Linked IFC projects enhancement (multiple links to same project file) (#7607)

* Linked IFC projects enhancement (multiple links to same project file)

- Implement link management system using UUIDs as identifiers to support multiple links to the same IFC file
- Add georeferencing compatibility detection and UI display (NONE, NOT_COMPATIBLE, PARTIAL_COMPATIBLE, FULL_COMPATIBLE)
- Support for duplicate link creation with Shift+D shortcut and automatic position offset
- Add false origin and project north calculation from 3D cursor for MANUAL mode
- Only store one cache per file, regardless of the amount of links
- Prevent duplicate links based on filepath and position comparison
- Improve error handling for missing files and loading failures
- Update tests

* Remove duplicate georef UI

I try to avoid duplicate UI (especially for one that can be as
sophisticated as georef - e.g. missing is WCS) as it means double the
code, double the tests, potential user confusion. BTW the note about
vertical datum isn't quite accurate as it may be included in the CRS
definition so vertical datum is optional.

* Remove depsgraph_update_post handler for update_link_ui_on_transform as per core developer feedback

* Move get_projected_crs to geolocation module

* Refactor get_projected_crs to simplify as per core developer feedback

* Remove unused import of bonsai.tool from project module

* Use IfcDocumentInformation per linked file and IfcDocumentReference for locaiton information

* Refactor SaveBlendMetadataFile operator to remove  try-except blocks and remove linked projects collections since they are recreated by bonsai

* Cleanup removing empty collection instances for linked models in metadata.blend file and call determine_georeferencing_compatibility on link reload

* Add locking mechanism for linked models and update UI to reflect lock status

* Update logic that track IFC to execute_ifc_duplicate_operator instead of having it in execute() which does not track IFC undo/redo

* Refactor link handling to use get_link_empty_handle and set_link_empty_handle methods which in turn use the standard blender-ifc integrations patters (tool.Ifc.get_object(doc_reference) and tool.Ifc.link(doc_reference, empty_handle)

* remove operator.DuplicateLink and move it to tool.Project.duplicate_link()

* Refactor link handling to use sequential identifiers (no need for STEP ID DocRef)

* Refactor IFC linking logic to handle cases without a parent IFC file loaded. Firts link flase origin becomes parent origin

* Lock should not affect selection.

This makes it consistent with grid / spatial lock, and also toggle
selectability is already implemented.

* Remove unnecessary check for loaded library as Blender seems to do this internally already

* Rename util to get_crs because in IFC4X3 you can also have geographic CRS not just projected

* Remove unnecessary call to determine_georeferencing_compatibility

This function is already always called prior to calculate_link_position
so shouldn't be called here. It's also a very expensive function: as it
currently stands, just to link a single IFC, ifcopenshell.open() is
called 3 times. This reduces it to 2.

* Store CRS as metadata for linked models, and compare metadata when indicating georeferencing compatibility

Previously, to check georeferencing compatibility, ifcopenshell.open()
was used. When linking large models, this adds considerable time and
memory usage. This instead captures the georef as standard metadata in
our .cache.json. This now reduces the ifcopenshell.open() calls back
down to only 1 as necessary (see previous commit).

* Use link index instead of link name to fetch link collection item

Link name runs into issues with name uniqueness. This is why you created
a function for "get next link ID". After this refactoring, we can no
longer worry about uniqueness and that function may be removed.

* Simplify reloadlink into just unload and reload (with cache disabled)

This function should not be responsible for editing any data.

* Remove unnecessary get_next_link_id as names no longer need uniqueness

This now frees up the name variable to track a more meaningful, human
name like IfcDocumentInformation's Name attribute.

* Rewrite get / set link_empty_handle to just use the link directly

This prevents needless logic to fetch the link and also removes issues
related to duplicate names.

* Temporarily remove logic in prop callback

Right now, pretty much all the logic is done in a prop callback. In
general logic in prop callbacks should be minimised, since it's hard to
test and easily triggered as a domino effect of another change, and may
also impact undo/redo.

* Remove code that unnecessarily removes cache

This code removes cache, which means any project unlinking an IFC auto
clears the cache for any other project which doesn't make sense, and
also breaks the ability to readd it quickly.

* Rewrite link, unlink, load, and unload IFC

There were a few issues tackled here:

 - Operators that change any IFC data must use tool.Ifc.Operator and
_execute, otherwise undo/redo will break. That's one of the risks of
using prop callbacks, as it is not explicit when an IFC edit happens.
 - The usage of IfcDocumentReference was not correct. The Location
should store the URL, _not_ the position. The position should be in the
Identification attribute.
 - The URL was stored in IfcDocumentInformation location, which does not
work in IFC2X3. There are a few changes here to make it IFC2X3
compatible.
 - Generally move logic in operators, not prop callback.

* Remove restriction around manual mode.

Users should be able to use manual mode if they want.

* Restore AUTOMATIC mode to identical behaviour to file open

This is the first step to reusing cache files agnostic of the host.

* Revert tests for a fresh start for updating tests

* Revert "test_feature - clean up .ifc.cache. files after test was executed"

This reverts commit 99ae768ddf.

* Update tests and reimplement calculations for matrix of empty handle

Previously, the empty would always be placed at the origin, unless a
"position" offset was present. This is a problem, because the "position"
is simply a local offset relative to the Blender cache! If the cache was
regenerated, the offsets would be outdated. Also, the cache appeared in
different locations depending on the false origin mode, so the offset
would mean different things to different people.

Instead, a more robust method is:

 1. When you link a file, a Blender cache is generated. The Blender
origin of this cache is arbitrary! It depends on the user's false origin
mode and is purely a Blender session specific thing.
 2. When you load a link, a link is _always_ loaded into the correct
location with regards to IFC global coordinates. All math is done from
the perspective of IFC.
 3. If you choose to transform (move / rotate / scale!?) this link from
its correct location, that gets recorded as a 4x4 transformation matrix.
Note: I haven't implemented this properly yet.

Tests all pass, with a minor modification to the new behaviour that
false origin mode now won't affect the location it ends up in, only the
generation of the cache.

* Remove arbitrary convention around display name

Not needed anymore now that A/M/D is a detail and not significant on
actual coordinates, and also that the UUID is no longer needed.

* Simplify implementation of loading linked models when opening an IFC

* Move link matrix calculation from operator to tool for reuse

* Implement editing link location and calculation of transformation matrix

I changed my mind on the is_locked thing, since it isn't clear to the
user that locking need to be done to save changes.

* Remove old is_locked, prop update callback no longer needed (dedicated operator instead), remove old calculation code

* Simplify code related to placed_as_per_georef

* For now, simple skip for duplicate / delete

IMO duplicate / delete / move a link are very rare and explicit
operations.

* Update tests

* Remove host_model coordinate data as cache is no longer host model dependent

* Move icons outside list because there are too many

* Minor tweaks

---------

Co-authored-by: Dion Moult <dionmoult@gmail.com>
Co-authored-by: Dion Moult <dion@thinkmoult.com>

.gitignore

@@ -82,6 +82,8 @@ src/bonsai/bonsai/translations.py
 
 # bonsai test temp files
 src/bonsai/test/files/temp
+src/bonsai/test/files/basic.ifc.cache.blend
+src/bonsai/test/files/basic.ifc.cache.sqlite
 
 # bonsai data
 src/bonsai/bonsai/bim/data/build/

src/bonsai/bonsai/bim/export_ifc.py

@@ -52,7 +52,6 @@ class IfcExporter:
         self.set_header()
         IfcStore.update_cache()
         self.sync_all_objects()
-        tool.Project.save_linked_models_to_ifc()
         extension = self.ifc_export_settings.output_file.split(".")[-1].lower()
         if extension == "ifczip":
             with tempfile.TemporaryDirectory() as unzipped_path:

src/bonsai/bonsai/bim/module/drawing/operator.py

@@ -928,7 +928,7 @@ class CreateDrawing(bpy.types.Operator):
 
         props = tool.Project.get_project_props()
         for link in props.get_loaded_links_for_drawings():
-            files[link.name] = self.get_linked_file(link)
+            files[link.filepath] = self.get_linked_file(link)
 
         target_view = ifcopenshell.util.element.get_psets(self.camera_element)["EPset_Drawing"]["TargetView"]
         self.setup_serialiser(target_view)
@@ -1374,7 +1374,7 @@ class CreateDrawing(bpy.types.Operator):
         return True
 
     def get_linked_file(self, link: "Link") -> ifcopenshell.file:
-        link_path = link.name
+        link_path = link.filepath
         ifc_file = IfcStore.session_files.get(link_path, None)
         if ifc_file is not None:
             return ifc_file

src/bonsai/bonsai/bim/module/drawing/ui.py

@@ -89,7 +89,7 @@ class BIM_PT_camera(Panel):
                     for link in links:
                         row = panel.row(align=True)
                         split = row.split(factor=0.9)
-                        split.label(text=link.name, icon="FILE")
+                        split.label(text=link.filepath, icon="FILE")
                         split.prop(link, "include_in_drawings", text="")
                 else:
                     panel.label(text="No IFC projects linked and loaded.")

src/bonsai/bonsai/bim/module/geometry/operator.py

@@ -902,6 +902,7 @@ class OverrideDelete(bpy.types.Operator):
 
             if not is_valid_data_block:
                 continue
+            
             element = tool.Ifc.get_entity(obj)
             if element:
                 if tool.Geometry.is_locked(element):
@@ -912,6 +913,9 @@ class OverrideDelete(bpy.types.Operator):
                 if ifcopenshell.util.element.get_pset(element, "BBIM_Array"):
                     self.report({"INFO"}, "Elements that are part of an array cannot be deleted.")
                     continue
+                if element.is_a("IfcDocumentReference"):
+                    self.report({"INFO"}, "Linked models cannot be deleted.")
+                    continue
                 if element.is_a("IfcGridAxis"):
                     # Deleting the last W axis is OK
                     if ((grid := element.PartOfU) and len(grid[0].UAxes) == 1) or (
@@ -1208,6 +1212,11 @@ class OverrideDuplicateMove(bpy.types.Operator):
                 operator.report({"ERROR"}, f"Drawing '{obj.name}' not duplicated.")
                 continue
 
+            if element.is_a("IfcDocumentReference"):
+                objects_to_remove.add(obj)
+                operator.report({"ERROR"}, f"Linked model '{obj.name}' not duplicated.")
+                continue
+
             if tool.Geometry.is_locked(element):
                 objects_to_remove.add(obj)
                 operator.report({"ERROR"}, lock_error_message(obj.name))

src/bonsai/bonsai/bim/module/georeference/operator.py

@@ -51,7 +51,7 @@ class RemoveGeoreferencing(bpy.types.Operator, tool.Ifc.Operator):
     bl_description = "Remove the georeferencing"
 
     def _execute(self, context):
-        core.remove_georeferencing(tool.Ifc)
+        core.remove_georeferencing(tool.Ifc, tool.Georeference)
 
 
 class EditGeoreferencing(bpy.types.Operator, tool.Ifc.Operator):

src/bonsai/bonsai/bim/module/georeference/prop.py

@@ -224,16 +224,12 @@ class BIMGeoreferenceProperties(PropertyGroup):
     x_axis_ordinate: StringProperty(name="X Axis Ordinate", update=update_grid_north_vector)
     x_axis_is_null: BoolProperty(name="X Axis Is Null")
 
