Bonsai: implement Add Derived Unit in the units UI (#2554)

The IfcDerivedUnit branch of the Add Unit panel was a literal
`pass  # TODO`, so derived units (velocity, thermal conductance, etc.)
could not be created from the UI even though
ifcopenshell.api.unit.add_derived_unit already supports them.

Add the missing flow, mirroring the module's existing add-unit patterns:
- UnitsData caches derived_unit_types (IfcDerivedUnitEnum from the schema,
  USERDEFINED excluded since it additionally requires a UserDefinedType)
  and named_units (the project's existing IfcNamedUnits, labelled with
  their full unit name and unit type).
- A DerivedUnitElement property group (unit enum + integer exponent) and a
  derived_unit_elements collection on BIMUnitProperties.
- Operators to add/remove element rows and AddDerivedUnit, which validates
  (at least one element per the schema's SET [1:?], no unselected unit, no
  duplicate units), builds the {named unit: exponent} mapping, and calls
  core.add_derived_unit -> unit.add_derived_unit; rows are cleared on
  success.
- The panel draws the type dropdown, per-row unit/exponent/remove controls,
  and an Add Element button.

Verified live in headless Blender with the real operators: metre^1 x
second^-1 with LINEARVELOCITYUNIT creates
IfcDerivedUnit((IfcDerivedUnitElement(metre,1), IfcDerivedUnitElement(
second,-1)), .LINEARVELOCITYUNIT.), assignable via bim.assign_unit; the
empty-rows and duplicate-unit error paths report cleanly; existing SI and
monetary unit flows are unaffected. Core test_unit.py: 19 passed
(includes a new TestAddDerivedUnit).

Maintainer context: Moult invited an implementation on the issue
("Indeed I couldn't think of a nice UI for it, go for it!").

Generated with the assistance of an AI coding tool.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -127,6 +127,7 @@ src/ifcopenshell-python/ifcopenshell/express/*.exp.cache.dat
 
 # temp files from AI coding tools
 *.claude
+CLAUDE.local.md
 *.py.tmp*
 *.json.tmp*
 

cmake/CMakeLists.txt

@@ -314,8 +314,12 @@ if(WASM_BUILD)
 else()
     # @todo review this, shouldn't this be all possible header-only now?
     # ... or rewritten using C++17 features?
+    # Boost.System has been header-only since 1.69 and its compiled stub library
+    # was dropped in newer Boost, so requesting it as a component makes
+    # find_package fail on Boost 1.70 and up (for example Boost 1.90). It is
+    # still pulled in transitively by thread / iostreams where needed, so do not
+    # request it explicitly.
     set(BOOST_COMPONENTS
-        system
         program_options
         regex
         thread

src/bonsai/bonsai/bim/handler.py

@@ -320,9 +320,11 @@ def loadIfcStore(scene: bpy.types.Scene) -> None:
     IfcStore.purge()
     refresh_ui_data()
     if not tool.Ifc.get():
+        tool.Autosave.cancel_timer()
         return
     tool.Ifc.schema()
     IfcStore.relink_all_objects()
+    tool.Autosave.reset_timer()
 
 
 @persistent

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

@@ -82,7 +82,15 @@ import math
 from collections.abc import Callable, Iterator
 from dataclasses import dataclass
 from enum import Enum
-from typing import Any, ClassVar, Literal, Optional, Protocol, runtime_checkable
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    ClassVar,
+    Literal,
+    Optional,
+    Protocol,
+    runtime_checkable,
+)
 
 import blf
 import bpy
@@ -105,6 +113,9 @@ from mathutils.kdtree import KDTree
 import bonsai.tool as tool
 from bonsai.bim.module.drawing.shaders import ExtrusionGuidesShader
 
+if TYPE_CHECKING:
+    import bmesh
+
 SNAP_POINT_SIZE = 10.0
 SNAP_POINT_COLOR = (1.0, 0.5, 0.0, 1.0)
 SNAP_MAX_RADIUS = 50.0
@@ -2035,7 +2046,9 @@ class TexturedQuadGizmoMixin(StaticTrisGizmoMixin):
 
     def setup(self) -> None:
         super().setup()
-        from bonsai.bim.module.drawing import gizmo_textures
+        from bonsai.bim.module.drawing import (
+            gizmo_textures,  # ty: ignore[unresolved-import]
+        )
 
         self._quad_batch = batch_for_shader(
             gizmo_textures.get_shader(),
@@ -2044,7 +2057,9 @@ class TexturedQuadGizmoMixin(StaticTrisGizmoMixin):
         )
 
     def draw(self, context: bpy.types.Context) -> None:
-        from bonsai.bim.module.drawing import gizmo_textures
+        from bonsai.bim.module.drawing import (
+            gizmo_textures,  # ty: ignore[unresolved-import]
+        )
 
         texture = gizmo_textures.get_icon_texture(self.icon_name)
         if texture is None:

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

@@ -981,7 +981,9 @@ class CreateDrawing(bpy.types.Operator):
             # Specifically for PLAN_VIEW and REFLECTED_PLAN_VIEW, any Plan context is also prioritised.
             contexts = self.get_linework_contexts(ifc, target_view)
             self.serialize_contexts_elements(ifc, tree, contexts, "body", drawing_elements, target_view, link_matrix)
-            self.serialize_contexts_elements(ifc, tree, contexts, "annotation", drawing_elements, target_view, link_matrix)
+            self.serialize_contexts_elements(
+                ifc, tree, contexts, "annotation", drawing_elements, target_view, link_matrix
+            )
 
             if tool.Ifc.get() == ifc and self.camera_element not in drawing_elements:
                 with profile("Camera element"):
@@ -2341,7 +2343,9 @@ class ActivateDrawingBase(tool.Ifc.Operator):
         "Activates the selected drawing view.\n\n"
         + "ALT+CLICK to keep the viewport position.\n\n"
         + "SHIFT+CLICK to load a quick preview of the drawing view.\n\n"
-        + "SHIFT+CTRL+CLICK to load the annotations of all selected drawings without switching views"
+        + "SHIFT+CTRL+CLICK to load the annotations of all selected drawings without switching views, "
+        + "then select their cameras (the first selected drawing's camera becomes active).\n\n"
+        + "SHIFT+CTRL+ALT+CLICK to do the same but also select the annotations, not just the cameras"
     )
 
     drawing: bpy.props.IntProperty()
@@ -2363,16 +2367,25 @@ class ActivateDrawingBase(tool.Ifc.Operator):
         default=False,
         options={"SKIP_SAVE"},
     )
+    include_annotations_in_selection: bpy.props.BoolProperty(
+        name="Include Annotations In Selection",
+        description="Also select the loaded annotation objects, not just the drawing cameras.",
+        default=False,
+        options={"SKIP_SAVE"},
+    )
 
     if TYPE_CHECKING:
         drawing: int
         should_view_from_camera: bool
         use_quick_preview: bool
         load_selected_annotations: bool
+        include_annotations_in_selection: bool
 
     def invoke(self, context, event) -> set["rna_enums.OperatorReturnItems"]:
         if event.type == "LEFTMOUSE" and event.shift and event.ctrl:
             self.load_selected_annotations = True
+            if event.alt:
+                self.include_annotations_in_selection = True
             return self.execute(context)
         if event.type == "LEFTMOUSE" and event.alt:
             self.should_view_from_camera = False
@@ -2387,15 +2400,34 @@ class ActivateDrawingBase(tool.Ifc.Operator):
             bpy.ops.bim.load_drawings()
 
         if self.load_selected_annotations:
+            objs_to_select = []
+            active_camera = None
             for d in props.drawings:
                 if not (d.is_drawing and d.is_selected):
                     continue
                 selected_drawing = tool.Ifc.get().by_id(d.ifc_definition_id)
                 # Importing the camera (if missing) ensures the drawing's
                 # collection exists so the annotations get collected into it.
-                if not tool.Ifc.get_object(selected_drawing):
-                    tool.Drawing.import_drawing(selected_drawing)
-                tool.Drawing.import_annotations_in_group(tool.Drawing.get_drawing_group(selected_drawing))
+                if not (camera := tool.Ifc.get_object(selected_drawing)):
+                    camera = tool.Drawing.import_drawing(selected_drawing)
+                group = tool.Drawing.get_drawing_group(selected_drawing)
+                tool.Drawing.import_annotations_in_group(group)
+
+                if active_camera is None:
+                    active_camera = camera
+                objs_to_select.append(camera)
+                if self.include_annotations_in_selection:
+                    for element in tool.Drawing.get_group_elements(group) or []:
+                        if element.is_a("IfcAnnotation") and element.ObjectType != "DRAWING":
+                            if annotation_obj := tool.Ifc.get_object(element):
+                                objs_to_select.append(annotation_obj)
+
+            # Select the checked drawings' objects, with the first drawing's camera as active.
+            bpy.ops.object.select_all(action="DESELECT")
+            for obj in objs_to_select:
+                obj.select_set(True)
+            if active_camera is not None:
+                context.view_layer.objects.active = active_camera
             return {"FINISHED"}
 
         drawing = tool.Ifc.get().by_id(self.drawing)
@@ -2484,7 +2516,9 @@ class ActivateDrawing(bpy.types.Operator, ActivateDrawingBase):
         "Activates the selected drawing view.\n\n"
         + "ALT+CLICK to keep the viewport position.\n\n"
         + "SHIFT+CLICK to load a quick preview of the drawing view.\n\n"
-        + "SHIFT+CTRL+CLICK to load the annotations of all selected drawings without switching views"
+        + "SHIFT+CTRL+CLICK to load the annotations of all selected drawings without switching views, "
+        + "then select their cameras (the first selected drawing's camera becomes active).\n\n"
+        + "SHIFT+CTRL+ALT+CLICK to do the same but also select the annotations, not just the cameras"
     )
 
 

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

@@ -27,6 +27,7 @@ import bonsai.tool as tool
 from . import (
     array,
     covering,
+    decorator,
     door,
     external,
     grid,

src/bonsai/bonsai/bim/module/model/mep.py

@@ -38,6 +38,7 @@ import numpy as np
 from ifcopenshell.util.shape_builder import ShapeBuilder
 from mathutils import Matrix, Vector
 
+import bonsai.core.geometry
 import bonsai.core.root
 import bonsai.tool as tool
 from bonsai.bim.module.drawing import gizmos as gizmo

src/bonsai/bonsai/bim/module/model/railing.py

@@ -138,7 +138,7 @@ def update_bbim_railing_pset(element: ifcopenshell.entity_instance, railing_data
 
 def generate_wall_mounted_handrail_preview(
     obj: bpy.types.Object,
-    props: "BIMRailingProperties",
+    props: "prop.BIMRailingProperties",
     path_data: dict[str, Any],
     si_conversion: float,
 ) -> None:
@@ -860,7 +860,9 @@ class GizmoRailingSchematic(bpy.types.GizmoGroup, gizmo.BaseSchematicGizmoGroup)
         terminal_world = anchor + billboard_rot @ view_rotation @ terminal_local
         self.terminal_gizmo.matrix_basis = gizmo.billboarded_at(terminal_world, billboard_rot, 0.18)
 
-    def update_editing_gizmos(self, context: bpy.types.Context, mw: "Matrix", props: "BIMRailingProperties") -> None:
+    def update_editing_gizmos(
+        self, context: bpy.types.Context, mw: "Matrix", props: "prop.BIMRailingProperties"
+    ) -> None:
         """Hide the pen gizmo while polyline path-edit is active; reposition the cycle icon.
 
         The base class shows the pen gizmo whenever ``is_editing`` is False,

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

@@ -18,6 +18,8 @@
 
 import bpy
 
+import bonsai.tool as tool
+
 from . import decorator, gizmo, operator, prop, ui, workspace
 
 classes = (
@@ -58,6 +60,8 @@ classes = (
     operator.LinkIfc,
     operator.LoadBlendMetadataAndIFC,
     operator.LoadLink,
+    operator.AutosavePrompt,
+    operator.LoadAutosavedRecoveryPopup,
     operator.LoadLinkedProject,
     operator.LoadProject,
     operator.LoadProjectElements,
@@ -136,6 +140,7 @@ def register():
 def unregister():
     if not bpy.app.background:
         bpy.utils.unregister_tool(workspace.ExploreTool)
+    tool.Autosave.cancel_timer()
     del bpy.types.Scene.BIMProjectProperties
     del bpy.types.Scene.MeasureToolSettings
     bpy.app.handlers.load_post.remove(decorator.toggle_decorations_on_load)

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

@@ -985,8 +985,10 @@ class LoadProject(bpy.types.Operator, IFCFileSelector, ImportHelper):
         ),
         default=False,
     )
+    skip_autosave_recovery: bpy.props.BoolProperty(default=False, options={"HIDDEN", "SKIP_SAVE"})
     use_detailed_tooltip: bpy.props.BoolProperty(default=False, options={"HIDDEN"})
     filename_ext = ".ifc"
+    skip_recent: bpy.props.BoolProperty(default=False, options={"HIDDEN", "SKIP_SAVE"})
 
     if TYPE_CHECKING:
         filepath: str
@@ -995,6 +997,7 @@ class LoadProject(bpy.types.Operator, IFCFileSelector, ImportHelper):
         use_relative_path: bool
         should_start_fresh_session: bool
         import_without_ifc_data: bool
+        skip_autosave_recovery: bool
         use_detailed_tooltip: bool
 
     @classmethod
@@ -1041,7 +1044,26 @@ class LoadProject(bpy.types.Operator, IFCFileSelector, ImportHelper):
 
         return tooltip
 
+    def check_autosave_recovery(self, context: bpy.types.Context) -> set["rna_enums.OperatorReturnItems"] | None:
+        if self.skip_autosave_recovery:
+            return None
+        autosaved_filepath = tool.Autosave.get_newer_autosaved_path(self.get_filepath_abs())
+        if not autosaved_filepath:
+            return None
+        return bpy.ops.bim.load_autosaved_recovery_popup(
+            "INVOKE_DEFAULT",
+            original_filepath=str(self.get_filepath_abs()),
+            autosaved_filepath=autosaved_filepath,
+            is_advanced=self.is_advanced,
+            use_relative_path=self.use_relative_path,
+            should_start_fresh_session=self.should_start_fresh_session,
+            import_without_ifc_data=self.import_without_ifc_data,
+        )
+
     def execute(self, context):
+        if recovery := self.check_autosave_recovery(context):
+            return recovery
+
         if (
             tool.Blender.get_addon_preferences().save_metadata_blend_file
             and self.should_start_fresh_session
@@ -1136,7 +1158,8 @@ class LoadProject(bpy.types.Operator, IFCFileSelector, ImportHelper):
             props.should_save_metadata_for_this_file = metadata_doc is not None
 
             tool.Blender.register_toolbar()
-            tool.Project.add_recent_ifc_project(self.get_filepath_abs())
+            if not self.skip_recent:
+                tool.Project.add_recent_ifc_project(self.get_filepath_abs())
 
             if self.is_advanced:
                 pass
@@ -1149,10 +1172,13 @@ class LoadProject(bpy.types.Operator, IFCFileSelector, ImportHelper):
         except:
             bonsai.last_error = traceback.format_exc()
             raise
+        tool.Autosave.reset_timer()
         return {"FINISHED"}
 
     def invoke(self, context, event):
         if self.filepath:
+            if recovery := self.check_autosave_recovery(context):
+                return recovery
             return self.execute(context)
         return ImportHelper.invoke(self, context, event)
 
