BIM_PT_linked_aggregate(Panel):

    @classmethod
    def poll(cls, context):
-        if not context.active_object:
+        if not (obj := context.active_object):
            return False
-        props = context.active_object.BIMObjectProperties
+        props = tool.Blender.get_object_bim_props(obj)
        if not props.ifc_definition_id:
            return False
        if not tool.Ifc.get_object_by_identifier(props.ifc_definition_id):
@@ -131,9 +133,8 @@ class BIM_PT_linked_aggregate(Panel):
        if not AggregateData.is_loaded:
            AggregateData.load()

-        obj = context.active_object
-        element = tool.Ifc.get_entity(obj)
-        props = obj.BIMObjectAggregateProperties
+        assert (obj := context.active_object)
+        assert (element := tool.Ifc.get_entity(obj))
        row = layout.row(align=True)

        if element.Decomposes:
@@ -0,0 +1,36 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2020, 2021 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+
+import bpy
+
+# from . import ui, prop, operator
+from . import operator
+
+classes = (operator.ImportAlignmentCSV,)
+
+
+def menu_func_import(self, context):
+    self.layout.operator(operator.ImportAlignmentCSV.bl_idname, text="Alignment (.csv)")
+
+
+def register():
+    bpy.types.TOPBAR_MT_file_import.append(menu_func_import)
+
+
+def unregister():
+    bpy.types.TOPBAR_MT_file_import.remove(menu_func_import)
@@ -0,0 +1,114 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2020, 2021 Dion Moult <dion@thinkmoult.com>, 2022 Yassine Oualid <yassine@sigmadimensions.com>
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+
+# pyright: reportUnnecessaryTypeIgnoreComment=error
+
+import os
+
+import ifcopenshell.api.alignment
+import ifcopenshell.api.alignment.add_stationing_to_alignment
+
+import bpy
+import json
+import time
+import calendar
+import isodate
+import bonsai.core.sequence as core
+import bonsai.tool as tool
+import bonsai.bim.module.sequence.helper as helper
+import ifcopenshell.api.spatial
+import ifcopenshell.geom
+import ifcopenshell.util.sequence
+import ifcopenshell.util.selector
+from datetime import datetime
+from dateutil import parser, relativedelta
+from bpy_extras.io_utils import ImportHelper
+from typing import get_args, TYPE_CHECKING
+from typing_extensions import assert_never
+
+
+class ImportAlignmentCSV(bpy.types.Operator, tool.Ifc.Operator, ImportHelper):
+    bl_idname = "bim.import_alignment_csv"
+    bl_label = "Import Alignment CSV"
+    bl_description = " Import alignment from the provided .csv file."
+    bl_options = {"REGISTER", "UNDO"}
+    filename_ext = ".csv"
+    filter_glob: bpy.props.StringProperty(default="*.csv", options={"HIDDEN"})
+
+    @classmethod
+    def poll(cls, context):
+        ifc_file = tool.Ifc.get()
+        if ifc_file is None:
+            cls.poll_message_set("No IFC file is loaded.")
+            return False
+        elif ifc_file.schema != "IFC4X3":
+            cls.poll_message_set("Schema must be IFC4x3.")
+            return False
+        return True
+
+    def _execute(self, context):
+        self.file = tool.Ifc.get()
+        start = time.time()
+        alignment = ifcopenshell.api.alignment.create_alignment_from_csv(self.file, self.filepath)
+        ifcopenshell.api.alignment.create_geometric_representation(self.file, alignment)
+        ifcopenshell.api.alignment.add_stationing_to_alignment(self.file, alignment=alignment, start_station=0.0)
+
+        # IFC 4.1.5.1 alignments cannot be contained in spatial structures, but can be referenced into them
+        sites = self.file.by_type("IfcSite")
+        for site in sites:
+            ifcopenshell.api.spatial.reference_structure(self.file, products=[alignment], relating_structure=site)
+
+        # process the generated IfcReferent for the alignment
+        for rel in alignment.IsNestedBy:
+            for referent in rel.RelatedObjects:
+                if referent.is_a("IfcReferent"):
+                    referent_obj = bpy.data.objects.new(tool.Loader.get_name(referent), None)
+                    tool.Geometry.link(referent, referent_obj)
+                    tool.Collector.assign(referent_obj, should_clean_users_collection=False)
+
+        # an alignment can be an aggregation of multiple child alignments (ie. multiple verticals for a single horizontal)
+        # get all the alignment curves
+        curves = []
+        for rel in alignment.IsDecomposedBy:
+            for agg in rel.RelatedObjects:
+                if agg.is_a("IfcAlignment"):
+                    curves.append(ifcopenshell.api.alignment.get_curve(agg))  # 3D curve
+
+        # if there aren't any curves from aggregation, then there is only a single vertical or no vertical
+        if len(curves) == 0:
+            curves.append(ifcopenshell.api.alignment.get_curve(alignment))
+
+        settings = ifcopenshell.geom.settings()
+        for curve in curves:
+            shape = ifcopenshell.geom.create_shape(settings, curve)
+
+            # create a new Blender mesh
+            mesh_name = tool.Loader.get_mesh_name_from_shape(shape)
+            mesh = bpy.data.meshes.new(mesh_name)
+            m = tool.Loader.convert_geometry_to_mesh(shape, mesh)
+
+            # create a new Blender object
+            alignment_obj = bpy.data.objects.new(tool.Loader.get_name(alignment), m)
+
+            # link the blender object to with the alignment element
+            tool.Geometry.link(alignment, alignment_obj)
+
+            # assign the object to the blender collections
+            tool.Collector.assign(alignment_obj, should_clean_users_collection=False)
+
+        self.report({"INFO"}, "Imported in %s seconds" % (time.time() - start))
@@ -26,30 +26,42 @@ import bonsai.bim.helper
 import bonsai.tool as tool
 import bonsai.core.attribute as core
 import bonsai.core.spatial
+from typing import TYPE_CHECKING


-def get_objs_for_operation(operator_properties, context):
+def get_objs_for_operation(
+    operator_properties: "AttributesOperator", context: bpy.types.Context
+) -> list[bpy.types.Object]:
    if operator_properties.obj:
        return [bpy.data.objects[operator_properties.obj]]
    if operator_properties.mass_operation:
        return context.selected_objects[:]
-    return [context.active_object]
+    obj = context.active_object
+    assert obj
+    return [obj]


-class EnableEditingAttributes(bpy.types.Operator):
-    bl_idname = "bim.enable_editing_attributes"
-    bl_label = "Enable Editing Attributes"
-    bl_description = "ALT + Left Click to enable editing attributes on all selected objects"
-    bl_options = {"REGISTER", "UNDO"}
+class AttributesOperator:
    obj: bpy.props.StringProperty(options={"SKIP_SAVE"})
    mass_operation: bpy.props.BoolProperty(default=False, options={"SKIP_SAVE"})

+    if TYPE_CHECKING:
+        obj: str
+        mass_operation: bool
+
    def invoke(self, context, event):
        self.mass_operation = event.alt
        return self.execute(context)

-    def enable_editing_attribute_on_obj(self, obj):
-        props = obj.BIMAttributeProperties
+
+class EnableEditingAttributes(bpy.types.Operator, AttributesOperator):
+    bl_idname = "bim.enable_editing_attributes"
+    bl_label = "Enable Editing Attributes"
+    bl_description = "ALT + Left Click to enable editing attributes on all selected objects"
+    bl_options = {"REGISTER", "UNDO"}
+
+    def enable_editing_attribute_on_obj(self, obj: bpy.types.Object) -> None:
+        props = tool.Blender.get_object_attribute_props(obj)
        props.attributes.clear()

        element = tool.Ifc.get_entity(obj)
@@ -87,20 +99,14 @@ class EnableEditingAttributes(bpy.types.Operator):
        return {"FINISHED"}


-class DisableEditingAttributes(bpy.types.Operator):
+class DisableEditingAttributes(bpy.types.Operator, AttributesOperator):
    bl_idname = "bim.disable_editing_attributes"
    bl_label = "Disable Editing Attributes"
    bl_description = "ALT + Left Click to disable editing attributes on all selected objects"
    bl_options = {"REGISTER", "UNDO"}
-    obj: bpy.props.StringProperty(options={"SKIP_SAVE"})
-    mass_operation: bpy.props.BoolProperty(default=False, options={"SKIP_SAVE"})

-    def invoke(self, context, event):
-        self.mass_operation = event.alt
-        return self.execute(context)
-
-    def disable_editing_attributes_on_obj(self, obj):
-        props = obj.BIMAttributeProperties
+    def disable_editing_attributes_on_obj(self, obj: bpy.types.Object) -> None:
+        props = tool.Blender.get_object_attribute_props(obj)
        props.is_editing_attributes = False

    def execute(self, context):
@@ -118,7 +124,7 @@ class EditAttributes(bpy.types.Operator, tool.Ifc.Operator):
    def _execute(self, context):
        self.file = tool.Ifc.get()
        obj = tool.Blender.get_active_object(is_selected=False)
-        if not (element := tool.Ifc.get_entity(obj)):
+        if not obj or not (element := tool.Ifc.get_entity(obj)):
            return

        def callback(attributes, prop):
@@ -130,7 +136,7 @@ class EditAttributes(bpy.types.Operator, tool.Ifc.Operator):
                        attributes[prop.name] = None
                    return True

-        props = obj.BIMAttributeProperties
+        props = tool.Blender.get_object_attribute_props(obj)
        attributes = bonsai.bim.helper.export_attributes(props.attributes, callback=callback)
        ifcopenshell.api.attribute.edit_attributes(self.file, product=element, attributes=attributes)

@@ -165,13 +171,12 @@ class GenerateGlobalId(bpy.types.Operator, tool.Ifc.Operator):
                element.GlobalId = ifcopenshell.guid.new()

        obj = context.active_object
-        if not obj or not obj.BIMAttributeProperties.is_editing_attributes:
+        if not obj or not (props := tool.Blender.get_object_attribute_props(obj)).is_editing_attributes:
            return {"FINISHED"}

-        props = obj.BIMAttributeProperties
        element = tool.Ifc.get_entity(obj)

-        if not element.is_a("IfcRoot"):
+        if not element or not element.is_a("IfcRoot"):
            return {"FINISHED"}

        if self.use_selected and obj in context.selected_objects:
@@ -191,7 +196,10 @@ class CopyAttributeToSelection(bpy.types.Operator, tool.Ifc.Operator):
    name: bpy.props.StringProperty()

    def _execute(self, context):
-        value = tool.Blender.get_active_object().BIMAttributeProperties.attributes.get(self.name).get_value()
+        obj = tool.Blender.get_active_object()
+        assert obj
+        props = tool.Blender.get_object_attribute_props(obj)
+        value = props.attributes[self.name].get_value()
        total = core.copy_attribute_to_selection(
            tool.Ifc, tool.Blender, tool.Root, tool.Spatial, name=self.name, value=value
        )
@@ -29,8 +29,13 @@ from bpy.props import (
    FloatVectorProperty,
    CollectionProperty,
 )
+from typing import TYPE_CHECKING


 class BIMAttributeProperties(PropertyGroup):
    attributes: CollectionProperty(name="Attributes", type=Attribute)
    is_editing_attributes: BoolProperty(name="Is Editing Attributes")
+
+    if TYPE_CHECKING:
+        attributes: bpy.types.bpy_prop_collection_idprop[Attribute]
+        is_editing_attributes: bool
@@ -17,14 +17,16 @@
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.

 import bonsai.bim.helper
+import bpy.types
 from bpy.types import Panel
 from bonsai.bim.module.attribute.data import AttributesData
 import bonsai.tool as tool


-def draw_ui(context, layout, attributes):
+def draw_ui(context: bpy.types.Context, layout: bpy.types.UILayout, attributes) -> None:
    obj = context.active_object
-    props = obj.BIMAttributeProperties
+    assert obj
+    props = tool.Blender.get_object_attribute_props(obj)

    if props.is_editing_attributes:
        row = layout.row(align=True)
@@ -42,6 +42,7 @@ import ifcopenshell.util.unit
 import bonsai.tool as tool
 import bonsai.bim.module.bcf.prop as bcf_prop
 import bonsai.bim.module.bcf.bcfstore as bcfstore
+from bpy_extras.io_utils import ImportHelper, ExportHelper
 from pathlib import Path
 from math import radians, degrees, atan, tan, cos, sin
 from mathutils import Vector, Matrix, Euler, geometry
@@ -63,12 +64,14 @@ class NewBcfProject(bpy.types.Operator):
        return {"FINISHED"}


-class LoadBcfProject(bpy.types.Operator):
+class LoadBcfProject(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.load_bcf_project"
    bl_label = "Load BCF Project"
+    bl_description = "Load the BCF file."
    bl_options = {"REGISTER", "UNDO"}
    filepath: bpy.props.StringProperty(subtype="FILE_PATH", options={"SKIP_SAVE"})
    filter_glob: bpy.props.StringProperty(default="*.bcf;*.bcfzip", options={"HIDDEN"})
+    filename_ext = ".bcf"

    def execute(self, context):
        # Operator is also used when new project is created by not yet saved.
@@ -108,10 +111,6 @@ class LoadBcfProject(bpy.types.Operator):
        self.report({"INFO"}, f"BCF Project '{Path(self.filepath).name}' is loaded.")
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-

 class UnloadBcfProject(bpy.types.Operator):
    bl_idname = "bim.unload_bcf_project"
@@ -341,13 +340,15 @@ class EditBcfTopic(bpy.types.Operator):
        return {"FINISHED"}


-class SaveBcfProject(bpy.types.Operator):
+class SaveBcfProject(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.save_bcf_project"
    bl_label = "Save BCF Project"
+    bl_description = "Save active BCF project by the provided filepath."
    bl_options = {"REGISTER", "UNDO"}
    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.bcf;*.bcfzip", options={"HIDDEN"})
    save_current_bcf: bpy.props.BoolProperty(default=False, options={"SKIP_SAVE"})
+    filename_ext = ".bcf"

    def execute(self, context):
        bcfxml = bcfstore.BcfStore.get_bcfxml()
@@ -364,8 +365,7 @@ class SaveBcfProject(bpy.types.Operator):
                self.filepath = str(path)
                return self.execute(context)

-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
+        return ExportHelper.invoke(self, context, event)


 class AddBcfTopic(bpy.types.Operator):
@@ -1534,12 +1534,13 @@ class OpenBcfReferenceLink(bpy.types.Operator):
        return {"FINISHED"}


-class SelectBcfHeaderFile(bpy.types.Operator):
+class SelectBcfHeaderFile(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_bcf_header_file"
    bl_label = "Select BCF Header File"
+    bl_description = "Select filepath for BCF header reference."
    bl_options = {"REGISTER", "UNDO"}
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.ifc;*.ifczip;*.ifcxml;*.ifcjson", options={"HIDDEN"})
+    filename_ext = ".ifc"

    def execute(self, context):
        if self.filepath:
@@ -1547,16 +1548,12 @@ class SelectBcfHeaderFile(bpy.types.Operator):
            props.file_reference = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class SelectBcfBimSnippetReference(bpy.types.Operator):
+class SelectBcfBimSnippetReference(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_bcf_bim_snippet_reference"
    bl_label = "Select BCF BIM Snippet Reference"
+    bl_description = "Select filepath for BCF snippet reference."
    bl_options = {"REGISTER", "UNDO"}
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")

    def execute(self, context):
        if self.filepath:
@@ -1564,16 +1561,12 @@ class SelectBcfBimSnippetReference(bpy.types.Operator):
            props.bim_snippet_reference = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class SelectBcfDocumentReference(bpy.types.Operator):
+class SelectBcfDocumentReference(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_bcf_document_reference"
    bl_label = "Select BCF Document Reference"
+    bl_description = "Select filepath for BCF document reference."
    bl_options = {"REGISTER", "UNDO"}
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")

    def execute(self, context):
        if self.filepath:
@@ -1581,10 +1574,6 @@ class SelectBcfDocumentReference(bpy.types.Operator):
            props.document_reference = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-

 class LoadBcfHeaderIfcFile(bpy.types.Operator):
    bl_idname = "bim.load_bcf_header_ifc_file"
@@ -43,6 +43,8 @@ class BoundaryDecorator:
        cls.installed = None

    def draw_batch(self, shader_type, content_pos, color, indices=None):
+        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
+            return
        shader = self.line_shader if shader_type == "LINES" else self.shader
        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
        shader.uniform_float("color", color)
@@ -26,6 +26,7 @@ import numpy as np
 import multiprocessing
 import ifcopenshell.api
 import ifcopenshell.api.boundary
+import ifcopenshell.api.root
 import ifcopenshell.geom
 import ifcopenshell.util.unit
 import ifcopenshell.util.shape
@@ -41,6 +42,7 @@ from bonsai.bim.module.model.decorator import ProfileDecorator
 from bonsai.bim.module.boundary.decorator import BoundaryDecorator
 import bonsai.core
 import bonsai.core.geometry
+from typing import Union, Optional


 def disable_editing_boundary_geometry(context):
@@ -58,7 +60,7 @@ def disable_editing_boundary_geometry(context):


 class Loader:
-    def __init__(self, operator=None):
+    def __init__(self, operator: Optional[bpy.types.Operator] = None):
        self.operator = operator
        self.ifc_file = None
        self.logger = None
@@ -67,17 +69,20 @@ class Loader:
        self.fallback_settings = self.load_fallback_settings()
        self.load_importer()

-    def create_mesh(self, boundary):
+    def create_mesh(self, boundary: ifcopenshell.entity_instance) -> Union[bpy.types.Mesh, None]:
        # ConnectionGeometry is optional in IFC schema for some reasons.
        if not boundary.ConnectionGeometry:
            return None
+        assert self.ifc_importer
+        assert self.operator
        surface = boundary.ConnectionGeometry.SurfaceOnRelatingElement
        # Workaround for invalid geometry provided by Revit. See https://github.com/Autodesk/revit-ifc/issues/270
        if surface.is_a("IfcCurveBoundedPlane") and not getattr(surface, "InnerBoundaries", None):
            surface.InnerBoundaries = ()
        try:
            shape = ifcopenshell.geom.create_shape(self.settings, surface)
-            mesh = self.ifc_importer.create_mesh(None, shape)
+            mesh = self.ifc_importer.create_mesh(boundary, shape)
+            assert mesh
            tool.Loader.link_mesh(shape, mesh)
        except RuntimeError:
            # Fallback solution for invalid geometry provided by Revit. (InnerBoundaries cuting OuterBoundary)
@@ -97,7 +102,8 @@ class Loader:
                return None
            mesh = bpy.data.meshes.new(str(surface.id()))
            bm = bmesh.new()
-            verts = [bm.verts.new(shape.verts[i : i + 3]) for i in range(0, len(shape.verts), 3)]
+            coords = ifcopenshell.util.shape.get_vertices(shape)
+            verts = [bm.verts.new(coord) for coord in coords]
            bm.faces.new(verts)
            for inner_boundary in surface.InnerBoundaries:
                try:
@@ -108,7 +114,9 @@ class Loader:
                        f"Skipping an inner boundary for IfcRelSpaceBoundary with ID {boundary.id()}. Geometry might be invalid",
                    )
                    return None
-                verts = [bm.verts.new(shape.verts[i : i + 3]) for i in range(0, len(shape.verts), 3)]
+                coords = ifcopenshell.util.shape.get_vertices(shape)
+                verts = [bm.verts.new(coord) for coord in coords]
+                bm.faces.new(verts)
                for i in range(len(verts) - 1):
                    bm.edges.new(verts[i : i + 2])
                bm.edges.new((verts[-1], verts[0]))
@@ -131,7 +139,7 @@ class Loader:
        settings.set("dimensionality", ifcopenshell.ifcopenshell_wrapper.CURVES_SURFACES_AND_SOLIDS)
        return settings

-    def load_importer(self):
+    def load_importer(self) -> None:
        self.ifc_file = tool.Ifc.get()
        self.logger = logging.getLogger("ImportIFC")
        ifc_import_settings = import_ifc.IfcImportSettings.factory(bpy.context, IfcStore.path, self.logger)
@@ -280,7 +288,7 @@ class SelectProjectBoundaries(bpy.types.Operator):
        return {"FINISHED"}


-def get_colour(ifc_boundary):
+def get_colour(ifc_boundary: ifcopenshell.entity_instance) -> tuple[float, float, float, float]:
    """Return a color depending on IfcClass given"""
    product_colors = {
        "IfcWall": (0.7, 0.3, 0, 1),
@@ -316,7 +324,8 @@ class ColourByRelatedBuildingElement(bpy.types.Operator):

    def _execute(self, context):
        for obj in context.visible_objects:
-            if not obj.BIMObjectProperties.ifc_definition_id:
+            props = tool.Blender.get_object_bim_props(obj)
+            if not props.ifc_definition_id:
                continue
            element = tool.Ifc.get_entity(obj)
            if not element.is_a("IfcRelSpaceBoundary"):
@@ -583,47 +592,70 @@ class DecorateBoundaries(bpy.types.Operator, tool.Ifc.Operator):
 class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
    bl_idname = "bim.add_boundary"
    bl_label = "Add Boundary"
+    bl_description = (
+        "There are two options for this operator:\n"
+        "- just 1 IfcSpace is selected - generate a boundary based on "
+        "potential nearby (0.1m) boundary elements.\n"
+        "- 1 IfcSpace and 1 IfcElement are selected - generate a boundary "
+        "for IfcSpace and use selected IfcElement as boundary's building element."
+    )
    bl_options = {"REGISTER", "UNDO"}

    def _execute(self, context):
-        relating_space = None
-        related_building_element = None
-        relating_space_obj = None
-        related_building_element_obj = None
-        parent_boundaries = []
+        parent_boundaries: list[ifcopenshell.entity_instance] = []

-        objs = context.selected_objects
+        objs = tool.Blender.get_selected_objects()
+        ifc_objects = {element: obj for obj in objs if (element := tool.Ifc.get_entity(obj))}
+        if len(ifc_objects) not in (1, 2):
+            self.report({"ERROR"}, "Please select one or two IFC elements.")
+            return {"CANCELLED"}

-        if not any((element := tool.Ifc.get_entity(obj)) and element.is_a("IfcSpace") for obj in objs):
-            self.report({"INFO"}, "No IfcSpace elements selected.")
-            return {"FINISHED"}
+        if not any(element.is_a("IfcSpace") for element in ifc_objects):
+            self.report({"ERROR"}, "One of the selected objects must be an IfcSpace.")
+            return {"CANCELLED"}

        if len(objs) == 2:
-            # The user may select two objects, a space and its related building element
-            for obj in objs:
-                element = tool.Ifc.get_entity(obj)
-                if not element:
-                    continue
-                if element.is_a("IfcSpace"):
-                    relating_space = element
-                    relating_space_obj = obj
-                else:
-                    related_building_element = element
-                    related_building_element_obj = obj
+            # Validate input.
+            space = next((e for e in ifc_objects.keys() if e.is_a("IfcSpace")), None)
+            if not space:
+                self.report({"ERROR"}, "One of the selected objects must be an IfcSpace.")
+                return {"CANCELLED"}
+            element = next((e for e in ifc_objects.keys() if e.is_a("IfcElement")), None)
+            if not element:
+                self.report({"ERROR"}, "One of the selected objects must be an IfcElement.")
+                return {"CANCELLED"}
+
            parent_boundary = self.create_element_boundary(
-                context, relating_space, relating_space_obj, related_building_element, related_building_element_obj
+                context, space, ifc_objects[space], element, ifc_objects[element]
            )
-            if parent_boundary:
-                parent_boundaries.append(parent_boundary)
+
+            if not parent_boundary:
+                self.report({"ERROR"}, "Failed to create a boundary.")
+                return {"FINISHED"}
+            parent_boundaries.append(parent_boundary)
+
        elif len(objs) == 1:
+            space = next(iter(ifc_objects))
+            if not space.is_a("IfcSpace"):
+                self.report({"ERROR"}, "1 element selected but it's not an IfcSpace - please, select IfcSpace..")
+                return {"CANCELLED"}
+
            # New prototype, old code not yet removed. Still testing.
-            space = tool.Ifc.get_entity(objs[0])
-            if space.is_a("IfcSpace"):
-                self.auto_generate_boundaries(space, objs[0])
-        elif len(objs) == 1:
+            res = self.auto_generate_boundaries(space, ifc_objects[space])
+            if isinstance(res, str):
+                self.report({"ERROR"}, res)
+                return {"FINISHED"}
+            parent_boundaries.extend(res)
+
+        elif len(objs) == 1 and False:
            # Optionally the user may select just the space, and the building element shall be auto-detected
            # TODO : refactor to be able to generate all boundaries for selected space automatically or with an option

+            relating_space = None
+            related_building_element = None
+            relating_space_obj = None
+            related_building_element_obj = None
+
            def msg(self, context):
                self.layout.label(text="Please set an active container to detect space boundaries from.")

@@ -660,8 +692,17 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
            obj = tool.Ifc.get_object(parent_boundary)
            obj.select_set(True)

-    def auto_generate_boundaries(self, space, space_obj):
+    def auto_generate_boundaries(
+        self, space: ifcopenshell.entity_instance, space_obj: bpy.types.Object
+    ) -> Union[str, list[ifcopenshell.entity_instance]]:
+        """
+        :return: list of created boundaries or a string with error description.
+        """
+        ifc_file = tool.Ifc.get()
        props = tool.Model.get_model_props()
+        boundaries: list[ifcopenshell.entity_instance] = []
+        assert isinstance(space_obj.data, bpy.types.Mesh)
+
        # Identify all potential building elements
        # TODO: don't select everything, use AABB culling in Blender
        building_elements = (
@@ -681,7 +722,7 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
        shapes = {}
        settings = ifcopenshell.geom.settings()
        settings.set("disable-opening-subtractions", True)
-        iterator = ifcopenshell.geom.iterator(settings, tool.Ifc.get(), multiprocessing.cpu_count(), include=include)
+        iterator = ifcopenshell.geom.iterator(settings, ifc_file, multiprocessing.cpu_count(), include=include)
        if iterator.initialize():
            while True:
                tree.add_element(iterator.get_native())
@@ -694,12 +735,12 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
        building_elements = [e for e in tree.select(space, extend=0.1) if e != space]

        if not building_elements:
-            return
+            return "No building elements found to create boundaries."

        # Create a dissolved bmesh for the space
        space_bm = bmesh.new()
        space_bm.from_mesh(space_obj.data)
-        bmesh.ops.dissolve_limit(space_bm, angle_limit=pi * 2 / 360, verts=space_bm.verts, edges=space_bm.edges)
+        bmesh.ops.dissolve_limit(space_bm, angle_limit=pi * 2 / 360, verts=space_bm.verts[:], edges=space_bm.edges[:])

        # Create dissolved bmeshes for all boundary elements
        building_element_bms = {}
@@ -777,7 +818,7 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
                    # we cheat by using the exterior boundary to mean "gross".
                    exterior_boundary_polygon = shapely.Polygon(gross_boundary_polygon.exterior.coords)

-                    parent_boundary = tool.Ifc.run("root.create_entity", ifc_class=props.boundary_class)
+                    parent_boundary = ifcopenshell.api.root.create_entity(ifc_file, ifc_class=props.boundary_class)
                    if building_element.is_a("IfcVirtualElement"):
                        parent_boundary.PhysicalOrVirtualBoundary = "VIRTUAL"
                    else:
@@ -809,6 +850,7 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
                        exterior_boundary_polygon, space_face_matrix
                    )
                    self.set_boundary_name(parent_boundary)
+                    boundaries.append(parent_boundary)

                    for rel in getattr(building_element, "HasOpenings", []):
                        opening = rel.RelatedOpeningElement
@@ -854,7 +896,7 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
                        if opening_polygon.intersection(exterior_boundary_polygon).area == 0:
                            continue

-                        boundary = tool.Ifc.run("root.create_entity", ifc_class=props.boundary_class)
+                        boundary = ifcopenshell.api.root.create_entity(ifc_file, ifc_class=props.boundary_class)
                        boundary.RelatingSpace = space
                        boundary.RelatedBuildingElement = filling or opening
                        boundary.ConnectionGeometry = self.create_connection_geometry_from_polygon(
@@ -868,29 +910,39 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
                        if boundary.is_a() != "IfcRelSpaceBoundary":
                            boundary.ParentBoundary = parent_boundary
                        self.set_boundary_name(boundary)
+                        boundaries.append(boundary)
+
+        return boundaries

    def create_element_boundary(
-        self, context, relating_space, relating_space_obj, related_building_element, related_building_element_obj
-    ):
-        if not relating_space or not related_building_element:
-            return
+        self,
+        context: bpy.types.Context,
+        space: ifcopenshell.entity_instance,
+        space_obj: bpy.types.Object,
+        building_element: ifcopenshell.entity_instance,
+        building_element_obj: bpy.types.Object,
+    ) -> Union[ifcopenshell.entity_instance, None]:
+        """Create element boundary for IfcSpace and IfcElement as building element.