-    # These are only for reference to capture data about a host model from a linked model
-    # If you relink a model from a new host origin, we can autodetect it in theory with this
-    host_model_origin: StringProperty(name="Host Model Origin")
-    host_model_origin_si: StringProperty(name="Host Model Origin SI")
-    host_model_project_north: StringProperty(name="Host Model Angle to Grid North")
-
     # This is the ENH in project units and SI units of the Blender session's 0,0,0.
     # These are only for reference, using tool.Georeference.set_model_origin on
     # project load, project create, and when linking for the first time from an
     # empty Blender session.
+    model_is_georeferenced: BoolProperty(name="Model Is Georeferenced")
+    model_crs: StringProperty(name="Model CRS")
     model_origin: StringProperty(name="Model Origin")
     model_origin_si: StringProperty(name="Model Origin SI")
     model_project_north: StringProperty(name="Model Angle to Grid North")
@@ -275,10 +271,6 @@ class BIMGeoreferenceProperties(PropertyGroup):
         x_axis_ordinate: str
         x_axis_is_null: bool
 
-        host_model_origin: str
-        host_model_origin_si: str
-        host_model_project_north: str
-
         model_origin: str
         model_origin_si: str
         model_project_north: str

src/bonsai/bonsai/bim/module/project/__init__.py

@@ -31,27 +31,31 @@ classes = (
     operator.BIM_OT_load_clipping_planes,
     operator.BIM_OT_save_clipping_planes,
     operator.ChangeLibraryElement,
+    operator.ClearMeasurement,
     operator.ClearRecentIFCProjects,
     operator.CreateClippingPlane,
     operator.CreateProject,
     operator.DisableCulling,
     operator.DisableEditingHeader,
+    operator.DisableEditingLink,
     operator.EditHeader,
+    operator.EditLink,
     operator.EditProjectLibrary,
     operator.EnableCulling,
     operator.EnableEditingHeader,
+    operator.EnableEditingLink,
     operator.ExportIFC,
     operator.FlipClippingPlane,
     operator.IFCFileHandlerOperator,
     operator.ImageScalingTool,
     operator.LinkIfc,
+    operator.LoadBlendMetadataAndIFC,
     operator.LoadLink,
     operator.LoadLinkedProject,
     operator.LoadProject,
     operator.LoadProjectElements,
-    operator.MeasureTool,
     operator.MeasureFaceAreaTool,
-    operator.ClearMeasurement,
+    operator.MeasureTool,
     operator.NewProject,
     operator.QueryLinkedElement,
     operator.RefreshClippingPlanes,
@@ -69,7 +73,6 @@ classes = (
     operator.UnassignLibraryDeclaration,
     operator.UnlinkIfc,
     operator.UnloadLink,
-    operator.LoadBlendMetadataAndIFC,
     workspace.ExploreHotkey,
     prop.LibraryBreadcrumb,
     prop.LibraryElement,

src/bonsai/bonsai/bim/module/project/operator.py

@@ -18,6 +18,7 @@
 
 import datetime
 import json
+import math
 import logging
 import os
 import subprocess
@@ -59,6 +60,15 @@ import bonsai.core.project as core
 import bonsai.tool as tool
 from bonsai.bim import export_ifc, import_ifc
 from bonsai.bim.ifc import IfcStore
+from bonsai.bim.ui import IFCFileSelector
+from bonsai.bim import import_ifc
+from bonsai.bim import export_ifc
+from math import radians, degrees
+from pathlib import Path
+from collections import defaultdict
+from mathutils import Vector, Matrix
+from bpy.app.handlers import persistent
+from ifcopenshell.geom import ShapeElementType
 from bonsai.bim.module.model.decorator import FaceAreaDecorator, PolylineDecorator
 from bonsai.bim.module.model.polyline import PolylineOperator
 from bonsai.bim.module.project.data import LinksData, ProjectLibraryData
@@ -1321,7 +1331,7 @@ class ToggleFilterCategories(bpy.types.Operator):
         return {"FINISHED"}
 
 
-class LinkIfc(bpy.types.Operator, ImportHelper):
+class LinkIfc(bpy.types.Operator, ImportHelper, tool.Ifc.Operator):
     bl_idname = "bim.link_ifc"
     bl_label = "Link IFC"
     bl_options = {"REGISTER", "UNDO"}
@@ -1360,134 +1370,148 @@ class LinkIfc(bpy.types.Operator, ImportHelper):
             row = self.layout.row()
             row.prop(pprops, "project_north")
 
-    def execute(self, context):
+    def invoke(self, context, event):
+        pprops = tool.Project.get_project_props()
+
+        # Populate false origin and project north from 3D cursor for user convenience
+        cursor = context.scene.cursor
+        cursor_loc = cursor.location
+        cursor_rot = cursor.rotation_euler
+        angle = -cursor_rot.z
+
+        # Calculate false origin based on the provided formulas
+        # x = -3Dcursor.x * cos(angle) - 3Dcursor.y * sin(angle)
+        # y = 3Dcursor.x * sin(angle) - 3Dcursor.y * cos(angle)
+        # z = -3Dcursor.z
+        false_origin_x = -cursor_loc.x * math.cos(angle) - cursor_loc.y * math.sin(angle)
+        false_origin_y = cursor_loc.x * math.sin(angle) - cursor_loc.y * math.cos(angle)
+        false_origin_z = -cursor_loc.z
+
+        # Set the false_origin value
+        pprops.false_origin = f"{false_origin_x:.3f},{false_origin_y:.3f},{false_origin_z:.3f}"
+        pprops.project_north = str(round(math.degrees(angle), 1))
+
+        return super().invoke(context, event)
+
+    def _execute(self, context):
         start = time.time()
         files = [f.name for f in self.files] if self.files else [self.filepath]
+
+        if not files or all(not f or not f.strip() for f in files):
+            self.report({"ERROR"}, "No file selected")
+            return {"CANCELLED"}
+
+        existing_links = tool.Project.get_linked_models_documents() if tool.Ifc.get() else {}
         for filename in files:
+            if not filename or not filename.strip():
+                continue
             filepath = Path(self.directory) / filename
             if bpy.data.filepath and filepath.samefile(bpy.data.filepath):
                 self.report({"INFO"}, "Can't link the current .blend file")
                 continue
             props = tool.Project.get_project_props()
-            new = props.links.add()
             filepath = tool.Ifc.get_uri(filepath, use_relative_path=self.use_relative_path)
+
+            new = props.links.add()
+            if tool.Ifc.get():
+                if not (document := existing_links.get(filepath)):
+                    document = ifcopenshell.api.document.add_information(tool.Ifc.get())
+                    document.Name = Path(filepath).name
+                    document.Scope = "LINKED_MODEL"
+                reference = ifcopenshell.api.document.add_reference(tool.Ifc.get(), information=document)
+                reference[1] = ",".join([str(o) for o in np.eye(4).flatten().tolist()])
+                reference.Location = filepath.replace("\\", "/")
+                new.ifc_definition_id = reference.id()
             new.name = filepath
-            status = bpy.ops.bim.load_link(filepath=filepath, use_cache=self.use_cache)
+            new.filepath = filepath
-            if status == {"CANCELLED"}:
+            bpy.ops.bim.load_link(link_index=-1, use_cache=self.use_cache)
-                error_msg = (
-                    f'Error processing IFC file "{filepath}" '
-                    "was critical and blend file either wasn't saved or wasn't updated. "
-                    "See logs above in system console for details."
-                )
-                print(error_msg)
-                self.report({"ERROR"}, error_msg)
-                return {"FINISHED"}
-        print(f"Finished linking {len(files)} IFCs", time.time() - start)
-        return {"FINISHED"}
 
 
-class UnlinkIfc(bpy.types.Operator):
+class UnlinkIfc(bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.unlink_ifc"
     bl_label = "Unlink IFC"
     bl_options = {"REGISTER", "UNDO"}
     bl_description = "Remove the selected file from the link list"
-    filepath: bpy.props.StringProperty()
+    link_index: bpy.props.IntProperty(name="Link Index")
 
-    def execute(self, context):
+    def _execute(self, context):
-        filepath = Path(self.filepath).as_posix()
-        bpy.ops.bim.unload_link(filepath=filepath)
         props = tool.Project.get_project_props()
-        index = props.links.find(filepath)
+        link = props.links[self.link_index]
-        if index != -1:
+        bpy.ops.bim.unload_link(link_index=self.link_index)
-            props.links.remove(index)
+        if tool.Ifc.get():
-        return {"FINISHED"}
+            reference = tool.Ifc.get().by_id(link.ifc_definition_id)
+            document = tool.Document.get_reference_document(reference)
+            ifcopenshell.api.document.remove_reference(tool.Ifc.get(), reference)
+            if document and not tool.Document.get_document_references(document):
+                ifcopenshell.api.document.remove_information(tool.Ifc.get(), document)
+        props.links.remove(self.link_index)
 
 
-class UnloadLink(bpy.types.Operator):
+class UnloadLink(bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.unload_link"
     bl_label = "Unload Link"
     bl_options = {"REGISTER", "UNDO"}
     bl_description = "Unload the selected linked file"
-    filepath: bpy.props.StringProperty()
+    link_index: bpy.props.IntProperty(name="Link Index")
 
-    def execute(self, context):
+    def _execute(self, context):
-        filepath = tool.Blender.ensure_blender_path_is_abs(Path(self.filepath))
+        link = tool.Project.get_project_props().links[self.link_index]
-        if filepath.suffix.lower() == ".ifc":
+        if obj := tool.Project.get_link_empty_handle(link):
-            filepath = filepath.with_suffix(".ifc.cache.blend")
+            collection = obj.instance_collection
-
+            library = collection.library
-        for library in list(bpy.data.libraries):
+            tool.Ifc.unlink(obj=obj)
-            if tool.Blender.ensure_blender_path_is_abs(Path(library.filepath)) == filepath:
+            bpy.data.objects.remove(obj)
+            if collection.users == 0:
+                bpy.data.collections.remove(collection)
+            if not len([c for c in bpy.data.collections if c.library == library]):
                 bpy.data.libraries.remove(library)
-
-        props = tool.Project.get_project_props()
-        links = props.links
-        link = links[self.filepath]
-        # Let's assume that user might delete it.
-        if empty_handle := link.empty_handle:
-            bpy.data.objects.remove(empty_handle)
-
-        # following lines removes the library also when use_relative_path=True, otherwise it doesn't
-        libraries = bpy.data.libraries
-        for library in libraries:
-            if library.name == self.filepath + ".cache.blend":
-                bpy.data.libraries.remove(library)
-
         link.is_loaded = False
-
-        if not any([l.is_loaded for l in links]):
-            ProjectDecorator.uninstall()
-        # we make sure we don't draw queried object from the file that was just unlinked
-        elif queried_obj := props.queried_obj:
-            queried_filepath = Path(queried_obj["ifc_filepath"])
-            if queried_filepath == filepath:
         ProjectDecorator.uninstall()
 