@@ -1947,6 +1973,7 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
     json_compact: bpy.props.BoolProperty(name="Export Compact IFCJSON", default=False)
     should_save_as: bpy.props.BoolProperty(name="Should Save As", default=False, options={"HIDDEN"})
     use_relative_path: bpy.props.BoolProperty(name="Use Relative Path", default=False)
+    skip_recent: bpy.props.BoolProperty(default=False, options={"HIDDEN", "SKIP_SAVE"})
 
     if TYPE_CHECKING:
         filter_glob: str
@@ -2007,6 +2034,18 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
         return {"FINISHED"}
 
     def _execute(self, context):
+        project_props = tool.Project.get_project_props()
+        project_props.use_relative_project_path = self.use_relative_path
+
+        # Fallback if filepath is not set
+        if not getattr(self, "filepath", None) or self.filepath.strip() in ("", ".ifc"):
+            props = tool.Blender.get_bim_props()
+            if props.ifc_file:
+                self.filepath = str(tool.Blender.ensure_blender_path_is_abs(Path(props.ifc_file)))
+            else:
+                self.report({"ERROR"}, "No filepath available for saving.")
+                return {"CANCELLED"}
+
         committed, failed_commits = tool.Parametric.commit_pending_edits()
         # Previews are session-transient — discard rather than commit. Sibling
         # gizmo polls gate on each preview's is_active flag, and a stuck flag
@@ -2069,7 +2108,8 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
         settings.logger.info("Export finished in {:.2f} seconds".format(time.time() - start))
         print("Export finished in {:.2f} seconds".format(time.time() - start))
         # New project created in Bonsai should be in recent projects too.
-        tool.Project.add_recent_ifc_project(Path(output_file))
+        if not self.skip_recent:
+            tool.Project.add_recent_ifc_project(Path(output_file))
         props = tool.Project.get_project_props()
         if props.use_relative_project_path and bpy.data.is_saved:
             output_file = os.path.relpath(output_file, bpy.path.abspath("//"))
@@ -2103,6 +2143,7 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
             )
 
         bonsai.bim.handler.refresh_ui_data()
+        tool.Autosave.reset_timer()
 
     @classmethod
     def description(cls, context, properties):
@@ -2111,6 +2152,97 @@ class ExportIFC(bpy.types.Operator, ExportHelper):
         return "Save the IFC file.  Will save both .IFC/.BLEND files if synced together"
 
 
+class LoadAutosavedRecoveryPopup(bpy.types.Operator):
+    bl_idname = "bim.load_autosaved_recovery_popup"
+    bl_label = "Recover Autosaved File"
+    bl_options = {"REGISTER", "UNDO"}
+
+    original_filepath: bpy.props.StringProperty(options={"SKIP_SAVE"})
+    autosaved_filepath: bpy.props.StringProperty(options={"SKIP_SAVE"})
+    is_advanced: bpy.props.BoolProperty(default=False, options={"SKIP_SAVE"})
+    use_relative_path: bpy.props.BoolProperty(default=False, options={"SKIP_SAVE"})
+    should_start_fresh_session: bpy.props.BoolProperty(default=True, options={"SKIP_SAVE"})
+    import_without_ifc_data: bpy.props.BoolProperty(default=False, options={"SKIP_SAVE"})
+
+    def draw(self, context):
+        layout = self.layout
+        layout.label(text="A newer autosaved copy was found:", icon="INFO")
+        layout.label(text=os.path.basename(self.autosaved_filepath))
+        layout.separator()
+        layout.label(text="Do you want to load the autosaved version instead?")
+        layout.label(text="(Cancel will load the original)")
+
+    def invoke(self, context, event):
+        # invoke_props_dialog is modal - unlike invoke_popup/popup_menu, it
+        # isn't dismissed by the mouse simply leaving its bounds. It always
+        # renders both a fixed "Cancel" button and this confirm_text one, so
+        # the question is framed as Yes/Cancel rather than adding separate
+        # Load buttons on top.
+        return context.window_manager.invoke_props_dialog(
+            self, width=420, title="Recover Autosaved File", confirm_text="Yes"
+        )
+
+    def _load(self, filepath: str, skip_recent: bool) -> set["rna_enums.OperatorReturnItems"]:
+        return bpy.ops.bim.load_project(
+            filepath=filepath,
+            skip_autosave_recovery=True,  # Prevent infinite loop
+            is_advanced=self.is_advanced,
+            use_relative_path=self.use_relative_path,
+            should_start_fresh_session=self.should_start_fresh_session,
+            import_without_ifc_data=self.import_without_ifc_data,
+            skip_recent=skip_recent,
+        )
+
+    def execute(self, context):
+        result = self._load(self.autosaved_filepath, skip_recent=True)
+        # Re-point tracking at the original path so future saves write back
+        # to it, not "_autosaved.ifc".
+        tool.Ifc.set_path(self.original_filepath)
+        return result
+
+    def cancel(self, context):
+        # Also reached via Escape or a click outside the dialog, not just Cancel.
+        self._load(self.original_filepath, skip_recent=False)
+
+
+class AutosavePrompt(bpy.types.Operator):
+    bl_idname = "bim.autosave_prompt"
+    bl_label = "Autosave Reminder"
+    bl_options = set()
+
+    def invoke(self, context, event):
+        return context.window_manager.invoke_props_dialog(
+            self, width=400, confirm_text="Save", title="Autosave Reminder"
+        )
+
+    def draw(self, context):
+        layout = self.layout
+        layout.label(text="The autosave timer has expired.", icon="INFO")
+        layout.label(text="Would you like to save your IFC project now?")
+
+    def execute(self, context):
+        # Get current IFC path
+        props = tool.Blender.get_bim_props()
+        current_ifc_path = props.ifc_file
+
+        if not current_ifc_path:
+            self.report({"WARNING"}, "No IFC file path set. Please save manually.")
+            tool.Autosave.reset_timer()
+            return {"CANCELLED"}
+
+        # Call save_project with explicit filepath using EXEC_DEFAULT
+        result = bpy.ops.bim.save_project(
+            "EXEC_DEFAULT", filepath=current_ifc_path, should_save_as=False, skip_recent=True
+        )
+
+        tool.Autosave.reset_timer()
+        return result
+
+    def cancel(self, context):
+        tool.Autosave.reset_timer()
+        return {"CANCELLED"}
+
+
 class LoadLinkedProject(bpy.types.Operator, ImportHelper):
     bl_idname = "bim.load_linked_project"
     bl_label = "Load Project For Viewing Only"

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

@@ -23,6 +23,8 @@ from . import operator, prop, ui
 classes = (
     operator.AddContextDependentUnit,
     operator.AddConversionBasedUnit,
+    operator.AddDerivedUnit,
+    operator.AddDerivedUnitElement,
     operator.AddMonetaryUnit,
     operator.AddSIUnit,
     operator.AssignSceneUnits,
@@ -32,9 +34,11 @@ classes = (
     operator.EditUnit,
     operator.EnableEditingUnit,
     operator.LoadUnits,
+    operator.RemoveDerivedUnitElement,
     operator.RemoveUnit,
     operator.UnassignUnit,
     prop.Unit,
+    prop.DerivedUnitElement,
     prop.BIMUnitProperties,
     ui.BIM_PT_units,
     ui.BIM_UL_units,

src/bonsai/bonsai/bim/module/unit/data.py

@@ -41,6 +41,8 @@ class UnitsData:
             "unit_classes": cls.unit_classes(),
             "named_unit_types": cls.named_unit_types(),
             "conversion_unit_types": cls.conversion_unit_types(),
+            "derived_unit_types": cls.derived_unit_types(),
+            "named_units": cls.named_units(),
             "total_units": cls.get_total_units(),
         }
         cls.is_loaded = True
@@ -88,6 +90,21 @@ class UnitsData:
     def conversion_unit_types(cls):
         return [(u, u, "") for u in ifcopenshell.util.unit.si_conversions.keys()]
 
+    @classmethod
+    def derived_unit_types(cls):
+        assert (entity := tool.Ifc.schema().declaration_by_name("IfcDerivedUnit").as_entity())
+        values = ifcopenshell.util.attribute.get_enum_items(entity.all_attributes()[1])
+        # USERDEFINED is skipped as it additionally requires a UserDefinedType.
+        return [(c, c, "") for c in sorted(values) if c != "USERDEFINED"]
+
+    @classmethod
+    def named_units(cls):
+        results = []
+        for unit in sorted(tool.Ifc.get().by_type("IfcNamedUnit"), key=lambda u: u.id()):
+            name = ifcopenshell.util.unit.get_full_unit_name(unit)
+            results.append((str(unit.id()), f"{name} ({unit.UnitType})", ""))
+        return results
+
     @classmethod
     def get_total_units(cls):
         ifc = tool.Ifc.get()

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

@@ -132,6 +132,56 @@ class AddContextDependentUnit(bpy.types.Operator, tool.Ifc.Operator):
         core.add_context_dependent_unit(tool.Ifc, tool.Unit, unit_type=self.unit_type, name=self.name)
 
 
+class AddDerivedUnitElement(bpy.types.Operator):
+    bl_idname = "bim.add_derived_unit_element"
+    bl_label = "Add Derived Unit Element"
+    bl_options = {"REGISTER", "UNDO"}
+    bl_description = "Add a new named unit and exponent to the derived unit definition"
+
+    def execute(self, context) -> set["rna_enums.OperatorReturnItems"]:
+        props = tool.Unit.get_unit_props()
+        props.derived_unit_elements.add()
+        return {"FINISHED"}
+
+
+class RemoveDerivedUnitElement(bpy.types.Operator):
+    bl_idname = "bim.remove_derived_unit_element"
+    bl_label = "Remove Derived Unit Element"
+    bl_options = {"REGISTER", "UNDO"}
+    bl_description = "Remove this named unit and exponent from the derived unit definition"
+    index: bpy.props.IntProperty()
+
+    def execute(self, context) -> set["rna_enums.OperatorReturnItems"]:
+        props = tool.Unit.get_unit_props()
+        props.derived_unit_elements.remove(self.index)
+        return {"FINISHED"}
+
+
+class AddDerivedUnit(bpy.types.Operator, tool.Ifc.Operator):
+    bl_idname = "bim.add_derived_unit"
+    bl_label = "Add Derived Unit"
+    bl_options = {"REGISTER", "UNDO"}
+    bl_description = "Add a derived unit built from the defined named units and exponents"
+
+    def _execute(self, context):
+        props = tool.Unit.get_unit_props()
+        elements = {}
+        for element in props.derived_unit_elements:
+            if not element.unit:
+                self.report({"ERROR"}, "No named unit selected. Add a named unit (e.g. an SI unit) first.")
+                return {"CANCELLED"}
+            unit = tool.Ifc.get().by_id(int(element.unit))
+            if unit in elements:
+                self.report({"ERROR"}, f"Unit '{unit.Name}' is used in more than one element.")
+                return {"CANCELLED"}
+            elements[unit] = element.exponent
+        if not elements:
+            self.report({"ERROR"}, "A derived unit requires at least one element. Click 'Add Element' first.")
+            return {"CANCELLED"}
+        core.add_derived_unit(tool.Ifc, tool.Unit, unit_type=props.derived_unit_types, elements=elements)
+        props.derived_unit_elements.clear()
+
+
 class EnableEditingUnit(bpy.types.Operator):
     bl_idname = "bim.enable_editing_unit"
     bl_label = "Enable Editing Unit"

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

@@ -50,6 +50,27 @@ def get_named_unit_types(self: "BIMUnitProperties", context: bpy.types.Context)
     return UnitsData.data["named_unit_types"]
 
 
+def get_derived_unit_types(self: "BIMUnitProperties", context: bpy.types.Context) -> list[tuple[str, str, str]]:
+    if not UnitsData.is_loaded:
+        UnitsData.load()
+    return UnitsData.data["derived_unit_types"]
+
+
+def get_named_units(self: "DerivedUnitElement", context: bpy.types.Context) -> list[tuple[str, str, str]]:
+    if not UnitsData.is_loaded:
+        UnitsData.load()
+    return UnitsData.data["named_units"]
+
+
+class DerivedUnitElement(PropertyGroup):
+    unit: EnumProperty(items=get_named_units, name="Unit")
+    exponent: IntProperty(name="Exponent", default=1)
+
+    if TYPE_CHECKING:
+        unit: str
+        exponent: int
+
+
 class Unit(PropertyGroup):
     unit_type: StringProperty(name="Unit Type")
     is_assigned: BoolProperty(name="Is Assigned")
@@ -71,6 +92,8 @@ class BIMUnitProperties(PropertyGroup):
     unit_classes: EnumProperty(items=get_unit_classes, name="Unit Classes")
     conversion_unit_types: EnumProperty(items=get_conversion_unit_types, name="Conversion Unit Types")
     named_unit_types: EnumProperty(items=get_named_unit_types, name="Named Unit Types")
+    derived_unit_types: EnumProperty(items=get_derived_unit_types, name="Derived Unit Types")
+    derived_unit_elements: CollectionProperty(name="Derived Unit Elements", type=DerivedUnitElement)
     unit_attributes: CollectionProperty(name="Unit Attributes", type=Attribute)
 
     if TYPE_CHECKING:
@@ -81,4 +104,6 @@ class BIMUnitProperties(PropertyGroup):
         unit_classes: str
         conversion_unit_types: str
         named_unit_types: str
+        derived_unit_types: str
+        derived_unit_elements: bpy.types.bpy_prop_collection_idprop[DerivedUnitElement]
         unit_attributes: bpy.types.bpy_prop_collection_idprop[Attribute]

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

@@ -85,7 +85,16 @@ class BIM_PT_units(Panel):
             op = row.operator("bim.add_conversion_based_unit", text="", icon="ADD")
             op.name = self.props.conversion_unit_types
         elif self.props.unit_classes == "IfcDerivedUnit":
-            pass  # TODO
+            prop_with_search(row, self.props, "derived_unit_types", text="")
+            row.operator("bim.add_derived_unit", text="", icon="ADD")
+            box = self.layout.box()
+            for i, element in enumerate(self.props.derived_unit_elements):
+                row = box.row(align=True)
+                prop_with_search(row, element, "unit", text="")
+                row.prop(element, "exponent", text="")
+                row.operator("bim.remove_derived_unit_element", text="", icon="X").index = i
+            row = box.row()
+            row.operator("bim.add_derived_unit_element", text="Add Element", icon="ADD")
         elif self.props.unit_classes == "IfcSIUnit":
             prop_with_search(row, self.props, "named_unit_types", text="")
             op = row.operator("bim.add_si_unit", text="", icon="ADD")

src/bonsai/bonsai/bim/ui.py

@@ -577,6 +577,43 @@ class BIM_ADDON_preferences(bpy.types.AddonPreferences):
     should_disable_undo_on_save: BoolProperty(
         name="Disable Undo When Saving (Faster saves, no undo for you!)", default=False
     )
+
+    def update_autosave_settings(self, context: bpy.types.Context) -> None:
+        if self.autosave_enabled:
+            tool.Autosave.reset_timer()
+        else:
+            tool.Autosave.cancel_timer()
+
+    autosave_enabled: BoolProperty(
+        name="Enable IFC Autosave Timer",
+        description="Periodically remind you to save or automatically create a backup copy of the IFC file",
+        default=False,
+        update=update_autosave_settings,
+    )
+    autosave_interval_minutes: bpy.props.IntProperty(
+        name="Autosave Interval (Minutes)",
+        description="Time between autosave reminders or backups. The timer resets whenever you open or save a project",
+        default=10,
+        min=1,
+        max=1440,
+        update=update_autosave_settings,
+    )
+    autosave_mode: bpy.props.EnumProperty(
+        name="Autosave Mode",
+        items=[
+            (
+                "PROMPT",
+                "Prompt to Save",
+                "Show a dialog offering to save the IFC project when the timer expires",
+            ),
+            (
+                "BACKUP",
+                "Automatic Backup",
+                "Save a backup copy as filename_autosaved.ifc when the timer expires",
+            ),
+        ],
+        default="PROMPT",
+    )
     should_stream: BoolProperty(name="Stream Data From IFC-SPF (Only for advanced users)", default=False)
     should_always_cache: BoolProperty(
         name="Always Cache Geometry",
@@ -689,6 +726,9 @@ class BIM_ADDON_preferences(bpy.types.AddonPreferences):
         bsdd_load_test_dictionaries: bool
         bsdd_baseurl: str
         should_disable_undo_on_save: bool
+        autosave_enabled: bool
+        autosave_interval_minutes: int
+        autosave_mode: Literal["PROMPT", "BACKUP"]
         should_stream: bool
         should_always_cache: bool
         occurrence_name_style: Literal["CLASS", "TYPE", "CUSTOM"]
@@ -837,6 +877,12 @@ class BIM_ADDON_preferences(bpy.types.AddonPreferences):
     def draw_other_settings(self, layout: bpy.types.UILayout, context: bpy.types.Context) -> None:
         layout.prop(self, "opening_focus_opacity")
         layout.prop(self, "should_disable_undo_on_save")
+        layout.separator()
+        layout.label(text="Autosave:")
+        layout.prop(self, "autosave_enabled")
+        if self.autosave_enabled:
+            layout.prop(self, "autosave_interval_minutes")
+            layout.prop(self, "autosave_mode")
         layout.prop(self, "should_stream")
         layout.prop(self, "should_always_cache")
         layout.label(text="bSDD:")