+        :return: IfcRelSpaceBoundary or ``None`` if couldn't find a face on ``space_obj``
+            that would be close enough to ``related_building_element_obj``.
+        """
        props = tool.Model.get_model_props()
        # Find which face on space should be bounded to related building element
        # TODO: Handle round wall where multiple faces need to be bound to the same related building element
-        bm = bmesh.new()
-        bm.from_mesh(relating_space_obj.data)
-        bmesh.ops.dissolve_limit(bm, angle_limit=pi * 2 / 360, verts=bm.verts, edges=bm.edges)
+        space_bm = bmesh.new()
+        assert isinstance(space_obj.data, bpy.types.Mesh)
+        space_bm.from_mesh(space_obj.data)
+        bmesh.ops.dissolve_limit(space_bm, angle_limit=pi * 2 / 360, verts=space_bm.verts[:], edges=space_bm.edges[:])

        target_distance = inf
        target_face = None
-        for face in bm.faces:
-            centroid = relating_space_obj.matrix_world @ face.calc_center_median()
-            raycast = related_building_element_obj.closest_point_on_mesh(
-                related_building_element_obj.matrix_world.inverted() @ centroid, distance=1
-            )
+        to_building_obj_space = building_element_obj.matrix_world.inverted()
+        for face in space_bm.faces:
+            centroid = space_obj.matrix_world @ face.calc_center_median()
+            raycast = building_element_obj.closest_point_on_mesh(to_building_obj_space @ centroid, distance=1)
            if raycast[0]:
-                distance = (related_building_element_obj.matrix_world @ raycast[1] - centroid).length
+                distance = (building_element_obj.matrix_world @ raycast[1] - centroid).length
                if distance < target_distance:
                    target_face = face
                    target_distance = distance
@@ -905,9 +957,7 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):

        target_face_polygon = shapely.Polygon([tuple((target_face_matrix_i @ v).xy) for v in target_face_verts])

-        related_building_element_polygon = self.get_flattened_polygon(
-            related_building_element, relating_space_obj, target_face_matrix_i
-        )
+        related_building_element_polygon = self.get_flattened_polygon(building_element, space_obj, target_face_matrix_i)

        gross_boundary_polygon = target_face_polygon.intersection(related_building_element_polygon)

@@ -923,7 +973,8 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
        ):
            return

-        parent_boundary = tool.Ifc.run("root.create_entity", ifc_class=props.boundary_class)
+        ifc_file = tool.Ifc.get()
+        parent_boundary = ifcopenshell.api.root.create_entity(ifc_file, ifc_class=props.boundary_class)
        parent_boundary.PhysicalOrVirtualBoundary = "PHYSICAL"
        # Set to EXTERNAL by default and turn later to internal if there is a corresponding boundary relating to an
        # internal space
@@ -936,14 +987,14 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
        # space.
        exterior_boundary_polygon = shapely.Polygon(gross_boundary_polygon.exterior.coords)

-        for rel in getattr(related_building_element, "HasOpenings", []):
+        for rel in getattr(building_element, "HasOpenings", []):
            opening = rel.RelatedOpeningElement
            if not opening.HasFillings:
                continue
            # TODO: HasFilling is a zero to many relationship. How to handle many ?
            filling = opening.HasFillings[0].RelatedBuildingElement

-            opening_polygon = self.get_flattened_polygon(opening, relating_space_obj, target_face_matrix_i)
+            opening_polygon = self.get_flattened_polygon(opening, space_obj, target_face_matrix_i)

            # An inner boundary is supposed to overlap its parent boundary according to IFC4 documentation
            # so we extend our exterior boundary with all opening which has a filling
@@ -959,10 +1010,10 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):

            connection_geometry = self.create_connection_geometry_from_polygon(opening_polygon, target_face_matrix)
            boundary = tool.Ifc.run("root.create_entity", ifc_class=props.boundary_class)
-            boundary.RelatingSpace = relating_space
+            boundary.RelatingSpace = space
            boundary.RelatedBuildingElement = filling
            boundary.ConnectionGeometry = connection_geometry
-            if related_building_element.is_a("IfcVirtualElement"):
+            if building_element.is_a("IfcVirtualElement"):
                boundary.PhysicalOrVirtualBoundary = "VIRTUAL"
            else:
                boundary.PhysicalOrVirtualBoundary = "PHYSICAL"
@@ -974,20 +1025,23 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):
        connection_geometry = self.create_connection_geometry_from_polygon(
            exterior_boundary_polygon, target_face_matrix
        )
-        parent_boundary.RelatingSpace = relating_space
-        parent_boundary.RelatedBuildingElement = related_building_element
+        parent_boundary.RelatingSpace = space
+        parent_boundary.RelatedBuildingElement = building_element
        parent_boundary.ConnectionGeometry = connection_geometry
        self.set_boundary_name(parent_boundary)
        return parent_boundary

-    def get_face_matrix(self, p1, p2, p3):
+    def get_face_matrix(self, p1: Vector, p2: Vector, p3: Vector) -> Matrix:
        edge1 = p2 - p1
        edge2 = p3 - p1
        normal = edge1.cross(edge2)
+        assert isinstance(normal, Vector)
+
        z_axis = normal.normalized()
        x_axis = p2 - p1
        x_axis.normalize()
        y_axis = z_axis.cross(x_axis)
+        assert isinstance(y_axis, Vector)

        mat = Matrix()
        mat.col[0][:3] = x_axis
@@ -1057,7 +1111,7 @@ class AddBoundary(bpy.types.Operator, tool.Ifc.Operator):

        return surface

-    def set_boundary_name(self, boundary):
+    def set_boundary_name(self, boundary: ifcopenshell.entity_instance):
        """
        By convention 1stLevel and 2ndLevel boundary have specific name and description
        See https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcRelSpaceBoundary.htm
@@ -52,9 +52,9 @@ class BIM_PT_Boundary(Panel):

    @classmethod
    def poll(cls, context):
-        if not context.active_object:
+        if not (obj := context.active_object):
            return False
-        props = context.active_object.BIMObjectProperties
+        props = tool.Blender.get_object_bim_props(obj)
        if not props.ifc_definition_id:
            return False
        if not tool.Ifc.get_object_by_identifier(props.ifc_definition_id):
@@ -65,7 +65,7 @@ class BIM_PT_Boundary(Panel):
    def draw(self, context):
        obj = context.active_object
        assert obj
-        props = obj.BIMObjectProperties
+        props = tool.Blender.get_object_bim_props(obj)
        ifc_file = tool.Ifc.get()
        boundary = ifc_file.by_id(props.ifc_definition_id)
        self.bprops = tool.Boundary.get_object_boundary_props(obj)
@@ -128,9 +128,9 @@ class BIM_PT_SpaceBoundaries(Panel):

    @classmethod
    def poll(cls, context):
-        if not context.active_object:
+        if not (obj := context.active_object):
            return False
-        props = context.active_object.BIMObjectProperties
+        props = tool.Blender.get_object_bim_props(obj)
        if not props.ifc_definition_id:
            return False
        if not tool.Ifc.get_object_by_identifier(props.ifc_definition_id):
@@ -145,7 +145,9 @@ class BIM_PT_SpaceBoundaries(Panel):
        if not SpaceBoundariesData.is_loaded:
            SpaceBoundariesData.load()

-        self.props = context.active_object.BIMObjectProperties
+        obj = context.active_object
+        assert obj
+        self.props = tool.Blender.get_object_bim_props(obj)
        self.ifc_file = tool.Ifc.get()
        row = self.layout.row()
        row.operator("bim.load_space_boundaries")
@@ -52,7 +52,7 @@ class BrickschemaData:
    def active_relations(cls):
        if BrickStore.graph is None:
            return []
-        props = bpy.context.scene.BIMBrickProperties
+        props = tool.Brick.get_brick_props()
        try:
            brick = props.bricks[props.active_brick_index]
        except:
@@ -22,29 +22,26 @@ import ifcopenshell.api
 import bonsai.tool as tool
 import bonsai.core.brick as core
 import bonsai.bim.handler
+from bpy_extras.io_utils import ImportHelper, ExportHelper
 from bonsai.bim.ifc import IfcStore
 from bonsai.tool.brick import BrickStore


-class LoadBrickProject(bpy.types.Operator, tool.Ifc.Operator):
+class LoadBrickProject(bpy.types.Operator, tool.Ifc.Operator, ImportHelper):
    bl_idname = "bim.load_brick_project"
    bl_label = "Load Brickschema Project"
    bl_options = {"REGISTER", "UNDO"}
    bl_description = "Load in a Brick project from a file"
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.ttl", options={"HIDDEN"})
+    filename_ext = ".ttl"

    def _execute(self, context):
        if os.path.exists(self.filepath) and "ttl" in os.path.splitext(self.filepath)[1].lower():
-            root = context.scene.BIMBrickProperties.brick_list_root
+            root = tool.Brick.get_brick_props().brick_list_root
            core.load_brick_project(tool.Brick, filepath=self.filepath, brick_root=root)
        else:
            self.report({"ERROR"}, f"Failed to load {self.filepath}")

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-

 class ViewBrickClass(bpy.types.Operator, tool.Ifc.Operator):
    bl_idname = "bim.view_brick_class"
@@ -111,10 +108,10 @@ class AssignBrickReference(bpy.types.Operator, tool.Ifc.Operator):
    bl_description = "Assign the selected Ifc entity to the selected Brick entity"

    def _execute(self, context):
-        if not context.active_object:
+        if not (obj := context.active_object) or not (element := tool.Ifc.get_entity(obj)):
            self.report({"ERROR"}, f"No Ifc selected")
            return
-        props = context.scene.BIMBrickProperties
+        props = tool.Brick.get_brick_props()
        try:
            props.bricks[props.active_brick_index]
        except:
@@ -123,7 +120,7 @@ class AssignBrickReference(bpy.types.Operator, tool.Ifc.Operator):
        core.assign_brick_reference(
            tool.Ifc,
            tool.Brick,
-            element=tool.Ifc.get_entity(context.active_object),
+            element=element,
            library=tool.Ifc.get().by_id(int(props.libraries)),
            brick_uri=props.bricks[props.active_brick_index].uri,
        )
@@ -136,7 +133,7 @@ class AddBrick(bpy.types.Operator, tool.Ifc.Operator):
    bl_description = "Create the Brick entity"

    def _execute(self, context):
-        props = context.scene.BIMBrickProperties
+        props = tool.Brick.get_brick_props()
        core.add_brick(
            tool.Ifc,
            tool.Brick,
@@ -155,7 +152,7 @@ class AddBrickRelation(bpy.types.Operator, tool.Ifc.Operator):
    bl_description = "Create the Brick relationship"

    def _execute(self, context):
-        props = context.scene.BIMBrickProperties
+        props = tool.Brick.get_brick_props()
        brick = props.bricks[props.active_brick_index]
        if props.new_brick_relation_type == "http://www.w3.org/2000/01/rdf-schema#label":
            object = props.new_brick_relation_object
@@ -173,7 +170,7 @@ class ConvertIfcToBrick(bpy.types.Operator, tool.Ifc.Operator):
    bl_description = "Convert Ifc entities and relations to Brick entities and relations"

    def _execute(self, context):
-        props = context.scene.BIMBrickProperties
+        props = tool.Brick.get_brick_props()
        library = None
        if props.libraries:
            library = tool.Ifc.get().by_id(int(props.libraries))
@@ -201,7 +198,8 @@ class NewBrickFile(bpy.types.Operator):
        return {"FINISHED"}

    def _execute(self, context):
-        root = context.scene.BIMBrickProperties.brick_list_root
+        props = tool.Brick.get_brick_props()
+        root = props.brick_list_root
        core.new_brick_file(tool.Brick, brick_root=root)

    def rollback(self, data):
@@ -230,7 +228,7 @@ class RemoveBrick(bpy.types.Operator, tool.Ifc.Operator):
    bl_description = "Delete this entity"

    def _execute(self, context):
-        props = context.scene.BIMBrickProperties
+        props = tool.Brick.get_brick_props()
        core.remove_brick(
            tool.Ifc,
            tool.Brick,
@@ -239,18 +237,20 @@ class RemoveBrick(bpy.types.Operator, tool.Ifc.Operator):
        )


-class SerializeBrick(bpy.types.Operator):
+class SerializeBrick(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.serialize_brick"
    bl_label = "Serialize Brick"
+    # Prevents crash on Blender 4.4.0.
+    bl_description = "Save active Brick project by the provided filepath."
+
+    filename_ext = ".ttl"
    filter_glob: bpy.props.StringProperty(default="*.ttl", options={"HIDDEN"})
    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    should_save_as: bpy.props.BoolProperty(name="Should Save As", default=False, options={"HIDDEN"})

    def invoke(self, context, event):
        if self.should_save_as or not BrickStore.path:
-            WindowManager = context.window_manager
-            WindowManager.fileselect_add(self)
-            return {"RUNNING_MODAL"}
+            return ExportHelper.invoke(self, context, event)
        else:
            return self.execute(context)

@@ -273,7 +273,7 @@ class AddBrickNamespace(bpy.types.Operator, tool.Ifc.Operator):
    bl_description = "Bind a new namespace to the Brick project"

    def _execute(self, context):
-        props = context.scene.BIMBrickProperties
+        props = tool.Brick.get_brick_props()
        alias = props.new_brick_namespace_alias
        uri = props.new_brick_namespace_uri
        core.add_brick_namespace(tool.Brick, alias=alias, uri=uri)
@@ -288,6 +288,6 @@ class RemoveBrickRelation(bpy.types.Operator, tool.Ifc.Operator):
    object: bpy.props.StringProperty(name="Object")

    def _execute(self, context):
-        props = context.scene.BIMBrickProperties
+        props = tool.Brick.get_brick_props()
        brick = props.bricks[props.active_brick_index]
        core.remove_brick_relation(tool.Brick, brick_uri=brick.uri, predicate=self.predicate, object=self.object)
@@ -33,6 +33,7 @@ from bpy.props import (
 import bonsai.core.brick as core
 import bonsai.tool.brick as tool
 from bonsai.tool.brick import BrickStore
+from typing import TYPE_CHECKING


 def update_active_brick_index(self, context):
@@ -74,13 +75,13 @@ def get_brick_relations(self, context):
    return BRICK_RELATIONS_ENUM_ITEMS


-def update_view(self, context):
-    root = context.scene.BIMBrickProperties.brick_list_root
+def update_view(self: "BIMBrickProperties", context: bpy.types.Context) -> None:
+    root = self.brick_list_root
    core.set_brick_list_root(tool.Brick, brick_root=root, split_screen=False)


-def split_screen_update_view(self, context):
-    root = context.scene.BIMBrickProperties.split_screen_brick_list_root
+def split_screen_update_view(self: "BIMBrickProperties", context: bpy.types.Context) -> None:
+    root = self.split_screen_brick_list_root
    core.set_brick_list_root(tool.Brick, brick_root=root, split_screen=True)


@@ -90,6 +91,11 @@ class Brick(PropertyGroup):
    uri: StringProperty(name="URI")
    total_items: IntProperty(name="Total Items")

+    if TYPE_CHECKING:
+        label: str
+        uri: str
+        total_items: int
+

 class BIMBrickProperties(PropertyGroup):
    active_brick_class: StringProperty(name="Active Brick Class")
@@ -124,3 +130,28 @@ class BIMBrickProperties(PropertyGroup):
    split_screen_brick_list_root: EnumProperty(
        name="Split Screen Brick List Root", items=get_brick_roots, update=split_screen_update_view
    )
+
+    if TYPE_CHECKING:
+        active_brick_class: str
+        brick_breadcrumbs: bpy.types.bpy_prop_collection_idprop[StrProperty]
+        bricks: bpy.types.bpy_prop_collection_idprop[Brick]
+        active_brick_index: int
+        libraries: str
+        set_list_root_toggled: bool
+        brick_list_root: str
+        namespace: str
+        new_brick_namespace_alias: str
+        new_brick_namespace_uri: str
+        new_brick_label: str
+        brick_entity_create_type: str
+        brick_entity_class: str
+        brick_create_relations_toggled: bool
+        brick_edit_relations_toggled: bool
+        new_brick_relation_type: str
+        new_brick_relation_object: str
+        split_screen_toggled: bool
+        split_screen_bricks: bpy.types.bpy_prop_collection_idprop[Brick]
+        split_screen_active_brick_index: int
+        split_screen_active_brick_class: str
+        split_screen_brick_breadcrumbs: bpy.types.bpy_prop_collection_idprop[StrProperty]
+        split_screen_brick_list_root: str
@@ -45,7 +45,7 @@ class BIM_PT_brickschema_project_info(Panel):
    bl_parent_id = "BIM_PT_brickschema"

    def draw(self, context):
-        self.props = context.scene.BIMBrickProperties
+        self.props = tool.Brick.get_brick_props()

        if not BrickschemaData.data["is_loaded"]:
            row = self.layout.row(align=True)
@@ -87,7 +87,7 @@ class BIM_PT_brickschema_namespaces(Panel):
        return BrickStore.graph != None

    def draw(self, context):
-        self.props = context.scene.BIMBrickProperties
+        self.props = tool.Brick.get_brick_props()

        row = self.layout.row(align=True)
        row.label(text="Active Namespace:")
@@ -122,7 +122,7 @@ class BIM_PT_brickschema_create_entity(Panel):
        return BrickStore.graph != None

    def draw(self, context):
-        self.props = context.scene.BIMBrickProperties
+        self.props = tool.Brick.get_brick_props()
        # TO DO: hide this if selected entity already has a reference, or something similar

        row = self.layout.row(align=True)
@@ -156,7 +156,7 @@ class BIM_PT_brickschema_viewport(Panel):
        return BrickStore.graph != None

    def draw(self, context):
-        self.props = context.scene.BIMBrickProperties
+        self.props = tool.Brick.get_brick_props()

        row = self.layout.row(align=True)
        row.column().alignment = "RIGHT"
@@ -178,7 +178,14 @@ class BIM_PT_brickschema_viewport(Panel):

        row = grid_left.row()
        BIM_UL_bricks.split_screen = False
-        row.template_list("BIM_UL_bricks", "", self.props, "bricks", self.props, "active_brick_index")
+        row.template_list(
+            BIM_UL_bricks.__name__,
+            BIM_UL_bricks.__name__ + "_bricks",
+            self.props,
+            "bricks",
+            self.props,
+            "active_brick_index",
+        )

        if self.props.split_screen_toggled:
            grid_right = grid.column(align=True)
@@ -195,7 +202,12 @@ class BIM_PT_brickschema_viewport(Panel):
            row = grid_right.row()
            BIM_UL_bricks.split_screen = True
            row.template_list(
-                "BIM_UL_bricks", "", self.props, "split_screen_bricks", self.props, "split_screen_active_brick_index"
+                BIM_UL_bricks.__name__,
+                BIM_UL_bricks.__name__ + "_split_screen_bricks",
+                self.props,
+                "split_screen_bricks",
+                self.props,
+                "split_screen_active_brick_index",
            )

        if BrickschemaData.data["active_relations"]:
@@ -292,7 +304,7 @@ class BIM_PT_ifc_brickschema_references(Panel):
    def draw(self, context):
        if not BrickschemaReferencesData.is_loaded:
            BrickschemaReferencesData.load()
-        self.props = context.scene.BIMBrickProperties
+        self.props = tool.Brick.get_brick_props()

        if not BrickschemaReferencesData.data["is_loaded"]:
            row = self.layout.row()
@@ -128,9 +128,10 @@ class CadMitre(bpy.types.Operator):
 class CadFillet(bpy.types.Operator):
    bl_idname = "bim.cad_fillet"
    bl_label = "CAD Fillet"
+    bl_description = "Add fillet to the 2 selected edges."
    bl_options = {"REGISTER", "UNDO"}
    resolution: bpy.props.IntProperty(name="Arc Resolution", min=0, default=1)
-    radius: bpy.props.FloatProperty(name="Radius", default=0.1)
+    radius: bpy.props.FloatProperty(name="Radius", default=0.1, subtype="DISTANCE")

    @classmethod
    def poll(cls, context):
@@ -143,18 +144,15 @@ class CadFillet(bpy.types.Operator):
            layout.prop(self, prop)

    def execute(self, context):
-        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-        self.radius = self.radius * si_conversion
-
        bpy.ops.object.mode_set(mode="OBJECT")
        bpy.ops.object.mode_set(mode="EDIT")

        obj = bpy.context.active_object
-        cursor = obj.matrix_world.inverted() @ bpy.context.scene.cursor.location
-        mesh = obj.data
+        assert obj and isinstance((mesh := obj.data), bpy.types.Mesh)
        bm = bmesh.from_edit_mesh(mesh)
        selected_edges = [e for e in bm.edges if e.select]
        if len(selected_edges) != 2:
+            self.report({"ERROR"}, "Exactly 2 edges should be selected.")
            return {"CANCELLED"}

        # Assume the user has selected two edges sharing a vert, but merge verts
@@ -219,6 +217,7 @@ class CadFillet(bpy.types.Operator):
 class CadArcFrom2Points(bpy.types.Operator):
    bl_idname = "bim.cad_arc_from_2_points"
    bl_label = "CAD Arc from 2 Points"
+    bl_description = "Add an arc to the active mesh based on 2 selected vertices."
    bl_options = {"REGISTER", "UNDO"}
    resolution: bpy.props.IntProperty(name="Arc Resolution", min=1, default=1)
    should_flip: bpy.props.BoolProperty(name="Flip", description="Flip arc", default=False)
@@ -235,6 +234,7 @@ class CadArcFrom2Points(bpy.types.Operator):
        if bpy.context.mode != "EDIT_MESH":
            return {"CANCELLED"}
        obj = bpy.context.active_object
+        assert obj
        region = bpy.context.region
        region_3d = bpy.context.area.spaces.active.region_3d
        cursor = bpy.context.scene.cursor.location
@@ -242,10 +242,12 @@ class CadArcFrom2Points(bpy.types.Operator):
        if not center:
            return {"CANCELLED"}
        mesh = obj.data
+        assert isinstance(mesh, bpy.types.Mesh)
        mw = obj.matrix_world
        bm = bmesh.from_edit_mesh(mesh)
        selected_verts = [v for v in bm.verts if v.select]
        if len(selected_verts) != 2:
+            self.report({"ERROR"}, "Exactly 2 vertices should be selected.")
            return {"CANCELLED"}
        v1 = bpy_extras.view3d_utils.location_3d_to_region_2d(region, region_3d, mw @ selected_verts[0].co)
        v2 = bpy_extras.view3d_utils.location_3d_to_region_2d(region, region_3d, mw @ selected_verts[1].co)
@@ -342,11 +344,12 @@ class CadArcFrom3Points(bpy.types.Operator):
 class CadOffset(bpy.types.Operator):
    bl_idname = "bim.cad_offset"
    bl_label = "CAD Offset"
+    bl_description = "Copy selected mesh geometry at provided offset. Mesh copied based on the current viewport angle."
    bl_options = {"REGISTER", "UNDO"}
-    distance: bpy.props.FloatProperty(name="Distance", default=0.1)
+    distance: bpy.props.FloatProperty(name="Distance", default=0.1, subtype="DISTANCE")

    @classmethod
-    def poll(self, context):
+    def poll(cls, context):
        return context.mode == "EDIT_MESH"

    def draw(self, context):
@@ -369,9 +372,6 @@ class CadOffset(bpy.types.Operator):
        # effect of converting an unclosed loop into a closed loop which is also
        # not what users expect.

-        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-        self.distance = self.distance * si_conversion
-
        bpy.ops.object.mode_set(mode="OBJECT")
        bpy.ops.object.mode_set(mode="EDIT")

@@ -543,7 +543,8 @@ class CadOffset(bpy.types.Operator):
 class AddIfcCircle(bpy.types.Operator):
    bl_idname = "bim.add_ifccircle"
    bl_label = "Add IfcCircle"
-    radius: bpy.props.FloatProperty(name="Radius", default=0.5)
+    bl_description = "Add IfcCircle to the currently active mesh."
+    radius: bpy.props.FloatProperty(name="Radius", default=0.5, subtype="DISTANCE")

    @classmethod
    def poll(cls, context):
@@ -551,18 +552,19 @@ class AddIfcCircle(bpy.types.Operator):
        return bool(obj) and obj.type == "MESH"

    def execute(self, context):
-        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-        self.radius = self.radius * si_conversion
-
+        obj = context.active_object
+        assert obj and isinstance((mesh := obj.data), bpy.types.Mesh)
+        self.obj = obj
+        self.mesh = mesh
        if self.has_selected_existing_circle(context):
            self.change_radius(context)
        else:
            self.create_circle(context)
        return {"FINISHED"}

-    def has_selected_existing_circle(self, context):
-        obj = context.active_object
-        bm = bmesh.from_edit_mesh(obj.data)
+    def has_selected_existing_circle(self, context: bpy.types.Context) -> bool:
+        obj = self.obj
+        bm = bmesh.from_edit_mesh(self.mesh)
        verts = [v for v in bm.verts if v.select and not v.hide]
        if len(verts) != 2:
            return False
@@ -575,32 +577,32 @@ class AddIfcCircle(bpy.types.Operator):
        for group in groups:
            if group in verts[0][deform_layer] and group in verts[1][deform_layer]:
                return True
+        return False

-    def change_radius(self, context):
-        obj = context.active_object
-        bm = bmesh.from_edit_mesh(obj.data)
+    def change_radius(self, context: bpy.types.Object) -> None:
+        bm = bmesh.from_edit_mesh(self.mesh)
        verts = [v for v in bm.verts if v.select and not v.hide]
        center = verts[0].co.lerp(verts[1].co, 0.5)
        verts[0].co = center + ((verts[0].co - center).normalized() * self.radius)
        verts[1].co = center + ((verts[1].co - center).normalized() * self.radius)
        bm.verts.index_update()
        bm.edges.index_update()
-        bmesh.update_edit_mesh(obj.data)
+        bmesh.update_edit_mesh(self.mesh)

-    def create_circle(self, context):
-        obj = context.active_object
+    def create_circle(self, context: bpy.types.Context) -> None:
+        obj = self.obj
        bpy.ops.object.mode_set(mode="OBJECT")
        # The last group may be the result of a prior run of this operator.
        # I tried looping through all groups but Blender group indices seem to behave unpredictably.
        if len(obj.vertex_groups):
            last_group = obj.vertex_groups[-1]
-            verts_in_group = [v for v in obj.data.vertices if last_group.index in [vg.group for vg in v.groups]]
+            verts_in_group = [v for v in self.mesh.vertices if last_group.index in [vg.group for vg in v.groups]]
            if "IFCCIRCLE" in last_group.name and len(verts_in_group) != 2:
                obj.vertex_groups.remove(last_group)
        group = obj.vertex_groups.new(name="IFCCIRCLE")
        bpy.ops.object.mode_set(mode="EDIT")

-        bm = bmesh.from_edit_mesh(obj.data)
+        bm = bmesh.from_edit_mesh(self.mesh)

        bm.verts.layers.deform.verify()
        deform_layer = bm.verts.layers.deform.active
@@ -617,7 +619,7 @@ class AddIfcCircle(bpy.types.Operator):

        bm.verts.index_update()
        bm.edges.index_update()
-        bmesh.update_edit_mesh(obj.data)
+        bmesh.update_edit_mesh(self.mesh)


 class AddIfcArcIndexFillet(bpy.types.Operator):
@@ -638,18 +640,19 @@ class AddIfcArcIndexFillet(bpy.types.Operator):
            layout.prop(self, prop)

    def execute(self, context):
-        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-        self.radius = self.radius * si_conversion
-
+        obj = context.active_object
+        assert obj and isinstance((mesh := obj.data), bpy.types.Mesh)
+        self.obj = obj
+        self.mesh = mesh
        if self.has_selected_existing_arc(context):
            self.change_radius(context)
        else:
-            self.create_arc(context)
+            return self.create_arc(context)
        return {"FINISHED"}

    def has_selected_existing_arc(self, context: bpy.types.Context) -> bool:
-        obj = context.active_object
-        bm = bmesh.from_edit_mesh(obj.data)
+        obj = self.obj
+        bm = bmesh.from_edit_mesh(self.mesh)
        verts = [v for v in bm.verts if v.select and not v.hide]
        if len(verts) != 3:
            return False
@@ -668,13 +671,14 @@ class AddIfcArcIndexFillet(bpy.types.Operator):
        return False

    def change_radius(self, context: bpy.types.Context) -> None:
-        obj = context.active_object
-        bm = bmesh.from_edit_mesh(obj.data)
+        obj = self.obj
+        bm = bmesh.from_edit_mesh(self.mesh)
        edges = [e for e in bm.edges if e.select and not e.hide]

        mid = list(set(edges[0].verts) & set(edges[1].verts))[0]
        v1 = edges[0].other_vert(mid)
        v2 = edges[1].other_vert(mid)
+        assert v1 and v2
        center = tool.Cad.get_center_of_arc([v1.co, mid.co, v2.co])

        if len(v1.link_edges) != 2 or len(v2.link_edges) != 2:
@@ -682,6 +686,7 @@ class AddIfcArcIndexFillet(bpy.types.Operator):

        v3 = v1.link_edges[1].other_vert(v1) if mid in v1.link_edges[0].verts else v1.link_edges[0].other_vert(v1)
        v4 = v2.link_edges[1].other_vert(v2) if mid in v2.link_edges[0].verts else v2.link_edges[0].other_vert(v2)
+        assert v3 and v4
        dir1 = (v3.co - v1.co).normalized()
        dir2 = (v4.co - v2.co).normalized()

@@ -702,11 +707,10 @@ class AddIfcArcIndexFillet(bpy.types.Operator):

        bm.verts.index_update()
        bm.edges.index_update()
-        bmesh.update_edit_mesh(obj.data)
-
-    def create_arc(self, context):
-        obj = bpy.context.active_object
+        bmesh.update_edit_mesh(self.mesh)

+    def create_arc(self, context: bpy.types.Context) -> set[str]:
+        obj = self.obj
        bpy.ops.object.mode_set(mode="OBJECT")
        # The last group may be the result of a prior run of this operator.
        # I tried looping through all groups but Blender group indices seem to behave unpredictably.
@@ -718,7 +722,7 @@ class AddIfcArcIndexFillet(bpy.types.Operator):
        group = obj.vertex_groups.new(name="IFCARCINDEX")
        bpy.ops.object.mode_set(mode="EDIT")

-        bm = bmesh.from_edit_mesh(obj.data)
+        bm = bmesh.from_edit_mesh(self.mesh)

        bm.verts.layers.deform.verify()
        deform_layer = bm.verts.layers.deform.active
@@ -737,6 +741,7 @@ class AddIfcArcIndexFillet(bpy.types.Operator):
        shared_vert = list(set(selected_edges[0].verts) & set(selected_edges[1].verts))[0]
        v1 = selected_edges[0].other_vert(shared_vert)
        v2 = selected_edges[1].other_vert(shared_vert)
+        assert v1 and v2
        dir1 = (v1.co - shared_vert.co).normalized()
        dir2 = (v2.co - shared_vert.co).normalized()
        edge_angle = dir1.angle(dir2)
@@ -770,7 +775,8 @@ class AddIfcArcIndexFillet(bpy.types.Operator):

        bm.verts.index_update()
        bm.edges.index_update()
-        bmesh.update_edit_mesh(obj.data)
+        bmesh.update_edit_mesh(self.mesh)
+        return {"FINISHED"}


 class AlignViewToProfile(bpy.types.Operator):
@@ -806,8 +812,9 @@ class AlignViewToProfile(bpy.types.Operator):
 class AddRectangle(bpy.types.Operator):
    bl_idname = "bim.add_rectangle"
    bl_label = "Add Rectangle"
-    x: bpy.props.FloatProperty(name="X", default=1)
-    y: bpy.props.FloatProperty(name="Y", default=1)
+    bl_description = "Add rectangle shape to the active mesh."
+    x: bpy.props.FloatProperty(name="X", default=1, subtype="DISTANCE")
+    y: bpy.props.FloatProperty(name="Y", default=1, subtype="DISTANCE")

    @classmethod
    def poll(cls, context):
@@ -815,11 +822,8 @@ class AddRectangle(bpy.types.Operator):
        return bool(obj) and obj.type == "MESH"

    def execute(self, context):
-        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-        self.x = self.x * si_conversion
-        self.y = self.y * si_conversion
-
        obj = context.active_object
+        assert obj and isinstance(obj.data, bpy.types.Mesh)
        bm = bmesh.from_edit_mesh(obj.data)
        cursor = obj.matrix_world.inverted() @ context.scene.cursor.location
        new_verts = [
@@ -20,6 +20,7 @@ import bpy
 from bonsai.bim.module.model.data import AuthoringData
 from bpy.types import PropertyGroup
 from math import pi
+from typing import TYPE_CHECKING


 class BIMCadProperties(PropertyGroup):
@@ -31,3 +32,11 @@ class BIMCadProperties(PropertyGroup):
    gable_roof_edge_angle: bpy.props.FloatProperty(
        name="Gable Roof Edge Angle", default=pi / 2, soft_min=0, soft_max=pi / 2, subtype="ANGLE"
    )
+
+    if TYPE_CHECKING:
+        resolution: int
+        radius: float
+        distance: float
+        x: float
+        y: float
+        gable_roof_edge_angle: float
@@ -23,7 +23,7 @@ import bonsai.bim.module.type.prop as type_prop
 import ifcopenshell.util.unit
 from bpy.types import WorkSpaceTool
 from bonsai.bim.module.model.data import AuthoringData, RailingData, RoofData
-from typing import Union
+from functools import partial


 def load_custom_icons():
@@ -114,11 +114,11 @@ class CadTool(WorkSpaceTool):
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
            add_layout_hotkey_operator(row, "Fillet", "S_F", bpy.ops.bim.add_ifcarcindex_fillet.__doc__, ui_context)
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
-            add_layout_hotkey_operator(row, "Offset", "S_O", "Offset", ui_context)
+            add_layout_hotkey_operator(row, "Offset", "S_O", bpy.ops.bim.cad_offset.__doc__, ui_context)
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
-            add_layout_hotkey_operator(row, "Rectangle", "S_R", "Rectangle", ui_context)
+            add_layout_hotkey_operator(row, "Rectangle", "S_R", bpy.ops.bim.add_rectangle.__doc__, ui_context)
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
-            add_layout_hotkey_operator(row, "Circle", "S_C", "Circle", ui_context)
+            add_layout_hotkey_operator(row, "Circle", "S_C", bpy.ops.bim.add_ifccircle.__doc__, ui_context)
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
            add_layout_hotkey_operator(row, "3-Point Arc", "S_V", bpy.ops.bim.set_arc_index.__doc__, ui_context)
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
@@ -138,15 +138,15 @@ class CadTool(WorkSpaceTool):
                row, "Join", "S_T", "Joins two non-parallel paths at their intersection", ui_context
            )
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
-            add_layout_hotkey_operator(row, "Fillet", "S_F", "Fillet", ui_context)
+            add_layout_hotkey_operator(row, "Fillet", "S_F", bpy.ops.bim.cad_fillet.__doc__, ui_context)
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
-            add_layout_hotkey_operator(row, "Offset", "S_O", "Offset", ui_context)
+            add_layout_hotkey_operator(row, "Offset", "S_O", bpy.ops.bim.cad_offset.__doc__, ui_context)

        else:
            if (
                (RailingData.is_loaded or not RailingData.load())
                and RailingData.data["pset_data"]
-                and obj.BIMRailingProperties.is_editing_path
+                and tool.Model.get_railing_props(obj).is_editing_path
            ):
                add_header_apply_button(
                    layout,
@@ -159,7 +159,7 @@ class CadTool(WorkSpaceTool):
            elif (
                (RoofData.is_loaded or not RoofData.load())
                and RoofData.data["pset_data"]
-                and obj.BIMRoofProperties.is_editing_path
+                and tool.Model.get_roof_props(obj).is_editing_path
            ):
                add_header_apply_button(
                    layout, "Edit Roof Path", "bim.finish_editing_roof_path", "bim.cancel_editing_roof_path", ui_context
@@ -176,17 +176,17 @@ class CadTool(WorkSpaceTool):
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
            add_layout_hotkey_operator(row, "Fillet", "S_F", bpy.ops.bim.add_ifcarcindex_fillet.__doc__, ui_context)
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
-            add_layout_hotkey_operator(row, "Offset", "S_O", "Offset", ui_context)
+            add_layout_hotkey_operator(row, "Offset", "S_O", bpy.ops.bim.cad_offset.__doc__, ui_context)
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
-            add_layout_hotkey_operator(row, "2-Point Arc", "S_C", "2-Point Arc", ui_context)
+            add_layout_hotkey_operator(row, "2-Point Arc", "S_C", bpy.ops.bim.cad_arc_from_2_points.__doc__, ui_context)
            row = row if ui_context == "TOOL_HEADER" else layout.row(align=True)
            add_layout_hotkey_operator(row, "3-Point Arc", "S_V", bpy.ops.bim.cad_arc_from_3_points.__doc__, ui_context)


 class CadHotkey(bpy.types.Operator):
    bl_idname = "bim.cad_hotkey"
-    bl_label = "CAD Hotkey"
-    bl_options = {"REGISTER", "UNDO"}
+    bl_label = ""
+    bl_options = {"REGISTER", "UNDO", "INTERNAL"}
    hotkey: bpy.props.StringProperty()
    description: bpy.props.StringProperty()