-        return {"FINISHED"}
 
-
+class LoadLink(bpy.types.Operator, tool.Ifc.Operator):
-class LoadLink(bpy.types.Operator):
     bl_idname = "bim.load_link"
     bl_label = "Load Link"
     bl_options = {"REGISTER", "UNDO"}
     bl_description = "Load the selected file"
-    filepath: bpy.props.StringProperty(name="Link Filepath")
+    link_index: bpy.props.IntProperty(name="Link Index")
     use_cache: bpy.props.BoolProperty(name="Use Cache", default=True)
 
-    filepath_: Path
+    def _execute(self, context):
-
+        self.link = tool.Project.get_project_props().links[self.link_index]
-    def execute(self, context):
+        filepath = Path(tool.Ifc.resolve_uri(self.link.filepath))
-        filepath = Path(tool.Ifc.resolve_uri(self.filepath))
         if not filepath.exists():
             self.report({"ERROR"}, f"File does not exist: '{filepath}'")
             return {"CANCELLED"}
         self.filepath_ = filepath
-        if filepath.suffix.lower().endswith(".blend"):
+        if filepath.suffix.lower().endswith(".ifc"):
-            self.link_blend(filepath)
+            return self.link_ifc()
-        elif filepath.suffix.lower().endswith(".ifc"):
-            status = self.link_ifc()
-            if status:
-                return status
-        return {"FINISHED"}
 
     def link_blend(self, filepath: Path) -> None:
         with bpy.data.libraries.load(str(filepath), link=True) as (data_from, data_to):
-            data_to.scenes = data_from.scenes
+            data_to.collections = [c for c in data_from.collections if "IfcProject" in c]
-        link = tool.Project.get_project_props().links[self.filepath]
+
-        for scene in bpy.data.scenes:
+        # Find the linked collection
-            if not scene.library or Path(scene.library.filepath) != filepath:
+        for collection in bpy.data.collections:
+            if not collection.library or Path(collection.library.filepath) != filepath:
                 continue
-            for child in scene.collection.children:
+            # Create unique empty instance for this link
-                if "IfcProject" not in child.name:
+            empty_name = collection.name
-                    continue
+            empty = bpy.data.objects.new(empty_name, None)
-                empty = bpy.data.objects.new(child.name, None)
             empty.instance_type = "COLLECTION"
-                empty.instance_collection = child
+            empty.instance_collection = collection
-                link.empty_handle = empty
+            empty.matrix_world = Matrix(tool.Project.calculate_link_matrix(self.link))
+
+            tool.Project.set_link_empty_handle(self.link, empty)
             bpy.context.scene.collection.objects.link(empty)
-                break
+            self.link.is_loaded = True
-            break
+            if tool.Ifc.get():  # For non-IFC projects, locking has no meaning
-        link.is_loaded = True
+                tool.Geometry.lock_object(empty)
             tool.Blender.select_and_activate_single_object(bpy.context, empty)
+            break
+        else:
+            print(f"WARNING: No IfcProject collection found in {filepath}")
+            self.link.is_loaded = False
 
     def link_ifc(self) -> Union[set[str], None]:
         blend_filepath = self.filepath_.with_suffix(".ifc.cache.blend")
@@ -1502,14 +1526,12 @@ class LoadLink(bpy.types.Operator):
 
             code = f"""
 import bpy
+import sys
 
 def run():
     import bonsai.tool as tool
     gprops = tool.Georeference.get_georeference_props()
     # Our model origin becomes their host model origin
-    gprops.host_model_origin = "{gprops.model_origin}"
-    gprops.host_model_origin_si = "{gprops.model_origin_si}"
-    gprops.host_model_project_north = "{gprops.model_project_north}"
     gprops.has_blender_offset = {gprops.has_blender_offset}
     gprops.blender_offset_x = "{gprops.blender_offset_x}"
     gprops.blender_offset_y = "{gprops.blender_offset_y}"
@@ -1522,7 +1544,12 @@ def run():
     pprops.false_origin = "{pprops.false_origin}"
     pprops.project_north = "{pprops.project_north}"
     # Use absolute path to be safe from cwd changes.
+    try:
         bpy.ops.bim.load_linked_project(filepath=r"{str(self.filepath_)}")
+    except RuntimeError as e:
+        # Operator failed (returned CANCELLED with error report)
+        print(f"Failed to load linked project: {{e}}")
+        sys.exit(1)
     # Use str instead of as_posix to avoid issues with Windows shared paths.
     bpy.ops.wm.save_as_mainfile(filepath=r"{str(blend_filepath)}")
 
@@ -1557,13 +1584,16 @@ except Exception as e:
                     return {"CANCELLED"}
 
         self.set_model_origin_from_link()
-
+        self.set_georeferencing_indicator()
         self.link_blend(blend_filepath)
 
     def set_model_origin_from_link(self) -> None:
         if tool.Ifc.get():
             return  # The current model's coordinates always take priority.
 
+        if len(tool.Project.get_project_props().links) > 1:
+            return  # Only the first link sets the origin
+
         json_filepath = self.filepath_.with_suffix(".ifc.cache.json")
         if not json_filepath.exists():
             return
@@ -1576,21 +1606,36 @@ except Exception as e:
             if (value := data.get(prop, None)) is not None:
                 setattr(gprops, prop, value)
 
+    def set_georeferencing_indicator(self) -> None:
+        if not tool.Ifc.get():
+            self.link.georeferenced = "NONE"
+            return
+        if not (crs_name := (ifcopenshell.util.geolocation.get_crs(tool.Ifc.get()) or {}).get("Name", "")):
+            self.link.georeferenced = "NONE"
+            return
+        reference = tool.Ifc.get().by_id(self.link.ifc_definition_id)
+        json_filepath = Path(reference.Location).with_suffix(".ifc.cache.json")
+        if not json_filepath.exists():
+            self.link.georeferenced = "NONE"
+            return
+        with open(json_filepath, "r") as f:
+            data = json.load(f)
+        if not data["model_is_georeferenced"]:
+            self.link.georeferenced = "NONE"
+        else:
+            self.link.georeferenced = "FULL_COMPATIBLE" if crs_name == data["model_crs"] else "NOT_COMPATIBLE"
+
 
 class ReloadLink(bpy.types.Operator):
     bl_idname = "bim.reload_link"
     bl_label = "Reload Link"
     bl_options = {"REGISTER", "UNDO"}
     bl_description = "Reload the selected file"
-    filepath: bpy.props.StringProperty()
+    link_index: bpy.props.IntProperty(name="Link Index")
 
     def execute(self, context):
-        is_abs = os.path.isabs(Path(self.filepath))
+        bpy.ops.bim.unload_link(link_index=self.link_index)
-        use_relative_path = not is_abs
+        return bpy.ops.bim.load_link(link_index=self.link_index, use_cache=False) or {"FINISHED"}
-        bpy.ops.bim.unlink_ifc(filepath=self.filepath)
-        filepath = tool.Ifc.resolve_uri(self.filepath)
-        status = bpy.ops.bim.link_ifc(filepath=filepath, use_cache=False, use_relative_path=use_relative_path)
-        return {"FINISHED"}
 
 
 class ToggleLinkSelectability(bpy.types.Operator):
@@ -1598,16 +1643,18 @@ class ToggleLinkSelectability(bpy.types.Operator):
     bl_label = "Toggle Link Selectability"
     bl_options = {"REGISTER", "UNDO"}
     bl_description = "Toggle selectability"
-    link: bpy.props.StringProperty(name="Linked IFC Filepath")
+    link_index: bpy.props.IntProperty(name="Link Index")
 
     def execute(self, context):
         props = tool.Project.get_project_props()
-        link = props.links[self.link]
+        link = props.links[self.link_index]
-        self.library_filepath = tool.Blender.ensure_blender_path_is_abs(Path(self.link).with_suffix(".ifc.cache.blend"))
+        self.library_filepath = tool.Blender.ensure_blender_path_is_abs(
+            Path(link.filepath).with_suffix(".ifc.cache.blend")
+        )
         link.is_selectable = (is_selectable := not link.is_selectable)
         for collection in self.get_linked_collections():
             collection.hide_select = not is_selectable
-        if handle := link.empty_handle:
+        if handle := tool.Project.get_link_empty_handle(link):
             handle.hide_select = not is_selectable
         return {"FINISHED"}
 
@@ -1624,13 +1671,15 @@ class ToggleLinkVisibility(bpy.types.Operator):
     bl_label = "Toggle Link Visibility"
     bl_options = {"REGISTER", "UNDO"}
     bl_description = "Toggle visibility between SOLID and WIREFRAME"
-    link: bpy.props.StringProperty(name="Linked IFC Filepath")
+    link_index: bpy.props.IntProperty(name="Link Index")
     mode: bpy.props.EnumProperty(name="Visibility Mode", items=((i, i, "") for i in ("WIREFRAME", "VISIBLE")))
 
     def execute(self, context):
         props = tool.Project.get_project_props()
-        link = props.links[self.link]
+        link = props.links[self.link_index]
-        self.library_filepath = tool.Blender.ensure_blender_path_is_abs(Path(self.link).with_suffix(".ifc.cache.blend"))
+        self.library_filepath = tool.Blender.ensure_blender_path_is_abs(
+            Path(link.filepath).with_suffix(".ifc.cache.blend")
+        )
         if self.mode == "WIREFRAME":
             self.toggle_wireframe(link)
         elif self.mode == "VISIBLE":
@@ -1652,7 +1701,7 @@ class ToggleLinkVisibility(bpy.types.Operator):
         layer_collections = tool.Blender.get_layer_collections_mapping(linked_collections)
         for layer_collection in layer_collections.values():
             layer_collection.exclude = is_hidden
-        if handle := link.empty_handle:
+        if handle := tool.Project.get_link_empty_handle(link):
             handle.hide_set(is_hidden)
 
     def get_linked_collections(self) -> list[bpy.types.Collection]:
@@ -1663,17 +1712,95 @@ class ToggleLinkVisibility(bpy.types.Operator):
         ]
 