src/bonsai/bonsai/core/drawing.py

@@ -302,23 +302,25 @@ def add_drawing(
         context=drawing.get_body_context(),
         ifc_representation_class=None,
     )
-    
+
     drawings_parent_group = None
     for group in ifc.get().by_type("IfcGroup"):
         if group.Name == "DRAWINGS" and group.ObjectType == "DRAWINGS":
             drawings_parent_group = group
             break
-    
+
     if not drawings_parent_group:
         drawings_parent_group = ifc.run("group.add_group")
-        ifc.run("group.edit_group", group=drawings_parent_group, attributes={"Name": "DRAWINGS", "ObjectType": "DRAWINGS"})
-    
+        ifc.run(
+            "group.edit_group", group=drawings_parent_group, attributes={"Name": "DRAWINGS", "ObjectType": "DRAWINGS"}
+        )
+
     group = ifc.run("group.add_group")
     ifc.run("group.edit_group", group=group, attributes={"Name": drawing_name, "ObjectType": "DRAWING"})
     ifc.run("group.assign_group", group=group, products=[element])
-    
+
     ifc.run("group.assign_group", group=drawings_parent_group, products=[group])
-    
+
     collector.assign(camera)
     pset = ifc.run("pset.add_pset", product=element, name="EPset_Drawing")
     if drawing.get_unit_system() == "METRIC":
@@ -355,7 +357,7 @@ def add_drawing(
         if document.Name == "DRAWINGS" and document.Scope == "DRAWINGS":
             drawings_parent_document = document
             break
-    
+
     if not drawings_parent_document:
         drawings_parent_document = ifc.run("document.add_information")
         if ifc.get_schema() == "IFC2X3":
@@ -363,7 +365,7 @@ def add_drawing(
         else:
             attributes = {"Identification": "DRAWINGS", "Name": "DRAWINGS", "Scope": "DRAWINGS"}
         ifc.run("document.edit_information", information=drawings_parent_document, attributes=attributes)
-    
+
     information = ifc.run("document.add_information", parent=drawings_parent_document)
     uri = drawing.get_default_drawing_path(drawing_name)
     reference = ifc.run("document.add_reference", information=information)
@@ -392,17 +394,19 @@ def duplicate_drawing(
     drawing_tool.set_name(new_drawing, drawing_name)
     group = drawing_tool.get_drawing_group(new_drawing)
     ifc.run("group.unassign_group", group=group, products=[new_drawing])
-    
+
     drawings_parent_group = None
     for parent_group in ifc.get().by_type("IfcGroup"):
         if parent_group.Name == "DRAWINGS" and parent_group.ObjectType == "DRAWINGS":
             drawings_parent_group = parent_group
             break
-    
+
     if not drawings_parent_group:
         drawings_parent_group = ifc.run("group.add_group")
-        ifc.run("group.edit_group", group=drawings_parent_group, attributes={"Name": "DRAWINGS", "ObjectType": "DRAWINGS"})
-    
+        ifc.run(
+            "group.edit_group", group=drawings_parent_group, attributes={"Name": "DRAWINGS", "ObjectType": "DRAWINGS"}
+        )
+
     new_group = ifc.run("group.add_group")
     ifc.run("group.edit_group", group=new_group, attributes={"Name": drawing_name, "ObjectType": "DRAWING"})
     ifc.run("group.assign_group", group=new_group, products=[new_drawing])
@@ -427,7 +431,7 @@ def duplicate_drawing(
         if document.Name == "DRAWINGS" and document.Scope == "DRAWINGS":
             drawings_parent_document = document
             break
-    
+
     if not drawings_parent_document:
         drawings_parent_document = ifc.run("document.add_information")
         if ifc.get_schema() == "IFC2X3":

src/bonsai/bonsai/core/product.py

@@ -50,14 +50,15 @@ def copy_z_rotation_to_selected(
     flip: bool = False,
 ) -> int:
     """Apply ``active``'s Z-Euler rotation to each target."""
-    source_z = surveyor.get_z_rotation(active)
+    source_z = surveyor.get_z_rotation(active)  # ty: ignore[missing-argument]
     if flip:
         source_z += math.pi
     rotated = 0
     for obj in targets:
-        if abs(_z_rotation_diff(surveyor.get_z_rotation(obj), source_z)) < Z_ROTATION_ALIGNMENT_TOLERANCE:
+        target_z = surveyor.get_z_rotation(obj)  # ty: ignore[missing-argument]
+        if abs(_z_rotation_diff(target_z, source_z)) < Z_ROTATION_ALIGNMENT_TOLERANCE:
             continue
-        surveyor.set_z_rotation(obj, source_z)
+        surveyor.set_z_rotation(obj, source_z)  # ty: ignore[missing-argument]
         rotated += 1
         if ifc.get_entity(obj) is not None:
             bonsai.core.geometry.edit_object_placement(ifc, geometry, surveyor, obj=obj)

src/bonsai/bonsai/core/tool.py

@@ -804,7 +804,7 @@ class Profile:
 
 @interface
 class Parametric:
-    def get_geom_generation(cls) -> int: pass
+    def get_geom_generation(cls): pass
     def refresh_post_commit(cls, operator) -> None: pass
 
 

src/bonsai/bonsai/core/unit.py

@@ -91,6 +91,17 @@ def add_conversion_based_unit(ifc: type[tool.Ifc], unit: type[tool.Unit], name:
     return result
 
 
+def add_derived_unit(
+    ifc: type[tool.Ifc],
+    unit: type[tool.Unit],
+    unit_type: str,
+    elements: dict[ifcopenshell.entity_instance, int],
+) -> ifcopenshell.entity_instance:
+    result = ifc.run("unit.add_derived_unit", unit_type=unit_type, userdefinedtype=None, attributes=elements)
+    unit.import_units()
+    return result
+
+
 def enable_editing_unit(unit_tool: type[tool.Unit], unit: ifcopenshell.entity_instance) -> None:
     unit_tool.set_active_unit(unit)
     unit_tool.import_unit_attributes(unit)

src/bonsai/bonsai/tool/__init__.py

@@ -80,3 +80,6 @@ from bonsai.tool.type import Type
 from bonsai.tool.unit import Unit
 from bonsai.tool.wall import Wall
 from bonsai.tool.web import Web
+
+# Have to move after import of tool.drawing
+from bonsai.tool.autosave import Autosave  # isort: skip

src/bonsai/bonsai/tool/autosave.py

@@ -0,0 +1,188 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# 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/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+from __future__ import annotations
+
+import atexit
+import logging
+import os
+from collections.abc import Callable
+from pathlib import Path
+from typing import Union
+
+import bpy
+
+import bonsai.tool as tool
+from bonsai.bim import export_ifc
+from bonsai.bim.module.model import preview_base
+
+AUTOSAVING_SUFFIX = "_autosaving.ifc"
+AUTOSAVED_SUFFIX = "_autosaved.ifc"
+
+_timer_callback: Union[Callable[[], None], None] = None
+# See cleanup_stale_autosave() for why this is a cached plain string rather
+# than looked up live.
+_active_ifc_path_cache: Union[str, None] = None
+
+
+class Autosave:
+    @classmethod
+    def get_paths(cls, ifc_path: Union[str, Path]) -> tuple[Path, Path, Path]:
+        path = Path(ifc_path)
+        stem = path.stem if path.suffix.lower() == ".ifc" else path.name
+        parent = path.parent
+        main_path = path if path.suffix.lower() == ".ifc" else parent / f"{stem}.ifc"
+        autosaving_path = parent / f"{stem}{AUTOSAVING_SUFFIX}"
+        autosaved_path = parent / f"{stem}{AUTOSAVED_SUFFIX}"
+        return main_path, autosaving_path, autosaved_path
+
+    @classmethod
+    def get_active_ifc_path(cls) -> Union[Path, None]:
+        props = tool.Blender.get_bim_props()
+        if not props.ifc_file:
+            return None
+        path = tool.Blender.ensure_blender_path_is_abs(Path(props.ifc_file))
+        if path.suffix.lower() != ".ifc":
+            return None
+        return path
+
+    @classmethod
+    def _update_active_ifc_path_cache(cls) -> None:
+        global _active_ifc_path_cache
+        ifc_path = cls.get_active_ifc_path()
+        _active_ifc_path_cache = ifc_path.as_posix() if ifc_path is not None else None
+
+    @classmethod
+    def is_enabled(cls) -> bool:
+        return bool(tool.Blender.get_addon_preferences().autosave_enabled)
+
+    @classmethod
+    def get_interval_seconds(cls) -> float:
+        minutes = tool.Blender.get_addon_preferences().autosave_interval_minutes
+        return max(1.0, float(minutes) * 60.0)
+
+    @classmethod
+    def is_eligible(cls) -> bool:
+        return cls.is_enabled() and tool.Ifc.get() is not None and cls.get_active_ifc_path() is not None
+
+    @classmethod
+    def cancel_timer(cls) -> None:
+        global _timer_callback
+        if _timer_callback is not None and bpy.app.timers.is_registered(_timer_callback):
+            bpy.app.timers.unregister(_timer_callback)
+        _timer_callback = None
+
+    @classmethod
+    def reset_timer(cls) -> None:
+        cls.cancel_timer()
+        cls._update_active_ifc_path_cache()
+        if not cls.is_eligible():
+            return
+
+        def on_timer() -> None:
+            cls._on_timer_expired()
+            return None
+
+        global _timer_callback
+        _timer_callback = on_timer
+        bpy.app.timers.register(on_timer, first_interval=cls.get_interval_seconds())
+
+    @classmethod
+    def _on_timer_expired(cls) -> None:
+        if not cls.is_eligible():
+            return
+
+        prefs = tool.Blender.get_addon_preferences()
+        bim_props = tool.Blender.get_bim_props()
+
+        if bim_props.is_dirty:
+            if prefs.autosave_mode == "PROMPT":
+                bpy.ops.bim.autosave_prompt("INVOKE_DEFAULT")
+            elif prefs.autosave_mode == "BACKUP":
+                try:
+                    cls.perform_backup(bpy.context)
+                except Exception as error:
+                    print(f"Bonsai: autosave backup failed: {error}")
+        cls.reset_timer()
+
+    @classmethod
+    def perform_backup(cls, context: bpy.types.Context) -> None:
+        ifc_path = cls.get_active_ifc_path()
+        if ifc_path is None:
+            return
+
+        _, autosaving_path, autosaved_path = cls.get_paths(ifc_path)
+        autosaving_path.parent.mkdir(parents=True, exist_ok=True)
+
+        tool.Parametric.commit_pending_edits()
+        preview_base.discard_pending_previews(context.scene)
+
+        logger = logging.getLogger("ExportIFC")
+        output_file = autosaving_path.as_posix().replace("\\", "/")
+        settings = export_ifc.IfcExportSettings.factory(context, output_file, logger)
+        export_ifc.IfcExporter(settings).export()
+
+        try:
+            os.replace(autosaving_path, autosaved_path)
+        except OSError:
+            if autosaving_path.is_file():
+                autosaving_path.unlink(missing_ok=True)
+            raise
+
+    @classmethod
+    def get_newer_autosaved_path(cls, ifc_path: Union[str, Path]) -> Union[str, None]:
+        path = Path(ifc_path)
+        if path.suffix.lower() != ".ifc" or not path.is_file():
+            return None
+
+        _, _, autosaved_path = cls.get_paths(path)
+        if not autosaved_path.is_file():
+            return None
+        if autosaved_path.stat().st_mtime > path.stat().st_mtime:
+            return autosaved_path.as_posix().replace("\\", "/")
+        return None
+
+    @classmethod
+    def cleanup_stale_autosave(cls) -> None:
+        """Remove the active IFC's autosave file(s) on a graceful shutdown.
+
+        Registered via `atexit`, which only runs on a normal interpreter
+        shutdown - never on an actual crash. So a deliberate quit (whether
+        the user saved or chose "don't save") clears the recovery file and
+        won't prompt on next startup, while a genuine crash leaves it in
+        place for recovery, since no atexit callbacks fire then.
+
+        Deliberately reads only `_active_ifc_path_cache` - a plain string
+        kept up to date by `reset_timer()` - rather than touching `bpy` here.
+        By the time `atexit` fires, Blender's own C++ side is torn down far
+        enough that even reading `bpy.context.scene` aborts the process
+        (std::bad_optional_access) instead of raising a catchable exception.
+        """
+        if _active_ifc_path_cache is None:
+            return
+        try:
+            _, autosaving_path, autosaved_path = cls.get_paths(_active_ifc_path_cache)
+            autosaving_path.unlink(missing_ok=True)
+            autosaved_path.unlink(missing_ok=True)
+        except Exception:
+            pass
+
+
+atexit.register(Autosave.cleanup_stale_autosave)

src/bonsai/bonsai/tool/model.py

@@ -59,6 +59,7 @@ from ifcopenshell.util.shape_builder import ShapeBuilder, np_to_3d
 from mathutils import Matrix, Vector
 
 import bonsai.core.geometry
+import bonsai.core.model
 import bonsai.core.tool
 import bonsai.tool as tool
 from bonsai.bim import import_ifc

src/bonsai/test/bim/module/model/test_array_batch_recut.py

@@ -35,6 +35,7 @@ from unittest.mock import Mock, patch
 
 import bpy
 import ifcopenshell
+import ifcopenshell.api.pset
 import pytest
 
 import bonsai.tool as tool

src/bonsai/test/bim/module/model/test_array_duplicate_batched.py

@@ -37,6 +37,8 @@ from unittest.mock import patch
 
 import bpy
 import ifcopenshell
+import ifcopenshell.api.pset
+import ifcopenshell.util.element
 import pytest
 
 import bonsai.tool as tool

src/bonsai/test/bim/module/model/test_mep_distribution_fit_smoke.py

@@ -146,7 +146,9 @@ def test_fit_flow_segments_with_single_segment_dispatches_obstruction():
         mep.tool.Model, "get_flow_segment_profile", return_value=segment_profile
     ), patch.object(mep.MEPAddObstruction, "_execute", return_value=None) as obstruction, patch.object(
         mep.MEPAddBend, "_execute", return_value=None
-    ) as bend, patch.object(mep.MEPAddTransition, "_execute", return_value=None) as transition:
+    ) as bend, patch.object(
+        mep.MEPAddTransition, "_execute", return_value=None
+    ) as transition:
         mep.FitFlowSegments._execute(op, context=context)
 
     assert obstruction.call_count == 1
@@ -178,7 +180,9 @@ def test_fit_flow_segments_refuses_mixed_pipe_and_duct():
         mep.tool.Model, "get_flow_segment_profile", return_value=profile
     ), patch.object(mep.MEPAddObstruction, "_execute", return_value=None) as obstruction, patch.object(
         mep.MEPAddBend, "_execute", return_value=None
-    ) as bend, patch.object(mep.MEPAddTransition, "_execute", return_value=None) as transition:
+    ) as bend, patch.object(
+        mep.MEPAddTransition, "_execute", return_value=None
+    ) as transition:
         mep.FitFlowSegments._execute(op, context=context)
 
     obstruction.assert_not_called()

src/bonsai/test/bim/module/model/test_mep_segment_edition.py

@@ -173,8 +173,9 @@ def test_gizmo_group_class_wiring(gizmo_cls_name, bl_idname, is_element_predicat
     predicate = getattr(tool.Parametric, is_element_predicate)
     fake_element = Mock()
     fake_element.is_a.return_value = True
-    with patch.object(tool.Parametric, is_element_predicate, side_effect=predicate) as p, patch.object(
-        tool.System, "has_parametric_body", return_value=True
+    with (
+        patch.object(tool.Parametric, is_element_predicate, side_effect=predicate) as p,
+        patch.object(tool.System, "has_parametric_body", return_value=True),
     ):
         cls.is_element_type(fake_element)
     assert p.called, f"{gizmo_cls_name}.is_element_type did not delegate to Parametric.{is_element_predicate}"