@@ -195,12 +195,14 @@ class CadHotkey(bpy.types.Operator):
        return operator.description or ""

    def execute(self, context):
-        self.props = context.scene.BIMCadProperties
+        self.props = tool.Cad.get_cad_props()
        getattr(self, f"hotkey_{self.hotkey}")()
        return {"FINISHED"}

    def draw(self, context):
-        props = context.scene.BIMCadProperties
+        props = tool.Cad.get_cad_props()
+        obj = context.active_object
+
        if self.hotkey == "S_C":
            if tool.Geometry.is_profile_object_active():
                row = self.layout.row()
@@ -226,7 +228,7 @@ class CadHotkey(bpy.types.Operator):
            elif (
                (RoofData.is_loaded or not RoofData.load())
                and RoofData.data["pset_data"]
-                and bpy.context.active_object.BIMRoofProperties.is_editing_path
+                and tool.Model.get_roof_props(obj).is_editing_path
            ):
                self.layout.row().prop(props, "gable_roof_edge_angle")

@@ -236,9 +238,8 @@ class CadHotkey(bpy.types.Operator):
                row.prop(props, "resolution")

    def hotkey_S_C(self):
-        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
        if tool.Geometry.is_profile_object_active():
-            bpy.ops.bim.add_ifccircle(radius=self.props.radius / si_conversion)
+            bpy.ops.bim.add_ifccircle(radius=self.props.radius)
        else:
            bpy.ops.bim.cad_arc_from_2_points()

@@ -246,15 +247,13 @@ class CadHotkey(bpy.types.Operator):
        bpy.ops.bim.cad_trim_extend()

    def hotkey_S_F(self):
-        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
        if tool.Geometry.is_profile_object_active():
-            bpy.ops.bim.add_ifcarcindex_fillet(radius=self.props.radius / si_conversion)
+            bpy.ops.bim.add_ifcarcindex_fillet(radius=self.props.radius)
        else:
-            bpy.ops.bim.cad_fillet(resolution=self.props.resolution, radius=self.props.radius / si_conversion)
+            bpy.ops.bim.cad_fillet(resolution=self.props.resolution, radius=self.props.radius)

    def hotkey_S_O(self):
-        si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-        bpy.ops.bim.cad_offset(distance=self.props.distance / si_conversion)
+        bpy.ops.bim.cad_offset(distance=self.props.distance)

    def hotkey_S_Q(self):
        obj = bpy.context.active_object
@@ -281,13 +280,16 @@ class CadHotkey(bpy.types.Operator):
            bpy.ops.bim.edit_extrusion_axis()

    def hotkey_S_R(self):
+        obj = bpy.context.active_object
+        if not obj:
+            return
+
        if tool.Geometry.is_profile_object_active():
-            si_conversion = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-            bpy.ops.bim.add_rectangle(x=self.props.x / si_conversion, y=self.props.y / si_conversion)
+            bpy.ops.bim.add_rectangle(x=self.props.x, y=self.props.y)
        elif (
            (RoofData.is_loaded or not RoofData.load())
            and RoofData.data["pset_data"]
-            and bpy.context.active_object.BIMRoofProperties.is_editing_path
+            and tool.Model.get_roof_props(obj).is_editing_path
        ):
            bpy.ops.bim.set_gable_roof_edge_angle(angle=self.props.gable_roof_edge_angle)

@@ -305,7 +307,9 @@ class CadHotkey(bpy.types.Operator):
            bpy.ops.bim.reset_vertex()


-def add_header_apply_button(layout, text, apply_operator, cancel_operator, ui_context=""):
+def add_header_apply_button(
+    layout: bpy.types.UILayout, text: str, apply_operator: str, cancel_operator: str, ui_context: str = ""
+) -> None:
    custom_icon = custom_icon_previews.get(text.upper().replace(" ", "_"), custom_icon_previews["IFC"]).icon_id
    row = layout.row(align=True)
    row.label(text=f"{text} Mode", icon_value=custom_icon)
@@ -324,34 +328,8 @@ def add_header_apply_button(layout, text, apply_operator, cancel_operator, ui_co
    row.label(text="Tools")


-def add_layout_hotkey_operator(
-    layout: bpy.types.UILayout, text: str, hotkey: str, description: Union[str, None], ui_context: str = ""
-) -> bpy.types.OperatorProperties:
-    parts = hotkey.split("_")
-    modifier, key = parts
-    op_text = "" if ui_context == "TOOL_HEADER" else text
-    custom_icon = custom_icon_previews.get(text.upper().replace(" ", "_"), custom_icon_previews["IFC"]).icon_id
-    modifier_icon, modifier_str = MODIFIERS.get(modifier, ("NONE", ""))
-
-    row = layout if ui_context == "TOOL_HEADER" else layout.row(align=True)
-    op = row.operator("bim.cad_hotkey", text=op_text, icon_value=custom_icon)
-
-    if ui_context != "TOOL_HEADER" and len(parts) == 2:
-        layout = layout.row(align=True)  # Create a new line for hotkey display
-        layout.label(text="", icon=modifier_icon)
-        layout.label(text="", icon=f"EVENT_{key}")
-
-    hotkey_description = f"Hotkey: {modifier_str} {key}"
-    description = "\n\n".join(filter(None, [hotkey_description if description else ""]))
-    op.hotkey = hotkey
-    op.description = description or hotkey_description
-
-    return op
+add_layout_hotkey_operator = partial(tool.Blender.add_layout_hotkey_operator, tool_name="cad", module_name=__name__)


 custom_icon_previews = None
 display_mode = None
-
-MODIFIERS = {
-    "S": ("EVENT_SHIFT", "⇧"),
-}
@@ -49,6 +49,8 @@ class ClashDecorator:
        cls.is_installed = False

    def draw_batch(self, shader_type, content_pos, color, indices=None):
+        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
+            return
        shader = self.line_shader if shader_type == "LINES" else self.shader
        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
        shader.uniform_float("color", color)
@@ -60,8 +62,9 @@ class ClashDecorator:
        unselected_elements_color = self.addon_prefs.decorator_color_unselected
        special_elements_color = self.addon_prefs.decorator_color_special

-        text = context.scene.BIMClashProperties.active_clash_text
-        p = context.scene.BIMClashProperties.p1.lerp(context.scene.BIMClashProperties.p2, 0.5)
+        props = tool.Clash.get_clash_props()
+        text = props.active_clash_text
+        p = props.p1.lerp(props.p2, 0.5)

        font_id = 0
        blf.size(font_id, 12)
@@ -92,7 +95,8 @@ class ClashDecorator:
        # general shader
        self.shader = gpu.shader.from_builtin("UNIFORM_COLOR")

-        selected_vertices = [context.scene.BIMClashProperties.p1, context.scene.BIMClashProperties.p2]
+        props = tool.Clash.get_clash_props()
+        selected_vertices = [props.p1, props.p2]
        selected_edges = []
        if selected_vertices[0] != selected_vertices[1]:
            selected_edges = [[0, 1]]
@@ -24,26 +24,20 @@ import logging
 import numpy as np
 import ifcopenshell
 import bonsai.tool as tool
+from bpy_extras.io_utils import ExportHelper, ImportHelper
 from math import radians
 from mathutils import Matrix, Vector
 from bonsai.bim.ifc import IfcStore
 from bonsai.bim.module.clash.decorator import ClashDecorator


-class ExportClashSets(bpy.types.Operator):
+class ExportClashSets(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.export_clash_sets"
    bl_label = "Export Clash Sets"
    bl_description = "Export clash sets to a selected file"
    filename_ext = ".json"
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.json", options={"HIDDEN"})

-    def invoke(self, context, event):
-        self.filepath = bpy.path.ensure_ext(bpy.data.filepath, ".json")
-        WindowManager = context.window_manager
-        WindowManager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-
    def execute(self, context):
        self.filepath = bpy.path.ensure_ext(self.filepath, ".json")
        clash_sets = tool.Clash.export_clash_sets()
@@ -52,26 +46,24 @@ class ExportClashSets(bpy.types.Operator):
        return {"FINISHED"}


-class ImportClashSets(bpy.types.Operator):
+class ImportClashSets(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.import_clash_sets"
    bl_label = "Import Clash Sets"
    bl_options = {"REGISTER", "UNDO"}
    bl_description = "Import clash sets from a selected file"
    filename_ext = ".json"
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.json", options={"HIDDEN"})

    def invoke(self, context, event):
        self.filepath = bpy.path.ensure_ext(bpy.data.filepath, ".json")
-        WindowManager = context.window_manager
-        WindowManager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
+        return ImportHelper.invoke(self, context, event)

    def execute(self, context):
        tool.Clash.load_clash_sets(self.filepath)
-        context.scene.BIMClashProperties.clash_sets.clear()
+        props = tool.Clash.get_clash_props()
+        props.clash_sets.clear()
        for clash_set in tool.Clash.get_clash_sets():
-            new = context.scene.BIMClashProperties.clash_sets.add()
+            new = props.clash_sets.add()
            new.name = clash_set["name"]
            new.mode = clash_set["mode"]
            if new.mode == "intersection":
@@ -106,7 +98,8 @@ class AddClashSet(bpy.types.Operator):
    bl_description = "Add a clash set"

    def execute(self, context):
-        new = context.scene.BIMClashProperties.clash_sets.add()
+        props = tool.Clash.get_clash_props()
+        new = props.clash_sets.add()
        new.name = "New Clash Set"
        return {"FINISHED"}

@@ -119,7 +112,8 @@ class RemoveClashSet(bpy.types.Operator):
    index: bpy.props.IntProperty()

    def execute(self, context):
-        context.scene.BIMClashProperties.clash_sets.remove(self.index)
+        props = tool.Clash.get_clash_props()
+        props.clash_sets.remove(self.index)
        return {"FINISHED"}


@@ -131,7 +125,8 @@ class AddClashSource(bpy.types.Operator):
    group: bpy.props.StringProperty()

    def execute(self, context):
-        clash_set = context.scene.BIMClashProperties.active_clash_set
+        props = tool.Clash.get_clash_props()
+        clash_set = props.active_clash_set
        source = getattr(clash_set, self.group).add()
        return {"FINISHED"}

@@ -145,78 +140,74 @@ class RemoveClashSource(bpy.types.Operator):
    group: bpy.props.StringProperty()

    def execute(self, context):
-        clash_set = context.scene.BIMClashProperties.active_clash_set
+        props = tool.Clash.get_clash_props()
+        clash_set = props.active_clash_set
        getattr(clash_set, self.group).remove(self.index)
        return {"FINISHED"}


-class SelectClashSource(bpy.types.Operator):
+class SelectClashSource(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_clash_source"
    bl_label = "Select Clash Source"
    bl_options = {"REGISTER", "UNDO"}
    bl_description = "Select an IFC file to add as a clash source"
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.ifc", options={"HIDDEN"})
    index: bpy.props.IntProperty()
    group: bpy.props.StringProperty()
+    filename_ext = ".ifc"

    def execute(self, context):
-        clash_set = context.scene.BIMClashProperties.active_clash_set
+        props = tool.Clash.get_clash_props()
+        clash_set = props.active_clash_set
        getattr(clash_set, self.group)[self.index].name = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class SelectClashResults(bpy.types.Operator):
+class SelectClashResults(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_clash_results"
    bl_label = "Select Clash Results"
+    bl_description = "Select filepath for clash results."
    bl_options = {"REGISTER", "UNDO"}
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")

    def execute(self, context):
-        context.scene.BIMClashProperties.clash_results_path = self.filepath
+        props = tool.Clash.get_clash_props()
+        props.clash_results_path = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class SelectSmartGroupedClashesPath(bpy.types.Operator):
+class SelectSmartGroupedClashesPath(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_smart_grouped_clashes_path"
    bl_label = "Select Smart-Grouped Clashes Path"
+    bl_description = "Select filepath for smart-grouped clashes."
    bl_options = {"REGISTER", "UNDO"}
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")

    def execute(self, context):
-        context.scene.BIMClashProperties.smart_grouped_clashes_path = self.filepath
+        props = tool.Clash.get_clash_props()
+        props.smart_grouped_clashes_path = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class ExecuteIfcClash(bpy.types.Operator):
+class ExecuteIfcClash(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.execute_ifc_clash"
    bl_label = "Execute IFC Clash"
    bl_description = "Execute clash detection and save the information to a .bcf or .json file"
    filter_glob: bpy.props.StringProperty(default="*.bcf;*.json", options={"HIDDEN"})
+    format: bpy.props.EnumProperty(name="Format", items=[(i, i, "") for i in ("bcf", "json")])
    filepath: bpy.props.StringProperty(subtype="FILE_PATH", options={"SKIP_SAVE"})

+    @property
+    def filename_ext(self) -> str:
+        return f".{self.format.lower()}"
+
    def invoke(self, context, event):
        if self.filepath:
            return self.execute(context)
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
+        return ExportHelper.invoke(self, context, event)

    def execute(self, context):
        from ifcclash import ifcclash

-        self.props = context.scene.BIMClashProperties
+        self.props = tool.Clash.get_clash_props()

        _, extension = os.path.splitext(self.filepath)
        if extension != ".bcf":
@@ -284,19 +275,17 @@ class ExecuteIfcClash(bpy.types.Operator):
        return {"FINISHED"}


-class SelectIfcClashResults(bpy.types.Operator):
+class SelectIfcClashResults(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_ifc_clash_results"
    bl_label = "Select IFC Clash Results"
    bl_options = {"REGISTER", "UNDO"}
    bl_description = "Select the clashing IFC geometry stored in a file"
+    filter_glob: bpy.props.StringProperty(default="*.json", options={"HIDDEN"})
    filename_ext = ".json"
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")

    def invoke(self, context, event):
        self.filepath = bpy.path.ensure_ext(bpy.data.filepath, ".json")
-        WindowManager = context.window_manager
-        WindowManager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
+        return ImportHelper.invoke(self, context, event)

    def execute(self, context):
        # TODO refactor into new clash results system
@@ -304,7 +293,9 @@ class SelectIfcClashResults(bpy.types.Operator):
        self.filepath = bpy.path.ensure_ext(self.filepath, ".json")
        with open(self.filepath) as f:
            clash_sets = json.load(f)
-        clash_set_name = context.scene.BIMClashProperties.active_clash_set.name
+        clash_props = tool.Clash.get_clash_props()
+        assert clash_props.active_clash_set
+        clash_set_name = clash_props.active_clash_set.name
        global_ids = []
        for clash_set in clash_sets:
            if clash_set["name"] != clash_set_name:
@@ -316,7 +307,8 @@ class SelectIfcClashResults(bpy.types.Operator):
                global_ids.extend([clash["a_global_id"], clash["b_global_id"]])

        for obj in context.visible_objects:
-            if not obj.BIMObjectProperties.ifc_definition_id:
+            props = tool.Blender.get_object_bim_props(obj)
+            if not props.ifc_definition_id:
                continue

            ifc_file = ""
@@ -335,7 +327,7 @@ class SelectIfcClashResults(bpy.types.Operator):
                element_file = self.file

            try:
-                element = element_file.by_id(obj.BIMObjectProperties.ifc_definition_id)
+                element = element_file.by_id(props.ifc_definition_id)
            except:
                continue

@@ -355,7 +347,7 @@ class SelectClash(bpy.types.Operator):
    index: bpy.props.IntProperty()

    def execute(self, context):
-        self.props = context.scene.BIMClashProperties
+        self.props = tool.Clash.get_clash_props()
        clash_set = tool.Clash.get_clash_set(self.props.active_clash_set.name)
        active_clash = self.props.active_clash
        clash = tool.Clash.get_clash(clash_set, active_clash.a_global_id, active_clash.b_global_id)
@@ -389,13 +381,15 @@ class SmartClashGroup(bpy.types.Operator):

    @classmethod
    def poll(cls, context):
-        return context.scene.BIMClashProperties.clash_results_path
+        props = tool.Clash.get_clash_props()
+        return bool(props.clash_results_path)

    def execute(self, context):
        from ifcclash import ifcclash

        settings = ifcclash.ClashSettings()
-        self.filepath = bpy.path.ensure_ext(context.scene.BIMClashProperties.clash_results_path, ".json")
+        props = tool.Clash.get_clash_props()
+        self.filepath = bpy.path.ensure_ext(props.clash_results_path, ".json")
        settings.output = self.filepath
        settings.logger = logging.getLogger("Clash")
        settings.logger.setLevel(logging.DEBUG)
@@ -405,19 +399,18 @@ class SmartClashGroup(bpy.types.Operator):
            clash_sets = json.load(f)

        # execute the smart grouping
-        save_path = bpy.path.ensure_ext(context.scene.BIMClashProperties.smart_grouped_clashes_path, ".json")
-        smart_grouped_clashes = ifc_clasher.smart_group_clashes(
-            clash_sets, context.scene.BIMClashProperties.smart_clash_grouping_max_distance
-        )
+        save_path = bpy.path.ensure_ext(props.smart_grouped_clashes_path, ".json")
+        smart_grouped_clashes = ifc_clasher.smart_group_clashes(clash_sets, props.smart_clash_grouping_max_distance)

        # save smart_groups to json
        with open(save_path, "w") as f:
            f.write(json.dumps(smart_grouped_clashes))

-        clash_set_name = context.scene.BIMClashProperties.active_clash_set.name
+        assert props.active_clash_set
+        clash_set_name = props.active_clash_set.name

        # Reset the list of smart_clash_groups for the UI
-        context.scene.BIMClashProperties.smart_clash_groups.clear()
+        props.smart_clash_groups.clear()

        for clash_set, smart_groups in smart_grouped_clashes.items():
            # Only select the clashes that correspond to the actively selected IFC Clash Set
@@ -425,7 +418,7 @@ class SmartClashGroup(bpy.types.Operator):
                continue
            else:
                for smart_group, global_id_pairs in smart_groups[0].items():
-                    new_group = context.scene.BIMClashProperties.smart_clash_groups.add()
+                    new_group = props.smart_clash_groups.add()
                    new_group.number = f"{smart_group}"

                    for pair in global_id_pairs:
@@ -443,18 +436,21 @@ class LoadSmartGroupsForActiveClashSet(bpy.types.Operator):

    @classmethod
    def poll(cls, context):
-        return context.scene.BIMClashProperties.active_clash_set
+        props = tool.Clash.get_clash_props()
+        return bool(props.active_clash_set)

    def execute(self, context):
-        smart_groups_path = bpy.path.ensure_ext(context.scene.BIMClashProperties.smart_grouped_clashes_path, ".json")
+        props = tool.Clash.get_clash_props()
+        smart_groups_path = bpy.path.ensure_ext(props.smart_grouped_clashes_path, ".json")

-        clash_set_name = context.scene.BIMClashProperties.active_clash_set.name
+        assert props.active_clash_set
+        clash_set_name = props.active_clash_set.name

        with open(smart_groups_path) as f:
            smart_grouped_clashes = json.load(f)

        # Reset the list of smart_clash_groups for the UI
-        context.scene.BIMClashProperties.smart_clash_groups.clear()
+        props.smart_clash_groups.clear()

        for clash_set, smart_groups in smart_grouped_clashes.items():
            # Only select the clashes that correspond to the actively selected IFC Clash Set
@@ -462,12 +458,12 @@ class LoadSmartGroupsForActiveClashSet(bpy.types.Operator):
                continue
            else:
                for smart_group, global_id_pairs in smart_groups[0].items():
-                    new_group = context.scene.BIMClashProperties.smart_clash_groups.add()
+                    new_group = props.smart_clash_groups.add()
                    new_group.number = f"{smart_group}"
                    for pair in global_id_pairs:
                        for guid in pair:
                            new_global_id = new_group.global_ids.add()
-                            new_global_id.guid = guid
+                            new_global_id.name = guid

        return {"FINISHED"}

@@ -479,15 +475,19 @@ class SelectSmartGroup(bpy.types.Operator):

    @classmethod
    def poll(cls, context):
-        return tool.Ifc.get() and context.visible_objects and context.scene.BIMClashProperties.active_smart_group
+        props = tool.Clash.get_clash_props()
+        return tool.Ifc.get() and context.visible_objects and props.active_smart_group

    def execute(self, context):
-        selected_smart_group = context.scene.BIMClashProperties.active_smart_group
-        products = []
+        ifc_file = tool.Ifc.get()
+        props = tool.Clash.get_clash_props()
+        selected_smart_group = props.active_smart_group
+        assert selected_smart_group
+        products: list[ifcopenshell.entity_instance] = []
        for global_id in selected_smart_group.global_ids:
            try:
-                products.append(tool.Ifc.get().by_guid(global_id.guid))
-            except:
+                products.append(ifc_file.by_guid(global_id.name))
+            except RuntimeError:
                continue
        tool.Spatial.select_products(products, unhide=True)
        context_override = tool.Blender.get_viewport_context()
@@ -17,6 +17,7 @@
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.

 import bpy
+import bonsai.tool as tool
 from bonsai.bim.prop import StrProperty, Attribute, BIMFilterGroup
 from bpy.types import PropertyGroup
 from bpy.props import (
@@ -29,6 +30,8 @@ from bpy.props import (
    FloatVectorProperty,
    CollectionProperty,
 )
+from mathutils import Vector
+from typing import TYPE_CHECKING, Literal, Union


 class ClashSource(PropertyGroup):
@@ -43,6 +46,10 @@ class ClashSource(PropertyGroup):
        name="Mode",
    )

+    if TYPE_CHECKING:
+        filter_groups: bpy.types.bpy_prop_collection_idprop[BIMFilterGroup]
+        mode: Literal["a", "i", "e"]
+

 class Clash(PropertyGroup):
    a_global_id: StringProperty(name="A")
@@ -51,9 +58,15 @@ class Clash(PropertyGroup):
    b_name: StringProperty(name="B Name")
    status: BoolProperty(name="Status", default=False)

+    if TYPE_CHECKING:
+        a_global_id: str
+        b_global_id: str
+        a_name: str
+        b_name: str
+        status: bool
+

 class ClashSet(PropertyGroup):
-    name: StringProperty(name="Name")
    mode: EnumProperty(
        items=[
            (
@@ -76,11 +89,25 @@ class ClashSet(PropertyGroup):
    b: CollectionProperty(name="Group B", type=ClashSource)
    clashes: CollectionProperty(name="Clashes", type=Clash)

+    if TYPE_CHECKING:
+        mode: Literal["intersection", "collision", "clearance"]
+        tolerance: float
+        clearance: float
+        allow_touching: bool
+        check_all: bool
+        a: bpy.types.bpy_prop_collection_idprop[ClashSource]
+        b: bpy.types.bpy_prop_collection_idprop[ClashSource]
+        clashes: bpy.types.bpy_prop_collection_idprop[Clash]
+

 class SmartClashGroup(PropertyGroup):
    number: StringProperty(name="Number")
    global_ids: CollectionProperty(name="GlobalIDs", type=StrProperty)

+    if TYPE_CHECKING:
+        number: str
+        global_ids: bpy.types.bpy_prop_collection_idprop[StrProperty]
+

 class BIMClashProperties(PropertyGroup):
    blender_clash_set_a: CollectionProperty(name="Blender Clash Set A", type=StrProperty)
@@ -107,17 +134,33 @@ class BIMClashProperties(PropertyGroup):
        subtype="FILE_PATH",
    )

-    @property
-    def active_clash_set(self):
-        if self.active_clash_set_index < len(self.clash_sets):
-            return self.clash_sets[self.active_clash_set_index]
+    if TYPE_CHECKING:
+        blender_clash_set_a: bpy.types.bpy_prop_collection_idprop[StrProperty]
+        blender_clash_set_b: bpy.types.bpy_prop_collection_idprop[StrProperty]
+        clash_sets: bpy.types.bpy_prop_collection_idprop[ClashSet]
+        should_create_clash_snapshots: bool
+        clash_results_path: str
+        smart_grouped_clashes_path: str
+        active_clash_set_index: int
+        active_clash_index: int
+        smart_clash_groups: bpy.types.bpy_prop_collection_idprop[SmartClashGroup]
+        active_smart_group_index: int
+        smart_clash_grouping_max_distance: int
+        p1: Vector
+        p2: Vector
+        active_clash_text: str
+        export_path: str

    @property
-    def active_smart_group(self):
-        if self.active_smart_group_index < len(self.smart_clash_groups):
-            return self.smart_clash_groups[self.active_smart_group_index]
+    def active_clash_set(self) -> Union[ClashSet, None]:
+        return tool.Blender.get_active_uilist_element(self.clash_sets, self.active_clash_set_index)

    @property
-    def active_clash(self):
-        if self.active_clash_index < len(self.active_clash_set.clashes):
-            return self.active_clash_set.clashes[self.active_clash_index]
+    def active_smart_group(self) -> Union[SmartClashGroup, None]:
+        return tool.Blender.get_active_uilist_element(self.smart_clash_groups, self.active_smart_group_index)
+
+    @property
+    def active_clash(self) -> Union[Clash, None]:
+        if not (clash_set := self.active_clash_set):
+            return None
+        return tool.Blender.get_active_uilist_element(clash_set.clashes, self.active_clash_index)
@@ -17,6 +17,7 @@
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.

 import bpy
+import bonsai.tool as tool
 import bonsai.bim.helper
 from bpy.types import Panel
 from bonsai.bim.module.clash.data import ClashData
@@ -36,9 +37,7 @@ class BIM_PT_ifcclash(Panel):
            ClashData.load()

        layout = self.layout
-
-        scene = context.scene
-        props = scene.BIMClashProperties
+        props = tool.Clash.get_clash_props()

        row = layout.row(align=True)
        row.operator("bim.add_clash_set")
@@ -157,7 +156,7 @@ class BIM_PT_smart_clash_manager(Panel):

    def draw(self, context):
        layout = self.layout
-        props = context.scene.BIMClashProperties
+        props = tool.Clash.get_clash_props()

        row = layout.row()
        layout.label(text="Select clash results to group:")
@@ -145,11 +145,8 @@ class CostClassificationsData(ReferencesData):
    @classmethod
    def references(cls):
        results = []
-        element = tool.Ifc.get().by_id(
-            bpy.context.scene.BIMCostProperties.cost_items[
-                bpy.context.scene.BIMCostProperties.active_cost_item_index
-            ].ifc_definition_id
-        )
+        props = tool.Cost.get_cost_props()
+        element = tool.Ifc.get().by_id(props.cost_items[props.active_cost_item_index].ifc_definition_id)
        if element:
            for reference in ifcopenshell.util.classification.get_references(element):
                data = reference.get_info()
@@ -25,19 +25,16 @@ import ifcopenshell.util.classification
 import ifcopenshell.util.element
 import bonsai.tool as tool
 import bonsai.bim.helper
+from bpy_extras.io_utils import ImportHelper
 from bonsai.bim.ifc import IfcStore


-class LoadClassificationLibrary(bpy.types.Operator, tool.Ifc.Operator):
+class LoadClassificationLibrary(bpy.types.Operator, tool.Ifc.Operator, ImportHelper):
    bl_idname = "bim.load_classification_library"
    bl_label = "Load Classification Library"
+    bl_description = "Load classification library from the provided filepath."
    filename_ext = ".ifc"
    filter_glob: bpy.props.StringProperty(default="*.ifc;*.ifczip;*.ifcxml", options={"HIDDEN"})
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
-
-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

    def _execute(self, context):
        IfcStore.classification_file = ifcopenshell.open(self.filepath)
@@ -460,6 +457,7 @@ class AddClassificationReferenceFromBSDD(bpy.types.Operator, tool.Ifc.Operator):
                for prop in blender_properties:
                    properties[prop.name] = prop.get_value()

+                # TODO: is this still the correct approach?
                if classification_pset.name == "undefined_set":
                    if "ObjectType" in properties:
                        if hasattr(element, "ObjectType"):
@@ -338,7 +338,8 @@ class BIM_PT_cost_classifications(Panel, ReferenceUI):
    def poll(cls, context):
        if not tool.Ifc.get():
            return False
-        return bool(context.scene.BIMCostProperties.cost_items)
+        props = tool.Cost.get_cost_props()
+        return bool(props.cost_items)

    def draw(self, context):
        if not CostClassificationsData.is_loaded:
@@ -161,8 +161,12 @@ class AssignConstraint(bpy.types.Operator, tool.Ifc.Operator):

    def _execute(self, context):
        self.file = tool.Ifc.get()
-        objs = [bpy.data.objects.get(self.obj)] if self.obj else context.selected_objects
-        products = [self.file.by_id(obj_id) for obj in objs if (obj_id := obj.BIMObjectProperties.ifc_definition_id)]
+        objs = [bpy.data.objects[self.obj]] if self.obj else context.selected_objects
+        products = [
+            self.file.by_id(obj_id)
+            for obj in objs
+            if (obj_id := tool.Blender.get_object_bim_props(obj).ifc_definition_id)
+        ]
        if products:
            ifcopenshell.api.run(
                "constraint.assign_constraint",
@@ -184,8 +188,12 @@ class UnassignConstraint(bpy.types.Operator, tool.Ifc.Operator):

    def _execute(self, context):
        self.file = tool.Ifc.get()
-        objs = [bpy.data.objects.get(self.obj)] if self.obj else context.selected_objects
-        products = [self.file.by_id(obj_id) for obj in objs if (obj_id := obj.BIMObjectProperties.ifc_definition_id)]
+        objs = [bpy.data.objects[self.obj]] if self.obj else context.selected_objects
+        products = [
+            self.file.by_id(obj_id)
+            for obj in objs
+            if (obj_id := tool.Blender.get_object_bim_props(obj).ifc_definition_id)
+        ]
        if products:
            ifcopenshell.api.run(
                "constraint.unassign_constraint",
@@ -79,18 +79,18 @@ class BIM_PT_object_constraints(Panel):