 
+class EnableEditingLink(bpy.types.Operator):
+    bl_idname = "bim.enable_editing_link"
+    bl_label = "Enable Editing Link"
+    bl_options = {"REGISTER", "UNDO"}
+    bl_description = "Enable editing link location"
+
+    def execute(self, context):
+        link = tool.Project.get_project_props().active_link
+        link.is_editing = True
+        tool.Geometry.unlock_object(tool.Project.get_link_empty_handle(link))
+        return {"FINISHED"}
+
+
+class DisableEditingLink(bpy.types.Operator):
+    bl_idname = "bim.disable_editing_link"
+    bl_label = "Disable Editing Link"
+    bl_options = {"REGISTER", "UNDO"}
+    bl_description = "Disable editing link and restore to previously saved location"
+
+    def execute(self, context):
+        link = tool.Project.get_project_props().active_link
+        link.is_editing = False
+        obj = tool.Project.get_link_empty_handle(link)
+        obj.matrix_world = Matrix(tool.Project.calculate_link_matrix(link))
+        tool.Geometry.lock_object(obj)
+        return {"FINISHED"}
+
+
+class EditLink(bpy.types.Operator, tool.Ifc.Operator):
+    bl_idname = "bim.edit_link"
+    bl_label = "Edit Link"
+    bl_options = {"REGISTER", "UNDO"}
+    bl_description = "Disable editing link and restore to previously saved location"
+
+    def _execute(self, context):
+        link = tool.Project.get_project_props().active_link
+        link.is_editing = False
+        obj = tool.Project.get_link_empty_handle(link)
+        new_obj_matrix = obj.matrix_world
+
+        filepath = Path(tool.Ifc.resolve_uri(link.filepath))
+        with open(filepath.with_suffix(".ifc.cache.json"), "r") as f:
+            metadata = json.load(f)
+
+        rot = ifcopenshell.util.shape_builder.np_rotation_matrix(
+            radians(-float(metadata["model_project_north"])), 4, "Z"
+        )
+        global_matrix = rot @ np.eye(4)
+        global_matrix[:, 3][:3] = [float(o) for o in metadata["model_origin_si"].split(",")]
+
+        gprops = tool.Georeference.get_georeference_props()
+        rot = ifcopenshell.util.shape_builder.np_rotation_matrix(radians(-float(gprops.model_project_north)), 4, "Z")
+        local_matrix = rot @ np.eye(4)
+        local_matrix[:, 3][:3] = [float(o) for o in gprops.model_origin_si.split(",")]
+
+        # obj_matrix is typically calculated as:
+        # obj_matrix = np.linalg.inv(local_matrix) @ transformation @ global_matrix
+        # So let's calculate the transformation
+
+        transformed_global_matrix = local_matrix @ np.array(new_obj_matrix)
+        transformation = transformed_global_matrix @ np.linalg.inv(global_matrix)
+        if np.allclose(transformation, np.eye(4)):
+            link.has_transformation = True
+            transformation = ",".join(map(str, np.eye(4).reshape(-1)))
+        else:
+            link.has_transformation = False
+            transformation = ",".join(map(str, transformation.reshape(-1)))
+
+        if tool.Ifc.get():
+            reference = tool.Ifc.get().by_id(link.ifc_definition_id)
+            reference[1] = transformation
+        else:
+            link.transformation = transformation
+
+        obj.matrix_world = Matrix(tool.Project.calculate_link_matrix(link))
+        tool.Geometry.lock_object(obj)
+
+
 class SelectLinkHandle(bpy.types.Operator):
     bl_idname = "bim.select_link_handle"
     bl_label = "Select Link Handle"
     bl_options = {"REGISTER", "UNDO"}
     bl_description = "Select link empty object handle"
-    index: bpy.props.IntProperty(name="Link Index")
+    link_index: bpy.props.IntProperty(name="Link Index")
 
     def execute(self, context):
         props = tool.Project.get_project_props()
-        link = props.links[self.index]
+        link = props.links[self.link_index]
-        handle = link.empty_handle
+        handle = tool.Project.get_link_empty_handle(link)
         if not handle:
             self.report({"ERROR"}, "Link has no empty handle (probably it was deleted).")
             return {"CANCELLED"}
@@ -1866,7 +1993,14 @@ class LoadLinkedProject(bpy.types.Operator, ImportHelper):
         print("Processing", self.filepath)
 
         self.collection = bpy.data.collections.new("IfcProject/" + os.path.basename(self.filepath))
+
+        try:
             self.file = ifcopenshell.open(self.filepath)
+        except Exception as e:
+            self.report({"ERROR"}, f"Failed to open IFC file: {str(e)}")
+            bpy.data.collections.remove(self.collection)
+            return {"CANCELLED"}
+
         tool.Ifc.set(self.file)
         print("Finished opening")
 
@@ -1897,20 +2031,13 @@ class LoadLinkedProject(bpy.types.Operator, ImportHelper):
         if tool.Loader.settings.false_origin_mode == "MANUAL" and tool.Loader.settings.false_origin:
             tool.Loader.set_manual_blender_offset(self.file)
         elif tool.Loader.settings.false_origin_mode == "AUTOMATIC":
-            if host_model_origin_si := gprops.host_model_origin_si:
-                host_model_origin_si = [float(o) / self.unit_scale for o in host_model_origin_si.split(",")]
-                tool.Loader.settings.false_origin = host_model_origin_si
-                tool.Loader.settings.project_north = float(gprops.host_model_project_north)
-                tool.Loader.set_manual_blender_offset(self.file)
-            else:
             tool.Loader.guess_false_origin(self.file)
 
         tool.Georeference.set_model_origin()
         self.json_filepath = self.filepath + ".cache.json"
         data = {
-            "host_model_origin": gprops.host_model_origin,
+            "model_is_georeferenced": gprops.model_is_georeferenced,
-            "host_model_origin_si": gprops.host_model_origin_si,
+            "model_crs": gprops.model_crs,
-            "host_model_project_north": gprops.host_model_project_north,
             "model_origin": gprops.model_origin,
             "model_origin_si": gprops.model_origin_si,
             "model_project_north": gprops.model_project_north,

src/bonsai/bonsai/bim/module/project/prop.py

@@ -16,8 +16,9 @@
 # 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 math
 from collections.abc import Generator
+from pathlib import Path
 from typing import TYPE_CHECKING, Literal, Union, assert_never, get_args
 
 import bpy
@@ -219,29 +220,62 @@ class FilterCategory(PropertyGroup):
 
 
 class Link(PropertyGroup):
-    name: StringProperty(
+    name: StringProperty(name="Name")
-        name="Name",
+    filepath: StringProperty(
+        name="Filepath",
         description="Filepath to linked .ifc file, stored in posix format (could be relative to .ifc file, not to .blend)",
     )
+    transformation: StringProperty(
+        name="Transformation",
+        description="4x4 matrix transformation as a flattened comma separated list for the linked model",
+        default="",
+    )
+    georeferenced: EnumProperty(
+        name="Georeferenced",
+        description="Georeferencing status: compatibility between host and linked model",
+        items=[
+            ("NONE", "No Georef", "Linked model has no georeferencing"),
+            ("NOT_COMPATIBLE", "Not Compatible", "Has geo data but CRS differ from host"),
+            ("FULL_COMPATIBLE", "Full Compatible", "Both CRS name and vertical datum match host"),
+        ],
+        default="NONE",
+    )
+    has_transformation: BoolProperty(
+        name="Has Transformation",
+        description="Whether there is a transformation from its global coordinates",
+        default=False,
+    )
     is_loaded: BoolProperty(name="Is Loaded", default=False)
+    is_editing: BoolProperty(name="Is Editing", description="Whether the link is being transformed", default=False)
     is_selectable: BoolProperty(name="Is Selectable", default=True)
     is_wireframe: BoolProperty(name="Is Wireframe", default=False)
     is_hidden: BoolProperty(name="Is Hidden", default=False)
     include_in_drawings: BoolProperty(name="Include in Drawings", default=True, options=set())
     empty_handle: PointerProperty(
         name="Empty Object Handle",
-        description="We use empty object handle to allow simple manipulations with a linked model (moving, scaling, rotating)",
+        description="Storage for empty handle. Used in non-IFC scenarios or temporarily during link creation",
         type=bpy.types.Object,
     )
+    ifc_definition_id: IntProperty(
+        name="IFC Definition ID",
+        description="STEP ID of the IfcDocumentReference when linked to a parent IFC project. Zero when no parent IFC exists",
+        default=0,
+    )
 
     if TYPE_CHECKING:
         name: str
+        filepath: str
+        transformation: str
+        georeferenced: Literal["NONE", "NOT_COMPATIBLE", "FULL_COMPATIBLE"]
+        has_transformation: bool
         is_loaded: bool
+        is_editing: bool
         is_selectable: bool
         is_wireframe: bool
         is_hidden: bool
         include_in_drawings: bool
         empty_handle: Union[bpy.types.Object, None]
+        ifc_definition_id: int
 
 
 class EditedObj(PropertyGroup):
@@ -424,6 +458,10 @@ class BIMProjectProperties(PropertyGroup):
     clipping_planes_active_index: bpy.props.IntProperty(min=0, default=0, max=5)
     edited_objs: bpy.props.CollectionProperty(type=EditedObj)
 
+    @property
+    def active_link(self) -> Union[Link, None]:
+        return tool.Blender.get_active_uilist_element(self.links, self.active_link_index)
+
     @property
     def active_clipping_plane(self) -> ObjProperty | None:
         return tool.Blender.get_active_uilist_element(self.clipping_planes, self.clipping_planes_active_index)

src/bonsai/bonsai/bim/module/project/ui.py

@@ -22,6 +22,7 @@ import os
 from typing import TYPE_CHECKING
 
 import bpy
+import math
 import ifcopenshell
 from bpy.types import Menu, Panel, UIList
 