src/bonsai/test/bim/module/project/test_autosave.py

@@ -0,0 +1,68 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# 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/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+import os
+import time
+from pathlib import Path
+
+import pytest
+
+from bonsai.tool.autosave import AUTOSAVED_SUFFIX, AUTOSAVING_SUFFIX, Autosave
+
+pytestmark = pytest.mark.project
+
+
+class TestAutosavePaths:
+    def test_get_paths_for_ifc_file(self):
+        main_path, autosaving_path, autosaved_path = Autosave.get_paths("/tmp/myfile.ifc")
+        assert main_path == Path("/tmp/myfile.ifc")
+        assert autosaving_path == Path(f"/tmp/myfile{AUTOSAVING_SUFFIX}")
+        assert autosaved_path == Path(f"/tmp/myfile{AUTOSAVED_SUFFIX}")
+
+    def test_get_newer_autosaved_path_when_missing(self, tmp_path):
+        ifc_path = tmp_path / "myfile.ifc"
+        ifc_path.write_text("ifc")
+        assert Autosave.get_newer_autosaved_path(ifc_path) is None
+
+    def test_get_newer_autosaved_path_when_older(self, tmp_path):
+        ifc_path = tmp_path / "myfile.ifc"
+        autosaved_path = tmp_path / f"myfile{AUTOSAVED_SUFFIX}"
+        ifc_path.write_text("ifc")
+        autosaved_path.write_text("autosaved")
+        past = time.time() - 10
+        os.utime(ifc_path, (past, past))
+        os.utime(autosaved_path, (time.time(), time.time()))
+        assert Autosave.get_newer_autosaved_path(ifc_path) == autosaved_path.as_posix()
+
+    def test_get_newer_autosaved_path_when_not_newer(self, tmp_path):
+        ifc_path = tmp_path / "myfile.ifc"
+        autosaved_path = tmp_path / f"myfile{AUTOSAVED_SUFFIX}"
+        ifc_path.write_text("ifc")
+        autosaved_path.write_text("autosaved")
+        now = time.time()
+        os.utime(ifc_path, (now, now))
+        past = now - 10
+        os.utime(autosaved_path, (past, past))
+        assert Autosave.get_newer_autosaved_path(ifc_path) is None
+
+    def test_get_newer_autosaved_path_ignores_non_ifc(self, tmp_path):
+        path = tmp_path / "myfile.ifczip"
+        path.write_text("zip")
+        assert Autosave.get_newer_autosaved_path(path) is None

src/bonsai/test/bim/test_preview_cancel_ops_forward_compat.py

@@ -139,6 +139,5 @@ def test_every_cancel_ops_entry_has_a_real_preview_propertygroup() -> None:
     orphaned = [attr for attr, _op in preview_base.PREVIEW_CANCEL_OPS if attr not in declared_attrs]
     assert not orphaned, (
         "PREVIEW_CANCEL_OPS contains entries whose PointerProperty child no longer "
-        f"exists on {UMBRELLA_CLASS}. Drop the stale tuple(s):\n  "
-        + "\n  ".join(orphaned)
+        f"exists on {UMBRELLA_CLASS}. Drop the stale tuple(s):\n  " + "\n  ".join(orphaned)
     )

src/bonsai/test/core/test_unit.py

@@ -174,6 +174,15 @@ class TestAddConversionBasedUnit:
         assert subject.add_conversion_based_unit(ifc, unit, name="name") == "unit"
 
 
+class TestAddDerivedUnit:
+    def test_run(self, ifc, unit):
+        ifc.run(
+            "unit.add_derived_unit", unit_type="unit_type", userdefinedtype=None, attributes="elements"
+        ).should_be_called().will_return("unit")
+        unit.import_units().should_be_called()
+        assert subject.add_derived_unit(ifc, unit, unit_type="unit_type", elements="elements") == "unit"
+
+
 class TestEnableEditingUnit:
     def test_run(self, unit):
         unit.set_active_unit("unit").should_be_called()

src/bonsai/test/modal/test_modal.py

@@ -24,6 +24,7 @@ import time
 
 import bpy
 import ifcopenshell
+import ifcopenshell.util.element
 import pytest
 
 from bonsai import tool as tool

src/bonsai/test/tool/test_model.py

@@ -23,6 +23,7 @@ import bpy
 import ifcopenshell
 import ifcopenshell.api.geometry
 import ifcopenshell.api.material
+import ifcopenshell.api.pset
 import ifcopenshell.api.root
 import ifcopenshell.api.style
 import ifcopenshell.api.type

src/ifc5d/ifc5d/csv2ifc.py

@@ -57,7 +57,8 @@ class CsvHeader(TypedDict):
 
     # Formula
     Formula: NotRequired[str]
-    #QuantityClass: NotRequired[str]
+    # QuantityClass: NotRequired[str]
+
 
 # Currently we assume that if column is not part of the main header,
 # then it is a cost value category. So here we list any additional column
@@ -97,7 +98,8 @@ class CostItem(TypedDict):
     Query: Union[str, None]
 
     Formula: Union[str, None]
-    #QuantityClass: Union[str, None]
+    # QuantityClass: Union[str, None]
+
 
 class Csv2Ifc:
     # Inputs.
@@ -420,7 +422,7 @@ class Csv2Ifc:
                     products=results,
                     formula=cost_item["Formula"],
                     ifc_class=ifc_quantity_class,
-                    )
+                )
 
         self.create_cost_items(cost_item["children"], cost_item["ifc"])
 

src/ifcconvert/IfcConvert.cpp

@@ -252,6 +252,10 @@ int main(int argc, char** argv) {
 		("stderr-progress", "output progress to stderr stream")
 		("yes,y", "answer 'yes' automatically to possible confirmation queries (e.g. overwriting an existing output file)")
 		("no-progress", "suppress possible progress bar type of prints that use carriage return")
+		("fail-on-error", "return a non-zero exit code when one or more errors were logged during "
+			"geometry conversion (e.g. an element failed to convert). By default IfcConvert exits "
+			"successfully as long as an output file could be written, even if some elements were "
+			"silently dropped. Enable this flag so scripts and CI can detect partial conversions.")
 		("log-format", po::value<std::string>(&log_format), "log format: plain or json")
 		("log-file", new po::typed_value<path_t, char_t>(&log_file), "redirect log output to file");
 
@@ -449,6 +453,7 @@ int main(int argc, char** argv) {
 
 	const bool mmap = vmap.count("mmap") != 0;
 	const bool no_progress = vmap.count("no-progress") != 0;
+	const bool fail_on_error = vmap.count("fail-on-error") != 0;
 	const bool quiet = vmap.count("quiet") != 0;
 	const bool stderr_progress = vmap.count("stderr-progress") != 0;
 
@@ -885,6 +890,7 @@ int main(int argc, char** argv) {
 	}
 
 	if (!serializer->ready()) {
+		logger.Error("SYS", 25, "Unable to open output file '" + IfcUtil::path::to_utf8(output_filename) + "' for writing; check that the directory exists and is writable");
 		IfcUtil::path::delete_file(IfcUtil::path::to_utf8(output_temp_filename));
 		write_log(!quiet);
 		return EXIT_FAILURE;
@@ -1220,6 +1226,11 @@ int main(int argc, char** argv) {
 		successful = false;
 	}
 
+	if (fail_on_error && logger.MaxSeverity() >= Logger::LOG_ERROR) {
+		logger.Error("SYS", 26, "Errors encountered during processing, failing due to --fail-on-error.");
+		successful = false;
+	}
+
 	if (logger.Verbosity() == Logger::LOG_PERF) {
 		logger.PrintPerformanceStats();
 	}

src/ifcgeom/ConversionSettings.h

@@ -361,8 +361,8 @@ namespace ifcopenshell {
 
 			struct CircleSegments : public SettingBase<CircleSegments, int> {
 				static constexpr const char* const name = "circle-segments";
-				static constexpr const char* const description = "Number of segments to approximate full circles in CGAL kernel.";
-				static constexpr int defaultvalue = 16;
+				static constexpr const char* const description = "Number of segments to approximate full circles in the CGAL kernel. When 0 (the default) the segment count is derived from mesher-linear-deflection instead, so curves stay within the deflection tolerance regardless of radius.";
+				static constexpr int defaultvalue = 0;
 			};
 
 			struct CgalSmoothAngleDegrees : public SettingBase<CgalSmoothAngleDegrees, double> {

src/ifcgeom/kernels/cgal/CgalKernel.cpp

@@ -391,6 +391,11 @@ namespace {
 		}
 	};
 
+	// Representative radius used to size the polygonal approximation of a conic.
+	// For an ellipse the larger semi-axis is the conservative choice.
+	inline double conic_radius(const taxonomy::circle::ptr& c) { return c->radius; }
+	inline double conic_radius(const taxonomy::ellipse::ptr& e) { return e->radius > e->radius2 ? e->radius : e->radius2; }
+
 	struct cgal_curve_creation_visitor {
 		Settings& settings_;
 		parameter_range param;
@@ -425,7 +430,36 @@ namespace {
 			if (b <= a) {
 				b += 2 * M_PI;
 			}
-			int num_segments = (int)std::ceil(std::fabs(a - b) / (2 * M_PI) * settings_.get<settings::CircleSegments>().get());
+			const double span = std::fabs(a - b);
+			// CircleSegments controls how conics (circles, ellipses, arcs) are approximated
+			// in the CGAL kernel. Two modes, one or the other:
+			//  - CircleSegments == 0 (the default): the segment count is derived from
+			//    MesherLinearDeflection, so the chord deviation stays within the mesher's
+			//    linear deflection regardless of radius. This matches the deflection based
+			//    meshing the OpenCascade kernel already does and fixes issue #8051, where
+			//    large radius arcs (curved curtain wall mullions) collapsed to straight chords
+			//    because a fixed segment count is radius agnostic.
+			//  - CircleSegments > 0: it is used directly as the number of segments for a full
+			//    circle, giving deterministic, radius independent output.
+			int num_segments;
+			const int circle_segments = settings_.get<settings::CircleSegments>().get();
+			if (circle_segments > 0) {
+				num_segments = (int)std::ceil(span / (2 * M_PI) * circle_segments);
+			} else {
+				const double radius = conic_radius(t);
+				const double deflection = settings_.get<settings::MesherLinearDeflection>().get();
+				if (deflection > 0. && radius > deflection) {
+					const double max_segment_angle = 2.0 * std::acos(1.0 - deflection / radius);
+					num_segments = (int)std::ceil(span / max_segment_angle);
+				} else {
+					// Radius within the deflection tolerance (or no deflection set): a chord per
+					// quarter turn already keeps the deviation within tolerance.
+					num_segments = (int)std::ceil(span / (M_PI / 2.));
+				}
+			}
+			if (num_segments < 1) {
+				num_segments = 1;
+			}
 			double du = (b - a) / num_segments;
 			taxonomy::point3 P;
 			// @nb for loop is not inclusive of the both end points

src/ifcgeom/kernels/opencascade/face.cpp

@@ -31,6 +31,7 @@
 #include <ShapeFix_Shape.hxx>
 #include <ShapeFix_ShapeTolerance.hxx>
 #include <BRep_Tool.hxx>
+#include <BRepExtrema_DistShapeShape.hxx>
 
 #include <Standard_Macro.hxx>
 #include <TopoDS_Shape.hxx>
@@ -356,6 +357,27 @@ bool OpenCascadeKernel::convert(const taxonomy::face::ptr face, TopoDS_Shape& re
 		return false;
 	}
 
+	// #527: A face whose inner boundary intersects the outer boundary (or
+	// another inner boundary) is invalid per the schema. Open Cascade heals or
+	// drops such a face silently, so the intended hole is lost with no
+	// diagnostic. The distance between two non-intersecting loops is strictly
+	// positive; a distance at (or below) the modelling precision means the
+	// boundaries touch or cross. Emit a clear warning so the invalid input is
+	// not silently lost. wires() is ordered outer-first, inner-bounds after.
+	if (fd.wires().size() > 1) {
+		const auto& fwires = fd.wires();
+		bool reported = false;
+		for (size_t i = 1; i < fwires.size() && !reported; ++i) {
+			for (size_t j = 0; j < i && !reported; ++j) {
+				BRepExtrema_DistShapeShape dss(fwires[i], fwires[j]);
+				if (dss.IsDone() && dss.Value() < precision_) {
+					logger().Warning("GEO", 402, "Face inner boundary intersects another face boundary", face->instance);
+					reported = true;
+				}
+			}
+		}
+	}
+
 	if (fd.surface().IsNull()) {
 		// Use the first wire to find a plane manually for polygonal wires
 		const TopoDS_Wire& wire = fd.wires().front();

src/ifcgeom/mapping/IfcAsymmetricIShapeProfileDef.cpp

@@ -0,0 +1,93 @@
+// This file was generated with the assistance of an AI coding tool.
+/********************************************************************************
+ *                                                                              *
+ * This file is part of IfcOpenShell.                                           *
+ *                                                                              *
+ * IfcOpenShell is free software: you can redistribute it and/or modify         *
+ * it under the terms of the Lesser GNU General Public License as published by  *
+ * the Free Software Foundation, either version 3.0 of the License, or          *
+ * (at your option) any later version.                                          *
+ *                                                                              *
+ * IfcOpenShell 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                 *
+ * Lesser GNU General Public License for more details.                          *
+ *                                                                              *
+ * You should have received a copy of the Lesser GNU General Public License     *
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.         *
+ *                                                                              *
+ ********************************************************************************/
+
+#include "mapping.h"
+#define mapping POSTFIX_SCHEMA(mapping)
+using namespace ifcopenshell::geometry;
+
+#include "../profile_helper.h"
+
+// In IFC2X3 IfcAsymmetricIShapeProfileDef is a subtype of IfcIShapeProfileDef and is
+// therefore dispatched (and handled) by the IfcIShapeProfileDef mapping. From IFC4
+// onwards it is a standalone subtype of IfcParameterizedProfileDef with its own
+// Bottom*/Top* attributes, so nothing mapped it and the extrusion came out empty.
+// The presence of the standalone BottomFlangeWidth attribute is the discriminator:
+// it is only defined in the schemas where the type is standalone (IFC4 / IFC4X3).
+#ifdef SCHEMA_IfcAsymmetricIShapeProfileDef_HAS_BottomFlangeWidth
+
+taxonomy::ptr mapping::map_impl(const IfcSchema::IfcAsymmetricIShapeProfileDef* inst) {
+	// Bottom flange (half width), overall depth (half), web (half thickness).
+	const double xb = inst->BottomFlangeWidth() / 2.0 * length_unit_;
+	const double xt = inst->TopFlangeWidth() / 2.0 * length_unit_;
+	const double y = inst->OverallDepth() / 2.0 * length_unit_;
+	const double d1 = inst->WebThickness() / 2.0 * length_unit_;
+
+	// Bottom flange thickness; top flange thickness defaults to the bottom one.
+	const double ftb = inst->BottomFlangeThickness() * length_unit_;
+	const double ftt = inst->TopFlangeThickness().get_value_or(inst->BottomFlangeThickness()) * length_unit_;
+
+	// Optional fillet radii (web/flange transition) and flange edge radii.
+	const double fb = inst->BottomFlangeFilletRadius().get_value_or(0.) * length_unit_;
+	const double ft_top = inst->TopFlangeFilletRadius().get_value_or(0.) * length_unit_;
+	const double feb = inst->BottomFlangeEdgeRadius().get_value_or(0.) * length_unit_;
+	const double fet = inst->TopFlangeEdgeRadius().get_value_or(0.) * length_unit_;
+
+	// Optional flange slopes: the inner edge of the flange rises towards the web.
+	const double bottomSlope = inst->BottomFlangeSlope().get_value_or(0.) * angle_unit_;
+	const double topSlope = inst->TopFlangeSlope().get_value_or(0.) * angle_unit_;
+	const double dyb = (xb - d1) * tan(bottomSlope);
+	const double dyt = (xt - d1) * tan(topSlope);
+
+	const double tol = settings_.get<settings::Precision>().get();
+
+	if (xb < tol || xt < tol || y < tol || d1 < tol || ftb < tol || ftt < tol) {
+		logger_.Message(Logger::LOG_NOTICE, "GEO", 264, "Skipping zero sized profile:", inst);
+		return nullptr;
+	}
+
+	taxonomy::matrix4::ptr m4;
+	bool has_position = true;
+#ifdef SCHEMA_IfcParameterizedProfileDef_Position_IS_OPTIONAL
+	has_position = !!inst->Position();
+#endif
+	if (has_position) {
+		m4 = taxonomy::cast<taxonomy::matrix4>(map(inst->Position()));
+	}
+
+	// Twelve corner points, running counter-clockwise from the bottom-left, with the
+	// bottom flange (xb) possibly wider than the top flange (xt). Fillet/edge radii are
+	// attached to the corner they round, matching the symmetric IfcIShapeProfileDef.
+	return profile_helper(m4, {
+		{{-xb,-y}},
+		{{xb,-y}},
+		{{xb,-y + ftb}, {feb}},
+		{{d1,-y + ftb + dyb},{fb} },
+		{{d1,y - ftt - dyt},{ft_top} },
+		{{xt,y - ftt}, {fet}},
+		{{xt,y}},
+		{{-xt,y}},
+		{{-xt,y - ftt}, {fet}},
+		{{-d1,y - ftt - dyt},{ft_top} },
+		{{-d1,-y + ftb + dyb},{fb} },
+		{{-xb,-y + ftb}, {feb}}
+	});
+}
+
+#endif

src/ifcgeom/mapping/IfcPolygonalFaceSet.cpp

@@ -39,8 +39,25 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcPolygonalFaceSet* inst) {
 
 	int max_index = (int)points.size();
 