    @classmethod
    def poll(cls, context):
-        if not context.active_object:
+        if not (obj := context.active_object):
            return False
-        if not tool.Ifc.get_object_by_identifier(context.active_object.BIMObjectProperties.ifc_definition_id):
-            return False
-        return bool(context.active_object.BIMObjectProperties.ifc_definition_id)
+        props = tool.Blender.get_object_bim_props(obj)
+        return bool(tool.Ifc.get_object_by_identifier(props.ifc_definition_id))

    def draw(self, context):
        if not ObjectConstraintsData.is_loaded:
            ObjectConstraintsData.load()

        obj = context.active_object
-        self.oprops = obj.BIMObjectProperties
+        assert obj
+        self.oprops = tool.Blender.get_object_bim_props(obj)
        self.sprops = context.scene.BIMConstraintProperties
        self.props = obj.BIMObjectConstraintProperties
        self.file = tool.Ifc.get()
@@ -66,8 +66,9 @@ class CostSchedulesData:
    @classmethod
    def schedules(cls):
        results = []
-        if bpy.context.scene.BIMCostProperties.active_cost_schedule_id:
-            schedule = tool.Ifc.get().by_id(bpy.context.scene.BIMCostProperties.active_cost_schedule_id)
+        props = tool.Cost.get_cost_props()
+        if props.active_cost_schedule_id:
+            schedule = tool.Ifc.get().by_id(props.active_cost_schedule_id)
            results.append(
                {
                    "id": schedule.id(),
@@ -88,7 +89,8 @@ class CostSchedulesData:

    @classmethod
    def is_editing_rates(cls):
-        ifc_id = bpy.context.scene.BIMCostProperties.active_cost_schedule_id
+        props = tool.Cost.get_cost_props()
+        ifc_id = props.active_cost_schedule_id
        if not ifc_id:
            return
        return tool.Ifc.get().by_id(ifc_id).PredefinedType == "SCHEDULEOFRATES"
@@ -256,7 +258,8 @@ class CostSchedulesData:
    @classmethod
    def cost_quantities(cls):
        results = []
-        ifc_id = bpy.context.scene.BIMCostProperties.active_cost_item_id
+        props = tool.Cost.get_cost_props()
+        ifc_id = props.active_cost_item_id
        if not ifc_id:
            return results
        for quantity in tool.Ifc.get().by_id(ifc_id).CostQuantities or []:
@@ -265,7 +268,8 @@ class CostSchedulesData:

    @classmethod
    def cost_values(cls):
-        ifc_id = bpy.context.scene.BIMCostProperties.active_cost_item_id
+        props = tool.Cost.get_cost_props()
+        ifc_id = props.active_cost_item_id
        if not ifc_id:
            return []
        return ifcopenshell.util.cost.get_cost_values(tool.Ifc.get().by_id(ifc_id))
@@ -324,7 +328,8 @@ class CostItemQuantitiesData:

    @classmethod
    def process_quantity_names(cls):
-        active_task_index = bpy.context.scene.BIMWorkScheduleProperties.active_task_index
+        props = tool.Sequence.get_work_schedule_props()
+        active_task_index = props.active_task_index
        tprops = tool.Sequence.get_task_tree_props()
        total_tasks = len(tprops.tasks)
        if not total_tasks or active_task_index >= total_tasks:
@@ -21,10 +21,10 @@
 import bpy
 import ifcopenshell.api
 import bonsai.tool as tool
-from bpy_extras.io_utils import ImportHelper
+from bpy_extras.io_utils import ImportHelper, ExportHelper
 import bonsai.tool as tool
 import bonsai.core.cost as core
-from typing import get_args, TYPE_CHECKING
+from typing import get_args, TYPE_CHECKING, Literal


 class AddCostSchedule(bpy.types.Operator, tool.Ifc.Operator):
@@ -36,16 +36,18 @@ class AddCostSchedule(bpy.types.Operator, tool.Ifc.Operator):
    object_type: bpy.props.StringProperty()

    def _execute(self, context):
-        predefined_type = context.scene.BIMCostProperties.cost_schedule_predefined_types
+        props = tool.Cost.get_cost_props()
+        predefined_type = props.cost_schedule_predefined_types
        if predefined_type == "USERDEFINED":
            predefined_type = self.object_type
        core.add_cost_schedule(tool.Ifc, name=self.name, predefined_type=predefined_type)

    def draw(self, context):
        layout = self.layout
+        props = tool.Cost.get_cost_props()
        layout.prop(self, "name", text="Name")
-        layout.prop(context.scene.BIMCostProperties, "cost_schedule_predefined_types", text="Type")
-        if context.scene.BIMCostProperties.cost_schedule_predefined_types == "USERDEFINED":
+        layout.prop(props, "cost_schedule_predefined_types", text="Type")
+        if props.cost_schedule_predefined_types == "USERDEFINED":
            layout.prop(self, "object_type", text="Object type")

    def invoke(self, context, event):
@@ -58,10 +60,11 @@ class EditCostSchedule(bpy.types.Operator, tool.Ifc.Operator):
    bl_options = {"REGISTER", "UNDO"}

    def _execute(self, context):
+        props = tool.Cost.get_cost_props()
        core.edit_cost_schedule(
            tool.Ifc,
            tool.Cost,
-            cost_schedule=tool.Ifc.get().by_id(context.scene.BIMCostProperties.active_cost_schedule_id),
+            cost_schedule=tool.Ifc.get().by_id(props.active_cost_schedule_id),
        )


@@ -533,6 +536,7 @@ class SelectCostScheduleProducts(bpy.types.Operator):
 class ImportCostScheduleCsv(bpy.types.Operator, ImportHelper, tool.Ifc.Operator):
    bl_idname = "bim.import_cost_schedule_csv"
    bl_label = "Import Cost Schedule CSV"
+    bl_description = "Import cost schdule from the provided .csv file."
    bl_options = {"REGISTER", "UNDO"}
    filename_ext = ".csv"
    filter_glob: bpy.props.StringProperty(default="*.csv", options={"HIDDEN"})
@@ -559,7 +563,8 @@ class AddCostColumn(bpy.types.Operator):

    @classmethod
    def poll(cls, context):
-        if not context.scene.BIMCostProperties.cost_column:
+        props = tool.Cost.get_cost_props()
+        if not props.cost_column:
            cls.poll_message_set("Cost column name is empty")
            return False
        return True
@@ -678,7 +683,7 @@ class CalculateCostItemResourceValue(bpy.types.Operator, tool.Ifc.Operator):
        return {"FINISHED"}


-class ExportCostSchedules(bpy.types.Operator):
+class ExportCostSchedules(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.export_cost_schedules"
    bl_label = "Export Cost Schedule"
    bl_options = {"REGISTER", "UNDO"}
@@ -691,6 +696,13 @@ class ExportCostSchedules(bpy.types.Operator):
        default=True,
    )

+    if TYPE_CHECKING:
+        format: Literal["CSV", "XLSX", "ODS"]
+
+    @property
+    def filename_ext(self) -> str:
+        return f".{self.format.lower()}"
+
    def execute(self, context):
        cost_schedule = tool.Ifc.get().by_id(self.cost_schedule) if self.cost_schedule else None
        r = core.export_cost_schedules(
@@ -701,9 +713,7 @@ class ExportCostSchedules(bpy.types.Operator):
        return {"FINISHED"}

    def invoke(self, context, event):
-        wm = context.window_manager
-        wm.fileselect_add(self)
-        return {"RUNNING_MODAL"}
+        return ExportHelper.invoke(self, context, event)

    def draw(self, context):
        self.layout.label(text="Choose a format")
@@ -740,15 +750,14 @@ class LoadProductCostItems(bpy.types.Operator):

    @classmethod
    def poll(cls, context):
-        if not tool.Ifc.get() or not (obj := context.active_object) or not (obj.BIMObjectProperties.ifc_definition_id):
+        if not tool.Ifc.get() or not (obj := context.active_object) or not (tool.Blender.get_ifc_definition_id(obj)):
            cls.poll_message_set("No IFC object is active.")
            return False
        return True

    def execute(self, context):
-        core.load_product_cost_items(
-            tool.Cost, product=tool.Ifc.get().by_id(context.active_object.BIMObjectProperties.ifc_definition_id)
-        )
+        obj = context.active_object
+        core.load_product_cost_items(tool.Cost, product=tool.Ifc.get_entity(obj))
        return {"FINISHED"}


@@ -33,6 +33,7 @@ from bpy.props import (
    FloatVectorProperty,
    CollectionProperty,
 )
+from typing import TYPE_CHECKING, Literal


 def get_schedule_of_rates(self, context):
@@ -78,8 +79,8 @@ def update_active_cost_item_index(self, context):
    CostClassificationsData.load()


-def update_cost_item_identification(self, context):
-    props = context.scene.BIMCostProperties
+def update_cost_item_identification(self: "CostItem", context: bpy.types.Context):
+    props = tool.Cost.get_cost_props()
    if not props.is_cost_update_enabled or self.identification == "XXX":
        return
    self.file = tool.Ifc.get()
@@ -93,8 +94,8 @@ def update_cost_item_identification(self, context):
        attribute.string_value = self.identification


-def update_cost_item_name(self, context):
-    props = context.scene.BIMCostProperties
+def update_cost_item_name(self: "CostItem", context: bpy.types.Context) -> None:
+    props = tool.Cost.get_cost_props()
    if not props.is_cost_update_enabled or self.name == "Unnamed":
        return
    self.file = tool.Ifc.get()
@@ -142,6 +143,14 @@ class CostItem(PropertyGroup):
    is_expanded: BoolProperty(name="Is Expanded")
    level_index: IntProperty(name="Level Index")

+    if TYPE_CHECKING:
+        name: str
+        identification: str
+        ifc_definition_id: int
+        has_children: bool
+        is_expanded: bool
+        level_index: int
+

 class CostItemQuantity(PropertyGroup):
    name: StringProperty(name="Name")
@@ -150,11 +159,22 @@ class CostItemQuantity(PropertyGroup):
    unit_symbol: StringProperty(name="Unit Symbol")
    total_cost_quantity: FloatProperty(name="Total Quantity")

+    if TYPE_CHECKING:
+        name: str
+        ifc_definition_id: int
+        total_quantity: float
+        unit_symbol: str
+        total_cost_quantity: float
+

 class CostItemType(PropertyGroup):
    name: StringProperty(name="Name")
    ifc_definition_id: IntProperty(name="IFC Definition ID")

+    if TYPE_CHECKING:
+        name: str
+        ifc_definition_id: int
+

 def update_cost_item_parent(self, context):
    cost_item = tool.Cost.get_highlighted_cost_item()
@@ -176,6 +196,9 @@ def update_active_cost_item_resources(self, context):
 class ScheduleColumn(PropertyGroup):
    schedule_id: IntProperty()

+    if TYPE_CHECKING:
+        schedule_id: int
+

 class BIMCostProperties(PropertyGroup):
    cost_schedule_predefined_types: EnumProperty(
@@ -249,3 +272,57 @@ class BIMCostProperties(PropertyGroup):
    custom_currency: StringProperty(
        name="Custom Currency", default="USD", description="Custom Currency in ISO 4217 format"
    )
+
+    if TYPE_CHECKING:
+        cost_schedule_predefined_types: str
+        is_cost_update_enabled: bool
+        cost_schedule_attributes: bpy.types.bpy_prop_collection_idprop[Attribute]
+        is_editing: str
+        active_cost_schedule_id: int
+        cost_items: bpy.types.bpy_prop_collection_idprop[CostItem]
+        active_cost_item_id: int
+        cost_item_editing_type: str
+        active_cost_item_index: int
+        cost_item_attributes: bpy.types.bpy_prop_collection_idprop[Attribute]
+        contracted_cost_items: str
+        quantity_types: str
+        product_quantity_names: str
+        process_quantity_names: str
+        resource_quantity_names: str
+        active_cost_item_quantity_id: int
+        quantity_attributes: bpy.types.bpy_prop_collection_idprop[Attribute]
+        cost_types: Literal["FIXED", "SUM", "CATEGORY"]
+        cost_category: str
+        fixed_cost_value: float
+        active_cost_value_id: int
+        cost_value_editing_type: str
+        cost_value_attributes: bpy.types.bpy_prop_collection_idprop[Attribute]
+        cost_value_formula: str
+        cost_column: str
+        should_show_column_ui: bool
+        should_show_currency_ui: bool
+        columns: bpy.types.bpy_prop_collection_idprop[StrProperty]
+        columns_storage: bpy.types.bpy_prop_collection_idprop[ScheduleColumn]
+        active_column_index: int
+        cost_item_products: bpy.types.bpy_prop_collection_idprop[CostItemQuantity]
+        active_cost_item_product_index: int
+        cost_item_processes: bpy.types.bpy_prop_collection_idprop[CostItemQuantity]
+        active_cost_item_process_index: int
+        cost_item_resources: bpy.types.bpy_prop_collection_idprop[CostItemQuantity]
+        active_cost_item_resource_index: int
+        cost_item_type_products: bpy.types.bpy_prop_collection_idprop[CostItemType]
+        active_cost_item_type_product_index: int
+        schedule_of_rates: str
+        cost_item_rates: bpy.types.bpy_prop_collection_idprop[CostItem]
+        active_cost_item_rate_index: int
+        contracted_cost_item_rates: str
+        product_cost_items: bpy.types.bpy_prop_collection_idprop[CostItemQuantity]
+        active_product_cost_item_index: int
+        enable_reorder: bool
+        show_nested_elements: bool
+        show_nested_tasks: bool
+        show_nested_resources: bool
+        change_cost_item_parent: bool
+        show_cost_item_operators: bool
+        currency: str
+        custom_currency: str
@@ -16,13 +16,17 @@
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.

+from __future__ import annotations
 import bpy
 import bonsai.bim.helper
 import bonsai.bim.module.cost.prop as CostProp
 import bonsai.tool as tool
 from bpy.types import Panel, UIList
 from bonsai.bim.module.cost.data import CostSchedulesData
-from typing import Any
+from typing import Any, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from bonsai.bim.module.cost.prop import BIMCostProperties, CostItemQuantity


 class BIM_PT_cost_schedules(Panel):
@@ -43,7 +47,7 @@ class BIM_PT_cost_schedules(Panel):
        if not CostSchedulesData.is_loaded:
            CostSchedulesData.load()

-        self.props = context.scene.BIMCostProperties
+        self.props = tool.Cost.get_cost_props()
        if not self.props.active_cost_schedule_id:
            row = self.layout.row(align=True)
            if CostSchedulesData.data["total_cost_schedules"]:
@@ -299,7 +303,7 @@ class BIM_PT_cost_item_types(Panel):

    @classmethod
    def poll(cls, context):
-        props = context.scene.BIMCostProperties
+        props = tool.Cost.get_cost_props()
        total_cost_items = len(props.cost_items)
        if not props.active_cost_schedule_id:
            return False
@@ -312,7 +316,7 @@ class BIM_PT_cost_item_types(Panel):
        return False

    def draw(self, context):
-        self.props = context.scene.BIMCostProperties
+        self.props = tool.Cost.get_cost_props()
        cost_item = self.props.cost_items[self.props.active_cost_item_index]
        grid = self.layout.grid_flow(columns=3, even_columns=True)

@@ -348,8 +352,8 @@ class BIM_PT_cost_item_types(Panel):

        row2 = col.row()
        row2.template_list(
-            "BIM_UL_cost_item_quantities",
-            "",
+            BIM_UL_cost_item_quantities.__name__,
+            BIM_UL_cost_item_quantities.__name__ + "_cost_item_processes",
            self.props,
            "cost_item_processes",
            self.props,
@@ -365,8 +369,8 @@ class BIM_PT_cost_item_types(Panel):

        row2 = col.row()
        row2.template_list(
-            "BIM_UL_cost_item_quantities",
-            "",
+            BIM_UL_cost_item_quantities.__name__,
+            BIM_UL_cost_item_quantities.__name__ + "_cost_item_resources",
            self.props,
            "cost_item_resources",
            self.props,
@@ -385,7 +389,7 @@ class BIM_PT_cost_item_quantities(Panel):

    @classmethod
    def poll(cls, context):
-        props = context.scene.BIMCostProperties
+        props = tool.Cost.get_cost_props()
        total_cost_items = len(props.cost_items)
        if not props.active_cost_schedule_id:
            return False
@@ -398,7 +402,7 @@ class BIM_PT_cost_item_quantities(Panel):
        return False

    def draw(self, context):
-        self.props = context.scene.BIMCostProperties
+        self.props = tool.Cost.get_cost_props()

        cost_item = self.props.cost_items[self.props.active_cost_item_index]

@@ -435,8 +439,8 @@ class BIM_PT_cost_item_quantities(Panel):
        row2.prop(self.props, "show_nested_elements", text="Show nested")
        row2 = col.row()
        row2.template_list(
-            "BIM_UL_cost_item_quantities",
-            "",
+            BIM_UL_cost_item_quantities.__name__,
+            BIM_UL_cost_item_quantities.__name__ + "_cost_item_products",
            self.props,
            "cost_item_products",
            self.props,
@@ -462,7 +466,7 @@ class BIM_PT_cost_item_quantities(Panel):
        row2.label(text="Tasks ({})".format(total_cost_item_processes))

        tprops = tool.Sequence.get_task_tree_props()
-        wprops = context.scene.BIMWorkScheduleProperties
+        wprops = tool.Sequence.get_work_schedule_props()
        if tprops.tasks and wprops.active_task_index < len(tprops.tasks):
            if has_quantity_names:
                op = row2.operator("bim.assign_cost_item_quantity", text="", icon="PROPERTIES")
@@ -480,8 +484,8 @@ class BIM_PT_cost_item_quantities(Panel):

        row2 = col.row()
        row2.template_list(
-            "BIM_UL_cost_item_quantities",
-            "",
+            BIM_UL_cost_item_quantities.__name__,
+            BIM_UL_cost_item_quantities.__name__ + "_cost_item_processes",
            self.props,
            "cost_item_processes",
            self.props,
@@ -528,8 +532,8 @@ class BIM_PT_cost_item_quantities(Panel):

        row2 = col.row()
        row2.template_list(
-            "BIM_UL_cost_item_quantities",
-            "",
+            BIM_UL_cost_item_quantities.__name__,
+            BIM_UL_cost_item_quantities.__name__ + "_cost_item_resources",
            self.props,
            "cost_item_resources",
            self.props,
@@ -557,7 +561,7 @@ class BIM_PT_cost_item_rates(Panel):

    @classmethod
    def poll(cls, context):
-        props = context.scene.BIMCostProperties
+        props = tool.Cost.get_cost_props()
        total_cost_items = len(props.cost_items)
        if not props.active_cost_schedule_id:
            return False
@@ -570,7 +574,7 @@ class BIM_PT_cost_item_rates(Panel):
        return False

    def draw(self, context):
-        self.props = context.scene.BIMCostProperties
+        self.props = tool.Cost.get_cost_props()
        row = self.layout.row(align=True)
        row.prop(self.props, "schedule_of_rates", text="")
        if self.props.active_cost_item_rate_index < len(self.props.cost_item_rates):
@@ -606,13 +610,14 @@ class BIM_UL_cost_items_trait:
            split2.label(text="Quantity")
        split2.label(text="Value")

-        for column in bpy.context.scene.BIMCostProperties.columns:
+        props = tool.Cost.get_cost_props()
+        for column in props.columns:
            split2.label(text=column.name)
        split2.label(text="Total Cost")

    def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
        if item:
-            self.props = context.scene.BIMCostProperties
+            self.props = tool.Cost.get_cost_props()
            cost_item = CostSchedulesData.data["cost_items"][item.ifc_definition_id]
            row = layout.row(align=True)

@@ -708,18 +713,16 @@ class BIM_UL_cost_items_trait:


 class BIM_UL_cost_items(BIM_UL_cost_items_trait, UIList):
-    def __init__(self):
-        self.contract_operator = "bim.contract_cost_item"
-        self.expand_operator = "bim.expand_cost_item"
+    contract_operator = "bim.contract_cost_item"
+    expand_operator = "bim.expand_cost_item"


 class BIM_UL_cost_item_rates(BIM_UL_cost_items_trait, UIList):
    # A schedule of rates UIList is identical to a regular cost items UIList but
    # we want a separate UIList instance so that you can browse both lists
    # independently in Blender. So we use a trait.
-    def __init__(self):
-        self.contract_operator = "bim.contract_cost_item_rate"
-        self.expand_operator = "bim.expand_cost_item_rate"
+    contract_operator = "bim.contract_cost_item_rate"
+    expand_operator = "bim.expand_cost_item_rate"

    def draw_quantity_column(self, layout, cost_item):
        self.draw_uom_column(layout, cost_item)
@@ -730,7 +733,6 @@ class BIM_UL_cost_item_rates(BIM_UL_cost_items_trait, UIList):

 class BIM_UL_cost_columns(UIList):
    def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
-        props = context.scene.BIMCostProperties
        if item:
            row = layout.row(align=True)
            row.prop(item, "name", emboss=False, text="")
@@ -739,7 +741,7 @@ class BIM_UL_cost_columns(UIList):

 class BIM_UL_cost_item_types(UIList):
    def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
-        props = context.scene.BIMCostProperties
+        props = tool.Cost.get_cost_props()
        cost_item = props.cost_items[props.active_cost_item_index]

        if item:
@@ -751,9 +753,17 @@ class BIM_UL_cost_item_types(UIList):


 class BIM_UL_cost_item_quantities(UIList):
-    def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
-        props = context.scene.BIMCostProperties
-        cost_item = props.cost_items[props.active_cost_item_index]
+    def draw_item(
+        self,
+        context: bpy.types.Context,
+        layout: bpy.types.UILayout,
+        data: BIMCostProperties,
+        item: CostItemQuantity,
+        icon,
+        active_data,
+        active_propname,
+    ):
+        cost_item = data.cost_items[data.active_cost_item_index]
        if item:
            row = layout.row(align=True)
            op = row.operator("bim.select_product", text="", icon="RESTRICT_SELECT_OFF")
@@ -790,15 +800,15 @@ class BIM_PT_Costing_Tools(Panel):
    bl_parent_id = "BIM_PT_tab_cost"

    def draw(self, context):
-        self.props = context.scene.BIMCostProperties
+        props = tool.Cost.get_cost_props()
        row = self.layout.row()
        row.operator("bim.load_product_cost_items", icon="FILE_REFRESH")
        row = self.layout.row()
        row.template_list(
            "BIM_UL_product_cost_items",
            "",
-            self.props,
+            props,
            "product_cost_items",
-            self.props,
+            props,
            "active_product_cost_item_index",
        )
@@ -18,9 +18,13 @@

 import bpy
 from bpy.types import PropertyGroup
+from typing import TYPE_CHECKING


 class BIMCoveringProperties(PropertyGroup):
    ceiling_height: bpy.props.FloatProperty(
        name="ceiling_height", default=2.7, subtype="DISTANCE", description="Ceiling height"
    )
+
+    if TYPE_CHECKING:
+        ceiling_height: float
@@ -24,6 +24,7 @@ import bonsai.tool as tool
 from bonsai.bim.helper import prop_with_search
 from bonsai.bim.module.model.data import AuthoringData
 from bpy.types import WorkSpaceTool
+from functools import partial


 class CoveringTool(WorkSpaceTool):
@@ -45,9 +46,7 @@ class CoveringTool(WorkSpaceTool):
        CoveringToolUI.draw(context, layout, ifc_element_type=cls.ifc_element_type)


-def add_layout_hotkey(layout: bpy.types.UILayout, text: str, hotkey: str, description: str) -> None:
-    args = ("covering", layout, text, hotkey, description)
-    tool.Blender.add_layout_hotkey_operator(*args)
+add_layout_hotkey = partial(tool.Blender.add_layout_hotkey_operator, tool_name="covering", module_name=__name__)


 class CoveringToolUI:
@@ -55,7 +54,7 @@ class CoveringToolUI:
    def draw(cls, context, layout, ifc_element_type=None):
        cls.layout = layout
        cls.props = tool.Model.get_model_props()
-        cls.covering_props = context.scene.BIMCoveringProperties
+        cls.covering_props = tool.Covering.get_covering_props()

        row = cls.layout.row(align=True)
        if not tool.Ifc.get():
@@ -88,7 +87,7 @@ class CoveringToolUI:
            row = cls.layout.row(align=True)
            row.label(text="", icon="EVENT_SHIFT")
            row.label(text="", icon="EVENT_A")
-            row.operator("bim.add_constr_type_instance", text="Add")
+            row.operator("bim.add_occurrence", text="Add")

            row = cls.layout.row(align=True)
            row.label(text="", icon="EVENT_SHIFT")
@@ -136,8 +135,8 @@ class CoveringToolUI:
        if AuthoringData.data["ifc_classes"]:
            if cls.props.ifc_class:
                box = cls.layout.box()
-                if AuthoringData.data["type_thumbnail"]:
-                    box.template_icon(icon_value=AuthoringData.data["type_thumbnail"], scale=5)
+                if thumbnail := AuthoringData.data["relating_type_data"].get("thumbnail"):
+                    box.template_icon(icon_value=thumbnail, scale=5)
                else:
                    op = box.operator("bim.load_type_thumbnails", text="Load Thumbnails", icon="FILE_REFRESH")
                    op.ifc_class = cls.props.ifc_class
@@ -145,8 +144,8 @@ class CoveringToolUI:

 class Hotkey(bpy.types.Operator, tool.Ifc.Operator):
    bl_idname = "bim.covering_hotkey"
-    bl_label = "Hotkey"
-    bl_options = {"REGISTER", "UNDO"}
+    bl_label = ""
+    bl_options = {"REGISTER", "UNDO", "INTERNAL"}
    hotkey: bpy.props.StringProperty()
    description: bpy.props.StringProperty()

@@ -159,12 +158,11 @@ class Hotkey(bpy.types.Operator, tool.Ifc.Operator):
        return operator.description or ""

    def _execute(self, context):
-        #        self.props = context.scene.BIMCoveringProperties
+        self.props = tool.Covering.get_covering_props()
        getattr(self, f"hotkey_{self.hotkey}")()

    def invoke(self, context, event):
        # https://blender.stackexchange.com/questions/276035/how-do-i-make-operators-remember-their-property-values-when-called-from-a-hotkey
-        # self.props = context.scene.BIMSpatialProperties
        return self.execute(context)

    def draw(self, context):
@@ -175,22 +173,22 @@ class Hotkey(bpy.types.Operator, tool.Ifc.Operator):
        element = tool.Ifc.get_entity(active_obj)
        container = tool.Root.get_default_container()

-        if AuthoringData.data["predefined_type"] == "FLOORING":
+        if AuthoringData.data["relating_type_data"].get("predefined_type") == "FLOORING":
            if element and bpy.context.selected_objects and element.is_a("IfcWall"):
                bpy.ops.bim.add_instance_flooring_coverings_from_walls()
            elif container:
                bpy.ops.bim.add_instance_flooring_covering_from_cursor()
            else:
-                bpy.ops.bim.add_constr_type_instance()
-        elif AuthoringData.data["predefined_type"] == "CEILING":
+                bpy.ops.bim.add_occurrence()
+        elif AuthoringData.data["relating_type_data"].get("predefined_type") == "CEILING":
            if element and bpy.context.selected_objects and element.is_a("IfcWall"):
                bpy.ops.bim.add_instance_ceiling_coverings_from_walls()
            elif container:
                bpy.ops.bim.add_instance_ceiling_covering_from_cursor()
            else:
-                bpy.ops.bim.add_constr_type_instance()
+                bpy.ops.bim.add_occurrence()
        else:
-            bpy.ops.bim.add_constr_type_instance()
+            bpy.ops.bim.add_occurrence()

    def hotkey_S_G(self):
        active_obj = bpy.context.active_object
@@ -181,12 +181,12 @@ class RunAnalysis(bpy.types.Operator):
            if modifier.type == "TRIANGULATE":
                return True

-    def get_covetool_category(self, obj):
+    def get_covetool_category(self, obj: bpy.types.Object):
        if not hasattr(obj, "data") or not isinstance(obj.data, bpy.types.Mesh):
            return
-        if not obj.BIMObjectProperties.ifc_definition_id:
+        if not (ifc_id := tool.Blender.get_ifc_definition_id(obj)):
            return
-        element = self.file.by_id(obj.BIMObjectProperties.ifc_definition_id)
+        element = self.file.by_id(ifc_id)
        ifc_class = element.is_a()
        if "IfcSlab" in ifc_class:
            return "floors"
@@ -27,6 +27,7 @@ import ifcopenshell
 import ifcopenshell.util.selector
 import bonsai.tool as tool
 import bonsai.bim.module.drawing.scheduler as scheduler
+from bpy_extras.io_utils import ExportHelper, ImportHelper
 from bonsai.bim.handler import refresh_ui_data
 from typing import TYPE_CHECKING
 from collections import Counter
@@ -42,7 +43,8 @@ class AddCsvAttribute(bpy.types.Operator):
    bl_options = {"REGISTER", "UNDO"}

    def execute(self, context):
-        attribute = context.scene.CsvProperties.csv_attributes.add()
+        props = tool.Blender.get_csv_props()
+        props.csv_attributes.add()
        return {"FINISHED"}


@@ -53,7 +55,8 @@ class RemoveCsvAttribute(bpy.types.Operator):
    index: bpy.props.IntProperty()

    def execute(self, context):
-        context.scene.CsvProperties.csv_attributes.remove(self.index)
+        props = tool.Blender.get_csv_props()
+        props.csv_attributes.remove(self.index)
        return {"FINISHED"}


@@ -64,7 +67,8 @@ class RemoveAllCsvAttributes(bpy.types.Operator):
    bl_options = {"REGISTER", "UNDO"}

    def execute(self, context):
-        context.scene.CsvProperties.csv_attributes.clear()
+        props = tool.Blender.get_csv_props()
+        props.csv_attributes.clear()
        return {"FINISHED"}


@@ -76,8 +80,9 @@ class ReorderCsvAttribute(bpy.types.Operator):
    new_index: bpy.props.IntProperty()

    def execute(self, context):
-        old = context.scene.CsvProperties.csv_attributes[self.old_index]
-        new = context.scene.CsvProperties.csv_attributes[self.new_index]
+        props = tool.Blender.get_csv_props()
+        old = props.csv_attributes[self.old_index]
+        new = props.csv_attributes[self.new_index]
        props = ["name", "header", "sort", "group", "varies_value", "summary", "formatting"]
        for prop in props:
            value = getattr(new, prop)
@@ -86,16 +91,16 @@ class ReorderCsvAttribute(bpy.types.Operator):
        return {"FINISHED"}


-class ImportCsvAttributes(bpy.types.Operator):
+class ImportCsvAttributes(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.import_csv_attributes"
    bl_label = "Load CSV Settings"
    bl_description = "Import a json template for CSV export"
    bl_options = {"REGISTER", "UNDO"}
    filter_glob: bpy.props.StringProperty(default="*.json", options={"HIDDEN"})
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
+    filename_ext = ".json"

    def execute(self, context):
-        props = context.scene.CsvProperties
+        props = tool.Blender.get_csv_props()
        data = json.load(open(self.filepath))
        tool.Search.import_filter_query(data["query"], props.filter_groups)

@@ -121,22 +126,17 @@ class ImportCsvAttributes(bpy.types.Operator):
                setattr(new, prop, attribute[prop])
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class ExportCsvAttributes(bpy.types.Operator):
+class ExportCsvAttributes(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.export_csv_attributes"
    bl_label = "Save CSV Settings"
    bl_options = {"REGISTER", "UNDO"}
    bl_description = "Save a json template for CSV export"
    filename_ext = ".json"
    filter_glob: bpy.props.StringProperty(default="*.json", options={"HIDDEN"})
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")

    def execute(self, context):
-        props = context.scene.CsvProperties
+        props = tool.Blender.get_csv_props()

        settings = {}
        for prop in [
@@ -175,40 +175,42 @@ class ExportCsvAttributes(bpy.types.Operator):

        return {"FINISHED"}

-    def invoke(self, context, event):
-        self.filepath = bpy.path.ensure_ext(bpy.data.filepath, ".json")
-        WindowManager = context.window_manager
-        WindowManager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class ExportIfcCsv(bpy.types.Operator):
+class ExportIfcCsv(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.export_ifccsv"
    bl_label = "Export IFC"
+    bl_description = "Export IFC data as a spreadsheet."
    filename_ext = ".csv"
+    filter_glob: bpy.props.StringProperty(default="*.csv", options={"HIDDEN"})
    filepath: bpy.props.StringProperty(subtype="FILE_PATH")