@@ -30,6 +31,7 @@ import bonsai.tool as tool
 from bonsai.bim.helper import draw_attributes, prop_with_search
 from bonsai.bim.ifc import IfcStore
 from bonsai.bim.module.project.data import LinksData, ProjectData
+from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
     from bonsai.bim.module.project.prop import (
@@ -477,17 +479,27 @@ class BIM_PT_links(Panel):
 
     def draw(self, context):
         self.props = tool.Project.get_project_props()
+
         row = self.layout.row(align=True)
         row.operator("bim.link_ifc")
         if self.props.links:
-            self.layout.template_list(
+            if self.props.active_link:
-                "BIM_UL_links",
+                row = self.layout.row(align=True)
-                "",
+                row.alignment = "RIGHT"
-                self.props,
+                index = self.props.active_link_index
-                "links",
+                if self.props.active_link.is_editing:
-                self.props,
+                    row.operator("bim.edit_link", text="", icon="CHECKMARK")
-                "active_link_index",
+                    row.operator("bim.disable_editing_link", text="", icon="CANCEL")
-            )
+                else:
+                    row.operator("bim.enable_editing_link", text="", icon="GREASEPENCIL")
+                if self.props.active_link.is_loaded:
+                    row.operator("bim.select_link_handle", text="", icon="OBJECT_DATA").link_index = index
+                    row.operator("bim.unload_link", text="", icon="UNLINKED").link_index = index
+                    row.operator("bim.reload_link", text="", icon="FILE_REFRESH").link_index = index
+                else:
+                    row.operator("bim.load_link", text="", icon="LINKED").link_index = index
+                    row.operator("bim.unlink_ifc", text="", icon="X").link_index = index
+            self.layout.template_list("BIM_UL_links", "", self.props, "links", self.props, "active_link_index")
 
         if LinksData.enable_culling:
             row = self.layout.row(align=True)
@@ -607,47 +619,30 @@ class BIM_UL_links(UIList):
         active_propname,
         index,
     ):
-        if item:
         row = layout.row(align=True)
         if item.is_loaded:
-                row.label(text=item.name)
+            if item.georeferenced == "NONE":
-                op = row.operator(
+                row.label(text="", icon="QUESTION")
-                    "bim.toggle_link_selectability",
+            elif item.georeferenced == "NOT_COMPATIBLE":
-                    text="",
+                row.label(text="", icon="ERROR")
-                    icon="RESTRICT_SELECT_OFF" if item.is_selectable else "RESTRICT_SELECT_ON",
+            elif item.georeferenced == "FULL_COMPATIBLE":
-                    emboss=False,
+                row.label(text="", icon="WORLD")
-                )
+            if item.has_transformation:
-                op.link = item.name
+                row.label(text="", icon="OBJECT_ORIGIN")
-                op = row.operator(
+
-                    "bim.toggle_link_visibility",
+            row.label(text=item.filepath)
-                    text="",
+            icon = "RESTRICT_SELECT_OFF" if item.is_selectable else "RESTRICT_SELECT_ON"
-                    icon="CUBE" if item.is_wireframe else "MESH_CUBE",
+            row.operator("bim.toggle_link_selectability", text="", icon=icon, emboss=False).link_index = index
-                    emboss=False,
+            icon = "CUBE" if item.is_wireframe else "MESH_CUBE"
-                )
+            op = row.operator("bim.toggle_link_visibility", text="", icon=icon, emboss=False)
-                op.link = item.name
+            op.link_index = index
             op.mode = "WIREFRAME"
-                op = row.operator(
+            icon = "HIDE_ON" if item.is_hidden else "HIDE_OFF"
-                    "bim.toggle_link_visibility",
+            op = row.operator("bim.toggle_link_visibility", text="", icon=icon, emboss=False)
-                    text="",
+            op.link_index = index
-                    icon="HIDE_ON" if item.is_hidden else "HIDE_OFF",
-                    emboss=False,
-                )
-                op.link = item.name
             op.mode = "VISIBLE"
-                op = row.operator("bim.select_link_handle", text="", icon="OBJECT_DATA")
-                op.index = index
-                op = row.operator("bim.unload_link", text="", icon="UNLINKED")
-                op.filepath = item.name
-                op = row.operator("bim.reload_link", text="", icon="FILE_REFRESH")
-                op.filepath = item.name
         else:
-                row.prop(item, "name", text="")
+            row.label(text=item.filepath)
-                op = row.operator("bim.select_uri_attribute", text="", icon="FILE_FOLDER")
-                op.attribute_data_path = tool.Blender.get_full_data_path(item, "name")
-                op = row.operator("bim.load_link", text="", icon="LINKED")
-                op.filepath = item.name
-                op = row.operator("bim.unlink_ifc", text="", icon="X")
-                op.filepath = item.name
 
 
 class BIM_PT_purge(Panel):

src/bonsai/bonsai/bim/operator.py

@@ -268,63 +268,45 @@ class SaveBlendMetadataFile(bpy.types.Operator):
 import bpy
 
 # Ensure all styles are loaded before attempting to remove them
-try:
+bpy.ops.bim.load_styles()
-    bpy.ops.bim.load_styles()
-except Exception:
-    pass
 
 # 1. Collect all IfcStyle material names
 ifcstyle_material_names = []
-try:
+styles_props = getattr(bpy.context.scene, "BIMStylesProperties", None)
-    styles_props = getattr(bpy.context.scene, "BIMStylesProperties", None)
+if styles_props is None and bpy.data.scenes:
-    if styles_props is None and bpy.data.scenes:
     styles_props = getattr(bpy.data.scenes[0], "BIMStylesProperties", None)
-    if styles_props:
+if styles_props:
     for style in list(styles_props.styles):
         material = getattr(style, "blender_material", None)
         if material and material.name:
             ifcstyle_material_names.append(material.name)
-except Exception:
-    pass
 
 # 2. Purge IfcStore
-try:
+from bonsai.bim.ifc import IfcStore
-    from bonsai.bim.ifc import IfcStore
+IfcStore.purge()
-except ImportError:
-    IfcStore = None
-
-if IfcStore:
-    try:
-        IfcStore.purge()
-    except Exception:
-        pass
 
 # 3. Remove all collections named IfcProject*
 for collection in list(bpy.data.collections):
     if collection.name.startswith('IfcProject'):
-        try:
         bpy.data.collections.remove(collection, do_unlink=True)
-        except Exception:
-            pass
 
-# 4. Purge orphaned data blocks after removing IfcProject collections
+# 4.1 Remove all collections from linked libraries (they will be recreated by bonsai)
-try:
+for collection in list(bpy.data.collections):
-    bpy.ops.outliner.orphans_purge(do_local_ids=True, do_linked_ids=True, do_recursive=True)
+    if collection.library:
-except Exception:
+        bpy.data.collections.remove(collection, do_unlink=True)
-    pass
 
-# 5. Remove all materials corresponding to the IfcStyles we collected
+# 4.2. Remove all empty objects that are collection instances for linked models
-materials_removed = 0
+for obj in list(bpy.data.objects):
-try:
+    if obj.type == 'EMPTY' and obj.instance_type == 'COLLECTION' and obj.name.startswith('IfcProject/'):
-    for mat_name in ifcstyle_material_names:
+        bpy.data.objects.remove(obj, do_unlink=True)
+
+# 5. Purge orphaned data blocks after removing IfcProject collections
+bpy.ops.outliner.orphans_purge(do_local_ids=True, do_linked_ids=True, do_recursive=True)
+
+# 6. Remove all materials corresponding to the IfcStyles we collected
+for mat_name in ifcstyle_material_names:
     if mat_name in bpy.data.materials:
-            try:
         bpy.data.materials.remove(bpy.data.materials[mat_name], do_unlink=True)
-                materials_removed += 1
-            except Exception:
-                pass
-except Exception:
-    pass
 
 bpy.ops.wm.save_as_mainfile(filepath=r'{blendmetadata_path}')
 """

src/bonsai/bonsai/core/georeference.py

@@ -29,6 +29,7 @@ if TYPE_CHECKING:
 
 def add_georeferencing(georeference: type[tool.Georeference]) -> None:
     georeference.add_georeferencing()
+    georeference.set_model_origin()
 
 
 def enable_editing_georeferencing(georeference: type[tool.Georeference]) -> None:
@@ -37,8 +38,9 @@ def enable_editing_georeferencing(georeference: type[tool.Georeference]) -> None
     georeference.enable_editing()
 
 
-def remove_georeferencing(ifc: type[tool.Ifc]) -> None:
+def remove_georeferencing(ifc: type[tool.Ifc], georeference: type[tool.Georeference]) -> None:
     ifc.run("georeference.remove_georeferencing")
+    georeference.set_model_origin()
 
 
 def disable_editing_georeferencing(georeference: type[tool.Georeference]) -> None:

src/bonsai/bonsai/tool/document.py

@@ -251,11 +251,19 @@ class Document(bonsai.core.tool.Document):
     def get_document_references(
         cls, document: ifcopenshell.entity_instance
     ) -> tuple[ifcopenshell.entity_instance, ...]:
+        # TODO: migrate to util.document and replace all instances
         """Get IfcDocumentReference.ReferencedDocuments, compatible with IFC2X3."""
         if document.file.schema == "IFC2X3":
             return document.DocumentReferences or ()
         return document.HasDocumentReferences
 
+    @classmethod
+    def get_reference_document(cls, reference: ifcopenshell.entity_instance) -> ifcopenshell.entity_instance | None:
+        # TODO: migrate to util.document and replace all instances
+        if reference.file.schema == "IFC2X3":
+            return (reference.ReferenceToDocument or (None))[0]
+        return reference.ReferencedDocument
+
     @classmethod
     def clear_active_document(cls) -> None:
         props = cls.get_document_props()

src/bonsai/bonsai/tool/georeference.py

@@ -315,6 +315,21 @@ class Georeference(bonsai.core.tool.Georeference):
             )
         return coordinates
 
+    @classmethod
+    def global2local(cls, matrix, is_specified_in_map_units: bool) -> tuple[float, float, float]:
+        matrix = ifcopenshell.util.geolocation.auto_global2local(tool.Ifc.get(), matrix, is_specified_in_map_units=is_specified_in_map_units)
+        props = cls.get_georeference_props()
+        if props.has_blender_offset:
+            matrix = ifcopenshell.util.geolocation.global2local(
+                matrix,
+                float(props.blender_offset_x),
+                float(props.blender_offset_y),
+                float(props.blender_offset_z),
+                float(props.blender_x_axis_abscissa),
+                float(props.blender_x_axis_ordinate),
+            )
+        return matrix
+
     @classmethod
     def import_plot(cls, filepath: str) -> None:
         import bmesh
@@ -385,6 +400,9 @@ class Georeference(bonsai.core.tool.Georeference):
         unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
         gprops = tool.Georeference.get_georeference_props()
         e, n, h = cls.xyz2enh((0, 0, 0), should_return_in_map_units=False)
+        crs = ifcopenshell.util.geolocation.get_crs(tool.Ifc.get()) or {}
+        gprops.model_is_georeferenced = bool(crs)
+        gprops.model_crs = crs.get("Name", "") or ""
         gprops.model_origin = f"{e},{n},{h}"
         gprops.model_origin_si = f"{e * unit_scale},{n * unit_scale},{h * unit_scale}"
         angle = ifcopenshell.util.geolocation.get_grid_north(tool.Ifc.get())

src/bonsai/bonsai/tool/project.py

@@ -19,10 +19,14 @@
 from __future__ import annotations
 
 import os
+import json
+import math
 import shutil
+import numpy as np
 from collections import defaultdict
+from math import radians
 from pathlib import Path
-from typing import TYPE_CHECKING, NamedTuple, Optional, Union
+from typing import TYPE_CHECKING, NamedTuple, Optional
 
 import bpy
 import ifcopenshell
@@ -58,6 +62,47 @@ class Project(bonsai.core.tool.Project):
         assert (scene := bpy.context.scene)
         return scene.MeasureToolSettings  # pyright: ignore[reportAttributeAccessIssue]
 