+	// When the optional PnIndex is present, CoordIndex values do not index into
+	// CoordList directly but into PnIndex, which in turn remaps to CoordList.
+	// Both index levels are 1-based per the IFC specification.
+	auto pn_index = inst->PnIndex();
+	auto resolve = [&](int idx) -> const taxonomy::point3::ptr& {
+		if (pn_index) {
+			if (idx < 1 || idx > (int)pn_index->size()) {
+				throw IfcParse::IfcException("IfcPolygonalFaceSet PnIndex out of bounds for index " + boost::lexical_cast<std::string>(idx));
+			}
+			idx = (*pn_index)[idx - 1];
+		}
+		if (idx < 1 || idx > max_index) {
+			throw IfcParse::IfcException("IfcPolygonalFaceSet index out of bounds for index " + boost::lexical_cast<std::string>(idx));
+		}
+		return points[idx - 1];
+	};
+
 	auto shell = taxonomy::make<taxonomy::shell>();
-	
+
 	for (auto& f : *polygonal_faces) {
 		auto fa = taxonomy::make<taxonomy::face>();
 		shell->children.push_back(fa);
@@ -52,17 +69,14 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcPolygonalFaceSet* inst) {
 			auto indices = f->CoordIndex();
 			taxonomy::point3::ptr previous;
 			for (std::vector<int>::const_iterator jt = indices.begin(); jt != indices.end(); ++jt) {
-				if (*jt < 1 || *jt > max_index) {
-					throw IfcParse::IfcException("IfcPolygonalFaceSet index out of bounds for index " + boost::lexical_cast<std::string>(*jt));
-				}
-				auto current = points[(*jt) - 1];
+				auto current = resolve(*jt);
 				if (jt != indices.begin()) {
 					loop->children.push_back(taxonomy::make<taxonomy::edge>(previous, current));
 				}
 				previous = current;
 			}
 			if (!indices.empty()) {
-				auto current = points[indices.front() - 1];
+				auto current = resolve(indices.front());
 				loop->children.push_back(taxonomy::make<taxonomy::edge>(previous, current));
 			}
 		}
@@ -77,17 +91,14 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcPolygonalFaceSet* inst) {
 					loop->external = false;
 
 					for (std::vector<int>::const_iterator jt = li.begin(); jt != li.end(); ++jt) {
-						if (*jt < 1 || *jt > max_index) {
-							throw IfcParse::IfcException("IfcPolygonalFaceSet index out of bounds for index " + boost::lexical_cast<std::string>(*jt));
-						}
-						auto current = points[(*jt) - 1];
+						auto current = resolve(*jt);
 						if (jt != li.begin()) {
 							loop->children.push_back(taxonomy::make<taxonomy::edge>(previous, current));
 						}
 						previous = current;
 					}
 					if (!li.empty()) {
-						auto current = points[li.front() - 1];
+						auto current = resolve(li.front());
 						loop->children.push_back(taxonomy::make<taxonomy::edge>(previous, current));
 					}
 				}

src/ifcgeom/mapping/IfcTriangulatedFaceSet.cpp

@@ -39,6 +39,23 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcTriangulatedFaceSet* inst) {
 
 	int max_index = (int)points.size();
 
+	// When the optional PnIndex is present, CoordIndex values do not index into
+	// CoordList directly but into PnIndex, which in turn remaps to CoordList.
+	// Both index levels are 1-based per the IFC specification.
+	auto pn_index = inst->PnIndex();
+	auto resolve = [&](int idx) -> const taxonomy::point3::ptr& {
+		if (pn_index) {
+			if (idx < 1 || idx > (int)pn_index->size()) {
+				throw IfcParse::IfcException("IfcTriangulatedFaceSet PnIndex out of bounds for index " + boost::lexical_cast<std::string>(idx));
+			}
+			idx = (*pn_index)[idx - 1];
+		}
+		if (idx < 1 || idx > max_index) {
+			throw IfcParse::IfcException("IfcTriangulatedFaceSet index out of bounds for index " + boost::lexical_cast<std::string>(idx));
+		}
+		return points[idx - 1];
+	};
+
 	auto shell = taxonomy::make<taxonomy::shell>();
 
 	for (auto& indices : indices_list) {
@@ -51,10 +68,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcTriangulatedFaceSet* inst) {
 			loop->external = true;
 			taxonomy::point3::ptr first, previous;
 			for (std::vector<int>::const_iterator jt = indices.begin(); jt != indices.end(); ++jt) {
-				if (*jt < 1 || *jt > max_index) {
-					throw IfcParse::IfcException("IfcTriangulatedFaceSet index out of bounds for index " + boost::lexical_cast<std::string>(*jt));
-				}
-				const taxonomy::point3::ptr& current = points[(*jt) - 1];
+				const taxonomy::point3::ptr& current = resolve(*jt);
 				if (jt == indices.begin()) {
 					first = current;
 				} else {

src/ifcgeom/mapping/mapping.i

@@ -89,7 +89,11 @@ BIND(IfcRectangleHollowProfileDef);
 BIND(IfcRectangleProfileDef);
 BIND(IfcTrapeziumProfileDef);
 BIND(IfcCShapeProfileDef);
-// IfcAsymmetricIShapeProfileDef included
+// In IFC2X3 IfcAsymmetricIShapeProfileDef is a subtype of IfcIShapeProfileDef and is
+// mapped by it; from IFC4 onwards it is a standalone type and needs its own binding.
+#ifdef SCHEMA_IfcAsymmetricIShapeProfileDef_HAS_BottomFlangeWidth
+BIND(IfcAsymmetricIShapeProfileDef);
+#endif
 BIND(IfcIShapeProfileDef);
 BIND(IfcLShapeProfileDef);
 BIND(IfcTShapeProfileDef);

src/ifcopenshell-python/docs/ifcconvert/usage.rst

@@ -311,8 +311,12 @@ CLI Manual
                                             output.
       --force-space-transparency arg        Overrides transparency of spaces in 
                                             geometry output.
-      --circle-segments arg (= 16)          Number of segments to approximate full 
-                                            circles in CGAL kernel.
+      --circle-segments arg (= 0)           Number of segments to approximate full
+                                            circles in the CGAL kernel. When 0 (the
+                                            default) the segment count is derived from
+                                            mesher-linear-deflection instead, so curves
+                                            stay within the deflection tolerance
+                                            regardless of radius.
       --cgal-smooth-angle-degrees arg (= -1)
                                             Angle in degrees under which adjacent 
                                             facets will have averaged vertex 

src/ifcopenshell-python/docs/ifcopenshell-python/selector_syntax.rst

@@ -72,6 +72,8 @@ Filtering is typically used to select any IFC element or type.
 
     "``IfcPump, location=""Level 3""``", "Locations bubble up the hierarchy. So if a pump is in a space and that space is on Level 3, then you can say ""all pumps on level 3"" which will include that pump in the space."
 
+    "``IfcElement, query:""parent.Name""=""My Site""``", "Only elements *immediately* under ""My Site"" in the spatial hierarchy. Unlike the ``location`` and ``parent`` filters, which both match at any depth, the ``parent`` query key resolves the direct parent only, so nested storeys (and their contents) are excluded."
+
 The filter elements syntax works by specifying one or more groups of filters
 separated by a ``+`` character. Each filter group will return a set of filtered
 elements, and these are unioned together.
@@ -111,6 +113,15 @@ will search through all IfcTypeProducts and IfcProducts in the IFC project.
     "Parent", "Filter", "``parent{{=}}{{value}}``", "``parent=Foo`` specifies the criteria that elements must be a direct or indirect child in the spatial hierarchy to an element with a ``Name`` attribute with a value of ``Foo``."
     "Query", "Filter", "``query:{{keys}}{{=}}{{value}}``", "``query:types.count=0`` specifies the criteria that elements must have zero type occurrences. The query keys corresponds to the syntax used in the `Getting element values`_ section"
 
+.. note::
+
+    The ``location`` and ``parent`` filters both match at **any depth** in the
+    spatial hierarchy. To match only elements *immediately* contained in (or
+    aggregated under) a spatial element, use the ``parent`` query key, which
+    resolves the direct parent only. For example,
+    ``query:"parent.Name"="My Site"`` selects elements directly under ``My
+    Site`` but excludes anything nested inside its sub-storeys or spaces.
+
 When you specify a filter with a ``{{=}}`` check, you can choose from one of
 the following comparison checks:
 
@@ -191,7 +202,7 @@ Valid keys are:
     "``storey``", "Gets the first IfcBuildingStorey spatial element that an element is contained in."
     "``building``", "Gets the first IfcBuilding spatial element that an element is contained in."
     "``site``", "Gets the first IfcSite spatial element that an element is contained in."
-    "``parent``", "Gets the parent element in the spatial hierarchy."
+    "``parent``", "Gets the **immediate** parent element in the spatial hierarchy (the direct spatial container, or the direct aggregate/nest/fill/void parent). Combine with ``.Name`` in a query filter to match only immediate children, e.g. ``query:""parent.Name""=""My Site""``."
     "``classification``", "Gets the element's classification reference(s)"
     "``group``", "Gets the element's group(s)"
     "``system``", "Gets the element's system(s). This is a subset of group(s)."

src/ifcopenshell-python/docs/ifcopenshell/geometry_settings.rst

@@ -228,10 +228,10 @@ circle-segments
 +------+-----------------------+---------+
 | Type | IfcConvert Option     | Default |
 +======+=======================+=========+
-| INT  | ``--circle-segments`` | 16      |
+| INT  | ``--circle-segments`` | 0       |
 +------+-----------------------+---------+
 
-Number of segments to approximate full circles in CGAL kernel.
+Number of segments to approximate full circles in the CGAL kernel. When 0 (the default) the segment count is derived from mesher-linear-deflection instead, so curves stay within the deflection tolerance regardless of radius.
 
 context-identifiers
 ^^^^^^^^^^^^^^^^^^^

src/ifcopenshell-python/ifcopenshell/__init__.py

@@ -231,7 +231,7 @@ def open(
         kwargs = {"mmap": mmap}
         if logger is not None:
             kwargs["logger"] = logger
-        f = ifcopenshell_wrapper.open(str(path.absolute()), **kwargs)  # ty: ignore[unknown-argument]
+        f = ifcopenshell_wrapper.open(str(path.absolute()), **kwargs)
     else:
         f = ifcopenshell_wrapper.open(str(path.absolute()), False, *((logger,) if logger is not None else ()))
     return file(f)

src/ifcopenshell-python/ifcopenshell/api/alignment/__init__.py

@@ -49,6 +49,7 @@ Future versions of this API may support:
 
 from ._get_segment_start_point_label import register_referent_name_callback
 from .add_stationing_referent import add_stationing_referent
+from .add_positioning_referent import add_positioning_referent
 from .add_vertical_layout import add_vertical_layout
 from .add_zero_length_segment import add_zero_length_segment
 from .create import create
@@ -94,6 +95,7 @@ from .util import *
 
 __all__ = [
     "add_stationing_referent",
+    "add_positioning_referent",
     "add_vertical_layout",
     "add_zero_length_segment",
     "create",

src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_curve.py

@@ -22,8 +22,6 @@ import numpy as np
 import ifcopenshell
 import ifcopenshell.api.alignment
 import ifcopenshell.geom
-import ifcopenshell.ifcopenshell_wrapper as ifcopenshell_wrapper
-import ifcopenshell.util.unit
 from ifcopenshell import entity_instance
 from ifcopenshell.api.alignment._get_segment_endpoint import _get_segment_endpoint
 from ifcopenshell.api.alignment._update_zero_length_segment_placement import _update_zero_length_segment_placement

src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_layout.py

@@ -22,28 +22,11 @@ import numpy as np
 
 import ifcopenshell
 import ifcopenshell.api.alignment
-from ifcopenshell.api.alignment import _map_alignment_cant_segment
 from ifcopenshell.api.alignment._update_zero_length_segment_placement import _update_zero_length_segment_placement
 import ifcopenshell.api.nest
-import ifcopenshell.api.pset
-import ifcopenshell.geom
-import ifcopenshell.util.alignment
-import ifcopenshell.util.unit
-from ifcopenshell import entity_instance, ifcopenshell_wrapper
+from ifcopenshell import entity_instance
 from ifcopenshell.api.alignment._add_segment_to_curve import _add_segment_to_curve
 from ifcopenshell.api.alignment._get_segment_endpoint import _get_segment_endpoint
-from ifcopenshell.api.alignment._get_segment_start_point_label import (
-    _get_segment_start_point_label,
-)
-from ifcopenshell.api.alignment._map_alignment_cant_segment import (
-    _map_alignment_cant_segment,
-)
-from ifcopenshell.api.alignment._map_alignment_horizontal_segment import (
-    _map_alignment_horizontal_segment,
-)
-from ifcopenshell.api.alignment._map_alignment_vertical_segment import (
-    _map_alignment_vertical_segment,
-)
 
 
 def _add_segment_to_layout(

src/ifcopenshell-python/ifcopenshell/api/alignment/_add_zero_length_segment.py

@@ -18,11 +18,7 @@
 
 import ifcopenshell
 import ifcopenshell.api.alignment
-import ifcopenshell.util.alignment
 from ifcopenshell import entity_instance
-from ifcopenshell.api.alignment._get_segment_start_point_label import (
-    _get_segment_start_point_label,
-)
 
 
 def _add_zero_length_segment(file: ifcopenshell.file, layout: entity_instance) -> None:

src/ifcopenshell-python/ifcopenshell/api/alignment/_get_segment_endpoint.py

@@ -18,6 +18,7 @@
 
 
 import ifcopenshell.api.alignment
+import ifcopenshell.geom
 from ifcopenshell import entity_instance, ifcopenshell_wrapper
 from ifcopenshell.api.alignment._map_alignment_segment import _map_alignment_segment
 from typing import Union