    @classmethod
    def poll(cls, context):
-        props = context.scene.CsvProperties
+        props = tool.Blender.get_csv_props()
        if not props.should_load_from_memory and not props.csv_ifc_file:
            cls.poll_message_set("Select an IFC file or use 'load from memory' if it's loaded in Bonsai.")
            return False
        return True

+    @classmethod
+    def description(cls, context, properties):
+        props = tool.Blender.get_csv_props()
+        if props.format == "web":
+            return "Open Web UI for spreadsheet data export."
+        return f"Export IFC data as a spreadsheet by the provided filepath in '{props.format}' format ."
+
    def invoke(self, context, event):
-        props = context.scene.CsvProperties
+        props = tool.Blender.get_csv_props()
        if props.format == "web":
            return self.execute(context)
-        self.filepath = bpy.path.ensure_ext(bpy.data.filepath, f".{props.format}")
-        WindowManager = context.window_manager
-        WindowManager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
+        self.filter_glob = f"*.{props.format}"
+        self.filename_ext = f".{props.format}"
+        return ExportHelper.invoke(self, context, event)

    def execute(self, context):
        import ifccsv

-        props = context.scene.CsvProperties
+        props = tool.Blender.get_csv_props()
        self.filepath = bpy.path.ensure_ext(self.filepath, f".{props.format}")
        if props.should_load_from_memory:
            ifc_file = tool.Ifc.get()
@@ -287,16 +289,16 @@ class ExportIfcCsv(bpy.types.Operator):
        ]


-class ImportIfcCsv(bpy.types.Operator, tool.Ifc.Operator):
+class ImportIfcCsv(bpy.types.Operator, tool.Ifc.Operator, ImportHelper):
    bl_idname = "bim.import_ifccsv"
    bl_label = "Import to IFC"
+    bl_description = "Import IFC data from a spreadsheet."
    bl_options = {"REGISTER", "UNDO"}
    filter_glob: bpy.props.StringProperty(default="*.csv;*.ods;*.xlsx", options={"HIDDEN"})
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")

    @classmethod
    def poll(cls, context):
-        props = context.scene.CsvProperties
+        props = tool.Blender.get_csv_props()
        if not props.should_load_from_memory and not props.csv_ifc_file:
            cls.poll_message_set("Select an IFC file or use 'load from memory' if it's loaded in Bonsai.")
            return False
@@ -304,14 +306,12 @@ class ImportIfcCsv(bpy.types.Operator, tool.Ifc.Operator):

    def invoke(self, context, event):
        self.filepath = bpy.path.ensure_ext(bpy.data.filepath, ".csv")
-        WindowManager = context.window_manager
-        WindowManager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
+        return ImportHelper.invoke(self, context, event)

    def _execute(self, context):
        import ifccsv

-        props = context.scene.CsvProperties
+        props = tool.Blender.get_csv_props()
        if props.should_load_from_memory:
            ifc_file = tool.Ifc.get()
        else:
@@ -337,18 +337,15 @@ class ImportIfcCsv(bpy.types.Operator, tool.Ifc.Operator):
        return {"FINISHED"}


-class SelectCsvIfcFile(bpy.types.Operator):
+class SelectCsvIfcFile(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_csv_ifc_file"
    bl_label = "Select CSV IFC File"
+    bl_description = "Select IFC file for spreadsheet import/export."
    bl_options = {"REGISTER", "UNDO"}
    filename_ext = ".ifc"
    filter_glob: bpy.props.StringProperty(default="*.ifc;*.ifczip;*.ifcxml", options={"HIDDEN"})
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")

    def execute(self, context):
-        context.scene.CsvProperties.csv_ifc_file = self.filepath
+        props = tool.Blender.get_csv_props()
+        props.csv_ifc_file = self.filepath
        return {"FINISHED"}
-
-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
@@ -29,6 +29,7 @@ from bpy.props import (
    FloatVectorProperty,
    CollectionProperty,
 )
+from typing import TYPE_CHECKING, Literal


 class CsvAttribute(PropertyGroup):
@@ -59,6 +60,15 @@ class CsvAttribute(PropertyGroup):
    )
    formatting: StringProperty(default="{{value}}", name="Formatting")

+    if TYPE_CHECKING:
+        name: str
+        header: str
+        sort: Literal["NONE", "ASC", "DESC"]
+        group: Literal["NONE", "GROUP", "CONCAT", "VARIES", "SUM", "AVERAGE", "MIN", "MAX"]
+        varies_value: str
+        summary: Literal["NONE", "SUM", "AVERAGE", "MIN", "MAX"]
+        formatting: str
+

 class CsvProperties(PropertyGroup):
    csv_ifc_file: StringProperty(default="", name="IFC File")
@@ -104,3 +114,26 @@ class CsvProperties(PropertyGroup):
        name="Load from Memory",
        description="Use IFC file currently loaded in Bonsai",
    )
+
+    if TYPE_CHECKING:
+        csv_ifc_file: str
+        ifc_selector: str
+        filter_groups: bpy.types.bpy_prop_collection_idprop[BIMFilterGroup]
+        csv_attributes: bpy.types.bpy_prop_collection_idprop[CsvAttribute]
+        should_generate_svg: bool
+        should_preserve_existing: bool
+        include_global_id: bool
+        null_value: str
+        empty_value: str
+        true_value: str
+        false_value: str
+        concat_value: str
+        csv_delimiter: Literal["NONE", "ASC", "DESC"]
+        format: Literal["csv", "xlsx", "ods", "web"]
+        csv_custom_delimiter: str
+        should_show_settings: bool
+        should_show_sort: bool
+        should_show_group: bool
+        should_show_summary: bool
+        should_show_formatting: bool
+        should_load_from_memory: bool
@@ -33,9 +33,7 @@ class BIM_PT_ifccsv(Panel):

    def draw(self, context):
        layout = self.layout
-
-        scene = context.scene
-        props = scene.CsvProperties
+        props = tool.Blender.get_csv_props()

        if tool.Ifc.get():
            row = layout.row(align=True)
@@ -126,5 +124,8 @@ class BIM_PT_ifccsv(Panel):
            row.operator("bim.remove_csv_attribute", icon="X", text="").index = index

        row = layout.row(align=True)
-        row.operator("bim.export_ifccsv", icon="EXPORT", text="Export IFC to " + props.format.upper())
+        if props.format == "web":
+            row.operator("bim.export_ifccsv", icon="EXPORT", text="Open Web UI")
+        else:
+            row.operator("bim.export_ifccsv", icon="EXPORT", text="Export IFC to " + props.format.upper())
        row.operator("bim.import_ifccsv", icon="IMPORT")
@@ -44,6 +44,7 @@ classes = (
    operator.SelectHighPolygonMeshes,
    operator.SelectHighestPolygonMeshes,
    operator.ToggleDetailedIOSLogs,
+    operator.ValidateIfcAssets,
    operator.ValidateIfcFile,
    prop.BIMDebugProperties,
    ui.BIM_PT_debug,
@@ -23,6 +23,7 @@ import time
 import random
 import logging
 import subprocess
+import platform
 import ifcopenshell
 import ifcopenshell.api
 import ifcopenshell.geom
@@ -36,6 +37,8 @@ import bonsai.core.profile
 import bonsai.core.type
 import bonsai.bim.handler
 import bonsai.bim.import_ifc as import_ifc
+from collections import defaultdict
+from bpy_extras.io_utils import ImportHelper, ExportHelper
 from pathlib import Path
 from bonsai import get_debug_info, format_debug_info
 from bonsai.bim.ifc import IfcStore
@@ -150,6 +153,67 @@ class ValidateIfcFile(bpy.types.Operator):
        return {"FINISHED"}


+class ValidateIfcAssets(bpy.types.Operator):
+    bl_idname = "bim.validate_ifc_assets"
+    bl_label = "Validate IFC Assets"
+    bl_description = (
+        "Run Bonsai validation for IFC assets.\n\n"
+        "There's an internal Bonsai convention to treat some IFC assets "
+        "as unique based on their name (e.g. profiles, materials, styles).\n"
+        "Though it's not required by IFC, it is a generally good practice "
+        "to keep asset names unique and it also helps with various issues.\n"
+        "If it's not conformed, it could lead to duplicated assets or "
+        "the opposite - different assets of the same name treated as one."
+    )
+    bl_options = set()
+
+    @classmethod
+    def poll(cls, context):
+        if not tool.Ifc.get():
+            cls.poll_message_set("IFC file is not loaded.")
+            return False
+        return True
+
+    def execute(self, context):
+        ifc_file = tool.Ifc.get()
+
+        ifc_classes = {
+            "IfcMaterial": "Name",
+            "IfcProfileDef": "ProfileName",
+            "IfcPresentationStyle": "Name",
+        }
+
+        issues_found = False
+        unique_assets: defaultdict[str, list[ifcopenshell.entity_instance]]
+        for ifc_class, name_attr in ifc_classes.items():
+            unique_assets = defaultdict(list)
+            for asset in ifc_file.by_type(ifc_class):
+                asset_name: Union[str, None] = getattr(asset, name_attr)
+                if asset_name is None:
+                    continue
+                unique_assets[asset_name].append(asset)
+
+            msg = ""
+            for asset_name, assets in unique_assets.items():
+                if len(assets) == 1:
+                    continue
+                msg += f"{ifc_class} name '{asset_name}' is used by multiple assets:\n"
+                for asset in assets:
+                    msg += f"- {asset}\n"
+
+            if msg:
+                issues_found = True
+                msg = f"Found issues validating {ifc_class} assets.\n" + msg
+                print(msg)
+
+        if issues_found:
+            self.report({"INFO"}, "Check asset validation results in the system console.")
+        else:
+            self.report({"INFO"}, "No asset validation issues found.")
+
+        return {"FINISHED"}
+
+
 class ProfileImportIFC(bpy.types.Operator):
    profile_filename = "blender.prof"
    bl_idname = "bim.profile_import_ifc"
@@ -382,7 +446,7 @@ class InspectFromObject(bpy.types.Operator):
    def get_active_object_ifc_definition(cls, context: bpy.types.Context) -> Union[int, None]:
        obj = context.active_object
        assert obj
-        if ifc_id := obj.BIMObjectProperties.ifc_definition_id:
+        if ifc_id := tool.Blender.get_ifc_definition_id(obj):
            return ifc_id
        if (
            (data := obj.data)
@@ -446,12 +510,11 @@ class ParseExpress(bpy.types.Operator):
        return {"FINISHED"}


-class SelectExpressFile(bpy.types.Operator):
+class SelectExpressFile(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_express_file"
    bl_label = "Select Express File"
    bl_options = {"REGISTER", "UNDO"}
    bl_description = "Select an IFC EXPRESS definition"
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.exp", options={"HIDDEN"})

    def execute(self, context):
@@ -460,10 +523,6 @@ class SelectExpressFile(bpy.types.Operator):
            props.express_file = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-

 class PurgeHdf5Cache(bpy.types.Operator):
    bl_idname = "bim.purge_hdf5_cache"
@@ -513,6 +572,7 @@ class PrintUnusedElementStats(bpy.types.Operator):
        if self.ignore_styled_items:
            ignore_classes += ["IfcStyledItem"]
        ignore_classes += [
+            "IfcDocumentReference",  # Document references for sheet elements (drawings, schedules, etc).
            "IfcIndexedColourMap",  # Only referenced by inverse attributes.
            "IfcIndexedTextureMap",  # Only referenced by inverse attributes.
        ]
@@ -522,21 +582,22 @@ class PrintUnusedElementStats(bpy.types.Operator):
        return {"FINISHED"}


-class PurgeUnusedElementsByClass(bpy.types.Operator, tool.Ifc.Operator):
+class PurgeUnusedElementsByClass(bpy.types.Operator, tool.Ifc.Operator, ExportHelper):
    bl_idname = "bim.purge_unused_elements_by_class"
    bl_label = "Purge Unused Elements By Class"
    bl_description = (
        "Will find all elements of class that have no inverse references and will remove them, use very carefully.\n"
-        "If IFC class is provided in neighbour field, will purge only elemnts of the provided class. Otherwise will purge all white-listed elements.\n"
+        "If IFC class is provided in neighbour field, will purge only elements of the provided class. Otherwise will purge all white-listed elements.\n"
        "ALT+CLICK to provide a path where to save the IFC file with the removed elements (note changes will be applied to the current IFC too)"
    )
    bl_options = {"REGISTER", "UNDO"}
+    filename_ext = ".ifc"
    filepath: bpy.props.StringProperty(subtype="FILE_PATH", options={"SKIP_SAVE"})
    filter_glob: bpy.props.StringProperty(default="*.ifc", options={"HIDDEN"})

    def invoke(self, context, event):
        if event.type == "LEFTMOUSE" and event.alt:
-            context.window_manager.fileselect_add(self)
+            return ExportHelper.invoke(self, context, event)
        return self.execute(context)

    @classmethod
@@ -613,18 +674,30 @@ class PurgeUnusedElementsByClass(bpy.types.Operator, tool.Ifc.Operator):
            "IfcUnitAssignment",
            "IfcVirtualGridIntersection",
        ]
+        whitelist_exceptions = {
+            # Document references for sheet elements (drawings, schedules, etc).
+            "IfcExternalReference": ("IfcDocumentReference",),
+        }

        total_purged = 0
+        schema = tool.Ifc.schema()
        while True:
            total_batches = 0
            print("*" * 100)
            total_batch_purged = 0
            for ifc_class in whitelisted_classes:
                total_class_purged = 0
+
+                # Ensure class is present in the schema.
                try:
-                    elements = tool.Ifc.get().by_type(ifc_class)
-                except:
-                    continue  # Probably not in this schema?
+                    schema.declaration_by_name(ifc_class)
+                except RuntimeError:
+                    continue
+
+                elements = tool.Ifc.get().by_type(ifc_class)
+                if ifc_class in whitelist_exceptions:
+                    elements = [e for e in elements if not any(e.is_a(c) for c in whitelist_exceptions[ifc_class])]
+
                to_purge = set()
                for element in elements:
                    try:
@@ -691,13 +764,13 @@ class PurgeUnusedObjects(bpy.types.Operator, tool.Ifc.Operator):
        if purged == 0:
            return

-        scene = context.scene
        if object_type == "PROFILE":
            props = tool.Profile.get_profile_props()
            if props.is_editing:
                bpy.ops.bim.load_profiles()
        elif object_type == "STYLE":
-            if scene.BIMStylesProperties.is_editing:
+            props = tool.Style.get_style_props()
+            if props.is_editing:
                bpy.ops.bim.load_styles()
        elif object_type == "MATERIAL":
            props = tool.Material.get_material_props()
@@ -741,13 +814,13 @@ class MergeIdenticalObjects(bpy.types.Operator, tool.Ifc.Operator):
        if merged == 0:
            return

-        scene = context.scene
        if object_type == "PROFILE":
            props = tool.Profile.get_profile_props()
            if props.is_editing:
                bpy.ops.bim.load_profiles()
        elif object_type == "STYLE":
-            if scene.BIMStylesProperties.is_editing:
+            props = tool.Style.get_style_props()
+            if props.is_editing:
                bpy.ops.bim.load_styles()
        elif object_type == "MATERIAL":
            props = tool.Material.get_material_props()
@@ -950,7 +1023,12 @@ class RestartBlender(bpy.types.Operator):
        ms_store_app_id = tool.Blender.get_microsoft_store_app_id()
        if not ms_store_app_id:
            path = bpy.app.binary_path
-            os.execv(path, sys.argv)
+            if platform.system() == "Windows":
+                args = sys.argv[1:]
+                command_line = subprocess.list2cmdline([path] + args)
+                os.execv(path, [command_line])
+            else:
+                os.execv(path, sys.argv)
        else:
            # Microsoft apps do not allow launching blender.exe directly
            # since Blender folder is kind of private.
@@ -50,6 +50,8 @@ class BIM_PT_debug(Panel):
        row.prop(props, "package_name", text="")
        row.operator("bim.pip_install", icon="EVENT_PAGEDOWN").name = props.package_name

+        layout.operator("bim.validate_ifc_assets", icon="CHECKMARK")
+
        row = layout.row()
        row.operator("bim.reload_ifc_file", text="Incrementally Reload Changes")

@@ -43,7 +43,7 @@ class DiffData:

    @classmethod
    def diff_json(cls):
-        props = bpy.context.scene.DiffProperties
+        props = tool.Blender.get_diff_props()
        if not props.diff_json_file:
            cls.diff = None
            return
@@ -24,24 +24,23 @@ import ifcopenshell
 import bonsai.bim.handler
 import bonsai.bim.import_ifc
 import bonsai.tool as tool
+from bpy_extras.io_utils import ImportHelper, ExportHelper
 from bonsai.bim.ifc import IfcStore


-class SelectDiffJsonFile(bpy.types.Operator):
+class SelectDiffJsonFile(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_diff_json_file"
    bl_label = "Select Diff JSON File"
+    bl_description = "Select filepath for IFC diff results."
    bl_options = {"REGISTER", "UNDO"}
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.json", options={"HIDDEN"})
+    filename_ext = ".json"

    def execute(self, context):
-        context.scene.DiffProperties.diff_json_file = self.filepath
+        props = tool.Blender.get_diff_props()
+        props.diff_json_file = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-

 class VisualiseDiff(bpy.types.Operator):
    bl_idname = "bim.visualise_diff"
@@ -50,7 +49,8 @@ class VisualiseDiff(bpy.types.Operator):

    def execute(self, context):
        ifc_file = tool.Ifc.get()
-        with open(context.scene.DiffProperties.diff_json_file, "r") as file:
+        props = tool.Blender.get_diff_props()
+        with open(props.diff_json_file, "r") as file:
            diff = json.load(file)
        for obj in context.visible_objects:
            obj.color = (1.0, 1.0, 1.0, 1.0)
@@ -65,7 +65,7 @@ class VisualiseDiff(bpy.types.Operator):
                obj.color = (0.0, 0.0, 0.7, 1.0)
                continue

-            if not obj.BIMObjectProperties.ifc_definition_id:
+            if not (ifc_id := tool.Blender.get_ifc_definition_id(obj)):
                continue

            ifc_file = ""
@@ -84,7 +84,7 @@ class VisualiseDiff(bpy.types.Operator):
                element_file = ifc_file

            try:
-                element = element_file.by_id(obj.BIMObjectProperties.ifc_definition_id)
+                element = element_file.by_id(ifc_id)
            except:
                continue
            global_id = getattr(element, "GlobalId", None)
@@ -101,55 +101,45 @@ class VisualiseDiff(bpy.types.Operator):
        return {"FINISHED"}


-class SelectDiffOldFile(bpy.types.Operator):
+class SelectDiffOldFile(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_diff_old_file"
    bl_label = "Select Diff Old File"
+    bl_description = "Select filepath for an old IFC file to compare."
    bl_options = {"REGISTER", "UNDO"}
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.ifc", options={"HIDDEN"})
+    filename_ext = ".ifc"

    def execute(self, context):
-        context.scene.DiffProperties.old_file = self.filepath
+        props = tool.Blender.get_diff_props()
+        props.old_file = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class SelectDiffNewFile(bpy.types.Operator):
+class SelectDiffNewFile(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_diff_new_file"
    bl_label = "Select Diff New File"
+    bl_description = "Select filepath for a new IFC file to compare."
    bl_options = {"REGISTER", "UNDO"}
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.ifc", options={"HIDDEN"})
+    filename_ext = ".ifc"

    def execute(self, context):
-        context.scene.DiffProperties.new_file = self.filepath
+        props = tool.Blender.get_diff_props()
+        props.new_file = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class ExecuteIfcDiff(bpy.types.Operator):
+class ExecuteIfcDiff(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.execute_ifc_diff"
    bl_label = "Execute IFC Diff"
+    bl_description = "Compare two IFC files and save a json diff report by the provided filepath."
    filename_ext = ".json"
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.json", options={"HIDDEN"})

-    def invoke(self, context, event):
-        self.filepath = bpy.path.ensure_ext(bpy.data.filepath, ".json")
-        WindowManager = context.window_manager
-        WindowManager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-
    def execute(self, context):
        import ifcdiff

-        self.props = context.scene.DiffProperties
+        self.props = tool.Blender.get_diff_props()

        if tool.Ifc.get():
            if self.props.active_file == "NONE":
@@ -238,7 +228,8 @@ class SelectDiffObjects(bpy.types.Operator):

    def execute(self, context):
        ifc_file = tool.Ifc.get()
-        with open(context.scene.DiffProperties.diff_json_file, "r") as file:
+        props = tool.Blender.get_diff_props()
+        with open(props.diff_json_file, "r") as file:
            diff = json.load(file)
        for obj in context.visible_objects:
            obj.select_set(False)
@@ -253,7 +244,7 @@ class SelectDiffObjects(bpy.types.Operator):
                obj.select_set(True)
                continue

-            if not obj.BIMObjectProperties.ifc_definition_id:
+            if not (ifc_id := tool.Blender.get_ifc_definition_id(obj)):
                continue

            ifc_file = ""
@@ -272,7 +263,7 @@ class SelectDiffObjects(bpy.types.Operator):
                element_file = ifc_file

            try:
-                element = element_file.by_id(obj.BIMObjectProperties.ifc_definition_id)
+                element = element_file.by_id(ifc_id)
            except:
                continue
            global_id = getattr(element, "GlobalId", None)
@@ -30,18 +30,25 @@ from bpy.props import (
    FloatVectorProperty,
    CollectionProperty,
 )
+from typing import TYPE_CHECKING, Literal, get_args


-def update_diff_json_file(self, context):
+def update_diff_json_file(self: "DiffProperties", context: bpy.types.Context) -> None:
    DiffData.data["diff_json"] = DiffData.diff_json()


+RelationshipType = Literal["type", "property", "container", "aggregate", "classification"]
+
+
 class Relationships(PropertyGroup):
    relationship: EnumProperty(
        name="Relationship",
-        items=[(r, r.capitalize(), r) for r in ["type", "property", "container", "aggregate", "classification"]],
+        items=[(r, r.capitalize(), r) for r in get_args(RelationshipType)],
    )

+    if TYPE_CHECKING:
+        relationship: RelationshipType
+

 class DiffProperties(PropertyGroup):
    diff_json_file: StringProperty(default="", name="JSON Output", update=update_diff_json_file)
@@ -59,3 +66,12 @@ class DiffProperties(PropertyGroup):
        name="Active File",
        default="NEW",
    )
+
+    if TYPE_CHECKING:
+        diff_json_file: str
+        old_file: str
+        new_file: str
+        diff_relationships: bpy.types.bpy_prop_collection_idprop[Relationships]
+        filter_groups: bpy.types.bpy_prop_collection_idprop[BIMFilterGroup]
+        should_load_changed_elements: bool
+        active_file: Literal["NONE", "OLD", "NEW"]
@@ -37,9 +37,7 @@ class BIM_PT_diff(Panel):

        layout = self.layout
        layout.use_property_split = True
-
-        scene = context.scene
-        props = scene.DiffProperties
+        props = tool.Blender.get_diff_props()

        layout.label(text="IFC Diff Setup:")

@@ -90,18 +90,20 @@ class BIM_PT_object_documents(Panel):

    @classmethod
    def poll(cls, context):
-        if not context.active_object:
+        if not (obj := context.active_object):
            return False
-        if not tool.Ifc.get_object_by_identifier(context.active_object.BIMObjectProperties.ifc_definition_id):
+        if not (ifc_id := tool.Blender.get_ifc_definition_id(obj)):
            return False
-        return bool(context.active_object.BIMObjectProperties.ifc_definition_id)
+        if not tool.Ifc.get_object_by_identifier(ifc_id):
+            return False
+        return True

    def draw(self, context):
        if not ObjectDocumentData.is_loaded:
            ObjectDocumentData.load()

        obj = context.active_object
-        self.oprops = obj.BIMObjectProperties
+        self.oprops = tool.Blender.get_object_bim_props(obj)
        self.props = tool.Document.get_document_props()
        self.file = tool.Ifc.get()

@@ -51,7 +51,7 @@ class Annotator:
        curve.font = font
        props = tool.Drawing.get_text_props(obj)
        props.font_size = "2.5"
-        collection = bpy.context.scene.camera.BIMObjectProperties.collection
+        collection = tool.Blender.get_object_bim_props(bpy.context.scene.camera).collection
        collection.objects.link(obj)
        Annotator.resize_text(obj)
        return obj
@@ -133,7 +133,7 @@ class Annotator:
        co1, _, _, _ = Annotator.get_placeholder_coords(camera)
        matrix_world = tool.Drawing.get_camera_matrix(camera)
        matrix_world.translation = co1
-        collection = camera.BIMObjectProperties.collection
+        collection = tool.Blender.get_object_bim_props(camera).collection

        if object_type == "TEXT":
            obj = bpy.data.objects.new(object_type, None)
@@ -236,7 +236,8 @@ class DecoratorData:
    # stores 1 type of data per object
    data = {}
    cut_cache = {}
-    layerset_cache = {}
+    slice_cache = {}
+    fill_cache = {}

    @classmethod
    def get_batting_thickness(cls, obj):
@@ -386,6 +387,8 @@ class DecoratorData:
        suppress_zero_inches = pset_data.get("SuppressZeroInches", False)
        text_prefix = pset_data.get("TextPrefix", None) or ""
        text_suffix = pset_data.get("TextSuffix", None) or ""
+        custom_unit_list = pset_data.get("CustomUnit", None) or ""
+        custom_unit = custom_unit_list[0] if custom_unit_list else ""

        dimension_data = {
            "dimension_style": dimension_style,
@@ -394,6 +397,7 @@ class DecoratorData:
            "text_prefix": text_prefix,
            "text_suffix": text_suffix,
            "fill_bg": fill_bg,
+            "custom_unit": custom_unit,
        }
        cls.data[obj.name] = dimension_data
        return dimension_data
@@ -16,7 +16,6 @@
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.

-import os
 import gpu
 import bpy
 import blf
@@ -29,7 +28,7 @@ import ifcopenshell.util.unit
 import bonsai.tool as tool
 import bonsai.bim.module.drawing.helper as helper
 from pathlib import Path
-from math import pi, sin, cos, tan, acos, atan, degrees, radians, ceil
+from math import pi, sin, cos, acos, atan, degrees, radians
 from bpy.types import SpaceView3D
 from mathutils import Vector, Matrix
 from bpy_extras.view3d_utils import location_3d_to_region_2d
@@ -319,6 +318,8 @@ class BaseDecorator:
        color: tuple[float, float, float, float],
        indices: Optional[list[tuple[int, int]]] = None,
    ) -> None:
+        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
+            return
        shader = self.line_shader if shader_type == "LINES" else self.base_shader
        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
        shader.uniform_float("color", color)
@@ -495,14 +496,20 @@ class BaseDecorator:
        self.draw_label(context, text=text, line_no=line_number_start, multiline=True, **draw_label_kwargs)

    @lru_cache(maxsize=None)
-    def format_value(self, context, value):
+    def format_value(self, context, value, custom_unit=None):
        drawing_pset_data = DrawingsData.data["active_drawing_pset_data"]
        precision = drawing_pset_data.get("MetricPrecision", None)
        if not precision:
            precision = drawing_pset_data.get("ImperialPrecision", None)

        decimal_places = drawing_pset_data.get("DecimalPlaces", None)
-        return format_distance(value, precision=precision, decimal_places=decimal_places)
+        return format_distance(
+            value,
+            precision=precision,
+            decimal_places=decimal_places,
+            suppress_zero_inches=True,
+            custom_unit=custom_unit,
+        )

    def draw_asterisk(self, context: bpy.types.Context, pos: Vector, rotation: float = 0.0, scale: float = 1.0) -> None:
        """`pos` is a world space position\n
@@ -589,7 +596,8 @@ class BaseDecorator:
        region3d = context.region_data
        text_dir = self.get_annotation_direction(context, obj)

-        pos = location_3d_to_region_2d(region, region3d, text_world_position)
+        if not (pos := location_3d_to_region_2d(region, region3d, text_world_position)):
+            return
        props = tool.Drawing.get_text_props(obj)
        text_data = DecoratorData.get_ifc_text_data(obj)
        if props.is_editing:
@@ -722,6 +730,8 @@ class DimensionDecorator(BaseDecorator):
            v1 = Vector(vertices[i1])
            p0 = location_3d_to_region_2d(region, region3d, v0)
            p1 = location_3d_to_region_2d(region, region3d, v1)
+            if not p0 or not p1:
+                return
            text_dir = p1 - p0
            if text_dir.length < 1:
                continue
@@ -737,7 +747,7 @@ class DimensionDecorator(BaseDecorator):

            if not show_description_only:
                length = (v1 - v0).length
-                text = self.format_value(context, length)
+                text = self.format_value(context, length, custom_unit=dimension_data["custom_unit"])
                if isinstance(self, DiameterDecorator):
                    text = "D" + text
                text = text_prefix + text + text_suffix
@@ -872,6 +882,8 @@ class AngleDecorator(BaseDecorator):

            # calculate angle position
            p0, p1, p2 = [location_3d_to_region_2d(region, region3d, p) for p in vertices[i0 : i1 + 2]]
+            if not p0 or not p1 or not p2:
+                continue
            edge0 = p0 - p1
            edge1 = p2 - p1
            radius = min(edge0.length_squared, edge1.length_squared) ** 0.5
@@ -936,6 +948,8 @@ class RadiusDecorator(BaseDecorator):
        spline_points = self.get_spline_points(obj)

        p0, p1 = [location_3d_to_region_2d(region, region3d, p) for p in self.get_spline_points(obj)]
+        if not p0 or not p1:
+            return
        element = tool.Ifc.get_entity(obj)
        description = element.Description
        dimension_data = DecoratorData.get_dimension_data(obj)
@@ -946,7 +960,7 @@ class RadiusDecorator(BaseDecorator):

        def get_text():
            length = (spline_points[-1] - spline_points[-2]).length
-            return "R" + self.format_value(context, length)
+            return "R" + self.format_value(context, length, custom_unit=dimension_data["custom_unit"])

        self.draw_dimension_text(
            context, get_text, description, dimension_data, pos=pos, text_dir=Vector((1, 0)), box_alignment="center"
@@ -968,7 +982,8 @@ class FallDecorator(BaseDecorator):
        region = context.region
        region3d = context.region_data
        dir = Vector((1, 0))
-        pos = location_3d_to_region_2d(region, region3d, self.get_spline_end(obj))
+        if not (pos := location_3d_to_region_2d(region, region3d, self.get_spline_end(obj))):
+            return

        spline = obj.data.splines[0]
        spline_points = spline.bezier_points if spline.bezier_points else spline.points
@@ -1159,7 +1174,6 @@ class PlanLevelDecorator(BaseDecorator):
        self.draw_labels(context, obj, self.get_splines(obj))

    def draw_labels(self, context, obj, splines):
-        unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
        region = context.region
        region3d = context.region_data

@@ -1169,6 +1183,8 @@ class PlanLevelDecorator(BaseDecorator):

        for verts in splines:
            p0, p1 = [location_3d_to_region_2d(region, region3d, v) for v in verts[:2]]
+            if not p0 or not p1:
+                continue
            text_dir = p1 - p0
            if text_dir.length < 1:
                continue
@@ -1435,8 +1451,10 @@ class GridDecorator(BaseDecorator):
        p1 = location_3d_to_region_2d(region, region3d, v1)
        dir = Vector((1, 0))
        text = obj.name.split("/")[1].split(".")[0]
-        self.draw_label(context, text, p0, dir, vcenter=True, gap=0)
-        self.draw_label(context, text, p1, dir, vcenter=True, gap=0)
+        if p0:
+            self.draw_label(context, text, p0, dir, vcenter=True, gap=0)
+        if p1:
+            self.draw_label(context, text, p1, dir, vcenter=True, gap=0)


 class ElevationDecorator(BaseDecorator):
@@ -1589,6 +1607,9 @@ class CutDecorator:

    @classmethod
    def install(cls, context):
+        DecoratorData.cut_cache.clear()
+        DecoratorData.slice_cache.clear()
+        DecoratorData.fill_cache.clear()
        if cls.installed:
            cls.uninstall()
        handler = cls()
@@ -1603,38 +1624,50 @@ class CutDecorator:
        cls.installed = None

    def __call__(self, context):
+        if not context.scene.camera:
+            return
+
        self.addon_prefs = tool.Blender.get_addon_preferences()
        selected_elements_color = self.addon_prefs.decorator_color_selected
+        self.fallback_colour = (0.3, 0.3, 0.3, 1)

        all_vertices = []
        all_edges = []
        selected_vertices = []
        selected_edges = []
-        layer_vertices = []
-        layer_edges = []
+        fills = {}
        all_vertex_i_offset = 0
        selected_vertex_i_offset = 0
-        layer_vertex_i_offset = 0

        for obj in [o for o in bpy.context.visible_objects if o.type == "MESH"]:
-            verts, edges = self.decorate(context, obj)
-            if not verts:
+            if not (element := tool.Ifc.get_entity(obj)):
                continue
+            self.decorate(context, obj, element)

-            obj_layer_verts, obj_layer_edges = self.slice_layersets(context, obj, verts, edges)
-            if obj_layer_verts:
-                layer_vertices.extend(obj_layer_verts)
-                layer_edges.extend([[vi + layer_vertex_i_offset for vi in e] for e in obj_layer_edges])
-                layer_vertex_i_offset += len(obj_layer_verts)
+            verts, edges = DecoratorData.cut_cache[element.id()]
+            if verts:
+                if obj.select_get():
+                    selected_vertices.extend(verts)
+                    selected_edges.extend([[vi + selected_vertex_i_offset for vi in e] for e in edges])
+                    selected_vertex_i_offset += len(verts)
+                else:
+                    all_vertices.extend(verts)
+                    all_edges.extend([[vi + all_vertex_i_offset for vi in e] for e in edges])
+                    all_vertex_i_offset += len(verts)

-            if obj.select_get():
-                selected_vertices.extend(verts)
-                selected_edges.extend([[vi + selected_vertex_i_offset for vi in e] for e in edges])
-                selected_vertex_i_offset += len(verts)
-            else:
-                all_vertices.extend(verts)
-                all_edges.extend([[vi + all_vertex_i_offset for vi in e] for e in edges])
-                all_vertex_i_offset += len(verts)
+            verts, edges = DecoratorData.slice_cache.get(element.id(), (None, None))
+            if verts:
+                if obj.select_get():
+                    selected_vertices.extend(verts)
+                    selected_edges.extend([[vi + selected_vertex_i_offset for vi in e] for e in edges])
+                    selected_vertex_i_offset += len(verts)
+                else:
+                    all_vertices.extend(verts)
+                    all_edges.extend([[vi + all_vertex_i_offset for vi in e] for e in edges])
+                    all_vertex_i_offset += len(verts)
+
+            for colour, element_fills in DecoratorData.fill_cache[element.id()].items():
+                fills.setdefault(colour, []).append(element_fills)

        gpu.state.point_size_set(1)
        gpu.state.blend_set("ALPHA")
@@ -1652,9 +1685,10 @@ class CutDecorator:

        black = (0, 0, 0, 1)

-        if layer_vertices:
-            self.draw_batch("LINES", layer_vertices, black, layer_edges)
-            self.draw_batch("POINTS", layer_vertices, black)
+        for colour, element_fills in fills.items():
+            for verts_tris in element_fills:
+                for verts, tris in verts_tris:
+                    self.draw_batch("TRIS", verts, colour, tris)

        gpu.state.point_size_set(2)
        self.line_shader.uniform_float("lineWidth", 3.0)
@@ -1667,315 +1701,183 @@ class CutDecorator:
            self.draw_batch("POINTS", selected_vertices, selected_elements_color)

    def draw_batch(self, shader_type, content_pos, color, indices=None):
+        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
+            return
        shader = self.line_shader if shader_type == "LINES" else self.shader
        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
        shader.uniform_float("color", color)
        batch.draw(shader)

-    def decorate(self, context, obj):
-        element = tool.Ifc.get_entity(obj)
-        if not element:
-            return None, None
+    def decorate(self, context, obj: bpy.types.Object, element: ifcopenshell.entity_instance) -> None:
+        has_cut_cache = element.id() in DecoratorData.cut_cache
+        has_fill_cache = element.id() in DecoratorData.fill_cache

-        # Currently selected objects shall not be cached as they may be being moved / edited.
-        # If the camera is selected, we also disable the cache as the user may be moving the camera.
-        if obj.select_get() or context.scene.camera.select_get():
-            verts, edges = None, None
-        else:
-            verts, edges = DecoratorData.cut_cache.get(element.id(), (None, None))
+        # Currently selected objects must be recalculated as they may be being moved / edited.
+        # If the camera is selected, we also recalculate as the user may be moving the camera.

-        if verts is False:
-            return None, None
-        elif verts:
-            return verts, edges
+        if not has_cut_cache or obj.select_get() or context.scene.camera.select_get():
+            self.recalculate_cut(context, obj, element)
+        if not has_fill_cache or obj.select_get() or context.scene.camera.select_get():
+            self.recalculate_fill(context, obj, element)

+    def recalculate_cut(self, context, obj: bpy.types.Object, element: ifcopenshell.entity_instance) -> None:
        if not tool.Drawing.is_intersecting_camera(obj, context.scene.camera):
            DecoratorData.cut_cache[element.id()] = (False, False)
-            return None, None
-
-        if verts is None:
+        else:
            verts, edges = tool.Drawing.bisect_mesh(obj, context.scene.camera)
            DecoratorData.cut_cache[element.id()] = (verts, edges)
-        return verts, edges

-    def slice_layersets(self, context, obj, cut_verts, cut_edges):
-        element = tool.Ifc.get_entity(obj)
-
-        # Currently selected objects shall not be cached as they may be being moved / edited.
-        # If the camera is selected, we also disable the cache as the user may be moving the camera.
-        if obj.select_get() or context.scene.camera.select_get():
-            verts, edges = None, None
-        else:
-            verts, edges = DecoratorData.layerset_cache.get(element.id(), (None, None))
-
-        if verts is False:
-            return None, None
-        elif verts is not None:
-            return verts, edges
+    def recalculate_fill(self, context, obj: bpy.types.Object, element: ifcopenshell.entity_instance) -> None:
+        element_id = element.id()

        if not tool.Drawing.is_intersecting_camera(obj, context.scene.camera):
-            DecoratorData.layerset_cache[element.id()] = (False, False)
-            return None, None
+            DecoratorData.fill_cache[element_id] = {}
+            return

-        if tool.Model.get_usage_type(element) != "LAYER2":
-            DecoratorData.layerset_cache[element.id()] = (False, False)
-            return None, None
+        DecoratorData.fill_cache[element_id] = {}

-        self.unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-        layers = self.get_layer_data(element)
+        mesh = obj.data
+        bm_original = bmesh.new()
+        bm_original.from_mesh(mesh)

-        if not layers:
-            DecoratorData.layerset_cache[element.id()] = (False, False)
-            return None, None
-
-        minx = min([co[0] for co in obj.bound_box])
-        maxx = max([co[0] for co in obj.bound_box])
-        min_edge = [Vector((minx, layers["offset"])), Vector((maxx, layers["offset"]))]
-        max_edge = [
-            Vector((minx, layers["offset"] + layers["thickness"])),
-            Vector((maxx, layers["offset"] + layers["thickness"])),
-        ]
-        centerline = [
-            Vector((minx, layers["offset"] + layers["thickness"] / 2)),
-            Vector((maxx, layers["offset"] + layers["thickness"] / 2)),
-        ]
-        connections = self.get_connections(element, obj, centerline, min_edge, max_edge)
-
-        start_point = None
-        end_point = None
-        if connections["ATSTART"]:
-            boundary_edge = min_edge if connections["ATSTART"]["angle"] > 0 else max_edge
-            rel_dir = connections["ATSTART"]["centerline"][1] - connections["ATSTART"]["centerline"][0]
-            offset, _ = tool.Cad.intersect_edges(boundary_edge, [centerline[0], centerline[0] + rel_dir])
-            offset_x = (offset - centerline[0]).length + abs(offset.x)
-            intersect, _ = tool.Cad.intersect_edges(boundary_edge, connections["ATSTART"]["centerline"])
-            if tool.Cad.is_point_on_edge(intersect, boundary_edge):
-                centerline[0] = centerline[0] + Vector((offset_x, 0))
-                start_point = centerline[0] + rel_dir
-        if connections["ATEND"]:
-            boundary_edge = min_edge if connections["ATEND"]["angle"] > 0 else max_edge
-            rel_dir = connections["ATEND"]["centerline"][1] - connections["ATEND"]["centerline"][0]
-            offset, _ = tool.Cad.intersect_edges(boundary_edge, [centerline[1], centerline[1] + rel_dir])
-
-            offset_x = (offset - centerline[1]).length + abs((maxx - abs(offset.x)))
-            intersect, _ = tool.Cad.intersect_edges(boundary_edge, connections["ATEND"]["centerline"])
-            if tool.Cad.is_point_on_edge(intersect, boundary_edge):
-                centerline[1] = centerline[1] - Vector((offset_x, 0))
-                end_point = centerline[1] + rel_dir
-
-        min_segments = self.get_segments(connections["MINPATH"], centerline, start_point, end_point)
-        max_segments = self.get_segments(connections["MAXPATH"], centerline, start_point, end_point)
-
-        final_segments = []
-        for segment in min_segments:
-            segment_line = shapely.LineString([co for co in segment])
-            for distance in layers["min_layers"]:
-                distance *= -1
-                layer_line = shapely.offset_curve(segment_line, distance, join_style=shapely.BufferJoinStyle.mitre)
-                final_segments.append(list(layer_line.coords))
-        for segment in max_segments:
-            segment_line = shapely.LineString([co for co in segment])
-            for distance in layers["max_layers"]:
-                layer_line = shapely.offset_curve(segment_line, distance, join_style=shapely.BufferJoinStyle.mitre)
-                final_segments.append(list(layer_line.coords))
-
-        # Extrude and bisect layers
-        bm = bmesh.new()
-        verts = []
-        edges = []
-        offset = 0
-        for segment in final_segments:
-            if not segment:
-                # Why does this occur?
-                continue
-            if isinstance(segment[0], tuple):
-                segment = [Vector(co) for co in segment]
-            verts.extend([bm.verts.new(co.to_3d()) for co in segment])
-            [bm.edges.new((verts[i + offset], verts[i + 1 + offset])) for i in range(0, len(segment) - 1)]
-            offset += len(segment)
-
-        extrusion_dir = (0, 0, 3)
-        extruded_geom = bmesh.ops.extrude_edge_only(bm, edges=bm.edges[:])
-        bmesh.ops.translate(
-            bm, vec=extrusion_dir, verts=[v for v in extruded_geom["geom"] if isinstance(v, bmesh.types.BMVert)]
-        )
-
-        verts, edges = self.bisect_mesh(obj, bm, context.scene.camera)
-        layer_linestrings = [shapely.LineString((verts[e[0]], verts[e[1]])) for e in edges]
-
-        clipped_linestrings = []
-
-        polygons = shapely.polygonize([shapely.LineString((cut_verts[e[0]], cut_verts[e[1]])) for e in cut_edges])
-        for polygon in polygons.geoms:
-            clipped_linestrings.extend([polygon.intersection(ls) for ls in layer_linestrings])
-
-        verts = []
-        edges = []
-        offset = 0
-        for linestring in clipped_linestrings:
-            try:
-                linestring = list(linestring.coords)
-            except:
-                print("Failed ... ", linestring)
-                continue
-            verts.extend(linestring)
-            edges.extend([(i + offset, i + 1 + offset) for i in range(0, len(linestring) - 1)])
-            offset += len(linestring)
-
-        DecoratorData.layerset_cache[element.id()] = (verts, edges)
-        return verts, edges
-
-    def bisect_mesh(self, obj, bm, camera):
-        camera_matrix = obj.matrix_world.inverted() @ camera.matrix_world
+        # Slice our mesh into a 2D drawing cut (2D is always easier)
+        camera_matrix = obj.matrix_world.inverted() @ context.scene.camera.matrix_world
+        global_offset = context.scene.camera.matrix_world.col[2].xyz * -context.scene.camera.data.clip_start
        plane_co = camera_matrix.translation
        plane_no = camera_matrix.col[2].xyz
+        geom = bm_original.verts[:] + bm_original.edges[:] + bm_original.faces[:]
+        bmesh.ops.bisect_plane(
+            bm_original,
+            geom=geom,
+            dist=0.0001,
+            plane_co=plane_co,
+            plane_no=plane_no,
+            clear_outer=True,
+            clear_inner=True,
+        )
+        bmesh.ops.remove_doubles(bm_original, verts=bm_original.verts, dist=0.000001)
+        bmesh.ops.triangle_fill(bm_original, use_dissolve=True, edges=bm_original.edges)

-        global_offset = camera.matrix_world.col[2].xyz * -camera.data.clip_start
+        if not (material := ifcopenshell.util.element.get_material(element)):
+            verts, tris = self.get_bmesh_tris(obj, bm_original, context.scene.camera)
+            DecoratorData.fill_cache[element_id].setdefault(self.fallback_colour, []).append((verts, tris))
+            return

-        # Run the bisect operation
-        geom = bm.verts[:] + bm.edges[:] + bm.faces[:]
-        results = bmesh.ops.bisect_plane(bm, geom=geom, dist=0.0001, plane_co=plane_co, plane_no=plane_no)
+        if material.is_a() not in ("IfcMaterialLayerSet", "IfcMaterialLayerSetUsage"):
+            # Constituents, lists, and item styles not supported yet
+            material = ifcopenshell.util.element.get_materials(element)[0]
+            verts, tris = self.get_bmesh_tris(obj, bm_original, context.scene.camera)
+            colour = self.get_material_colour(material)
+            DecoratorData.fill_cache[element_id].setdefault(colour, []).append((verts, tris))
+            return
+
+        self.unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
+
+        if material.is_a("IfcMaterialLayerSetUsage"):
+            usage = material
+            layer_set = material.ForLayerSet
+            offset = usage.OffsetFromReferenceLine * self.unit_scale
+            sense_factor = 1 if usage.DirectionSense == "POSITIVE" else -1
+        elif material.is_a("IfcMaterialLayerSet"):
+            usage = None
+            layer_set = material
+            offset = 0
+            sense_factor = 1
+
+        if len(layer_set.MaterialLayers) == 1:
+            material = layer_set.MaterialLayers[0].Material
+            verts, tris = self.get_bmesh_tris(obj, bm_original, context.scene.camera)
+            colour = self.get_material_colour(material)
+            DecoratorData.fill_cache[element_id].setdefault(colour, []).append((verts, tris))
+            return
+
+        bm = bm_original.copy()
+        prev_co = None
+        if not usage:
+            sense_factor = 1  # Assume the extrusion vector points in the direction sense
+            no = tool.Drawing.get_extrusion_vector(element).normalized()
+            co = Vector((0.0, 0.0, offset))
+        elif usage.LayerSetDirection == "AXIS2":
+            co = Vector((0.0, offset, 0.0))
+            no = tool.Drawing.get_extrusion_vector(element).normalized()
+            no = no.cross(Vector([1.0, 0.0, 0.0]))
+        elif usage.LayerSetDirection == "AXIS3":
+            co = Vector((0.0, 0.0, offset))
+            no = tool.Drawing.get_extrusion_vector(element).normalized()
+            no = Vector([0.0, 0.0, 1.0])
+        elif usage.LayerSetDirection == "AXIS1":
+            co = Vector((0.0, 0.0, offset))
+            no = tool.Drawing.get_extrusion_vector(element).normalized()
+            no = Vector([1.0, 0.0, 0.0])
+        no *= sense_factor
+        last_i = len(layer_set.MaterialLayers) - 1

        vert_map = {}
        verts = []
        edges = []
+        j = 0
+
+        for i, layer in enumerate(layer_set.MaterialLayers):
+            prev_co = co.copy()
+            co += no * layer.LayerThickness * self.unit_scale
+            if i != last_i:
+                bisect = bmesh.ops.bisect_plane(
+                    bm, geom=bm.verts[:] + bm.edges[:] + bm.faces[:], dist=0.0001, plane_co=co, plane_no=no
+                )
+                for geom in bisect["geom_cut"]:
+                    if isinstance(geom, bmesh.types.BMVert):
+                        verts.append(tuple((obj.matrix_world @ geom.co) + global_offset))
+                        vert_map[geom.index] = j
+                        j += 1
+                    else:
+                        # It seems as though edges always appear after verts
+                        edges.append([vert_map[v.index] for v in geom.verts])
+
+            colour = self.get_material_colour(layer.Material)
+            bm_fill = bm_original.copy()
+            if i != last_i:
+                geom = bm_fill.verts[:] + bm_fill.edges[:] + bm_fill.faces[:]
+                bmesh.ops.bisect_plane(bm_fill, geom=geom, dist=0.0001, plane_co=co, plane_no=no, clear_outer=True)
+            if i != 0:
+                geom = bm_fill.verts[:] + bm_fill.edges[:] + bm_fill.faces[:]
+                bmesh.ops.bisect_plane(bm_fill, geom=geom, dist=0.0001, plane_co=prev_co, plane_no=no, clear_inner=True)
+
+            DecoratorData.fill_cache[element_id].setdefault(colour, []).append(
+                self.get_bmesh_tris(obj, bm_fill, context.scene.camera)
+            )
+
+        DecoratorData.slice_cache[element.id()] = (verts, edges)
+        bm_original.free()
+
+    def get_material_colour(self, material: ifcopenshell.entity_instance) -> tuple[float, float, float, float]:
+        body = ifcopenshell.util.representation.get_context(tool.Ifc.get(), "Model", "Body", "MODEL_VIEW")
+        style = ifcopenshell.util.representation.get_material_style(material, body)
+        if not style:
+            return self.fallback_colour
+        if not (styles := [s for s in style.Styles if s.is_a("IfcSurfaceStyleShading")]):
+            return self.fallback_colour
+        colour = styles[0].SurfaceColour
+        return (colour.Red, colour.Green, colour.Blue, 1)
+
+    def get_bmesh_tris(self, obj, bm, camera):
+        global_offset = camera.matrix_world.col[2].xyz * -camera.data.clip_start
+        triangulate = bmesh.ops.triangulate(bm, faces=bm.faces)
+        vert_map = {}
+        verts = []
+        tris = []
        i = 0
-        for geom in results["geom_cut"]:
-            if isinstance(geom, bmesh.types.BMVert):
-                verts.append(tuple((obj.matrix_world @ geom.co) + global_offset))
-                vert_map[geom.index] = i
-                i += 1
-            else:
-                # It seems as though edges always appear after verts
-                edges.append([vert_map[v.index] for v in geom.verts])
-
-        bm.free()
-
-        return verts, edges
-
-    def get_layer_data(self, element):
-        usage = ifcopenshell.util.element.get_material(element)
-        offset = usage.OffsetFromReferenceLine * self.unit_scale
-        layer_set = usage.ForLayerSet
-
-        if len(layer_set.MaterialLayers) == 1:
-            return  # No use slicing if there's only one layer
-
-        total_thickness = layer_set.TotalThickness
-        half_thickness = total_thickness / 2
-        min_layers = []
-        max_layers = []
-        current_thickness = 0
-        for layer in layer_set.MaterialLayers:
-            current_thickness += layer.LayerThickness
-            if current_thickness / total_thickness < 0.5:
-                min_layers.append((half_thickness - current_thickness) * self.unit_scale)
-            else:
-                max_layers.append((current_thickness - half_thickness) * self.unit_scale)
-        min_layers.reverse()
-        max_layers.pop()
-        if usage.DirectionSense == "NEGATIVE":
-            total_thickness *= -1
-            offset *= -1
-            min_layers = [l * -1 for l in min_layers]
-            max_layers = [l * -1 for l in max_layers]
-        return {
-            "offset": offset,
-            "min_layers": min_layers,
-            "max_layers": max_layers,
-            "thickness": total_thickness * self.unit_scale,
-        }
-
-    def get_segments(self, connections, centerline, start_point, end_point):
-        segments = []
-        total_connections = len(connections)
-        if total_connections:
-            for i in range(0, total_connections + 1):
-                if i == 0:
-                    connection = connections[i]
-                    segments.append([centerline[0], connection["intersection"], connection["out_point"]])
-                elif i == total_connections:
-                    segments.append([segments[-1][-1], segments[-1][-2], centerline[1]])
+        for face in triangulate["faces"]:
+            tri = []
+            for vert in face.verts:
+                if index := vert_map.get(vert.index, None):
+                    tri.append(index)
                else:
-                    connection = connections[i]
-                    segments.append(
-                        [segments[-1][-1], segments[-1][-2], connection["intersection"], connection["out_point"]]
-                    )
-        else:
-            segments.append([centerline[0], centerline[1]])
-        if start_point:
-            segments[0].insert(0, start_point)
-        if end_point:
-            segments[-1].append(end_point)
-        return segments
-
-    def get_connections(self, wall, obj, centerline, min_edge, max_edge):
-        connections = {"ATEND": None, "ATSTART": None, "ATPATH": [], "MINPATH": [], "MAXPATH": []}
-        for rel in wall.ConnectedTo:
-            # How do you join to a non layered element? Not sure.
-            if tool.Model.get_usage_type(rel.RelatedElement) != "LAYER2":
-                continue
-            if rel.RelatingConnectionType == "ATPATH":
-                metadata = self.get_connection_metadata(obj, rel.RelatedElement, centerline, min_edge, max_edge)
-                if not metadata:
-                    continue
-                connections["ATPATH"].append(metadata)
-            else:
-                metadata = self.get_connection_metadata(obj, rel.RelatedElement, centerline, min_edge, max_edge)
-                if not metadata:
-                    continue
-                connections[rel.RelatingConnectionType] = metadata
-        for rel in wall.ConnectedFrom:
-            if tool.Model.get_usage_type(rel.RelatingElement) != "LAYER2":
-                continue
-            # We only consider ATPATH since in this situation, we have the
-            # priority. The non-priority wall never has any layers that need to
-            # "turn a corner".
-            if rel.RelatedConnectionType == "ATPATH":
-                metadata = self.get_connection_metadata(obj, rel.RelatingElement, centerline, min_edge, max_edge)
-                if not metadata:
-                    continue
-                connections["ATPATH"].append(metadata)
-        connections["ATPATH"] = sorted(connections["ATPATH"], key=lambda c: c["intersection"].x)
-        for connection in connections["ATPATH"]:
-            if connection["angle"] > 0:
-                connections["MINPATH"].append(connection)
-            else:
-                connections["MAXPATH"].append(connection)
-        return connections
-
-    def get_connection_metadata(self, obj, rel_element, centerline, min_edge, max_edge):
-        rel_obj = tool.Ifc.get_object(rel_element)
-        layers = self.get_layer_data(rel_element)
-        if not layers:
-            return
-        minx = min([co[0] for co in rel_obj.bound_box])
-        maxx = max([co[0] for co in rel_obj.bound_box])
-        rel_centerline = [
-            Vector((minx, layers["offset"] + layers["thickness"] / 2)),
-            Vector((maxx, layers["offset"] + layers["thickness"] / 2)),
-        ]
-        rel_centerline = [obj.matrix_world.inverted() @ rel_obj.matrix_world @ v.to_3d() for v in rel_centerline]
-        rel_centerline = [v.to_2d() for v in rel_centerline]
-        intersection = tool.Cad.intersect_edges(centerline, rel_centerline)
-        if intersection:
-            intersection, _ = intersection
-        else:
-            return
-        closest_centerline_point = tool.Cad.closest_vector(intersection, tuple(rel_centerline))
-        if closest_centerline_point == rel_centerline[1]:
-            rel_centerline = [rel_centerline[1], rel_centerline[0]]
-        angle = tool.Cad.angle_edges(centerline, rel_centerline, signed=True)
-        # A little extreme, but maybe it's OK?
-        out_point = tool.Cad.furthest_vector(intersection, tuple(rel_centerline))
-        return {
-            "element": rel_element,
-            "obj": rel_obj,
-            "centerline": rel_centerline,
-            "intersection": intersection,
-            "angle": angle,
-            "out_point": out_point,
-        }
+                    verts.append(tuple((obj.matrix_world @ vert.co) + global_offset))
+                    vert_map[vert.index] = i
+                    tri.append(i)
+                    i += 1
+            tris.append(tri)
+        return verts, tris


 class DecorationsHandler:
@@ -414,6 +414,8 @@ class ExtrusionGuidesGizmo(CustomGizmo, types.Gizmo):
        shader_wrapper = ExtrusionGuidesShader()
        verts = [Vector((0, 0, 0)), Vector((0, 0, 1))]
        verts, edges = shader_wrapper.process_geometry(verts)
+        if not tool.Blender.validate_shader_batch_data(verts, edges):
+            verts, edges = [], []
        self.custom_shape = shader_wrapper, shader_wrapper.batch(
            pos=verts,
            indices=edges,
@@ -20,6 +20,7 @@ import bpy
 import math
 import mathutils.geometry
 import ifcopenshell
+import ifcopenshell.util.unit
 import bonsai.tool as tool
 from mathutils import Vector
 from typing import Union
@@ -130,18 +131,53 @@ def format_distance(
    decimal_places=None,
    suppress_zero_inches=False,
    in_unit_length=False,
+    custom_unit=None,
 ):
-    s_code = "\u00b2"  # Superscript two THIS IS LEGACY (but being kept for when Area Measurements are re-implimented)
-
-    # Get Scene Unit Settings
-    scaleFactor = bpy.context.scene.unit_settings.scale_length
+    # Get Blender Scene Unit Settings
+    unit_scale = bpy.context.scene.unit_settings.scale_length
    unit_system = bpy.context.scene.unit_settings.system
    unit_length = bpy.context.scene.unit_settings.length_unit
-    area_unit_symbol = " " + ifcopenshell.util.unit.get_unit_symbol(
-        ifcopenshell.util.unit.get_project_unit(tool.Ifc.get(), "AREAUNIT")
-    )
+    area_unit_symbol = " m2" if unit_system == "METRIC" else " ft2"

-    value *= scaleFactor
+    # Get IFC Unit Settings
+    if tool.Ifc.get():
+        unit_scale = 1
+        if length_unit := ifcopenshell.util.unit.get_project_unit(tool.Ifc.get(), "LENGTHUNIT"):
+            unit_system = "METRIC" if length_unit.Name == "METRE" else "IMPERIAL"
+            unit_length = length_unit.Name.upper()
+            if hasattr(length_unit, "Prefix") and length_unit.Prefix:
+                unit_length = length_unit.Prefix + length_unit.Name
+            unit_length_mapping = {
+                "FOOT": "FEET",
+                "INCH": "INCHES",
+                "METRE": "METERS",
+                "DECIMETRE": "DECIMETERS",
+                "CENTIMETRE": "CENTIMETERS",
+                "MILLIMETRE": "MILLIMETERS",
+            }
+            unit_length = unit_length_mapping[unit_length]
+        # For now we only format area in IFC Units
+        if area_unit := ifcopenshell.util.unit.get_project_unit(tool.Ifc.get(), "AREAUNIT"):
+            area_unit_symbol = " " + ifcopenshell.util.unit.get_unit_symbol(area_unit)
+
+    unit_fraction = True if unit_system == "IMPERIAL" else False
+
+    # Custom Unit Settings
+    if custom_unit:
+        unit_mapping = {
+            "Feet and Inches - Fractional": ("IMPERIAL", "FEET", True),
+            "Feet - Decimal": ("IMPERIAL", "FEET", False),
+            "Inches - Fractional": ("IMPERIAL", "INCHES", True),
+            "Inches - Decimal": ("IMPERIAL", "INCHES", False),
+            "Meters": ("METRIC", "METERS", False),
+            "Decimeters": ("METRIC", "DECIMETERS", False),
+            "Centimeters": ("METRIC", "CENTIMETERS", False),
+            "Millimeters": ("METRIC", "MILLIMETERS", False),
+        }
+        if custom_unit in unit_mapping:
+            unit_system, unit_length, unit_fraction = unit_mapping[custom_unit]
+
+    value *= unit_scale

    # Imperial Formatting
    if unit_system == "IMPERIAL":
@@ -166,10 +202,14 @@ def format_distance(

        base = int(precision)
        decInches = value * toInches
+        decFeet = decInches / 12

        # Separate ft and inches
-        # Unless Inches are the specified Length Unit
-        if unit_length != "INCHES":
+        # Unless Inches are the specified Length Unit or unit_fraction is False
+        if unit_length == "FEET" and not unit_fraction:
+            feet = round(decInches / inPerFoot, 3)  # keep decimal
+            decInches = 0
+        elif unit_length != "INCHES":
            feet = int(decInches / inPerFoot)  # remove decimal
            decInches -= feet * inPerFoot
        else:
@@ -204,6 +244,10 @@ def format_distance(
                feet += 1
                inches = 0

+        # Check whether decimal or fractional
+        if not unit_fraction:
+            inches = round(decInches, 3)
+            frac = None
        if not isArea:
            add_inches = bool(inches) or not suppress_zero_inches or (inches == 0 and frac)
            tx_dist = ""
@@ -229,6 +273,8 @@ def format_distance(
                tx_dist += str(frac) + "/" + str(base)
            if add_inches or frac:
                tx_dist += '"'
+            if precision == "12" and unit_system == "IMPERIAL":
+                tx_dist = str(round(decFeet)) + "'"
        else:
            fmt = "%1.3f"
            sq_feet = round(value * toInches / inPerFoot, 4)
@@ -252,6 +298,8 @@ def format_distance(
    # METRIC FORMATTING
    elif unit_system == "METRIC":
        if in_unit_length:
+            if unit_length == "DECIMETERS":
+                value = value / 10
            if unit_length == "CENTIMETERS":
                value = value / 100
            if unit_length == "MILLIMETERS":
@@ -270,6 +318,14 @@ def format_distance(
            if hide_units is False:
                fmt += " m"
            tx_dist = fmt % value
+        # Decimeters
+        elif unit_length == "DECIMETERS":
+            if decimal_places is None:
+                fmt = "%1.1f"
+            if hide_units is False:
+                fmt += " dm"
+            d_dm = value * (10)
+            tx_dist = fmt % d_dm
        # Centimeters
        elif unit_length == "CENTIMETERS":
            if decimal_places is None:
@@ -343,7 +399,7 @@ def get_active_drawing(
    props = tool.Drawing.get_document_props()
    try:
        camera = tool.Ifc.get_object(tool.Ifc.get().by_id(props.active_drawing_id))
-        return camera.BIMObjectProperties.collection, camera
+        return tool.Blender.get_object_bim_props(camera).collection, camera
    except:
        return None, None

@@ -43,6 +43,7 @@ import bonsai.bim.module.drawing.svgwriter as svgwriter
 import bonsai.bim.module.drawing.annotation as annotation
 import bonsai.bim.module.drawing.sheeter as sheeter
 import bonsai.bim.export_ifc
+from bpy_extras.io_utils import ImportHelper
 from bonsai.bim.module.drawing.decoration import CutDecorator
 from bonsai.bim.module.drawing.data import DecoratorData, DrawingsData
 from typing import NamedTuple, List, Union, Optional, Literal
@@ -246,7 +247,7 @@ class CreateDrawing(bpy.types.Operator):
    def execute(self, context):
        self.props = tool.Drawing.get_document_props()