+    @classmethod
+    def get_link_empty_handle(cls, link) -> bpy.types.Object | None:
+        if tool.Ifc.get():
+            return tool.Ifc.get_object(tool.Ifc.get().by_id(link.ifc_definition_id))
+        return link.empty_handle
+
+    @classmethod
+    def set_link_empty_handle(cls, link, empty: bpy.types.Object) -> None:
+        if tool.Ifc.get():
+            tool.Ifc.link(tool.Ifc.get().by_id(link.ifc_definition_id), empty)
+        else:
+            link.empty_handle = empty
+
+    @classmethod
+    def calculate_link_matrix(cls, link) -> None:
+        filepath = Path(tool.Ifc.resolve_uri(link.filepath))
+        with open(filepath.with_suffix(".ifc.cache.json"), "r") as f:
+            metadata = json.load(f)
+
+        rot = ifcopenshell.util.shape_builder.np_rotation_matrix(
+            radians(-float(metadata["model_project_north"])), 4, "Z"
+        )
+        global_matrix = rot @ np.eye(4)
+        global_matrix[:, 3][:3] = [float(o) for o in metadata["model_origin_si"].split(",")]
+
+        if tool.Ifc.get():
+            transformation = tool.Ifc.get().by_id(link.ifc_definition_id)[1]  # Identification
+        else:
+            transformation = link.transformation
+
+        if transformation:
+            transformation = np.fromstring(transformation, sep=",", dtype=np.float64).reshape(4, 4)
+            if not np.allclose(transformation, np.eye(4)):
+                global_matrix = transformation @ global_matrix
+
+        gprops = tool.Georeference.get_georeference_props()
+        rot = ifcopenshell.util.shape_builder.np_rotation_matrix(radians(-float(gprops.model_project_north)), 4, "Z")
+        local_matrix = rot @ np.eye(4)
+        local_matrix[:, 3][:3] = [float(o) for o in gprops.model_origin_si.split(",")]
+        return np.linalg.inv(local_matrix) @ global_matrix
+
     @classmethod
     def append_all_types_from_template(cls, template: str) -> None:
         # TODO refactor
@@ -249,68 +294,32 @@ class Project(bonsai.core.tool.Project):
         tool.Root.reload_grid_decorator()
 
     @classmethod
-    def get_linked_models_document(cls) -> Union[ifcopenshell.entity_instance, None]:
+    def get_linked_models_documents(cls) -> dict[str, ifcopenshell.entity_instance]:
-        for document in tool.Ifc.get().by_type("IfcDocumentInformation"):
+        linked_docs = {}
-            if document.Name == "BBIM_Linked_Models":
+        for doc in tool.Ifc.get().by_type("IfcDocumentInformation"):
-                return document
+            if doc.Scope == "LINKED_MODEL":
+                for reference in tool.Drawing.get_document_references(doc):
+                    linked_docs[Path(reference.Location).as_posix()] = doc
+                    break
+        return linked_docs
 
     @classmethod
     def load_linked_models_from_ifc(cls) -> None:
         links = tool.Project.get_project_props().links
         links.clear()
-        links_document = cls.get_linked_models_document()
+        for doc in tool.Ifc.get().by_type("IfcDocumentInformation"):
-        if not links_document:
+            if doc.Scope != "LINKED_MODEL":
-            return
-
-        references = tool.Document.get_document_references(links_document)
-        if not references:
-            return
-
-        for reference in references:
-            link = links.add()
-            link.name = reference.Location
-
-    @classmethod
-    def save_linked_models_to_ifc(cls) -> None:
-        ifc_file = tool.Ifc.get()
-        links = tool.Project.get_project_props().links
-        filepaths: set[Path] = set()
-        for link in links:
-            filepaths.add(Path(link.name))
-
-        links_document = cls.get_linked_models_document()
-
-        if not filepaths and links_document is None:
-            return
-
-        paths_to_add = filepaths.copy()
-        references_to_remove: list[ifcopenshell.entity_instance] = []
-        if links_document:
-            references = tool.Document.get_document_references(links_document)
-            for reference in references:
-                # I guess got corrupted by the user.
-                if not (location := reference.Location):
-                    references_to_remove.remove(reference)
                 continue
-                path = Path(location)
+            for reference in tool.Drawing.get_document_references(doc):
-                if path in paths_to_add:
+                filepath = reference.Location
-                    paths_to_add.remove(path)
+                link = links.add()
-                else:
+                link.name = filepath
-                    references_to_remove.append(reference)
+                link.filepath = filepath
-
+                link.ifc_definition_id = reference.id()
-        if paths_to_add:
+                link.has_transformation = False
-            if links_document is None:
+                if reference[1]:
-                links_document = ifcopenshell.api.document.add_information(ifc_file)
+                    m = np.fromstring(reference[1], sep=",", dtype=np.float64).reshape(4, 4)
-                links_document.Name = "BBIM_Linked_Models"
+                    link.has_transformation = not np.allclose(m, np.eye(4))
-                links_document.Description = "Bonsai internal document containing references to currently linked models"
-
-            for path in paths_to_add:
-                reference = ifcopenshell.api.document.add_reference(ifc_file, links_document)
-                reference.Location = path.as_posix()
-
-        if references_to_remove:
-            for reference in references_to_remove:
-                ifcopenshell.api.document.remove_reference(ifc_file, reference)
 
     @classmethod
     def get_project_library_elements(

src/bonsai/test/bim/feature/project.feature

@@ -677,31 +677,43 @@ Scenario: Load project elements - all georeferencing coordinate situations with
     And the object "IfcActuator/J" has a vertex at "10.366,3.813,-1"
     And the object "IfcActuator/J" has a vertex at "12.298,4.331,-1"
 
-Scenario: Link IFC
+Scenario: Link IFC - from an empty IFC project
     Given an empty IFC project
-    When I link IFC project from "{cwd}/test/files/basic.ifc"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/basic.ifc')"
     Then "scene.BIMProjectProperties.links['{cwd}/test/files/basic.ifc'].is_loaded" is "True"
     And the collection "IfcProject/basic.ifc" exists
     And the object "Chunk" exists
     And the object "Chunk" is placed in the collection "IfcProject/basic.ifc"
 
-Scenario: Link IFC - disabled false origin mode
-    Given an empty IFC project
-    # Not currently possible via UI
-    And I set "scene.BIMProjectProperties.distance_limit" to "5"
-    And I set "scene.BIMProjectProperties.false_origin_mode" to "DISABLED"
-    When I link IFC project from "{cwd}/test/files/geolocation.ifc"
-    Then the object "Chunk" exists
-    And the object "Chunk" has a vertex at "2,2,-1"
-    And the object "Chunk" has a vertex at "9,-1,-1"
-    And the object "Chunk" has a vertex at "17,4,-1"
-
 Scenario: Link IFC - from an empty IFC project - automatic false origin mode (0,0,0 will be the false origin)
     Given an empty IFC project
     # Not currently possible via UI
     And I set "scene.BIMProjectProperties.distance_limit" to "5"
     And I set "scene.BIMProjectProperties.false_origin_mode" to "AUTOMATIC"
-    When I link IFC project from "{cwd}/test/files/geolocation.ifc"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation.ifc', use_cache=False)"
+    Then the object "Chunk" exists
+    And the object "Chunk" has a vertex at "2,2,-1"
+    And the object "Chunk" has a vertex at "9,-1,-1"
+    And the object "Chunk" has a vertex at "17,4,-1"
+
+Scenario: Link IFC - from an empty IFC project - manual false origin mode
+    Given an empty IFC project
+    # Not currently possible via UI
+    And I set "scene.BIMProjectProperties.distance_limit" to "5"
+    And I set "scene.BIMProjectProperties.false_origin_mode" to "MANUAL"
+    And I set "scene.BIMProjectProperties.false_origin" to "10000,0,0"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation.ifc', use_cache=False)"
+    Then the object "Chunk" exists
+    And the object "Chunk" has a vertex at "2,2,-1"
+    And the object "Chunk" has a vertex at "9,-1,-1"
+    And the object "Chunk" has a vertex at "17,4,-1"
+
+Scenario: Link IFC - from an empty IFC project - disabled false origin mode
+    Given an empty IFC project
+    # Not currently possible via UI
+    And I set "scene.BIMProjectProperties.distance_limit" to "5"
+    And I set "scene.BIMProjectProperties.false_origin_mode" to "DISABLED"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation.ifc', use_cache=False)"
     Then the object "Chunk" exists
     And the object "Chunk" has a vertex at "2,2,-1"
     And the object "Chunk" has a vertex at "9,-1,-1"
@@ -712,31 +724,42 @@ Scenario: Link IFC - from an empty Blender session - automatic false origin mode
     # Not currently possible via UI
     And I set "scene.BIMProjectProperties.distance_limit" to "5"
     And I set "scene.BIMProjectProperties.false_origin_mode" to "AUTOMATIC"
-    When I link IFC project from "{cwd}/test/files/geolocation.ifc"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation.ifc', use_cache=False)"
     Then the object "Chunk" exists
     And the object "Chunk" has a vertex at "-11,-2,0"
     And the object "Chunk" has a vertex at "-4,-5,0"
     And the object "Chunk" has a vertex at "4,0,0"
 
-Scenario: Link IFC - manual false origin mode
+Scenario: Link IFC - from an empty Blender session - manual false origin mode
     Given an empty Blender session
     # Not currently possible via UI
     And I set "scene.BIMProjectProperties.distance_limit" to "5"
     And I set "scene.BIMProjectProperties.false_origin_mode" to "MANUAL"
     And I set "scene.BIMProjectProperties.false_origin" to "10000,0,0"
-    When I link IFC project from "{cwd}/test/files/geolocation.ifc"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation.ifc', use_cache=False)"
     Then the object "Chunk" exists
     And the object "Chunk" has a vertex at "-8,2,-1"
     And the object "Chunk" has a vertex at "-1,-1,-1"
     And the object "Chunk" has a vertex at "7,4,-1"
 