src/ifcopenshell-python/ifcopenshell/api/alignment/add_positioning_referent.py

@@ -0,0 +1,113 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2025 Thomas Krijnen <thomas@aecgeeks.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell 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 Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import ifcopenshell
+import ifcopenshell.api.alignment
+from ifcopenshell.api.alignment.update_fallback_position import update_fallback_position
+import ifcopenshell.api.pset
+import ifcopenshell.guid
+from ifcopenshell import entity_instance
+
+
+def add_positioning_referent(
+    file: ifcopenshell.file,
+    name: str,
+    alignment: entity_instance,
+    distance_along: float,
+    station: float,
+    positioned_product: entity_instance,
+) -> entity_instance:
+    """
+    Semantically defines the position of a product along an alignment by adding an IfcReferent to the alignment that defines the stationing system.
+
+    :param alignment: the alignment to receive the referent
+    :param distance_along: distance along the alignment basis curve
+    :param station: station value
+    :param name: name to assign to IfcReferent.Name, typically a stringized version of the station value
+    :param positioned_product: the product whose position is informed by the referent
+    :return: referent
+
+    Example:
+
+    .. code:: python
+
+        alignment = model.by_type("IfcAlignment")[0]
+        pier = model.by_type("IfcBridgePart")[0]
+        ifcopenshell.api.alignment.add_positioning_referent(model,name="Pier 1 Sta 1+00",alignment=alignment,distance_along=0.0,station=100.0,positioned_product=pier)
+    """
+
+    curve = ifcopenshell.api.alignment.get_curve(alignment)
+
+    object_placement = None
+    representation = None
+    if curve and curve.is_a("IfcCompositeCurve") and 0 < len(curve.Segments):
+        object_placement = file.createIfcLinearPlacement(
+            RelativePlacement=file.createIfcAxis2PlacementLinear(
+                Location=file.createIfcPointByDistanceExpression(
+                    DistanceAlong=file.createIfcLengthMeasure(distance_along),
+                    OffsetLateral=None,
+                    OffsetVertical=None,
+                    OffsetLongitudinal=None,
+                    BasisCurve=curve,
+                )
+            ),
+        )
+
+        update_fallback_position(file, object_placement)
+    else:
+        object_placement = file.createIfcLocalPlacement(
+            PlacementRelTo=None,
+            RelativePlacement=file.createIfcAxis2Placement2D(
+                Location=file.createIfcCartesianPoint(alignment.ObjectPlacement.RelativePlacement.Location.Coordinates)
+            ),
+        )
+
+    # this commented out code is what you would do to add a geometric representation of the referent
+    # the example is a circle. a better way would be to pass a representation into the function
+    #    representation = file.create_entity(
+    #        name="IfcCircle",
+    #        position=file.createIfcAxis2Placement2D(Location=file.createIfcCartesianPoint(Coordinates=(0.0, 0.0)),
+    #        radius=1.0)
+    #    )
+
+    # create referent for the station
+    referent = file.createIfcReferent(
+        GlobalId=ifcopenshell.guid.new(),
+        OwnerHistory=None,
+        Name=name,
+        Description=None,
+        ObjectType=None,
+        ObjectPlacement=object_placement,
+        Representation=representation,
+        PredefinedType="POSITION",
+    )
+    pset_stationing = ifcopenshell.api.pset.add_pset(file, product=referent, name="Pset_Stationing")
+    ifcopenshell.api.pset.edit_pset(file, pset=pset_stationing, properties={"Station": station})
+
+    if len(referent.Positions) == 0:
+        rel_positions = file.createIfcRelPositions(
+            GlobalId=ifcopenshell.guid.new(),
+            RelatingPositioningElement=referent,
+            RelatedProducts=[
+                positioned_product,
+            ],
+        )
+    else:
+        referent.Positions[0].RelatedProducts += (positioned_product,)
+
+    return referent

src/ifcopenshell-python/ifcopenshell/api/alignment/add_stationing_referent.py

@@ -16,35 +16,35 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
-import numpy as np
+from typing import Optional
 
 import ifcopenshell
 import ifcopenshell.api.alignment
 from ifcopenshell.api.alignment.update_fallback_position import update_fallback_position
 import ifcopenshell.api.pset
-import ifcopenshell.geom
 import ifcopenshell.guid
 import ifcopenshell.util.element
-import ifcopenshell.util.unit
-from ifcopenshell import entity_instance, ifcopenshell_wrapper
+from ifcopenshell import entity_instance
 
 
 def add_stationing_referent(
     file: ifcopenshell.file,
+    name: str,
     alignment: entity_instance,
     distance_along: float,
     station: float,
-    name: str,
-    positioned_product: entity_instance,
+    incoming_station: Optional[float] = None,
+    on_basis_curve: Optional[bool] = None,
 ) -> entity_instance:
     """
-    Adds an IfcReferent to the alignment with the Pset_Stationing property set.
+    Adds an IfcReferent to the alignment that defines the stationing system.
 
+    :param name: name to assign to IfcReferent.Name, typically a stringized version of the station value
     :param alignment: the alignment to receive the referent
     :param distance_along: distance along the alignment basis curve
     :param station: station value
-    :param name: name to assign to IfcReferent.Name, typically a stringized version of the station value
-    :param positioned_product: the product whose position is informed by the referent
+    :param incoming_station: station value of the incoming segment, only set to specify a station equation
+    :param on_basis_curve: whether the referent is positioned on the basis curve or the alignment curve, if None the function will default to the basis curve
     :return: referent
 
     Example:
@@ -52,14 +52,21 @@ def add_stationing_referent(
     .. code:: python
 
         alignment = model.by_type("IfcAlignment")[0]
-        ifcopenshell.api.alignment.add_stationing_referent(model,alignment=alignment,distance_along=0.0,station=100.0)
+        ifcopenshell.api.alignment.add_stationing_referent(model,name="1+00.0",alignment=alignment,distance_along=0.0,station=100.0)
     """
 
-    basis_curve = ifcopenshell.api.alignment.get_basis_curve(alignment)
+    if on_basis_curve is None:
+        on_basis_curve = True
+
+    curve = (
+        ifcopenshell.api.alignment.get_basis_curve(alignment)
+        if on_basis_curve
+        else ifcopenshell.api.alignment.get_curve(alignment)
+    )
 
     object_placement = None
     representation = None
-    if basis_curve and basis_curve.is_a("IfcCompositeCurve") and 0 < len(basis_curve.Segments):
+    if curve and curve.is_a("IfcCompositeCurve") and 0 < len(curve.Segments):
         object_placement = file.createIfcLinearPlacement(
             RelativePlacement=file.createIfcAxis2PlacementLinear(
                 Location=file.createIfcPointByDistanceExpression(
@@ -67,7 +74,7 @@ def add_stationing_referent(
                     OffsetLateral=None,
                     OffsetVertical=None,
                     OffsetLongitudinal=None,
-                    BasisCurve=basis_curve,
+                    BasisCurve=curve,
                 )
             ),
         )
@@ -100,8 +107,12 @@ def add_stationing_referent(
         Representation=representation,
         PredefinedType="STATION",
     )
+    properties = {"Station": station}
+    if incoming_station is not None:
+        properties["IncomingStation"] = incoming_station
+
     pset_stationing = ifcopenshell.api.pset.add_pset(file, product=referent, name="Pset_Stationing")
-    ifcopenshell.api.pset.edit_pset(file, pset=pset_stationing, properties={"Station": station})
+    ifcopenshell.api.pset.edit_pset(file, pset=pset_stationing, properties=properties)
 
     nest = ifcopenshell.api.alignment.get_referent_nest(file, alignment)
     if nest is None:
@@ -115,15 +126,4 @@ def add_stationing_referent(
         nest.RelatedObjects, key=lambda x: ifcopenshell.util.element.get_pset(x, name="Pset_Stationing", prop="Station")
     )
 
-    if len(referent.Positions) == 0:
-        rel_positions = file.createIfcRelPositions(
-            GlobalId=ifcopenshell.guid.new(),
-            RelatingPositioningElement=referent,
-            RelatedProducts=[
-                positioned_product,
-            ],
-        )
-    else:
-        referent.Positions[0].RelatedProducts += (positioned_product,)
-
     return referent

src/ifcopenshell-python/ifcopenshell/api/alignment/add_vertical_layout.py

@@ -51,18 +51,6 @@ def _move_vertical_layout_to_child_alignment(
     # aggregate the child alignment to the parent alignment
     ifcopenshell.api.aggregate.assign_object(file, products=[child_alignment], relating_object=parent_alignment)
 
-    # move all referents positioning segments of the vertical layout to the referent nest of the child alignment
-    child_referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, child_alignment)
-    parent_referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, parent_alignment)
-    for referent in parent_referent_nest.RelatedObjects:
-        for product in referent.Positions[0].RelatedProducts:
-            if product.is_a("IfcAlignmentSegment") and product.Nests[0].RelatingObject == vertical_layout:
-                # ifcopenshell.api.nest.change_nest(file,referent,child_alignment) - this doesn't work because referent is assigned to child_alignment.IsNestedBy[0].RelatedObjects
-                # and it needs to be assigned to child_alignment.IsNestedBy[1].RelatedObjects
-                # move the referent manually - unassign it and add it to the child alignment's referent nest
-                ifcopenshell.api.nest.unassign_object(file, [referent])
-                child_referent_nest.RelatedObjects += (referent,)
-
     # if the parent alignment has a representation, move the Axis/Curve3D represention to the child alignment
     base_curve = ifcopenshell.api.alignment.get_basis_curve(parent_alignment)
     if base_curve:

src/ifcopenshell-python/ifcopenshell/api/alignment/add_zero_length_segment.py

@@ -23,18 +23,8 @@ import ifcopenshell.api.alignment
 from ifcopenshell.api.alignment._get_segment_endpoint import _get_segment_endpoint
 from ifcopenshell.api.alignment._update_zero_length_segment_placement import _update_zero_length_segment_placement
 import ifcopenshell.api.nest
-import ifcopenshell.ifcopenshell_wrapper as wrapper
 import ifcopenshell.util.unit
 from ifcopenshell import entity_instance
-from ifcopenshell.api.alignment._get_segment_start_point_label import (
-    _get_segment_start_point_label,
-)
-from ifcopenshell.api.alignment._map_alignment_horizontal_segment import (
-    _map_alignment_horizontal_segment,
-)
-from ifcopenshell.api.alignment._map_alignment_vertical_segment import (
-    _map_alignment_vertical_segment,
-)
 from ifcopenshell.api.alignment._update_curve_segment_transition_code import (
     _update_curve_segment_transition_code,
 )

src/ifcopenshell-python/ifcopenshell/api/alignment/create.py

@@ -87,9 +87,7 @@ def create(
         _create_geometric_representation(file, alignment)
 
     referent_name = ifcopenshell.util.alignment.station_as_string(file, start_station)
-    referent = ifcopenshell.api.alignment.add_stationing_referent(
-        file, alignment, 0.0, start_station, referent_name, alignment
-    )
+    referent = ifcopenshell.api.alignment.add_stationing_referent(file, referent_name, alignment, 0.0, start_station)
 
     for layout in alignment_layouts:
         _add_zero_length_segment(file, layout)

src/ifcopenshell-python/ifcopenshell/api/alignment/create_as_polyline.py

@@ -141,7 +141,7 @@ def create_as_polyline(
 
     # define stationing
     name = ifcopenshell.util.alignment.station_as_string(file, start_station)
-    referent = ifcopenshell.api.alignment.add_stationing_referent(file, alignment, 0.0, start_station, name, alignment)
+    referent = ifcopenshell.api.alignment.add_stationing_referent(file, name, alignment, 0.0, start_station)
 
     # IFC 4.1.4.1.1 Alignment Aggregation To Project
     project = file.by_type("IfcProject")[0]

src/ifcopenshell-python/ifcopenshell/api/alignment/create_layout_segment.py

@@ -21,9 +21,7 @@ from typing import Union
 import numpy as np
 
 import ifcopenshell
-import ifcopenshell.api.alignment
-import ifcopenshell.geom
-from ifcopenshell import entity_instance, ifcopenshell_wrapper
+from ifcopenshell import entity_instance
 from ifcopenshell.api.alignment._add_segment_to_layout import _add_segment_to_layout
 
 

src/ifcopenshell-python/ifcopenshell/api/alignment/distance_along_from_station.py

@@ -16,23 +16,47 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
+from typing import Optional
+
 import ifcopenshell
 import ifcopenshell.api.alignment
+import ifcopenshell.util.element
 from ifcopenshell import entity_instance
 
 
-def distance_along_from_station(file: ifcopenshell.file, alignment: entity_instance, station: float) -> float:
+def _distance_along_of_referent(referent: entity_instance) -> float:
+    placement = referent.ObjectPlacement
+    if placement.is_a("IfcLinearPlacement"):
+        return placement.RelativePlacement.Location.DistanceAlong.wrappedValue
+    # IfcLocalPlacement fallback (e.g. semantic-only alignment, or the placement could not yet
+    # be expressed relative to a basis curve) carries no DistanceAlong; it is only ever used for
+    # the starting referent, at distance 0.0.
+    return 0.0
+
+
+def distance_along_from_station(file: ifcopenshell.file, alignment: entity_instance, station: float) -> Optional[float]:
     """
     Given a station, returns the distance along the horizontal alignment.
 
     If the alignment does not have stationing defined with an IfcReferent, the start of the alignment is assumed
     to be at station 0.0. That is, the station is the distance along.
 
-    .. note:: The current implementation does not account for station equations and assumes stationing is increasing along the alignment.
+    Station equations (where Pset_Stationing.IncomingStation is set on a referent) are taken into account.
+    For each STATION referent nested to the alignment, DistanceAlong (D) and the outgoing station (S, i.e.
+    Pset_Stationing.Station) are read off, sorted by DistanceAlong. The requested station is located within
+    the segment defined by the last referent whose outgoing station is less than or equal to it, and the
+    distance along is computed as D + (station - S) for that referent.
+
+    If the station falls within a gap introduced by a forward (gap) station equation - that is, it was skipped
+    over by the equation - there is no distance along that corresponds to it, and None is returned.
+
+    Note that an overlap (backward) station equation causes a range of stations to correspond to two distinct
+    distances along the alignment, one on either side of the equation. This implementation returns the distance
+    along in the segment following the equation (i.e. the outgoing side).
 
     :param alignment: the alignment
     :param station: station value
-    :return: distance along the horizontal alignment
+    :return: distance along the horizontal alignment, or None if the station falls inside a station equation gap
 
     Example:
 
@@ -43,6 +67,36 @@ def distance_along_from_station(file: ifcopenshell.file, alignment: entity_insta
         print(dist_along) # 100.00
     """
 
-    start_station = ifcopenshell.api.alignment.get_alignment_start_station(file, alignment)
-    dist_along = station - start_station
-    return dist_along
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, alignment)
+    if referent_nest is None:
+        start_station = ifcopenshell.api.alignment.get_alignment_start_station(file, alignment)
+        return station - start_station
+
+    stations = [
+        (
+            _distance_along_of_referent(referent),
+            ifcopenshell.util.element.get_pset(referent, name="Pset_Stationing", prop="Station"),
+        )
+        for referent in referent_nest.RelatedObjects
+    ]
+    stations.sort(key=lambda entry: entry[0])
+
+    index = None
+    for i, (distance_along, outgoing_station) in enumerate(stations):
+        if outgoing_station <= station:
+            index = i
+
+    if index is None:
+        # station precedes the alignment's starting station; extrapolate from the first referent
+        distance_along, outgoing_station = stations[0]
+        return distance_along + (station - outgoing_station)
+
+    distance_along, outgoing_station = stations[index]
+
+    if index + 1 < len(stations):
+        next_distance_along, _ = stations[index + 1]
+        if station - outgoing_station > next_distance_along - distance_along:
+            # the station was skipped over by a forward (gap) station equation
+            return None
+
+    return distance_along + (station - outgoing_station)

src/ifcopenshell-python/ifcopenshell/api/alignment/get_curve_segment.py

@@ -16,7 +16,6 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
-from collections.abc import Sequence
 
 from ifcopenshell import entity_instance
 

src/ifcopenshell-python/ifcopenshell/api/alignment/update_end_point.py

@@ -19,6 +19,7 @@
 import numpy as np
 
 import ifcopenshell
+import ifcopenshell.api.alignment
 import ifcopenshell.util.placement
 from ifcopenshell import entity_instance
 

src/ifcopenshell-python/ifcopenshell/api/cost/assign_cost_item_quantity.py

@@ -117,7 +117,7 @@ def assign_cost_item_quantity(
         "products": products or [],
         "prop_name": prop_name,
         "formula": formula,
-        "ifc_class" : ifc_class
+        "ifc_class": ifc_class,
     }
     return usecase.execute()
 