-        active_drawing_id = context.scene.camera.BIMObjectProperties.ifc_definition_id
+        active_drawing_id = tool.Blender.get_ifc_definition_id(context.scene.camera)
        if self.print_all:
            original_drawing_id = active_drawing_id
            drawings_to_print = [d.ifc_definition_id for d in self.props.drawings if d.is_selected and d.is_drawing]
@@ -391,7 +392,7 @@ class CreateDrawing(bpy.types.Operator):
            bpy.ops.render.render(write_still=True)
        else:
            previous_visibility = {}
-            for obj in self.camera.BIMObjectProperties.collection.objects:
+            for obj in tool.Blender.get_object_bim_props(self.camera).collection.objects:
                if bpy.context.view_layer.objects.get(obj.name):
                    previous_visibility[obj.name] = obj.hide_get()
                    obj.hide_set(True)
@@ -562,6 +563,112 @@ class CreateDrawing(bpy.types.Operator):
                path.attrib["d"] = d
            group.append(g)

+    def generate_wall_layers(self, context: bpy.types.Context, root):
+        for el in root.findall(".//{http://www.w3.org/2000/svg}g[@{http://www.ifcopenshell.org/ns}guid]"):
+            if "projection" in el.get("class", "").split():
+                continue
+            element = self.get_element_by_guid(el.get("{http://www.ifcopenshell.org/ns}guid"))
+            if not (obj := tool.Ifc.get_object(element)):
+                continue
+            if not (material := ifcopenshell.util.element.get_material(element)):
+                continue
+            if material.is_a() not in ("IfcMaterialLayerSet", "IfcMaterialLayerSetUsage"):
+                continue
+
+            self.unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
+
+            if material.is_a("IfcMaterialLayerSetUsage"):
+                usage = material
+                layer_set = material.ForLayerSet
+                offset = usage.OffsetFromReferenceLine * self.unit_scale
+                sense_factor = 1 if usage.DirectionSense == "POSITIVE" else -1
+            elif material.is_a("IfcMaterialLayerSet"):
+                usage = None
+                layer_set = material
+                offset = 0
+                sense_factor = 1
+
+            camera_matrix_i = context.scene.camera.matrix_world.inverted()
+
+            group = root.find("{http://www.w3.org/2000/svg}g")
+            raw_width, raw_height = self.get_camera_dimensions()
+            x_offset = raw_width / 2
+            y_offset = raw_height / 2
+            svg_scale = self.scale * 1000  # IFC is in meters, SVG is in mm
+
+            mesh = obj.data
+            bm = bmesh.new()
+            bm.from_mesh(mesh)
+
+            # Slice our mesh into a 2D drawing cut (2D is always easier)
+            camera_matrix = obj.matrix_world.inverted() @ context.scene.camera.matrix_world
+            plane_co = camera_matrix.translation
+            plane_no = camera_matrix.col[2].xyz
+            geom = bm.verts[:] + bm.edges[:] + bm.faces[:]
+            bmesh.ops.bisect_plane(
+                bm, geom=geom, dist=0.0001, plane_co=plane_co, plane_no=plane_no, clear_outer=True, clear_inner=True
+            )
+            bmesh.ops.remove_doubles(bm, verts=bm.verts, dist=0.000001)
+            bmesh.ops.triangle_fill(bm, use_dissolve=True, edges=bm.edges)
+
+            prev_co = None
+            if not usage:
+                sense_factor = 1  # Assume the extrusion vector points in the direction sense
+                no = tool.Drawing.get_extrusion_vector(element).normalized()
+                co = Vector((0.0, 0.0, offset))
+            elif usage.LayerSetDirection == "AXIS2":
+                co = Vector((0.0, offset, 0.0))
+                no = tool.Drawing.get_extrusion_vector(element).normalized()
+                no = no.cross(Vector([1.0, 0.0, 0.0]))
+            elif usage.LayerSetDirection == "AXIS3":
+                co = Vector((0.0, 0.0, offset))
+                no = tool.Drawing.get_extrusion_vector(element).normalized()
+                no = Vector([0.0, 0.0, 1.0])
+            elif usage.LayerSetDirection == "AXIS1":
+                co = Vector((0.0, 0.0, offset))
+                no = tool.Drawing.get_extrusion_vector(element).normalized()
+                no = Vector([1.0, 0.0, 0.0])
+            no *= sense_factor
+            last_i = len(layer_set.MaterialLayers) - 1
+            for i, layer in enumerate(layer_set.MaterialLayers):
+                prev_co = co.copy()
+                co += no * layer.LayerThickness * self.unit_scale
+
+                bm_fill = bm.copy()
+                if i != last_i:
+                    geom = bm_fill.verts[:] + bm_fill.edges[:] + bm_fill.faces[:]
+                    bmesh.ops.bisect_plane(bm_fill, geom=geom, dist=0.0001, plane_co=co, plane_no=no, clear_outer=True)
+                if i != 0:
+                    geom = bm_fill.verts[:] + bm_fill.edges[:] + bm_fill.faces[:]
+                    bmesh.ops.bisect_plane(
+                        bm_fill, geom=geom, dist=0.0001, plane_co=prev_co, plane_no=no, clear_inner=True
+                    )
+
+                bm_fill.verts.ensure_lookup_table()
+                bm_fill.edges.ensure_lookup_table()
+                verts = [tuple(obj.matrix_world @ v.co) for v in bm_fill.verts]
+                edges = [[v.index for v in e.verts] for e in bm_fill.edges]
+
+                g = etree.SubElement(root, "{http://www.w3.org/2000/svg}g")
+                g.attrib["{http://www.ifcopenshell.org/ns}guid"] = element.GlobalId
+                g.attrib["{http://www.ifcopenshell.org/ns}name"] = element.Name or ""
+                g.attrib["{http://www.ifcopenshell.org/ns}layer-id"] = str(layer.id())
+
+                lines = []
+                for edge in edges:
+                    start = [o for o in (camera_matrix_i @ Vector(verts[edge[0]])).xy]
+                    end = [o for o in (camera_matrix_i @ Vector(verts[edge[1]])).xy]
+                    coords = [start, end]
+                    d = " ".join(
+                        ["L{},{}".format((x_offset + p[0]) * svg_scale, (y_offset - p[1]) * svg_scale) for p in coords]
+                    )
+                    d = "M{}".format(d[1:])
+                    path = etree.SubElement(g, "{http://www.w3.org/2000/svg}path")
+                    path.attrib["d"] = d
+                group.append(g)
+
+            bm.free()
+
    def generate_freestyle_linework(self, context: bpy.types.Context) -> str | None:
        if not ifcopenshell.util.element.get_pset(self.drawing, "EPset_Drawing", "HasLinework"):
            return
@@ -692,7 +799,6 @@ class CreateDrawing(bpy.types.Operator):
                exporter = bonsai.bim.export_ifc.IfcExporter(None)
                exporter.file = tool.Ifc.get()
                invalidated_elements = exporter.sync_all_objects()
-                invalidated_elements += exporter.sync_edited_objects()
                invalidated_guids = [e.GlobalId for e in invalidated_elements if hasattr(e, "GlobalId")]
                if cache := IfcStore.get_cache():
                    [cache.remove(guid) for guid in invalidated_guids]
@@ -717,6 +823,8 @@ class CreateDrawing(bpy.types.Operator):

        props = tool.Project.get_project_props()
        for link in props.links:
+            if not link.is_loaded:
+                continue
            if link.name not in IfcStore.session_files:
                IfcStore.session_files[link.name] = ifcopenshell.open(link.name)
            files[link.name] = IfcStore.session_files[link.name]
@@ -769,10 +877,12 @@ class CreateDrawing(bpy.types.Operator):
        if self.camera.data.BIMCameraProperties.cut_mode == "BISECT":
            self.remove_cut_linework(root)
            self.generate_bisect_linework(context, root)
+            self.generate_wall_layers(context, root)
            self.merge_linework_and_add_metadata(root)
            self.move_elements_to_top(root)
        elif self.camera.data.BIMCameraProperties.cut_mode == "OPENCASCADE":
            self.move_projection_to_bottom(root)
+            self.generate_wall_layers(context, root)
            self.merge_linework_and_add_metadata(root)
            self.move_elements_to_top(root)

@@ -1101,7 +1211,7 @@ class CreateDrawing(bpy.types.Operator):
        # the style of the face when running tree.select_ray()
        # tree.enable_face_styles(True)

-    def get_svg_classes(self, element):
+    def get_svg_classes(self, element, layer=None):
        classes = [element.is_a()]
        material = ifcopenshell.util.element.get_material(element, should_skip_usage=True)
        material_name = ""
@@ -1113,7 +1223,13 @@ class CreateDrawing(bpy.types.Operator):
            material_name = tool.Drawing.canonicalise_class_name(material_name)
            classes.append(f"material-{material_name}")
        else:
-            classes.append(f"material-null")
+            classes.append("material-null")
+
+        if layer:
+            classes.append(layer.is_a())
+            material_name = layer.Material.Name or "null"
+            material_name = tool.Drawing.canonicalise_class_name(material_name)
+            classes.append(f"layer-material-{material_name}")

        for key in self.metadata:
            value = ifcopenshell.util.selector.get_element_value(element, key)
@@ -1152,6 +1268,23 @@ class CreateDrawing(bpy.types.Operator):
                except:
                    continue

+    def get_element_by_id(self, step_id):
+        try:
+            step_id = int(step_id)
+        except:
+            return
+        try:
+            return tool.Ifc.get().by_id(step_id)
+        except:
+            props = tool.Project.get_project_props()
+            for link in props.links:
+                if link.name not in IfcStore.session_files:
+                    IfcStore.session_files[link.name] = ifcopenshell.open(link.name)
+                try:
+                    return IfcStore.session_files[link.name].by_id(step_id)
+                except:
+                    continue
+
    def remove_cut_linework(self, root):
        for el in root.findall(".//{http://www.w3.org/2000/svg}g[@{http://www.ifcopenshell.org/ns}guid]"):
            if "projection" not in el.get("class", "").split():
@@ -1163,15 +1296,15 @@ class CreateDrawing(bpy.types.Operator):
            join_criteria = join_criteria.split(",")
        else:
            # Drawing convention states that same objects classes with the same material are merged when cut.
-            join_criteria = ["class", "material.Name", "/Pset_.*Common/.Status", "EPset_Status.Status"]
+            join_criteria = ["class", "material.Name", "/Pset_.*Common/.Status", "EPset_Status.Status", "Material.Name"]

        group = root.find("{http://www.w3.org/2000/svg}g")
        joined_paths = {}
        self.is_manifold_cache = {}

-        ifc = tool.Ifc.get()
        for el in root.findall(".//{http://www.w3.org/2000/svg}g[@{http://www.ifcopenshell.org/ns}guid]"):
            element = self.get_element_by_guid(el.get("{http://www.ifcopenshell.org/ns}guid"))
+            layer = self.get_element_by_id(el.get("{http://www.ifcopenshell.org/ns}layer-id"))

            if "projection" in el.get("class", "").split():
                classes = self.get_svg_classes(element)
@@ -1179,7 +1312,7 @@ class CreateDrawing(bpy.types.Operator):
                el.set("class", " ".join(classes))
                continue
            else:
-                classes = self.get_svg_classes(element)
+                classes = self.get_svg_classes(element, layer)
                classes.append("cut")
                el.set("class", " ".join(classes))

@@ -1188,7 +1321,12 @@ class CreateDrawing(bpy.types.Operator):
            if not obj:  # This is a linked model object. For now, do nothing.
                continue

-            if not self.is_manifold(obj):
+            if (material := ifcopenshell.util.element.get_material(element)) and material.is_a() in (
+                "IfcMaterialLayerSet",
+                "IfcMaterialLayerSetUsage",
+            ):
+                pass  # These are always manifold
+            elif not self.is_manifold(obj):
                continue

            # An element group will contain a bunch of paths representing the
@@ -1273,6 +1411,15 @@ class CreateDrawing(bpy.types.Operator):
                else:
                    keys.append(key)

+            if layer:
+                for query in join_criteria:
+                    key = ifcopenshell.util.selector.get_element_value(layer, query)
+                    print("got layer key", query, key)
+                    if isinstance(key, (list, tuple)):
+                        keys.extend(key)
+                    else:
+                        keys.append(key)
+
            hash_keys = hash(tuple(keys))

            if el.findall("{http://www.w3.org/2000/svg}path"):
@@ -1289,7 +1436,8 @@ class CreateDrawing(bpy.types.Operator):
                for path in el.findall("{http://www.w3.org/2000/svg}path"):
                    for subpath in path.attrib["d"].split("M")[1:]:
                        subpath_co = "M" + subpath.strip(" Z")
-                        coords = [[float(o) for o in co[1:].split(",")] for co in subpath_co.split()]
+                        # Round due to inaccuracies from Blender meshes and bisection
+                        coords = [[round(float(o), 3) for o in co[1:].split(",")] for co in subpath_co.split()]
                        if subpath.strip().lower().endswith("z"):
                            coords.append(coords[0])
                        if len(coords) > 2 and coords[0] == coords[-1]:
@@ -2020,6 +2168,8 @@ class ActivateDrawingBase:
        camera_props = camera.data.BIMCameraProperties
        if camera_props.update_representation(camera):
            bpy.ops.bim.update_representation(obj=camera.name, ifc_representation_class="")
+        # See 6452 and 6478.
+        # bpy.ops.bim.refresh_clipping_planes("INVOKE_DEFAULT")

        return {"FINISHED"}

@@ -2040,7 +2190,6 @@ class ActivateDrawing(bpy.types.Operator, ActivateDrawingBase):

    @classmethod
    def poll(cls, context):
-        props = tool.Drawing.get_document_props()
        if not tool.Drawing.get_active_drawing_item():
            cls.poll_message_set("No drawing selected.")
            return False
@@ -2070,12 +2219,14 @@ class ActivateDrawingFromSheet(bpy.types.Operator, ActivateDrawingBase):
        return True


-class SelectDocIfcFile(bpy.types.Operator):
+# TODO: not exposed to the UI.
+class SelectDocIfcFile(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_doc_ifc_file"
    bl_label = "Select Documentation IFC File"
+    bl_description = "Selection .ifc file for documentation."
    bl_options = {"REGISTER", "UNDO"}
    filter_glob: bpy.props.StringProperty(default="*.ifc;*.ifczip;*.ifcxml", options={"HIDDEN"})
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
+    filename_ext = ".ifc"
    index: bpy.props.IntProperty()

    def execute(self, context):
@@ -2083,10 +2234,6 @@ class SelectDocIfcFile(bpy.types.Operator):
        props.ifc_files[self.index].name = self.filepath
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-

 class ResizeText(bpy.types.Operator):
    bl_idname = "bim.resize_text"
@@ -2095,7 +2242,7 @@ class ResizeText(bpy.types.Operator):
    # TODO: check undo redo

    def execute(self, context):
-        for obj in context.scene.camera.BIMObjectProperties.collection.objects:
+        for obj in tool.Blender.get_object_bim_props(context.scene.camera).collection.objects:
            if isinstance(obj.data, bpy.types.TextCurve):
                annotation.Annotator.resize_text(obj)
        return {"FINISHED"}
@@ -2465,13 +2612,12 @@ class RemoveSheet(bpy.types.Operator, tool.Ifc.Operator):
        core.remove_sheet(tool.Ifc, tool.Drawing, sheet=tool.Ifc.get().by_id(self.sheet))


-class AddSchedule(bpy.types.Operator, tool.Ifc.Operator):
+class AddSchedule(bpy.types.Operator, tool.Ifc.Operator, ImportHelper):
    bl_idname = "bim.add_schedule"
    bl_label = "Add Schedule"
    bl_options = {"REGISTER", "UNDO"}
    bl_description = "Add an .ods, .xls or .xlsx file as a schedule"

-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    filter_glob: bpy.props.StringProperty(default="*.ods;*.xls;*.xlsx", options={"HIDDEN"})
    use_relative_path: bpy.props.BoolProperty(name="Use Relative Path", default=True)

@@ -2479,10 +2625,6 @@ class AddSchedule(bpy.types.Operator, tool.Ifc.Operator):
        filepath = tool.Ifc.get_uri(self.filepath, use_relative_path=self.use_relative_path)
        core.add_document(tool.Ifc, tool.Drawing, "SCHEDULE", uri=filepath)

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-

 class RemoveSchedule(bpy.types.Operator, tool.Ifc.Operator):
    bl_idname = "bim.remove_schedule"
@@ -2652,24 +2794,20 @@ class AddReferenceToSheet(bpy.types.Operator, tool.Ifc.Operator):
        tool.Drawing.import_sheets()


-class AddReference(bpy.types.Operator, tool.Ifc.Operator):
+class AddReference(bpy.types.Operator, tool.Ifc.Operator, ImportHelper):
    bl_idname = "bim.add_reference"
    bl_label = "Add Reference"
    bl_description = "Import a .svg file to the project as a reference"
-
    bl_options = {"REGISTER", "UNDO"}
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
+
    filter_glob: bpy.props.StringProperty(default="*.svg", options={"HIDDEN"})
    use_relative_path: bpy.props.BoolProperty(name="Use Relative Path", default=True)
+    filename_ext = ".svg"

    def _execute(self, context):
        filepath = tool.Ifc.get_uri(self.filepath, use_relative_path=self.use_relative_path)
        core.add_document(tool.Ifc, tool.Drawing, "REFERENCE", uri=filepath)

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-

 class RemoveReference(bpy.types.Operator, tool.Ifc.Operator):
    bl_idname = "bim.remove_reference"
@@ -3152,14 +3290,22 @@ class DisableEditingDrawings(bpy.types.Operator, tool.Ifc.Operator):
 class ExpandTargetView(bpy.types.Operator):
    bl_idname = "bim.expand_target_view"
    bl_label = "Expand Target View"
-    bl_description = "Show views in this category"
+    bl_description = "\nSHIFT+CLICK to expand all view categories "

    bl_options = {"REGISTER", "UNDO"}
    target_view: bpy.props.StringProperty()
+    expand_all: bpy.props.BoolProperty(name="Expand All", default=False, options={"SKIP_SAVE"})
+
+    def invoke(self, context, event):
+        # Expanding all categories on shift+click.
+        # Make sure to use SKIP_SAVE on property, otherwise it might get stuck (copied from #4771).
+        if event.type == "LEFTMOUSE" and event.shift:
+            self.expand_all = True
+        return self.execute(context)

    def execute(self, context):
        props = tool.Drawing.get_document_props()
-        for drawing in [d for d in props.drawings if d.target_view == self.target_view]:
+        for drawing in [d for d in props.drawings if self.expand_all or d.target_view == self.target_view]:
            drawing.is_expanded = True
        core.load_drawings(tool.Drawing)
        return {"FINISHED"}
@@ -3168,14 +3314,22 @@ class ExpandTargetView(bpy.types.Operator):
 class ContractTargetView(bpy.types.Operator):
    bl_idname = "bim.contract_target_view"
    bl_label = "Contract Target View"
-    bl_description = "Hide views in this category"
+    bl_description = "\n\nSHIFT+CLICK to hide all view categories"

    bl_options = {"REGISTER", "UNDO"}
    target_view: bpy.props.StringProperty()
+    contract_all: bpy.props.BoolProperty(name="Contract All", default=False, options={"SKIP_SAVE"})
+
+    def invoke(self, context, event):
+        # Contracting all categories on shift+click.
+        # Make sure to use SKIP_SAVE on property, otherwise it might get stuck (copied from #4771).
+        if event.type == "LEFTMOUSE" and event.shift:
+            self.contract_all = True
+        return self.execute(context)

    def execute(self, context):
        props = tool.Drawing.get_document_props()
-        for drawing in [d for d in props.drawings if d.target_view == self.target_view]:
+        for drawing in [d for d in props.drawings if self.contract_all or d.target_view == self.target_view]:
            drawing.is_expanded = False
        core.load_drawings(tool.Drawing)
        return {"FINISHED"}
@@ -3184,14 +3338,20 @@ class ContractTargetView(bpy.types.Operator):
 class ExpandSheet(bpy.types.Operator):
    bl_idname = "bim.expand_sheet"
    bl_label = "Expand Sheet"
-    bl_description = "Show views, schedules, references etc\nplaced on this sheet"
-
+    bl_description = "Show views, schedules, references etc\nplaced on this sheet.\n\nShift+click to expand all sheets."
    bl_options = {"REGISTER", "UNDO"}
+
    sheet: bpy.props.IntProperty()
+    expand_all: bpy.props.BoolProperty(name="Expand All", default=False, options={"SKIP_SAVE"})
+
+    def invoke(self, context, event):
+        if event.type == "LEFTMOUSE" and event.shift:
+            self.expand_all = True
+        return self.execute(context)

    def execute(self, context):
        props = tool.Drawing.get_document_props()
-        for sheet in [s for s in props.sheets if s.ifc_definition_id == self.sheet]:
+        for sheet in [s for s in props.sheets if self.expand_all or s.ifc_definition_id == self.sheet]:
            sheet.is_expanded = True
        core.load_sheets(tool.Drawing)
        return {"FINISHED"}
@@ -3200,14 +3360,22 @@ class ExpandSheet(bpy.types.Operator):
 class ContractSheet(bpy.types.Operator):
    bl_idname = "bim.contract_sheet"
    bl_label = "Contract Sheet"
-    bl_description = "Hide views, schedules, references etc\nplaced on this sheet"
-
+    bl_description = (
+        "Hide views, schedules, references etc\nplaced on this sheet.\n\nShift+click to contract all sheets."
+    )
    bl_options = {"REGISTER", "UNDO"}
+
    sheet: bpy.props.IntProperty()
+    expand_all: bpy.props.BoolProperty(name="Expand All", default=False, options={"SKIP_SAVE"})
+
+    def invoke(self, context, event):
+        if event.type == "LEFTMOUSE" and event.shift:
+            self.expand_all = True
+        return self.execute(context)

    def execute(self, context):
        props = tool.Drawing.get_document_props()
-        for sheet in [s for s in props.sheets if s.ifc_definition_id == self.sheet]:
+        for sheet in [s for s in props.sheets if self.expand_all or s.ifc_definition_id == self.sheet]:
            sheet.is_expanded = False
        core.load_sheets(tool.Drawing)
        return {"FINISHED"}
@@ -3268,7 +3436,7 @@ class EditElementFilter(bpy.types.Operator, tool.Ifc.Operator):
        bpy.ops.bim.activate_drawing(drawing=element.id(), should_view_from_camera=False)


-class AddReferenceImage(bpy.types.Operator, tool.Ifc.Operator):
+class AddReferenceImage(bpy.types.Operator, tool.Ifc.Operator, ImportHelper):
    bl_idname = "bim.add_reference_image"
    bl_label = "Add Reference Image"
    bl_description = "Add or import reference image to the IFC project"
@@ -3276,9 +3444,6 @@ class AddReferenceImage(bpy.types.Operator, tool.Ifc.Operator):
    bl_options = {"REGISTER", "UNDO"}

    use_relative_path: bpy.props.BoolProperty(name="Use Relative Path", default=True)
-    filepath: bpy.props.StringProperty(
-        name="File Path", description="Filepath used to import from", maxlen=1024, default="", subtype="FILE_PATH"
-    )
    filter_image: bpy.props.BoolProperty(default=True, options={"HIDDEN", "SKIP_SAVE"})
    filter_folder: bpy.props.BoolProperty(default=True, options={"HIDDEN", "SKIP_SAVE"})

@@ -3306,10 +3471,6 @@ class AddReferenceImage(bpy.types.Operator, tool.Ifc.Operator):
        layout.prop(self, "override_existing_image")
        layout.prop(self, "use_existing_object_by_name")

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-
    def _execute(self, context):
        abs_path = Path(self.filepath).absolute().resolve()
        image_filepath = Path(tool.Ifc.get_uri(self.filepath, use_relative_path=self.use_relative_path))
@@ -3353,7 +3514,8 @@ class AddReferenceImage(bpy.types.Operator, tool.Ifc.Operator):
        obj.material_slots[0].material = material
        bpy.ops.bim.add_style()

-        style = ifc_file.by_id(material.BIMStyleProperties.ifc_definition_id)
+        style = tool.Ifc.get_entity(material)
+        assert style
        tool.Style.assign_style_to_object(style, obj)

        # TODO: IfcSurfaceStyleRendering is unnecessary here, added it only because
@@ -266,7 +266,7 @@ def update_titleblocks(self, context):
 def update_should_draw_decorations(self, context: bpy.types.Context) -> None:
    if self.should_draw_decorations:
        # TODO: design a proper text variable templating renderer
-        collection = context.scene.camera.BIMObjectProperties.collection
+        collection = tool.Blender.get_object_bim_props(context.scene.camera).collection
        for obj in collection.objects:
            element = tool.Ifc.get_entity(obj)
            if not element or not tool.Drawing.is_annotation_object_type(element, ["TEXT", "TEXT_LEADER"]):
@@ -32,6 +32,7 @@ from mathutils import Vector
 import re

 VIEW_TITLE_OFFSET_Y = 5
+DRAWING_PADDING = 10
 DEFAULT_POSITION = Vector((30, 30))
 SVG = "{http://www.w3.org/2000/svg}"
 XLINK = "{http://www.w3.org/1999/xlink}"
@@ -113,13 +114,15 @@ class SheetBuilder:
        view_width = self.convert_to_mm(view_root.attrib.get("width"))
        view_height = self.convert_to_mm(view_root.attrib.get("height"))

+        x, y = self.next_drawing_location(layout_root, view_width)
+
        # add background
        if os.path.isfile(underlay_path):
            background = ET.SubElement(view, "image")
            background.attrib["data-type"] = "background"
            background.attrib["xlink:href"] = os.path.relpath(underlay_path, layout_dir)
-            background.attrib["x"] = str(DEFAULT_POSITION.x)
-            background.attrib["y"] = str(DEFAULT_POSITION.y)
+            background.attrib["x"] = str(x)
+            background.attrib["y"] = str(y)
            background.attrib["width"] = str(view_width)
            background.attrib["height"] = str(view_height)

@@ -128,16 +131,49 @@ class SheetBuilder:
            foreground = ET.SubElement(view, "image")
            foreground.attrib["data-type"] = "foreground"
            foreground.attrib["xlink:href"] = os.path.relpath(drawing_path, layout_dir)
-            foreground.attrib["x"] = str(DEFAULT_POSITION.x)
-            foreground.attrib["y"] = str(DEFAULT_POSITION.y)
+            foreground.attrib["x"] = str(x)
+            foreground.attrib["y"] = str(y)
            foreground.attrib["width"] = str(view_width)
            foreground.attrib["height"] = str(view_height)

-        self.add_view_title(
-            DEFAULT_POSITION.x, view_height + DEFAULT_POSITION.y + VIEW_TITLE_OFFSET_Y, view, layout_dir
-        )
+        self.add_view_title(x, view_height + y + VIEW_TITLE_OFFSET_Y, view, layout_dir)
        layout_tree.write(layout_path)

+    def next_drawing_location(self, layout_root: ET.Element, next_width: float) -> list:
+        titleblocks = layout_root.findall(f'{SVG}g[@data-type="titleblock"]')
+        drawings = layout_root.findall(f'{SVG}g[@data-type="drawing"]')
+
+        # how wide is the title block frame
+        try:
+            titleblock_width = self.convert_to_mm(titleblocks[0][0].attrib.get("width"))
+        except (IndexError, AttributeError):
+            titleblock_width = 840.0
+
+        # where does the last drawing finish
+        try:
+            last = drawings[-1][0]
+            last_width = self.convert_to_mm(last.attrib.get("width"))
+            last_x = self.convert_to_mm(last.attrib.get("x"))
+            last_y = self.convert_to_mm(last.attrib.get("y"))
+        except (IndexError, AttributeError):
+            return [DEFAULT_POSITION.x, DEFAULT_POSITION.y]
+
+        # check if the new drawing fits in the current row
+        if last_x + last_width + DRAWING_PADDING + next_width + DEFAULT_POSITION.x < titleblock_width:
+            return [last_x + last_width + DRAWING_PADDING, last_y]
+
+        # start a new row, find the y
+        for drawing in drawings:
+            for image in drawing:
+                try:
+                    image_y = self.convert_to_mm(image.attrib.get("y"))
+                    image_height = self.convert_to_mm(image.attrib.get("height"))
+                except AttributeError:
+                    return [DEFAULT_POSITION.x, DEFAULT_POSITION.y]
+                if image_y + image_height + DRAWING_PADDING > last_y:
+                    last_y = image_y + image_height + DRAWING_PADDING
+        return [DEFAULT_POSITION.x, last_y]
+
    def update_sheet_drawing_sizes(self, sheet: ifcopenshell.entity_instance) -> None:
        ET.register_namespace("", "http://www.w3.org/2000/svg")

@@ -221,6 +257,8 @@ class SheetBuilder:
        view_width = self.convert_to_mm(view_root.attrib.get("width"))
        view_height = self.convert_to_mm(view_root.attrib.get("height"))

+        x, y = self.next_drawing_location(layout_root, view_width)
+
        view = ET.SubElement(layout_root, "g")
        view.attrib["data-id"] = str(reference.id())
        view.attrib["data-type"] = document.Scope.lower()
@@ -229,14 +267,12 @@ class SheetBuilder:
        foreground = ET.SubElement(view, "image")
        foreground.attrib["data-type"] = "content"
        foreground.attrib["xlink:href"] = os.path.relpath(view_path, layout_dir)
-        foreground.attrib["x"] = str(DEFAULT_POSITION.x)
-        foreground.attrib["y"] = str(DEFAULT_POSITION.y)
+        foreground.attrib["x"] = str(x)
+        foreground.attrib["y"] = str(y)
        foreground.attrib["width"] = str(view_width)
        foreground.attrib["height"] = str(view_height)

-        self.add_view_title(
-            DEFAULT_POSITION.x, view_height + DEFAULT_POSITION.y + VIEW_TITLE_OFFSET_Y, view, layout_dir
-        )
+        self.add_view_title(x, view_height + y + VIEW_TITLE_OFFSET_Y, view, layout_dir)
        layout_tree.write(layout_path)

    def add_view_title(self, x: float, y: float, parent: ET.Element, layout_dir: str) -> None:
@@ -1128,7 +1128,12 @@ class SvgWriter:

            def get_text():
                radius = (points[-1].co - points[-2].co).length
-                radius = helper.format_distance(radius, precision=self.precision, decimal_places=self.decimal_places)
+                radius = helper.format_distance(
+                    radius,
+                    precision=self.precision,
+                    decimal_places=self.decimal_places,
+                    custom_unit=dimension_data["custom_unit"],
+                )
                text = f"R{radius}"
                return text

@@ -1256,6 +1261,7 @@ class SvgWriter:
                    text_prefix=dimension_data["text_prefix"],
                    text_suffix=dimension_data["text_suffix"],
                    fill_bg=dimension_data["fill_bg"],
+                    custom_unit=dimension_data["custom_unit"],
                )

    def draw_dimension_annotations(self, obj):
@@ -1280,6 +1286,7 @@ class SvgWriter:
                    text_prefix=dimension_data["text_prefix"],
                    text_suffix=dimension_data["text_suffix"],
                    fill_bg=dimension_data["fill_bg"],
+                    custom_unit=dimension_data["custom_unit"],
                )

    def draw_measureit_arch_dimension_annotations(self):
@@ -1306,6 +1313,7 @@ class SvgWriter:
        text_prefix="",
        text_suffix="",
        fill_bg=False,
+        custom_unit=None,
    ):
        offset = Vector([self.raw_width, self.raw_height]) / 2
        v0 = self.project_point_onto_camera(v0_global)
@@ -1339,6 +1347,7 @@ class SvgWriter:
                precision=self.precision,
                decimal_places=self.decimal_places,
                suppress_zero_inches=suppress_zero_inches,
+                custom_unit=custom_unit,
            )
            text = text_prefix + str(dimension) + text_suffix
        else:
@@ -183,7 +183,14 @@ class BIM_PT_drawing_underlay(Panel):

        if not dprops.drawing_styles:
            return
-        layout.template_list("BIM_UL_generic", "", dprops, "drawing_styles", props, "active_drawing_style_index")
+        layout.template_list(
+            "BIM_UL_generic",
+            "BIM_UL_generic_drawing_styles",
+            dprops,
+            "drawing_styles",
+            props,
+            "active_drawing_style_index",
+        )

        if not drawing_index_is_valid:
            return
@@ -326,7 +333,12 @@ class BIM_PT_schedules(Panel):
                row.operator("bim.remove_schedule", icon="X", text="").schedule = active_schedule.ifc_definition_id

            self.layout.template_list(
-                "BIM_UL_generic", "", self.props, "schedules", self.props, "active_schedule_index"
+                "BIM_UL_generic",
+                "BIM_UL_generic_schedules",
+                self.props,
+                "schedules",
+                self.props,
+                "active_schedule_index",
            )