-Scenario: Link IFC - automatic false origin mode - two different false origins and project norths - grid north is up because we start with geolocation.ifc
+Scenario: Link IFC - from an empty Blender session - disabled false origin mode
+    Given an empty Blender session
+    # Not currently possible via UI
+    And I set "scene.BIMProjectProperties.distance_limit" to "5"
+    And I set "scene.BIMProjectProperties.false_origin_mode" to "DISABLED"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation.ifc', use_cache=False)"
+    Then the object "Chunk" exists
+    And the object "Chunk" has a vertex at "2,2,-1"
+    And the object "Chunk" has a vertex at "9,-1,-1"
+    And the object "Chunk" has a vertex at "17,4,-1"
+
+Scenario: Link IFC - from an empty Blender session - automatic false origin mode - two different false origins and project norths - grid north is up because we start with geolocation.ifc
     Given an empty Blender session
     # Not currently possible via UI
     And I set "scene.BIMProjectProperties.distance_limit" to "5"
     And I set "scene.BIMProjectProperties.false_origin_mode" to "AUTOMATIC"
-    When I link IFC project from "{cwd}/test/files/geolocation.ifc"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation.ifc', use_cache=False)"
-    And I link IFC project from "{cwd}/test/files/geolocation-mapconversion-angle.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation-mapconversion-angle.ifc', use_cache=False)"
     Then the object "Col:IfcProject/geolocation.ifc:Chunk" exists
     And the object "Col:IfcProject/geolocation-mapconversion-angle.ifc:Chunk" exists
     And the object "Col:IfcProject/geolocation.ifc:Chunk" has a vertex at "-11,-2,0"
@@ -746,13 +769,13 @@ Scenario: Link IFC - automatic false origin mode - two different false origins a
     And the object "Col:IfcProject/geolocation-mapconversion-angle.ifc:Chunk" has a vertex at "9.294,-9.366,0"
     And the object "Col:IfcProject/geolocation-mapconversion-angle.ifc:Chunk" has a vertex at "18.722,-9.036,0"
 
-Scenario: Link IFC - automatic false origin mode - two different false origins and project norths - project north is up because we start with geolocation-mapconversion-angle.ifc
+Scenario: Link IFC - from an empty Blender session - automatic false origin mode - two different false origins and project norths - project north is up because we start with geolocation-mapconversion-angle.ifc
     Given an empty Blender session
     # Not currently possible via UI
     And I set "scene.BIMProjectProperties.distance_limit" to "5"
     And I set "scene.BIMProjectProperties.false_origin_mode" to "AUTOMATIC"
-    When I link IFC project from "{cwd}/test/files/geolocation-mapconversion-angle.ifc"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation-mapconversion-angle.ifc', use_cache=False)"
-    And I link IFC project from "{cwd}/test/files/geolocation.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation.ifc', use_cache=False)"
     Then the object "Col:IfcProject/geolocation.ifc:Chunk" exists
     And the object "Col:IfcProject/geolocation-mapconversion-angle.ifc:Chunk" exists
     And the object "Col:IfcProject/geolocation-mapconversion-angle.ifc:Chunk" has a vertex at "-11,-2,0"
@@ -762,14 +785,14 @@ Scenario: Link IFC - automatic false origin mode - two different false origins a
     And the object "Col:IfcProject/geolocation.ifc:Chunk" has a vertex at "-17.696,-7.866,0"
     And the object "Col:IfcProject/geolocation.ifc:Chunk" has a vertex at "-13.268,0.464,0"
 
-Scenario: Link IFC - automatic false origin mode - three identical false origins but different project and map units
+Scenario: Link IFC - from an empty Blender session - automatic false origin mode - three identical false origins but different project and map units
     Given an empty Blender session
     # Not currently possible via UI
     And I set "scene.BIMProjectProperties.distance_limit" to "5"
     And I set "scene.BIMProjectProperties.false_origin_mode" to "AUTOMATIC"
-    When I link IFC project from "{cwd}/test/files/geolocation-unit1.ifc"
+    When I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation-unit1.ifc', use_cache=False)"
-    And I link IFC project from "{cwd}/test/files/geolocation-unit2.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation-unit2.ifc', use_cache=False)"
-    And I link IFC project from "{cwd}/test/files/geolocation-unit3.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/geolocation-unit3.ifc', use_cache=False)"
     Then the object "Col:IfcProject/geolocation-unit1.ifc:Chunk" exists
     And the object "Col:IfcProject/geolocation-unit2.ifc:Chunk" exists
     And the object "Col:IfcProject/geolocation-unit3.ifc:Chunk" exists
@@ -779,54 +802,54 @@ Scenario: Link IFC - automatic false origin mode - three identical false origins
 
 Scenario: Toggle link visibility - wireframe mode
     Given an empty IFC project
-    And I link IFC project from "{cwd}/test/files/basic.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/basic.ifc')"
-    When I press "bim.toggle_link_visibility(link='{cwd}/test/files/basic.ifc', mode='WIREFRAME')"
+    When I press "bim.toggle_link_visibility(link_index=0, mode='WIREFRAME')"
     Then "scene.BIMProjectProperties.links['{cwd}/test/files/basic.ifc'].is_wireframe" is "True"
     And the object "Chunk" should display as "WIRE"
-    When I press "bim.toggle_link_visibility(link='{cwd}/test/files/basic.ifc', mode='WIREFRAME')"
+    When I press "bim.toggle_link_visibility(link_index=0, mode='WIREFRAME')"
     Then "scene.BIMProjectProperties.links['{cwd}/test/files/basic.ifc'].is_wireframe" is "False"
     And the object "Chunk" should display as "TEXTURED"
 
 Scenario: Toggle link selectability
     Given an empty IFC project
-    And I link IFC project from "{cwd}/test/files/basic.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/basic.ifc')"
-    When I press "bim.toggle_link_selectability(link='{cwd}/test/files/basic.ifc')"
+    When I press "bim.toggle_link_selectability(link_index=0)"
     Then "scene.BIMProjectProperties.links['{cwd}/test/files/basic.ifc'].is_selectable" is "False"
     And the collection "IfcProject/basic.ifc" is unselectable
-    When I press "bim.toggle_link_selectability(link='{cwd}/test/files/basic.ifc')"
+    When I press "bim.toggle_link_selectability(link_index=0)"
     Then "scene.BIMProjectProperties.links['{cwd}/test/files/basic.ifc'].is_selectable" is "True"
     And the collection "IfcProject/basic.ifc" is selectable
 
 Scenario: Toggle link visibility - visible mode
     Given an empty IFC project
-    And I link IFC project from "{cwd}/test/files/basic.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/basic.ifc')"
-    When I press "bim.toggle_link_visibility(link='{cwd}/test/files/basic.ifc', mode='VISIBLE')"
+    When I press "bim.toggle_link_visibility(link_index=0, mode='VISIBLE')"
     Then "scene.BIMProjectProperties.links['{cwd}/test/files/basic.ifc'].is_hidden" is "True"
     And the object "IfcProject/basic.ifc" is not visible
-    When I press "bim.toggle_link_visibility(link='{cwd}/test/files/basic.ifc', mode='VISIBLE')"
+    When I press "bim.toggle_link_visibility(link_index=0, mode='VISIBLE')"
     Then "scene.BIMProjectProperties.links['{cwd}/test/files/basic.ifc'].is_hidden" is "False"
     And the object "IfcProject/basic.ifc" is visible
 
 Scenario: Unload link
     Given an empty Blender session
-    And I link IFC project from "{cwd}/test/files/basic.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/basic.ifc')"
-    When I press "bim.unload_link(filepath='{cwd}/test/files/basic.ifc')"
+    When I press "bim.unload_link(link_index=0)"
     Then "scene.BIMProjectProperties.links['{cwd}/test/files/basic.ifc'].is_loaded" is "False"
     And the collection "IfcProject/basic.ifc" does not exist
 
 Scenario: Load link
     Given an empty Blender session
-    And I link IFC project from "{cwd}/test/files/basic.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/basic.ifc')"
-    And I press "bim.unload_link(filepath='{cwd}/test/files/basic.ifc')"
+    And I press "bim.unload_link(link_index=0)"
-    When I press "bim.load_link(filepath='{cwd}/test/files/basic.ifc')"
+    When I press "bim.load_link(link_index=0)"
     Then "scene.BIMProjectProperties.links['{cwd}/test/files/basic.ifc'].is_loaded" is "True"
     And the object "IfcProject/basic.ifc" exists
 
 Scenario: Unlink IFC
     Given an empty Blender session
-    And I link IFC project from "{cwd}/test/files/basic.ifc"
+    And I press "bim.link_ifc(filepath='{cwd}/test/files/basic.ifc')"
-    And I press "bim.unload_link(filepath='{cwd}/test/files/basic.ifc')"
+    And I press "bim.unload_link(link_index=0)"
-    When I press "bim.unlink_ifc(filepath='{cwd}/test/files/basic.ifc')"
+    When I press "bim.unlink_ifc(link_index=0)"
     Then "scene.BIMProjectProperties.links.get('{cwd}/test/files/basic.ifc')" is "None"
     And "scene.collection.children.get('IfcProject/basic.ifc')" is "None"
     And the object "Chunk" does not exist

src/bonsai/test/bim/test_feature.py

@@ -70,10 +70,7 @@ Can be useful for debugging, but has caveats - can't use ``wm.read_homefile``
 as resets the ``bpy.context`` and some it's members become `None`.
 """
 
-TMP = Path.cwd() / "test/files/temp"
+TMP = Path(f"{variables['cwd']}/test/files/temp")
-TEST_FILES_DIR = Path.cwd() / "test/files"
-
-CLEAN_LINKED_FILES_CACHE = False
 
 EPSET_DRAWING = Path.cwd() / "bonsai/bim/data/pset/EPset_Drawing.ifc"
 EPSET_DRAWING_BYTES = EPSET_DRAWING.read_bytes()
@@ -311,25 +308,6 @@ def vectors_are_equal(v1, v2):
     return all(is_x(v1[i], v2[i]) for i in range(len(v1)))
 
 
-@pytest.fixture(scope="function", autouse=True)
-def run_for_each_test() -> Generator[None]:
-    # Code before this runs before each test
-    yield
-    # Code after this runs after each test
-
-    global CLEAN_LINKED_FILES_CACHE
-    if CLEAN_LINKED_FILES_CACHE:
-        for filepath in TEST_FILES_DIR.glob("*.ifc.cache.*"):
-            filepath.unlink()
-        CLEAN_LINKED_FILES_CACHE = False
-
-    # pset_template tests are editing EPset_Drawing.ifc, so we need to restore it.
-    global RELOAD_EPSET_DRAWING
-    if RELOAD_EPSET_DRAWING:
-        EPSET_DRAWING.write_bytes(EPSET_DRAWING_BYTES)
-        RELOAD_EPSET_DRAWING = False
-
-
 @given("an untestable scenario")
 def an_untestable_scenario():
     pass
@@ -384,16 +362,6 @@ def saving_ifc_project() -> None:
     tool.Project.save_test_project()
 