@@ -134,7 +134,7 @@ class Usecase:
                 continue
             self.assign_cost_control(related_object=product, cost_item=self.settings["cost_item"])
             if self.settings["formula"]:
-                tree = ast.parse(self.settings["formula"], mode = "eval")
+                tree = ast.parse(self.settings["formula"], mode="eval")
                 collector = VariableExtractor()
                 collector.visit(tree)
                 variables = collector.variables
@@ -144,10 +144,10 @@ class Usecase:
                     value = getter(product, variable)
 
                 if value is None:
-                        print(
-                            f"WARNING: Variable '{variable}' in product '{product.Name}' "
-                            f"is missing (None). Check Pset/Qset or property name."
-                        )
+                    print(
+                        f"WARNING: Variable '{variable}' in product '{product.Name}' "
+                        f"is missing (None). Check Pset/Qset or property name."
+                    )
                 elif value == 0:
                     print(
                         f"WARNING: Variable '{variable}' in product '{product.Name}' "
@@ -159,7 +159,9 @@ class Usecase:
 
                 new_quantity = None
                 for quantity in self.quantities:
-                    if quantity.Formula == self.settings["formula"] and len(self.settings["products"]) == 1: #Todo improve it
+                    if (
+                        quantity.Formula == self.settings["formula"] and len(self.settings["products"]) == 1
+                    ):  # Todo improve it
                         new_quantity = quantity
                         self.settings["ifc_class"] = quantity.is_a()
                         continue
@@ -184,23 +186,23 @@ class Usecase:
             self.update_cost_item_count()
 
     def get_value_from_pset(
-            self,
-            product:ifcopenshell.entity_instance,
-            v: str,
+        self,
+        product: ifcopenshell.entity_instance,
+        v: str,
     ) -> float:
         pset_name = v.split(".")[0]
         pset = ifcopenshell.util.element.get_pset(product, pset_name)
         pset_property_name = v.split(".")[1]
-        return (pset or {}).get(pset_property_name,None)
+        return (pset or {}).get(pset_property_name, None)
 
     def get_value_from_qset(
-            self,
-            product:ifcopenshell.entity_instance,
-            v: str,
+        self,
+        product: ifcopenshell.entity_instance,
+        v: str,
     ) -> float:
-        qtos = ifcopenshell.util.element.get_psets(product, qtos_only = True)
+        qtos = ifcopenshell.util.element.get_psets(product, qtos_only=True)
         quantities = next(iter(qtos.values()), {})
-        return (quantities or {}).get(v,None)
+        return (quantities or {}).get(v, None)
 
     def assign_cost_control(
         self, related_object: ifcopenshell.entity_instance, cost_item: ifcopenshell.entity_instance
@@ -243,6 +245,7 @@ class Usecase:
                             count += 1
                 quantity[3] = count
 
+
 OPERATORS = {
     ast.Add: operator.add,
     ast.Sub: operator.sub,
@@ -252,18 +255,20 @@ OPERATORS = {
     ast.USub: operator.neg,
 }
 
+
 def build_full_name(node):
-    #used for variables with dots
+    # used for variables with dots
     parts = []
     while isinstance(node, ast.Attribute):
-            parts.append(node.attr)
-            node = node.value
+        parts.append(node.attr)
+        node = node.value
 
     if isinstance(node, ast.Name):
         parts.append(node.id)
 
     return ".".join(reversed(parts))
 
+
 class VariableExtractor(ast.NodeVisitor):
     def __init__(self):
         self.variables = set()
@@ -274,6 +279,7 @@ class VariableExtractor(ast.NodeVisitor):
     def visit_Attribute(self, node):
         self.variables.add(build_full_name(node))
 
+
 class FormulaEvaluator(ast.NodeVisitor):
     def __init__(self, values):
         self.values = values
@@ -281,7 +287,7 @@ class FormulaEvaluator(ast.NodeVisitor):
     def visit_BinOp(self, node):
         left = self.visit(node.left)
         right = self.visit(node.right)
-        return OPERATORS[type(node.op)](left, right)
+        return OPERATORS[type(node.op)](left, right)  # ty: ignore[too-many-positional-arguments]
 
     def visit_Name(self, node):
         return self.values[node.id]

src/ifcopenshell-python/ifcopenshell/express/bootstrap.py

@@ -221,8 +221,7 @@ for id in to_emit:
     statements.append("%s << %s" % (id, stmt))
 
 if __name__ == "__main__":
-    print(
-        r"""
+    print(r"""
 # This file is generated by IfcOpenShell ifcexpressparser bootstrap.py
 
 from __future__ import annotations
@@ -261,6 +260,4 @@ if __name__ == "__main__":
         mdl = importlib.import_module(output)
         mdl.Generator(m).emit()
     sys.stdout.write(m.schema.name)
-"""
-        % ("\n        ".join(statements))
-    )
+""" % ("\n        ".join(statements)))

src/ifcopenshell-python/ifcopenshell/express/rule_compiler.py

@@ -695,6 +695,7 @@ codegen_rule("MOD", lambda context: "%")
 codegen_rule("TRUE", lambda context: "True")
 codegen_rule("FALSE", lambda context: "False")
 
+
 def _dotted_name(node: ast.AST):
     """Return dotted name for Name/Attribute chains, else None."""
     if isinstance(node, ast.Name):
@@ -704,6 +705,7 @@ def _dotted_name(node: ast.AST):
         return f"{base}.{node.attr}" if base else node.attr
     return None
 
+
 class AttributeGetattrTransformer(ast.NodeTransformer):
     def visit_Attribute(self, node):
         parents = []
@@ -720,7 +722,7 @@ class AttributeGetattrTransformer(ast.NodeTransformer):
         if isinstance(node.ctx, ast.Store):
             return node
 
-        if _dotted_name(node) in ('ifcopenshell.create_entity', 'str.lower'):
+        if _dotted_name(node) in ("ifcopenshell.create_entity", "str.lower"):
             return node
 
         if node.attr.startswith("__"):

src/ifcopenshell-python/ifcopenshell/express/schema_class.py

@@ -363,24 +363,18 @@ class EarlyBoundCodeWriter:
             )
         )
 
-        self.statements[self.statements.index("{factory_placeholder}")] = (
-            """
+        self.statements[self.statements.index("{factory_placeholder}")] = """
 class %(schema_name)s_instance_factory : public IfcParse::instance_factory {
     virtual IfcUtil::IfcBaseClass* operator()(const IfcParse::declaration* decl, IfcEntityInstanceData&& data) const {
         %(instance_mapping)s
     }
 };
-"""
-            % locals()
-        )
+""" % locals()
 
         ""
-        self.statements[self.statements.index("{string_pool_placeholder}")] = (
-            """
+        self.statements[self.statements.index("{string_pool_placeholder}")] = """
 const std::string strings[] = {%s};
-"""
-            % ",".join(map(lambda s: '"%s"s' % s, self.strings))
-        )
+""" % ",".join(map(lambda s: '"%s"s' % s, self.strings))
 
     def __str__(self):
         return "\n".join(self.statements)

src/ifcopenshell-python/ifcopenshell/geom/app.py

@@ -145,8 +145,7 @@ class configuration:
             config.set(
                 "snippets",
                 "print all wall ids",
-                self.config_encode(
-                    """
+                self.config_encode("""
 ###########################################################################
 # A simple script that iterates over all walls in the current model       #
 # and prints their Globally unique IDs (GUIDS) to the console window      #
@@ -154,15 +153,13 @@ class configuration:
 
 for wall in model.by_type("IfcWall"):
     print ("wall with global id: "+str(wall.GlobalId))
-""".lstrip()
-                ),
+""".lstrip()),
             )
 
             config.set(
                 "snippets",
                 "print properties of current selection",
-                self.config_encode(
-                    """
+                self.config_encode("""
 ###########################################################################
 # A simple script that iterates over all IfcPropertySets of the currently #
 # selected object and prints them to the console                          #
@@ -180,8 +177,7 @@ if selection:
              for prop in relDefinesByProperties.RelatingPropertyDefinition.HasProperties:
                  print ("{:<20} :{}".format(prop.Name,prop.NominalValue.wrappedValue))
          print ("\\n")
-""".lstrip()
-                ),
+""".lstrip()),
             )
             with open(conf_file, "w") as configfile:
                 config.write(configfile)

src/ifcopenshell-python/ifcopenshell/ifcopenshell_wrapper.pyi

@@ -1697,10 +1697,16 @@ class uninitialized_tag: ...
 
 def arrange_polygons(settings, polygons): ...
 def clear_schemas(): ...
-def construct_iterator(geometry_library, settings, file, num_threads): ...
-def construct_iterator_with_include_exclude(geometry_library, settings, file, elems, include, num_threads): ...
-def construct_iterator_with_include_exclude_globalid(geometry_library, settings, file, elems, include, num_threads): ...
-def construct_iterator_with_include_exclude_id(geometry_library, settings, file, elems, include, num_threads): ...
+def construct_iterator(geometry_library, settings, file, num_threads, logger=...): ...
+def construct_iterator_with_include_exclude(
+    geometry_library, settings, file, elems, include, num_threads, logger=...
+): ...
+def construct_iterator_with_include_exclude_globalid(
+    geometry_library, settings, file, elems, include, num_threads, logger=...
+): ...
+def construct_iterator_with_include_exclude_id(
+    geometry_library, settings, file, elems, include, num_threads, logger=...
+): ...
 def convert_loop_to_function_item(loop): ...
 def create_box(*args): ...
 def create_epeck(*args): ...
@@ -1717,8 +1723,8 @@ def line_segments_to_polygons(s, eps, segments): ...
 def map_shape(settings, instance): ...
 def nary_union(sequence): ...
 def new_IfcBaseClass(schema_identifier: str, name: str) -> entity_instance: ...
-def open(fn: str, readonly: bool = False) -> file: ...
-def parse_ifcxml(filename): ...
+def open(fn: str, readonly: bool = False, logger=...) -> file: ...
+def parse_ifcxml(filename, logger=...): ...
 def polygons_to_svg(*args): ...
 def read(data): ...
 def register_schema(arg1): ...

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

@@ -56,7 +56,7 @@ def append_zero_length_segments(file: ifcopenshell.file) -> ifcopenshell.file:
     for alignment in alignments:
         layouts = ifcopenshell.api.alignment.get_alignment_layouts(alignment)
         for layout in layouts:
-            ifcopenshell.api.alignment.add_zero_length_segment(patched_file, layout, include_referent=False)
+            ifcopenshell.api.alignment.add_zero_length_segment(patched_file, layout)
             curve = ifcopenshell.api.alignment.get_layout_curve(layout)
             if curve:
                 ifcopenshell.api.alignment.add_zero_length_segment(patched_file, curve)

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

@@ -355,8 +355,7 @@ def get_cost_rate(
 
 class CostValueUnserialiser:
     def parse(self, formula: str):
-        l = lark.Lark(
-            """start: formula
+        l = lark.Lark("""start: formula
                     formula: operand (operator operand)*
                     operand: value | category "(" formula ")"
                     value: NUMBER?
@@ -393,8 +392,7 @@ class CostValueUnserialiser:
                     NEWLINE: (CR? LF)+
 
                     %ignore WS // Disregard spaces in text
-                 """
-        )
+                 """)
         start = l.parse(formula)
         return self.get_formula(start.children[0])
 

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

@@ -39,8 +39,7 @@ import ifcopenshell.util.shape
 import ifcopenshell.util.system
 import ifcopenshell.util.unit
 
-filter_elements_grammar = lark.Lark(
-    """start: filter_group
+filter_elements_grammar = lark.Lark("""start: filter_group
     filter_group: facet_list ("+" facet_list)*
     facet_list: facet ("," facet)*
 
@@ -111,11 +110,9 @@ filter_elements_grammar = lark.Lark(
     NEWLINE: (CR? LF)+
 
     %ignore WS // Disregard spaces in text
-"""
-)
+""")
 
-get_element_grammar = lark.Lark(
-    """start: keys
+get_element_grammar = lark.Lark("""start: keys
 
     keys: key ("." key)*
     key: quoted_string | regex_string | unquoted_string
@@ -130,11 +127,9 @@ get_element_grammar = lark.Lark(
     WS: /[ \\t\\f\\r\\n]/+
 
     %ignore WS // Disregard spaces in text
- """
-)
+ """)
 
-format_grammar = lark.Lark(
-    """start: expression
+format_grammar = lark.Lark("""start: expression
 
     ?expression: add_sub
     ?add_sub: mul_div
@@ -193,8 +188,7 @@ format_grammar = lark.Lark(
     NEWLINE: (CR? LF)+
 
     %ignore WS // Disregard spaces in text
-"""
-)
+""")
 
 
 class FormatTransformer(lark.Transformer):

src/ifcopenshell-python/test/api/alignment/test_add_positioning_referent.py

@@ -0,0 +1,100 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2025 Thomas Krijnen <thomas@aecgeeks.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell 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 Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+
+import ifcopenshell.api.alignment
+import ifcopenshell.api.context
+import ifcopenshell.api.unit
+import ifcopenshell.util.element
+
+
+def test_add_positioning_referent():
+    file = ifcopenshell.file(schema="IFC4X3")
+    project = file.createIfcProject(GlobalId=ifcopenshell.guid.new(), Name="Test")
+    length = ifcopenshell.api.unit.add_si_unit(file, unit_type="LENGTHUNIT")
+    ifcopenshell.api.unit.assign_unit(file, units=[length])
+    geometric_representation_context = ifcopenshell.api.context.add_context(file, context_type="Model")
+    axis_model_representation_subcontext = ifcopenshell.api.context.add_context(
+        file,
+        context_type="Model",
+        context_identifier="Axis",
+        target_view="MODEL_VIEW",
+        parent=geometric_representation_context,
+    )
+
+    alignment = ifcopenshell.api.alignment.create(file, "TestAlignment", start_station=2000.0)
+
+    horizontal_layout = ifcopenshell.api.alignment.get_horizontal_layout(alignment)
+    segment = ifcopenshell.api.alignment.get_layout_segments(horizontal_layout)[0]
+
+    referent = ifcopenshell.api.alignment.add_positioning_referent(
+        file, "P.C.", alignment, distance_along=0.0, station=2000.0, positioned_product=segment
+    )
+
+    assert referent.is_a("IfcReferent")
+    assert referent.PredefinedType == "POSITION"
+    assert referent.Name == "P.C."
+    assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing")
+    assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing", prop="Station") == 2000.0
+    assert referent.ObjectPlacement != None
+
+    assert len(referent.Positions) == 1
+    rel_positions = referent.Positions[0]
+    assert rel_positions.is_a("IfcRelPositions")
+    assert rel_positions.RelatingPositioningElement == referent
+    assert rel_positions.RelatedProducts == (segment,)
+
+
+def test_add_positioning_referent_creates_separate_referent_per_call():
+    file = ifcopenshell.file(schema="IFC4X3")
+    project = file.createIfcProject(GlobalId=ifcopenshell.guid.new(), Name="Test")
+    length = ifcopenshell.api.unit.add_si_unit(file, unit_type="LENGTHUNIT")
+    ifcopenshell.api.unit.assign_unit(file, units=[length])
+    geometric_representation_context = ifcopenshell.api.context.add_context(file, context_type="Model")
+    axis_model_representation_subcontext = ifcopenshell.api.context.add_context(
+        file,
+        context_type="Model",
+        context_identifier="Axis",
+        target_view="MODEL_VIEW",
+        parent=geometric_representation_context,
+    )
+
+    alignment = ifcopenshell.api.alignment.create(file, "TestAlignment", start_station=2000.0)
+
+    horizontal_layout = ifcopenshell.api.alignment.get_horizontal_layout(alignment)
+    segment = ifcopenshell.api.alignment.get_layout_segments(horizontal_layout)[0]
+
+    first_referent = ifcopenshell.api.alignment.add_positioning_referent(
+        file, "P.C.", alignment, distance_along=0.0, station=2000.0, positioned_product=segment
+    )
+
+    other_product = file.createIfcBuildingElementProxy(GlobalId=ifcopenshell.guid.new(), Name="Sign")
+    second_referent = ifcopenshell.api.alignment.add_positioning_referent(
+        file, "P.C.", alignment, distance_along=0.0, station=2000.0, positioned_product=other_product
+    )
+
+    # each call creates its own IfcReferent, each with its own IfcRelPositions to the product passed in
+    assert first_referent != second_referent
+    assert len(first_referent.Positions) == 1
+    assert first_referent.Positions[0].RelatedProducts == (segment,)
+    assert len(second_referent.Positions) == 1
+    assert second_referent.Positions[0].RelatedProducts == (other_product,)
+
+
+test_add_positioning_referent()
+test_add_positioning_referent_creates_separate_referent_per_call()