@@ -373,7 +385,12 @@ class BIM_PT_references(Panel):
                row.operator("bim.remove_reference", icon="X", text="").reference = active_reference.ifc_definition_id

            self.layout.template_list(
-                "BIM_UL_generic", "", self.props, "references", self.props, "active_reference_index"
+                "BIM_UL_generic",
+                "BIM_UL_generic_references",
+                self.props,
+                "references",
+                self.props,
+                "active_reference_index",
            )


@@ -27,7 +27,7 @@ import ifcopenshell.util.representation
 from bonsai.bim.module.drawing.data import DecoratorData, AnnotationData
 from bonsai.bim.helper import prop_with_search
 from bpy.types import WorkSpaceTool
-from typing import Union
+from functools import partial


 class LaunchAnnotationTypeManager(bpy.types.Operator):
@@ -135,23 +135,9 @@ class AnnotationTool(WorkSpaceTool):
        AnnotationToolUI.draw(context, layout)


-def add_layout_hotkey_operator(
-    layout: bpy.types.UILayout, text: str, hotkey: str, description: Union[str, None]
-) -> tuple[bpy.types.OperatorProperties, bpy.types.UILayout]:
-    modifiers = {
-        "A": "EVENT_ALT",
-        "S": "EVENT_SHIFT",
-    }
-    modifier, key = hotkey.split("_")
-
-    row = layout.row(align=True)
-    row.label(text="", icon=modifiers[modifier])
-    row.label(text="", icon=f"EVENT_{key}")
-
-    op = row.operator("bim.annotation_hotkey", text=text)
-    op.hotkey = hotkey
-    op.description = description
-    return op, row
+add_layout_hotkey_operator = partial(
+    tool.Blender.add_layout_hotkey_operator, tool_name="annotation", module_name=__name__
+)


 # TODO: move to operator
@@ -265,8 +251,8 @@ class AnnotationToolUI:

 class Hotkey(bpy.types.Operator, tool.Ifc.Operator):
    bl_idname = "bim.annotation_hotkey"
-    bl_label = "Hotkey"
-    bl_options = {"REGISTER", "UNDO"}
+    bl_label = ""
+    bl_options = {"REGISTER", "UNDO", "INTERNAL"}
    hotkey: bpy.props.StringProperty()
    description: bpy.props.StringProperty()

@@ -24,14 +24,25 @@ import logging
 import tempfile
 import ifcopenshell
 import bonsai.tool as tool
+from bpy_extras.io_utils import ExportHelper, ImportHelper


-class ExecuteIfcFM(bpy.types.Operator):
+class ExecuteIfcFM(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.execute_ifcfm"
    bl_label = "Execute IfcFM"
-    file_format: bpy.props.StringProperty()
+    bl_description = "Export IfcFM data as a spreadsheet."
+
    filter_glob: bpy.props.StringProperty(default="*.csv;*.ods;*.xlsx", options={"HIDDEN"})
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
+
+    @property
+    def filename_ext(self) -> str:
+        props = bpy.context.scene.BIMFMProperties
+        return f".{props.format}"
+
+    def draw(self, context):
+        layout = self.layout
+        props = context.scene.BIMFMProperties
+        layout.prop(props, "format")

    @classmethod
    def poll(cls, context):
@@ -41,13 +52,6 @@ class ExecuteIfcFM(bpy.types.Operator):
            return False
        return True

-    def invoke(self, context, event):
-        props = context.scene.BIMFMProperties
-        self.filepath = bpy.path.ensure_ext(bpy.data.filepath, f".{props.format}")
-        WindowManager = context.window_manager
-        WindowManager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-
    def execute(self, context):
        props = context.scene.BIMFMProperties
        ifc_file = tool.Ifc.get()
@@ -82,12 +86,12 @@ class ExecuteIfcFM(bpy.types.Operator):
        return {"FINISHED"}


-class SelectFMSpreadsheetFiles(bpy.types.Operator):
+class SelectFMSpreadsheetFiles(bpy.types.Operator, ImportHelper):
    bl_idname = "bim.select_fm_spreadsheet_files"
    bl_label = "Select FM Spreadsheet Files"
+    bl_description = "Select FM spreadsheets to merge."
    bl_options = {"REGISTER", "UNDO"}
    filter_glob: bpy.props.StringProperty(default="*.ods;*.xlsx", options={"HIDDEN"})
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
    files: bpy.props.CollectionProperty(name="File Path", type=bpy.types.OperatorFileListElement)

    def execute(self, context):
@@ -99,16 +103,22 @@ class SelectFMSpreadsheetFiles(bpy.types.Operator):
            new.name = os.path.join(dirname, f.name)
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}

-
-class ExecuteIfcFMFederate(bpy.types.Operator):
+class ExecuteIfcFMFederate(bpy.types.Operator, ExportHelper):
    bl_idname = "bim.execute_ifcfm_federate"
    bl_label = "Merge IfcFM SpreadSheets"
+    bl_description = "Merge added IfcFM spreadsheets."
    filter_glob: bpy.props.StringProperty(default="*.ods;*.xlsx", options={"HIDDEN"})
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
+
+    @property
+    def filename_ext(self) -> str:
+        props = bpy.context.scene.BIMFMProperties
+        return f".{props.format}"
+
+    def draw(self, context):
+        layout = self.layout
+        props = context.scene.BIMFMProperties
+        layout.prop(props, "format")

    @classmethod
    def poll(cls, context):
@@ -118,13 +128,6 @@ class ExecuteIfcFMFederate(bpy.types.Operator):
            return False
        return True

-    def invoke(self, context, event):
-        props = context.scene.BIMFMProperties
-        self.filepath = bpy.path.ensure_ext(bpy.data.filepath, f".{props.format}")
-        WindowManager = context.window_manager
-        WindowManager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-
    def execute(self, context):
        props = context.scene.BIMFMProperties
        parser = ifcfm.Parser(preset=props.engine)
@@ -19,6 +19,7 @@
 import bpy
 from . import ui, prop, operator
 from bpy.app.handlers import persistent
+import ifcopenshell.util.element

 classes = (
    operator.AddCurvelikeItem,
@@ -102,9 +103,14 @@ def block_scale(scene: bpy.types.Scene) -> None:
    import bonsai.tool as tool

    if obj := (getattr(bpy.context, "active_object", None) or bpy.context.view_layer.objects.active):
-        if isinstance(obj, bpy.types.Object) and obj.BIMObjectProperties.ifc_definition_id:
-            if obj.scale != (1, 1, 1):
-                obj.scale = (1, 1, 1)
+        if isinstance(obj, bpy.types.Object) and tool.Blender.get_ifc_definition_id(obj):
+            if obj.type == "CAMERA":
+                camera = tool.Ifc.get_entity(obj)
+                if ifcopenshell.util.element.get_pset(camera, "EPset_Drawing", "TargetView") == "REFLECTED_PLAN_VIEW":
+                    obj.scale = (-1, -1, -1)
+            else:
+                if obj.scale != (1, 1, 1):
+                    obj.scale = (1, 1, 1)
        elif isinstance(obj, bpy.types.Mesh) and tool.Geometry.get_mesh_props(obj).ifc_definition_id:
            if obj.scale != (1, 1, 1):
                obj.scale = (1, 1, 1)
@@ -118,6 +124,7 @@ def register():
    operator.OverrideDuplicateMoveLinkedMacro.define("BIM_OT_override_object_duplicate_move_linked")
    operator.OverrideDuplicateMoveLinkedMacro.define("TRANSFORM_OT_translate")
    operator.DuplicateMoveLinkedAggregateMacro.define("BIM_OT_object_duplicate_move_linked_aggregate")
+    operator.DuplicateMoveLinkedAggregateMacro.define("BIM_OT_override_move")
    operator.DuplicateMoveLinkedAggregateMacro.define("TRANSFORM_OT_translate")
    operator.OverrideMoveMacro.define("BIM_OT_override_move")
    operator.OverrideMoveMacro.define("TRANSFORM_OT_translate")
@@ -157,15 +157,17 @@ class RepresentationsData:
        if not cls.data["representations"]:
            return []
        obj = tool.Geometry.get_active_or_representation_obj()
+        assert obj
        if not obj.data:
            return []
        element = tool.Ifc.get_entity(obj)
+        assert element
        base_representation = tool.Geometry.get_active_representation(obj)
        if not base_representation:
            return []  # Maybe in profile editing mode

        # shape aspects matching context of the active representation
-        matching_shape_aspects = []
+        matching_shape_aspects: list[ifcopenshell.entity_instance] = []
        for shape_aspect in ifcopenshell.util.element.get_shape_aspects(element):
            matching_representation = tool.Geometry.get_shape_aspect_representation(shape_aspect, base_representation)
            if matching_representation:
@@ -128,6 +128,8 @@ class ItemDecorator:
        cls.is_installed = False

    def draw_batch(self, shader_type, content_pos, color, indices=None):
+        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
+            return
        shader = self.line_shader if shader_type == "LINES" else self.shader
        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
        shader.uniform_float("color", color)
@@ -464,7 +464,8 @@ class UpdateRepresentation(bpy.types.Operator, tool.Ifc.Operator):
        assert tool.Geometry.is_data_supported_for_adding_representation(data)
        mprops = tool.Geometry.get_mesh_props(data)

-        product = self.file.by_id(obj.BIMObjectProperties.ifc_definition_id)
+        product = tool.Ifc.get_entity(obj)
+        assert product
        material = ifcopenshell.util.element.get_material(product, should_skip_usage=True)

        # NOTE: Currently iterator doesn't detect whether opening is actually affected the representation
@@ -903,7 +904,7 @@ class OverrideOutlinerDelete(bpy.types.Operator):
            if element := tool.Ifc.get_entity(obj):
                if tool.Geometry.is_locked(element):
                    self.report({"ERROR"}, lock_error_message(obj.name))
-                    if collection := obj.BIMObjectProperties.collection:
+                    if collection := tool.Blender.get_object_bim_props(obj).collection:
                        collections_to_delete.discard(collection)
                    continue
                tool.Geometry.delete_ifc_object(obj)
@@ -1067,7 +1068,7 @@ class OverrideDuplicateMove(bpy.types.Operator):
                continue

            # clear object's collection so it will be able to have it's own
-            new_obj.BIMObjectProperties.collection = None
+            tool.Blender.get_object_bim_props(new_obj).collection = None
            # copy the actual class
            new = bonsai.core.root.copy_class(tool.Ifc, tool.Collector, tool.Geometry, tool.Root, obj=new_obj)

@@ -1774,8 +1775,8 @@ class OverrideJoin(bpy.types.Operator, tool.Ifc.Operator):
                    obj.select_set(False)
                    self.report(
                        {"ERROR"},
-                        f"IFC join failed - object '{obj}' has a different representation type "
-                        f"({obj_rep.RepresentationType}) than target '{self.target}' ({representation_type}).",
+                        f"IFC join failed - object '{obj.name}' has a different representation type "
+                        f"({obj_rep.RepresentationType})\nthan target '{self.target.name}' ({representation_type}).",
                    )
                    return

@@ -1928,7 +1929,7 @@ class OverrideEscape(bpy.types.Operator):
            tool.Geometry.disable_item_mode()
        elif tool.Model.get_model_props().openings:
            bpy.ops.bim.hide_all_openings()
-        elif context.scene.BIMAggregateProperties.in_aggregate_mode:
+        elif tool.Aggregate.get_aggregate_props().in_aggregate_mode:
            bpy.ops.bim.disable_aggregate_mode()
        elif active_object := context.active_object:
            if tool.Blender.Modifier.try_canceling_editing_modifier_parameters_or_path(active_object):
@@ -1952,24 +1953,26 @@ class OverrideModeSetEdit(bpy.types.Operator, tool.Ifc.Operator):

    def _execute(self, context):
        selected_objs = context.selected_objects  # Purposely exclude active object
+        aprops = tool.Aggregate.get_aggregate_props()
+        nprops = tool.Nest.get_nest_props()

        if self.has_aggregates(selected_objs):
-            if not context.scene.BIMAggregateProperties.in_aggregate_mode:
+            if not aprops.in_aggregate_mode:
                bonsai.core.aggregate.enable_aggregate_mode(tool.Aggregate, context.active_object)
                return {"FINISHED"}

        if self.has_nests(selected_objs):
-            if not context.scene.BIMNestProperties.in_nest_mode:
+            if not nprops.in_nest_mode:
                bonsai.core.nest.enable_nest_mode(tool.Nest, context.active_object)
                return {"FINISHED"}

        if len(selected_objs) == 1 and context.active_object == selected_objs[0]:
            self.handle_single_object(context, context.active_object)
        elif len(selected_objs) == 0:
-            if context.scene.BIMAggregateProperties.in_aggregate_mode:
+            if aprops.in_aggregate_mode:
                bonsai.core.aggregate.disable_aggregate_mode(tool.Aggregate)
                return {"FINISHED"}
-            if context.scene.BIMNestProperties.in_nest_mode:
+            if nprops.in_nest_mode:
                bonsai.core.nest.disable_nest_mode(tool.Nest)
                return {"FINISHED"}
            tool.Geometry.disable_item_mode()
@@ -1980,9 +1983,10 @@ class OverrideModeSetEdit(bpy.types.Operator, tool.Ifc.Operator):
        element = tool.Ifc.get_entity(obj)
        props = tool.Geometry.get_geometry_props()
        pprops = tool.Project.get_project_props()
+        aprops = tool.Aggregate.get_aggregate_props()
        if obj == props.representation_obj:
            self.report({"ERROR"}, f"Element '{obj.name}' is in item mode and cannot be edited directly")
-        elif obj in [o.obj for o in context.scene.BIMAggregateProperties.not_editing_objects]:
+        elif obj in [o.obj for o in aprops.not_editing_objects]:
            obj.select_set(False)
            self.report(
                {"ERROR"}, f"Element '{obj.name}' does not belong to this aggregate and cannot be edited directly"
@@ -2098,7 +2102,8 @@ class OverrideModeSetEdit(bpy.types.Operator, tool.Ifc.Operator):
                continue
            aggregate = ifcopenshell.util.element.get_aggregate(element)
            parts = ifcopenshell.util.element.get_parts(element)
-            if (aggregate or parts) and not bpy.context.scene.BIMAggregateProperties.in_aggregate_mode:
+            props = tool.Aggregate.get_aggregate_props()
+            if (aggregate or parts) and not props.in_aggregate_mode:
                return True
            else:
                return False
@@ -2110,7 +2115,8 @@ class OverrideModeSetEdit(bpy.types.Operator, tool.Ifc.Operator):
                continue
            nest = ifcopenshell.util.element.get_nest(element)
            components = ifcopenshell.util.element.get_components(element)
-            if (nest or components) and not bpy.context.scene.BIMNestProperties.in_nest_mode:
+            props = tool.Nest.get_nest_props()
+            if (nest or components) and not props.in_nest_mode:
                return True
            else:
                return False
@@ -2256,8 +2262,10 @@ class OverrideModeSetObject(bpy.types.Operator, tool.Ifc.Operator):
                return

            old_profile = item.SweptArea
+            profile.ProfileName = old_profile.ProfileName
            for inverse in tool.Ifc.get().get_inverse(old_profile):
                ifcopenshell.util.element.replace_attribute(inverse, old_profile, profile)
+            tool.Profile.replace_profile_in_profiles_ui(old_profile.id(), profile.id())
            ifcopenshell.util.element.remove_deep2(tool.Ifc.get(), old_profile)

            tool.Geometry.reload_representation(props.representation_obj)
@@ -2506,11 +2514,12 @@ class RemoveRepresentationItem(bpy.types.Operator, tool.Ifc.Operator):
        return True

    def _execute(self, context):
-        obj = tool.Geometry.get_active_or_representation_obj()
+        assert (obj := tool.Geometry.get_active_or_representation_obj())
+        assert (element := tool.Ifc.get_entity(obj))
        ifc_file = tool.Ifc.get()

        representation_item = ifc_file.by_id(self.representation_item_id)
-        tool.Geometry.remove_representation_item(representation_item)
+        tool.Geometry.remove_representation_item(representation_item, element)
        tool.Geometry.reload_representation(obj)

        # reload items ui
@@ -2885,6 +2894,15 @@ class ImportRepresentationItems(bpy.types.Operator, tool.Ifc.Operator):
        else:
            assert False, "Unexpected mesh type."

+        if not item_ids:
+            # It is possible that the user has created a shape that
+            # IfcOpenShell cannot render (i.e. boolean clipped everything), but
+            # we still want to edit items. I'm not sure the best way to handle
+            # this, but for now perhaps we can detect when there are no
+            # item_ids at all.
+            representation = tool.Ifc.get_entity(data)
+            item_ids = [i["item"].id() for i in ifcopenshell.util.representation.resolve_items(representation)]
+
        queue = list(set(item_ids))
        processed_ids = set()
        boolean_ids = set()
@@ -3257,7 +3275,7 @@ class OverrideMove(bpy.types.Operator):
            self.new_active_obj = obj

        # Get aggregates
-        props = context.scene.BIMAggregateProperties
+        props = tool.Aggregate.get_aggregate_props()
        not_editing_objs = [o.obj for o in props.not_editing_objects]
        aggregates_to_move = []
        for obj in context.selected_objects:
@@ -3292,7 +3310,7 @@ class OverrideMove(bpy.types.Operator):
            return {"FINISHED"}

        # Get nests
-        props = context.scene.BIMNestProperties
+        props = tool.Nest.get_nest_props()
        not_editing_objs = [o.obj for o in props.not_editing_objects]
        nests_to_move = []
        for obj in context.selected_objects:
@@ -121,7 +121,7 @@ def get_layers_no_active(self, context):
    return LayersData.data["layers_enum_no_active"]


-def update_shape_aspect(self, context):
+def update_shape_aspect(self: "BIMObjectGeometryProperties", context: bpy.types.Context) -> None:
    shape_aspect_id = self.representation_item_shape_aspect
    attrs = self.shape_aspect_attrs

@@ -209,6 +209,7 @@ def update_is_editing_item_layer(self: "BIMObjectGeometryProperties", context: b
        item = ifc_file.by_id(active_ui_item.ifc_definition_id)
        if layer := next(iter(item.LayerAssignment), None):
            self.representation_item_layer = str(layer.id())
+        return

    if "representation_item_layer" in self:
        del self["representation_item_layer"]
@@ -250,9 +251,8 @@ class BIMObjectGeometryProperties(PropertyGroup):
    representation_item_layer: EnumProperty(items=get_layers, name="Representation Item's Layer")

    @property
-    def active_item(self):
-        if 0 <= self.active_item_index < len(self.items):
-            return self.items[self.active_item_index]
+    def active_item(self) -> Union[RepresentationItem, None]:
+        return tool.Blender.get_active_uilist_element(self.items, self.active_item_index)

    if TYPE_CHECKING:
        contexts: str
@@ -283,7 +283,14 @@ class BIMGeometryProperties(PropertyGroup):
    is_changing_mode: BoolProperty(name="Is Changing Mode", default=False)
    mode: EnumProperty(items=get_mode, name="IFC Interaction Mode", update=update_mode)
    representation_obj: PointerProperty(
-        name="Representation Object", type=bpy.types.Object, update=update_representation_obj
+        name="Representation Object",
+        description=(
+            "Only used for Item Mode. When element is in Item Mode, new objects are imported "
+            "for each element's representation item, original element's object is hidden and "
+            "representation_obj pointing to it. None if no object in Item Mode."
+        ),
+        type=bpy.types.Object,
+        update=update_representation_obj,
    )
    item_objs: CollectionProperty(name="Item Objects", type=RepresentationItemObject)

@@ -225,7 +225,7 @@ class BIM_PT_representation_items(Panel):
            RepresentationItemsData.load()

        props = tool.Geometry.get_geometry_props()
-        obj = props.representation_obj or tool.Blender.get_active_object()
+        obj = tool.Geometry.get_active_or_representation_obj()
        assert obj
        props = tool.Geometry.get_object_geometry_props(obj)

@@ -334,9 +334,9 @@ class BIM_PT_connections(Panel):

    @classmethod
    def poll(cls, context):
-        if not context.active_object:
+        if not (obj := context.active_object):
            return False
-        if not tool.Ifc.get_object_by_identifier(context.active_object.BIMObjectProperties.ifc_definition_id):
+        if not tool.Ifc.get_object_by_identifier(tool.Blender.get_ifc_definition_id(obj)):
            return False
        return tool.Ifc.get()

@@ -345,7 +345,6 @@ class BIM_PT_connections(Panel):
            ConnectionsData.load()

        layout = self.layout
-        props = context.active_object.BIMObjectProperties

        if not ConnectionsData.data["connections"] and not ConnectionsData.data["is_connection_realization"]:
            layout.label(text="No connections found")
@@ -480,12 +479,16 @@ class BIM_PT_placement(Panel):

    @classmethod
    def poll(cls, context):
-        return (obj := context.active_object) and obj.BIMObjectProperties.ifc_definition_id
+        return (obj := context.active_object) and tool.Blender.get_ifc_definition_id(obj)

    def draw(self, context):
        if not PlacementData.is_loaded:
            PlacementData.load()

+        obj = context.active_object
+        assert obj
+        props = tool.Blender.get_object_bim_props(obj)
+
        if not PlacementData.data["has_placement"]:
            row = self.layout.row()
            row.label(text="No Object Placement Found")
@@ -496,12 +499,12 @@ class BIM_PT_placement(Panel):
        row = self.layout.row()
        row.prop(context.active_object, "rotation_euler", text="Rotation")

-        if context.active_object.BIMObjectProperties.blender_offset_type != "NONE":
+        if props.blender_offset_type != "NONE":
            row = self.layout.row(align=True)
            row.label(text="Blender Offset", icon="TRACKING_REFINE_FORWARDS")
-            row.label(text=context.active_object.BIMObjectProperties.blender_offset_type)
+            row.label(text=props.blender_offset_type)

-            if context.active_object.BIMObjectProperties.blender_offset_type != "NOT_APPLICABLE":
+            if props.blender_offset_type != "NOT_APPLICABLE":
                row = self.layout.row(align=True)
                row.label(text=PlacementData.data["original_x"], icon="EMPTY_AXIS")
                row.label(text=PlacementData.data["original_y"])
@@ -54,6 +54,8 @@ class GeoreferenceDecorator:
        cls.is_installed = False

    def draw_batch(self, shader_type, content_pos, color, indices=None):
+        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
+            return
        props = tool.Georeference.get_georeference_props()
        self.scale = props.visualization_scale
        content_pos = [v * self.scale for v in content_pos]
@@ -20,6 +20,7 @@ import bpy

 import bonsai.tool as tool
 import bonsai.core.georeference as core
+from bpy_extras.io_utils import ImportHelper
 from bonsai.bim.module.georeference.decorator import GeoreferenceDecorator


@@ -87,22 +88,18 @@ class GetCursorLocation(bpy.types.Operator, tool.Ifc.Operator):
        core.get_cursor_location(tool.Georeference)


-class ImportPlot(bpy.types.Operator, tool.Ifc.Operator):
+class ImportPlot(bpy.types.Operator, tool.Ifc.Operator, ImportHelper):
    bl_idname = "bim.import_plot"
    bl_label = "Import Plot"
    bl_options = {"REGISTER", "UNDO"}
-    bl_description = "Import plot"
-    filepath: bpy.props.StringProperty(subtype="FILE_PATH")
+    bl_description = "Import plot from a csv file."
    filter_glob: bpy.props.StringProperty(default="*.csv", options={"HIDDEN"})
+    filename_ext = ".csv"

-    def execute(self, context):
+    def _execute(self, context):
        core.import_plot(tool.Georeference, filepath=self.filepath)
        return {"FINISHED"}

-    def invoke(self, context, event):
-        context.window_manager.fileselect_add(self)
-        return {"RUNNING_MODAL"}
-

 class EnableEditingWCS(bpy.types.Operator, tool.Ifc.Operator):
    bl_idname = "bim.enable_editing_wcs"
@@ -35,9 +35,13 @@ class LoadGroups(bpy.types.Operator, tool.Ifc.Operator):
        self.expanded_groups = json.loads(context.scene.ExpandedGroups.json_string)
        self.props.groups.clear()

-        for group in tool.Ifc.get().by_type("IfcGroup", include_subtypes=False):
-            if not group.HasAssignments:
-                self.load_group(group)
+        groups = [
+            group for group in tool.Ifc.get().by_type("IfcGroup", include_subtypes=False) if not group.HasAssignments
+        ]
+        sorted_groups = sorted(groups, key=lambda group: group.Name or "Unnamed")
+
+        for group in sorted_groups:
+            self.load_group(group)

        self.props.is_editing = True
        bpy.ops.bim.disable_editing_group()
@@ -51,14 +55,19 @@ class LoadGroups(bpy.types.Operator, tool.Ifc.Operator):
        new.has_children = False
        new.is_expanded = group.id() in self.expanded_groups

-        for rel in group.IsGroupedBy or []:
-            for related_object in rel.RelatedObjects:
-                if not related_object.is_a("IfcGroup"):
-                    continue
-                new.has_children = True
-                if not new.is_expanded:
-                    return
-                self.load_group(related_object, tree_depth=tree_depth + 1)
+        related_groups = [
+            related_object
+            for rel in group.IsGroupedBy or []
+            for related_object in rel.RelatedObjects
+            if related_object.is_a("IfcGroup")
+        ]
+        sorted_related_groups = sorted(related_groups, key=lambda group: group.Name or "Unnamed")
+
+        for related_group in sorted_related_groups:
+            new.has_children = True
+            if not new.is_expanded:
+                return
+            self.load_group(related_group, tree_depth=tree_depth + 1)


 class ToggleGroup(bpy.types.Operator, tool.Ifc.Operator):
@@ -91,9 +91,10 @@ class BIM_PT_object_groups(Panel):

    @classmethod
    def poll(cls, context):
-        if not context.active_object:
+        if not (obj := context.active_object):
            return False
-        return tool.Ifc.get() and context.active_object.BIMObjectProperties.ifc_definition_id
+        props = tool.Blender.get_object_bim_props(obj)
+        return tool.Ifc.get() and props.ifc_definition_id

    def draw(self, context):
        if not ObjectGroupsData.is_loaded:
@@ -374,16 +374,17 @@ class ObjectLog(bpy.types.Operator):

    @classmethod
    def poll(cls, context):
-        if not context.active_object:
+        if not (obj := context.active_object):
            cls.poll_message_set("No Active Object")
-        elif not context.active_object.BIMObjectProperties.ifc_definition_id:
+        elif not tool.Blender.get_ifc_definition_id(obj):
            cls.poll_message_set("Active Object doesn't have an IFC definition")
        else:
            return True

    def execute(self, context):
-
-        step_id = context.active_object.BIMObjectProperties.ifc_definition_id
+        obj = context.active_object
+        assert obj
+        step_id = tool.Blender.get_ifc_definition_id(obj)
        core.entity_log(tool.IfcGit, tool.Ifc, step_id, self)
        return {"FINISHED"}

@@ -52,6 +52,8 @@ class SolarDecorator:
        cls.is_installed = False

    def draw_batch(self, shader_type, content_pos, color, indices=None):
+        if not tool.Blender.validate_shader_batch_data(content_pos, indices):
+            return
        shader = self.line_shader if shader_type == "LINES" else self.shader
        batch = batch_for_shader(shader, shader_type, {"pos": content_pos}, indices=indices)
        shader.uniform_float("color", color)
@@ -638,6 +638,7 @@ class RADIANCE_OT_export_material_mappings(bpy.types.Operator, ExportHelper):
    bl_description = "Export material mappings to a JSON file"

    filename_ext = ".json"
+    filter_glob: bpy.props.StringProperty(default="*.json", options={"HIDDEN"})

    def execute(self, context):
        props = context.scene.radiance_exporter_properties
@@ -71,8 +71,8 @@ def update_sun_path_size(self, context):
    update_sun_path(self)


-def update_display_shadows(self, context):
-    if self.display_shadows:
+def update_shadow_mode(self, context):
+    if self.shadow_mode == "SHADING":
        update_sun_path(self)
        context.scene.render.engine = "BLENDER_WORKBENCH"
        context.scene.display.shading.light = "FLAT"
@@ -82,6 +82,20 @@ def update_display_shadows(self, context):
        context.scene.view_settings.view_transform = "Standard"  # Preserve shading colours
        space = tool.Blender.get_view3d_space()
        space.shading.type = "RENDERED"
+    elif self.shadow_mode == "RENDERING":
+        if context.scene.sun_pos_properties.sun_object is None:
+            bpy.ops.object.light_add(type="SUN", radius=1, align="WORLD", location=(0, 0, 0), scale=(1, 1, 1))
+            bpy.ops.object.move_to_collection(collection_index=0)
+            context.scene.sun_pos_properties.sun_object = bpy.context.active_object
+        update_sun_path(self)
+        context.scene.render.engine = "BLENDER_EEVEE_NEXT"
+        context.scene.display.shading.light = "FLAT"
+        context.scene.display.shading.show_shadows = True
+        context.scene.display.shading.show_object_outline = True
+        context.scene.display.shadow_focus = 1.0
+        context.scene.view_settings.view_transform = "Standard"  # Preserve shading colours
+        space = tool.Blender.get_view3d_space()
+        space.shading.type = "RENDERED"
    else:
        space = tool.Blender.get_view3d_space()
        space.shading.type = "SOLID"
@@ -394,11 +408,27 @@ class BIMSolarProperties(PropertyGroup):
    azimuth: FloatProperty(name="Azimuth")
    elevation: FloatProperty(name="Elevation")
    UTC_zone: FloatProperty(name="UTC Zone")
-    display_shadows: BoolProperty(
-        name="Display Shadows",
-        default=False,
-        description="Enables a visual style to display shadows easily",
-        update=update_display_shadows,
+    shadow_mode: bpy.props.EnumProperty(
+        items=(
+            ("NONE", "No Shadows", "No shadows"),
+            (
+                "SHADING",
+                "Shaded",
+                "Fast shadows sufficient for external shadow analysis based on shading styles",
+                "SHADING_SOLID",
+                1,
+            ),
+            (
+                "RENDERING",
+                "Rendered",
+                "Raycast (Eevee) shadows considering transparency based on rendering styles",
+                "SHADING_RENDERED",
+                2,
+            ),
+        ),
+        name="Shadow Mode",
+        description="How to display shadows in the scene",
+        update=update_shadow_mode,
    )
    display_sun_path: BoolProperty(
        name="Display Sun Path",
@@ -236,8 +236,14 @@ class BIM_PT_solar(bpy.types.Panel):
            row.operator("bim.move_sun_path_to_3d_cursor")

        row = self.layout.row(align=True)
-        row.prop(props, "display_shadows", icon="SHADING_RENDERED")
-        row.prop(context.scene.display.shading, "shadow_intensity", text="Shadow Intensity")
+        row.prop(props, "shadow_mode", icon="SHADING_RENDERED", expand=True)
+
+        if props.shadow_mode == "SHADING":
+            row = self.layout.row()
+            row.prop(context.scene.display.shading, "shadow_intensity", text="Shadow Intensity")
+        elif props.shadow_mode == "RENDERING":
+            row = self.layout.row()
+            row.prop(context.scene.sun_pos_properties.sun_object.data, "energy", text="Sun Intensity")

        row = self.layout.row(align=True)
        row.operator("bim.view_from_sun", icon="LIGHT_HEMI")
--- a/Show More
+++ b/Show More