 
-@given(parsers.parse('I link IFC project from "{filepath}"'))
-@when(parsers.parse('I link IFC project from "{filepath}"'))
-@then(parsers.parse('I link IFC project from "{filepath}"'))
-def i_link_ifc_project_from_filepath(filepath: str) -> None:
-    global CLEAN_LINKED_FILES_CACHE
-    filepath = replace_variables(filepath)
-    CLEAN_LINKED_FILES_CACHE = True
-    bpy.ops.bim.link_ifc(filepath=filepath, use_cache=False)
-
-
 @given("the Brickschema is stubbed")
 def the_brickschema_is_stubbed():
     # This makes things run faster since we don't need to load the entire brick schema
@@ -1587,10 +1555,19 @@ def the_object_name_has_a_vertex_at_location(name, location):
     is_pass = False
     target = Vector([float(co) for co in location.split(",")])
     verts = []
-    for v in obj.data.vertices:
+    depsgraph = bpy.context.evaluated_depsgraph_get()
-        verts.append(obj.matrix_world @ v.co)
+    obj_eval = obj.evaluated_get(depsgraph)
+    mesh = obj_eval.to_mesh(preserve_all_data_layers=False, depsgraph=depsgraph)
+    try:
+        for inst in depsgraph.object_instances:
+            if inst.object.original is obj:
+                mw = inst.matrix_world
+                for i, v in enumerate(mesh.vertices):
+                    verts.append(mw @ v.co)
                     if (verts[-1] - target).length < 0.001:
                         is_pass = True
+    finally:
+        obj_eval.to_mesh_clear()
     assert is_pass, f"No verts found at {location}: {verts}"
 
 

src/bonsai/test/tool/test_project.py

@@ -16,9 +16,12 @@
 # You should have received a copy of the GNU General Public License
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
 
+import json
 import contextlib
 import tempfile
+import numpy as np
 from pathlib import Path
+from tempfile import NamedTemporaryFile
 
 import bpy
 import ifcopenshell
@@ -263,7 +266,7 @@ class TestLoadLinkedModels(NewFile):
         props = tool.Project.get_project_props()
         ifcopenshell.api.root.create_entity(ifc, "IfcProject")
         document = ifcopenshell.api.document.add_information(ifc)
-        document.Name = "BBIM_Linked_Models"
+        document.Name = "X"
         tool.Ifc.set(ifc)
         subject.load_linked_models_from_ifc()
         assert len(props.links) == 0
@@ -273,86 +276,81 @@ class TestLoadLinkedModels(NewFile):
         props = tool.Project.get_project_props()
         ifcopenshell.api.root.create_entity(ifc, "IfcProject")
         document = ifcopenshell.api.document.add_information(ifc)
-        document.Name = "BBIM_Linked_Models"
+        document.Scope = "LINKED_MODEL"
         reference = ifcopenshell.api.document.add_reference(ifc, document)
-        linked_model_path = "test.ifc"
+        reference.Location = "test.ifc"
-        reference.Location = linked_model_path
+        reference.Identification = ""
+        reference2 = ifcopenshell.api.document.add_reference(ifc, document)
+        reference2.Location = "test2.ifc"
+        reference2.Identification = "1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16"
         tool.Ifc.set(ifc)
         subject.load_linked_models_from_ifc()
-        assert len(props.links) == 1
+        assert len(props.links) == 2
-        assert props.links[0].name == linked_model_path
+        assert props.links[0].name == "test.ifc"
+        assert props.links[0].ifc_definition_id == reference.id()
+        assert props.links[0].has_transformation is False
+        assert props.links[1].name == "test2.ifc"
+        assert props.links[1].ifc_definition_id == reference2.id()
+        assert props.links[1].has_transformation is True
 
 
-class TestSaveLinkedModelsToIfc(NewFile):
+class TestCalculateLinkMatrix(NewFile):
-    def test_save_linked_models_to_ifc_no_links(self):
+    def test_linking_a_model_without_an_offset_to_our_session_with_no_offset(self):
-        ifc = ifcopenshell.file()
-        tool.Ifc.set(ifc)
-        subject.save_linked_models_to_ifc()
-        assert len(ifc.by_type("IfcDocumentInformation")) == 0
-        assert len(ifc.by_type("IfcDocumentReference")) == 0
-
-    def test_save_linked_models_to_ifc_paths_to_add(self):
-        ifc = ifcopenshell.file()
-        ifcopenshell.api.root.create_entity(ifc, "IfcProject")
         props = tool.Project.get_project_props()
+        gprops = tool.Georeference.get_georeference_props()
+        with NamedTemporaryFile(suffix=".ifc.cache.json", mode="w", delete=True) as tmp:
             link = props.links.add()
-        linked_model_path = "test.ifc"
+            link.filepath = tmp.name.replace(".ifc.cache.json", ".ifc")
-        link.name = linked_model_path
+            json.dump({"model_project_north": "0", "model_origin_si": "0,0,0"}, tmp)
-        tool.Ifc.set(ifc)
+            tmp.flush()
-        subject.save_linked_models_to_ifc()
+            gprops.model_project_north = "0"
-        assert len(documents := ifc.by_type("IfcDocumentInformation")) == 1
+            gprops.model_origin_si = "0,0,0"
-        assert documents[0].Name == "BBIM_Linked_Models"
+            assert np.allclose(subject.calculate_link_matrix(link), np.eye(4))
-        assert len(references := ifc.by_type("IfcDocumentReference")) == 1
-        assert references[0].Location == linked_model_path
 
-    def test_save_linked_models_to_ifc_already_created_references(self):
+    def test_linking_an_offset_model_to_our_session_with_no_offset(self):
-        ifc = ifcopenshell.file()
+        props = tool.Project.get_project_props()
-        links = tool.Project.get_project_props().links
+        gprops = tool.Georeference.get_georeference_props()
-        ifcopenshell.api.root.create_entity(ifc, "IfcProject")
+        with NamedTemporaryFile(suffix=".ifc.cache.json", mode="w", delete=True) as tmp:
+            link = props.links.add()
+            link.filepath = tmp.name.replace(".ifc.cache.json", ".ifc")
+            json.dump({"model_project_north": "0", "model_origin_si": "5,0,0"}, tmp)
+            tmp.flush()
+            gprops.model_project_north = "0"
+            gprops.model_origin_si = "0,0,0"
+            m = np.eye(4)
+            m[0][3] = 5
+            assert np.allclose(subject.calculate_link_matrix(link), m)
 
-        document = ifcopenshell.api.document.add_information(ifc)
+    def test_linking_an_offset_model_to_our_session_with_offset(self):
-        document.Name = "BBIM_Linked_Models"
+        props = tool.Project.get_project_props()
-        document_id = document.id()
+        gprops = tool.Georeference.get_georeference_props()
-        reference = ifcopenshell.api.document.add_reference(ifc, document)
+        with NamedTemporaryFile(suffix=".ifc.cache.json", mode="w", delete=True) as tmp:
-        linked_model_path = "test.ifc"
+            link = props.links.add()
-        reference.Location = linked_model_path
+            link.filepath = tmp.name.replace(".ifc.cache.json", ".ifc")
-        reference_id = reference.id()
+            json.dump({"model_project_north": "0", "model_origin_si": "5,0,0"}, tmp)
+            tmp.flush()
+            gprops.model_project_north = "0"
+            gprops.model_origin_si = "2,0,0"
+            m = np.eye(4)
+            m[0][3] = 3
+            assert np.allclose(subject.calculate_link_matrix(link), m)
 
-        link = links.add()
+    def test_linking_an_offset_model_to_our_session_with_offset_and_transformation(self):
-        linked_model_path = "test.ifc"
+        props = tool.Project.get_project_props()
-        link.name = linked_model_path
+        gprops = tool.Georeference.get_georeference_props()
-        tool.Ifc.set(ifc)
+        with NamedTemporaryFile(suffix=".ifc.cache.json", mode="w", delete=True) as tmp:
-        subject.save_linked_models_to_ifc()
+            link = props.links.add()
-
+            link.filepath = tmp.name.replace(".ifc.cache.json", ".ifc")
-        # Information and references to stay intact.
+            transformation = np.eye(4)
-        assert len(documents := ifc.by_type("IfcDocumentInformation")) == 1
+            transformation[0][3] = 4
-        assert documents[0].id() == document_id
+            link.transformation = ",".join(map(str, transformation.reshape(-1)))
-        assert documents[0].Name == "BBIM_Linked_Models"
+            json.dump({"model_project_north": "0", "model_origin_si": "5,0,0"}, tmp)
-        assert len(references := ifc.by_type("IfcDocumentReference")) == 1
+            tmp.flush()
-        assert references[0].id() == reference_id
+            gprops.model_project_north = "0"
-        assert references[0].Location == linked_model_path
+            gprops.model_origin_si = "2,0,0"
-
+            m = np.eye(4)
-    def test_save_linked_models_to_ifc_references_to_remove(self):
+            m[0][3] = 7
-        ifc = ifcopenshell.file()
+            assert np.allclose(subject.calculate_link_matrix(link), m)
-        links = tool.Project.get_project_props().links
-        ifcopenshell.api.root.create_entity(ifc, "IfcProject")
-
-        document = ifcopenshell.api.document.add_information(ifc)
-        document.Name = "BBIM_Linked_Models"
-        document_id = document.id()
-        reference = ifcopenshell.api.document.add_reference(ifc, document)
-        linked_model_path = "test.ifc"
-        reference.Location = linked_model_path
-
-        tool.Ifc.set(ifc)
-        subject.save_linked_models_to_ifc()
-        links.clear()
-
-        # Remove reference for removed link.
-        assert len(documents := ifc.by_type("IfcDocumentInformation")) == 1
-        assert documents[0].id() == document_id
-        assert documents[0].Name == "BBIM_Linked_Models"
-        assert len(ifc.by_type("IfcDocumentReference")) == 0
 
 
 class TestLoadingIfcSqlite(NewFile):

src/ifcopenshell-python/ifcopenshell/util/geolocation.py

@@ -18,7 +18,7 @@
 
 import math
 from decimal import ROUND_HALF_UP, Decimal
-from typing import NamedTuple, Optional, Union
+from typing import NamedTuple, Optional, Union, Any
 
 import numpy as np
 
@@ -268,6 +268,15 @@ def get_helmert_transformation_parameters(ifc_file: ifcopenshell.file) -> Option
     return HelmertTransformation(e, n, h, xaa, xao, scale, factor_x, factor_y, factor_z)
 
 
+def get_crs(ifc_file: ifcopenshell.file) -> dict[str, Any]:
+    """Get CRS information from an IFC file."""
+    if ifc_file.schema == "IFC2X3":
+        return ifcopenshell.util.element.get_pset(ifc_file.by_type("IfcProject")[0], "ePSet_ProjectedCRS")
+    for context in ifc_file.by_type("IfcGeometricRepresentationContext", include_subtypes=False):
+        if operation := context.HasCoordinateOperation:
+            return operation[0].TargetCRS.get_info()
+
+
 def auto_z2e(ifc_file: ifcopenshell.file, z: float, should_return_in_map_units: bool = True) -> float:
     """Convert a Z coordinate to an elevation using model georeferencing data