src/ifcopenshell-python/test/api/alignment/test_add_stationing_referent.py

@@ -0,0 +1,115 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2025 Thomas Krijnen <thomas@aecgeeks.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell 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 Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+
+import ifcopenshell.api.alignment
+import ifcopenshell.api.context
+import ifcopenshell.api.unit
+import ifcopenshell.util.element
+
+
+def _create_test_file():
+    file = ifcopenshell.file(schema="IFC4X3")
+    project = file.createIfcProject(GlobalId=ifcopenshell.guid.new(), Name="Test")
+    length = ifcopenshell.api.unit.add_si_unit(file, unit_type="LENGTHUNIT")
+    ifcopenshell.api.unit.assign_unit(file, units=[length])
+    geometric_representation_context = ifcopenshell.api.context.add_context(file, context_type="Model")
+    axis_model_representation_subcontext = ifcopenshell.api.context.add_context(
+        file,
+        context_type="Model",
+        context_identifier="Axis",
+        target_view="MODEL_VIEW",
+        parent=geometric_representation_context,
+    )
+    return file
+
+
+def _create_test_alignment_with_vertical(file):
+    # include_vertical=True so that get_curve() (IfcGradientCurve, on the "Axis" representation)
+    # and get_basis_curve() (IfcCompositeCurve, on the "FootPrint" representation) are different
+    # entities, letting the on_basis_curve option be observed.
+    alignment = ifcopenshell.api.alignment.create(file, "TestAlignment", include_vertical=True, start_station=0.0)
+    assert ifcopenshell.api.alignment.get_basis_curve(alignment).is_a("IfcCompositeCurve")
+    assert ifcopenshell.api.alignment.get_curve(alignment).is_a("IfcGradientCurve")
+    assert ifcopenshell.api.alignment.get_basis_curve(alignment) != ifcopenshell.api.alignment.get_curve(alignment)
+    return alignment
+
+
+def _assert_common_referent_asserts(referent, name, station):
+    assert referent.is_a("IfcReferent")
+    assert referent.PredefinedType == "STATION"
+    assert referent.Name == name
+    assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing")
+    assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing", prop="Station") == station
+    assert referent.ObjectPlacement != None
+
+
+def test_add_stationing_referent_on_basis_curve_none_defaults_to_basis_curve():
+    # on_basis_curve=None should behave the same as on_basis_curve=True
+    file = _create_test_file()
+    alignment = _create_test_alignment_with_vertical(file)
+
+    referent = ifcopenshell.api.alignment.add_stationing_referent(
+        file, "1+00.000", alignment, distance_along=100.0, station=100.0, on_basis_curve=None
+    )
+
+    _assert_common_referent_asserts(referent, "1+00.000", 100.0)
+
+    assert referent.ObjectPlacement.is_a("IfcLinearPlacement")
+    assert referent.ObjectPlacement.RelativePlacement.Location.BasisCurve == ifcopenshell.api.alignment.get_basis_curve(
+        alignment
+    )
+
+
+def test_add_stationing_referent_on_basis_curve_true():
+    file = _create_test_file()
+    alignment = _create_test_alignment_with_vertical(file)
+
+    referent = ifcopenshell.api.alignment.add_stationing_referent(
+        file, "1+00.000", alignment, distance_along=100.0, station=100.0, on_basis_curve=True
+    )
+
+    _assert_common_referent_asserts(referent, "1+00.000", 100.0)
+
+    assert referent.ObjectPlacement.is_a("IfcLinearPlacement")
+    assert referent.ObjectPlacement.RelativePlacement.Location.BasisCurve == ifcopenshell.api.alignment.get_basis_curve(
+        alignment
+    )
+
+
+def test_add_stationing_referent_on_basis_curve_false():
+    # with a vertical layout present, on_basis_curve=False positions the referent on the
+    # alignment curve (IfcGradientCurve) rather than on the basis curve (IfcCompositeCurve).
+    file = _create_test_file()
+    alignment = _create_test_alignment_with_vertical(file)
+
+    referent = ifcopenshell.api.alignment.add_stationing_referent(
+        file, "1+00.000", alignment, distance_along=100.0, station=100.0, on_basis_curve=False
+    )
+
+    _assert_common_referent_asserts(referent, "1+00.000", 100.0)
+
+    assert referent.ObjectPlacement.is_a("IfcLinearPlacement")
+    basis_curve = referent.ObjectPlacement.RelativePlacement.Location.BasisCurve
+    assert basis_curve == ifcopenshell.api.alignment.get_curve(alignment)
+    assert basis_curve != ifcopenshell.api.alignment.get_basis_curve(alignment)
+
+
+test_add_stationing_referent_on_basis_curve_none_defaults_to_basis_curve()
+test_add_stationing_referent_on_basis_curve_true()
+test_add_stationing_referent_on_basis_curve_false()

src/ifcopenshell-python/test/api/alignment/test_add_stationing_to_alignment.py

@@ -48,5 +48,26 @@ def test_add_stationing_to_alignment():
     assert ifcopenshell.util.element.get_pset(element=referent, name="Pset_Stationing", prop="Station") == 2000.0
     assert referent.ObjectPlacement != None
 
+    # add a station equation at 1000 distance along. this is station 3+000 in coming and 4+000 outgoing.
+    # this is a gap equation.
+    second_referent = ifcopenshell.api.alignment.add_stationing_referent(
+        file, "4+000.000", alignment, distance_along=1000.0, station=4000.0, incoming_station=3000.0
+    )
+
+    referent_nest = ifcopenshell.api.alignment.get_referent_nest(file, alignment)
+    assert len(referent_nest.RelatedObjects) == 2
+
+    assert second_referent == referent_nest.RelatedObjects[1]
+
+    assert second_referent.PredefinedType == "STATION"
+    assert second_referent.Name == "4+000.000"
+    assert ifcopenshell.util.element.get_pset(element=second_referent, name="Pset_Stationing")
+    assert ifcopenshell.util.element.get_pset(element=second_referent, name="Pset_Stationing", prop="Station") == 4000.0
+    assert (
+        ifcopenshell.util.element.get_pset(element=second_referent, name="Pset_Stationing", prop="IncomingStation")
+        == 3000.0
+    )
+    assert second_referent.ObjectPlacement != None
+
 
 test_add_stationing_to_alignment()

src/ifcopenshell-python/test/api/alignment/test_create_representation.py

@@ -21,9 +21,12 @@ import math
 
 import pytest
 import ifcopenshell
+import ifcopenshell.api.aggregate
 import ifcopenshell.api.alignment
+import ifcopenshell.api.context
+import ifcopenshell.api.spatial
 import ifcopenshell.api.unit
-import numpy as np
+import ifcopenshell.util.unit
 
 
 def test_create_representation():

src/ifcopenshell-python/test/api/alignment/test_distance_along_from_station.py

@@ -53,4 +53,56 @@ def test_distance_along_from_station():
     assert ifcopenshell.api.alignment.distance_along_from_station(file, alignment, 17525.36) == pytest.approx(7525.36)
 
 
+def test_distance_along_from_station_with_station_equations():
+    # Reproduces the worked example from the IFC Alignment Geometry Implementation Guide, chapter 9.2.6:
+    # a gap equation (P3: incoming 14+00.00, outgoing 17+00.00) and an overlap equation
+    # (P4: incoming 19+00.00, outgoing 18+50.00).
+    file = ifcopenshell.file(schema="IFC4X3")
+    project = file.createIfcProject(GlobalId=ifcopenshell.guid.new(), Name="Test")
+    length = ifcopenshell.api.unit.add_conversion_based_unit(file, name="foot")
+    ifcopenshell.api.unit.assign_unit(file, units=[length])
+    geometric_representation_context = ifcopenshell.api.context.add_context(file, context_type="Model")
+    axis_model_representation_subcontext = ifcopenshell.api.context.add_context(
+        file,
+        context_type="Model",
+        context_identifier="Axis",
+        target_view="MODEL_VIEW",
+        parent=geometric_representation_context,
+    )
+
+    coordinates = [(500.0, 2500.0), (3340.0, 660.0), (4340.0, 5000.0), (7600.0, 4560.0), (8480.0, 2010.0)]
+    radii = [(1000.0), (1250.0), (950.0)]
+    vpoints = [(0.0, 100.0), (2000.0, 135.0), (5000.0, 105.0), (7400.0, 153.0), (9800.0, 105.0), (12800.0, 90.0)]
+    lengths = [(1600.0), (1200.0), (2000.0), (800.0)]
+
+    alignment = ifcopenshell.api.alignment.create_by_pi_method(
+        file, "TestAlignment", coordinates, radii, vpoints, lengths, start_station=1000.0
+    )
+
+    ifcopenshell.api.alignment.add_stationing_referent(
+        file, "P3", alignment, distance_along=400.0, station=1700.0, incoming_station=1400.0
+    )
+    ifcopenshell.api.alignment.add_stationing_referent(
+        file, "P4", alignment, distance_along=600.0, station=1850.0, incoming_station=1900.0
+    )
+
+    distance_along_from_station = ifcopenshell.api.alignment.distance_along_from_station
+
+    # between P2 and P3: Sta. 13+00.00
+    assert distance_along_from_station(file, alignment, 1300.0) == pytest.approx(300.0)
+
+    # between P3 and P4: Sta. 18+00.00
+    assert distance_along_from_station(file, alignment, 1800.0) == pytest.approx(500.0)
+
+    # between P4 and P5: Sta. 19+25.00
+    assert distance_along_from_station(file, alignment, 1925.0) == pytest.approx(675.0)
+
+    # Sta. 15+00.00 falls inside the gap opened by the equation at P3 and has no corresponding distance along
+    assert distance_along_from_station(file, alignment, 1500.0) is None
+
+    # Sta. 18+75.00 falls inside the overlap zone at P4; the post-equation (outgoing) match is returned
+    assert distance_along_from_station(file, alignment, 1875.0) == pytest.approx(625.0)
+
+
 test_distance_along_from_station()
+test_distance_along_from_station_with_station_equations()

src/ifcopenshell-python/test/test_parse.py

@@ -1,5 +1,6 @@
 import ifcopenshell
 
+
 def test_skip_over_non_entity_instance():
     data = """
 ISO-10303-21;

src/ifcopenshell-python/test/test_rules.py

@@ -46,4 +46,4 @@ def test_file(filename):
 
 
 if __name__ == "__main__":
-    pytest.main(["-sx", __file__, '--import-mode=importlib'])
+    pytest.main(["-sx", __file__, "--import-mode=importlib"])

src/ifcparse/IfcUtil.cpp

@@ -187,6 +187,15 @@ void IfcUtil::sanitate_material_name(std::string& str) {
 }
 
 void IfcUtil::escape_xml(std::string& str) {
+    // Strip characters that are illegal in XML 1.0. Control characters other
+    // than tab (0x09), newline (0x0A) and carriage return (0x0D) are not valid
+    // XML 1.0 characters and cannot even be represented as numeric character
+    // references, so they would otherwise make the serialized XML/SVG output
+    // non-well-formed. Bytes belonging to a valid UTF-8 multibyte sequence are
+    // always >= 0x80, so filtering on the low control range leaves them intact.
+    str.erase(std::remove_if(str.begin(), str.end(), [](unsigned char c) {
+        return c < 0x20 && c != '\t' && c != '\n' && c != '\r';
+    }), str.end());
     boost::replace_all(str, "&", "&amp;");
     boost::replace_all(str, "\"", "&quot;");
     boost::replace_all(str, "'", "&apos;");

src/ifcpatch/ifcpatch/recipes/ExtractElements.py

@@ -111,7 +111,7 @@ class Patcher(ifcpatch.BasePatcher):
         if element.is_a("IfcProject"):
             proj = self.new.add(element)
             for ctx in element.RepresentationContexts or ():
-                for coop in getattr(ctx, 'HasCoordinateOperation', ()):
+                for coop in getattr(ctx, "HasCoordinateOperation", ()):
                     self.new.add(coop)
             return proj
         return ifcopenshell.api.project.append_asset(

src/ifcpatch/test/test_DowngradeIndexedPolyCurve.py

@@ -33,9 +33,7 @@ class TestDowngradeIndexedPolyCurve(test.bootstrap.IFC4):
             Points=point_list,
             Segments=segments,
         )
-        self.file.create_entity(
-            "IfcArbitraryClosedProfileDef", ProfileType="AREA", OuterCurve=curve
-        )
+        self.file.create_entity("IfcArbitraryClosedProfileDef", ProfileType="AREA", OuterCurve=curve)
         return curve
 
     def test_run_without_segments(self):
@@ -80,9 +78,7 @@ class TestDowngradeIndexedPolyCurve(test.bootstrap.IFC4):
             Points=point_list,
             Segments=[self.file.createIfcLineIndex((1, 2, 3, 4, 1))],
         )
-        self.file.create_entity(
-            "IfcArbitraryClosedProfileDef", ProfileType="AREA", OuterCurve=curve
-        )
+        self.file.create_entity("IfcArbitraryClosedProfileDef", ProfileType="AREA", OuterCurve=curve)
         ifcpatch.execute(
             {"input": "input.ifc", "file": self.file, "recipe": "DowngradeIndexedPolyCurve", "arguments": []}
         )
@@ -110,9 +106,7 @@ class TestDowngradeIndexedPolyCurve(test.bootstrap.IFC4):
                 self.file.createIfcLineIndex((3, 4)),
             ],
         )
-        self.file.create_entity(
-            "IfcArbitraryClosedProfileDef", ProfileType="AREA", OuterCurve=curve
-        )
+        self.file.create_entity("IfcArbitraryClosedProfileDef", ProfileType="AREA", OuterCurve=curve)
         ifcpatch.execute(
             {"input": "input.ifc", "file": self.file, "recipe": "DowngradeIndexedPolyCurve", "arguments": []}
         )

src/ifcwrap/IfcGeomWrapper.i

@@ -977,12 +977,14 @@ struct ShapeRTTI : public boost::static_visitor<PyObject*>
 			if (item == nullptr) {
 				throw IfcParse::IfcException("Failed to convert placement");
 			}
+			/*
             if (st.get<ifcopenshell::geometry::settings::ConvertBackUnits>().get()) {
                 // we pass the settings to the Transformation object, but access the data just offloads to the
                 // generic cartesian_base<Matrix4> so there's no time to apply the settings to the translation part.
                 item = ifcopenshell::geometry::taxonomy::matrix4::ptr(item->clone_());
                 item->components().col(3).head<3>() /= kernel.settings().get<ifcopenshell::geometry::settings::LengthUnit>().get();
             }
+			*/
 			return new IfcGeom::Transformation(kernel.settings(), item);
 		} else {
 			if (!representation) {

src/serializers/schema_dependent/XmlSerializer.cpp

@@ -305,7 +305,7 @@ ptree* descend(Logger& logger, ifcopenshell::geometry::abstract_mapping* mapping
 			<IfcSchema::IfcObject, IfcSchema::IfcRelDefinesByProperties, IfcSchema::IfcPropertySetDefinition>
 			(logger, object, &IfcSchema::IfcObject::IsDefinedBy, &IfcSchema::IfcRelDefinesByProperties::RelatingPropertyDefinition);
 
-#ifdef SCHEMAS_HAS_IfcPropertySetDefinitionSet
+#ifdef SCHEMA_HAS_IfcPropertySetDefinitionSet
 		aggregate_of<IfcSchema::IfcPropertySetDefinitionSet>::ptr property_set_sets = get_related
 			<IfcSchema::IfcObject, IfcSchema::IfcRelDefinesByProperties, IfcSchema::IfcPropertySetDefinitionSet>
 			(logger, object, &IfcSchema::IfcObject::IsDefinedBy, &IfcSchema::IfcRelDefinesByProperties::RelatingPropertyDefinition);