Fix #5541. Creating an object from a mesh now separates by loose parts to prevent unwanted vertex fusing.

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

@@ -377,16 +377,18 @@ class AddElement(bpy.types.Operator, tool.Ifc.Operator):
 
         if representation_template == "EMTPY" or not ifc_context:
             pass
-        elif representation_template == "OBJ" and not props.representation_obj:
-            pass
-        elif representation_template == "OBJ":
+        elif representation_template == "OBJ" and props.representation_obj:
             obj.matrix_world = props.representation_obj.matrix_world
             builder = ifcopenshell.util.shape_builder.ShapeBuilder(tool.Ifc.get())
             unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-            verts = [v.co / unit_scale for v in props.representation_obj.data.vertices]
-            faces = [p.vertices[:] for p in props.representation_obj.data.polygons]
-            item = builder.mesh(verts, faces)
-            representation = builder.get_representation(ifc_context, [item])
+            items = []
+            meshes = tool.Geometry.split_by_loose_parts(props.representation_obj)
+            for mesh in meshes:
+                verts = [v.co / unit_scale for v in mesh.vertices]
+                faces = [p.vertices[:] for p in mesh.polygons]
+                items.append(builder.mesh(verts, faces))
+                bpy.data.meshes.remove(mesh)
+            representation = builder.get_representation(ifc_context, items)
             ifcopenshell.api.geometry.assign_representation(tool.Ifc.get(), element, representation)
             bonsai.core.geometry.switch_representation(
                 tool.Ifc,

src/bonsai/bonsai/tool/geometry.py

@@ -47,7 +47,7 @@ from collections import defaultdict
 from math import radians, pi
 from mathutils import Vector, Matrix
 from bonsai.bim.ifc import IfcStore
-from typing import Union, Iterable, Optional, Literal, Iterator
+from typing import Union, Iterable, Optional, Literal, Iterator, List
 from typing_extensions import TypeIs
 
 
@@ -1562,3 +1562,23 @@ class Geometry(bonsai.core.tool.Geometry):
         ifcopenshell.util.element.remove_deep2(tool.Ifc.get(), item)
         obj.data.BIMMeshProperties.ifc_definition_id = new_item.id()
         cls.reload_representation(bpy.context.scene.BIMGeometryProperties.representation_obj)
+
+    @classmethod
+    def split_by_loose_parts(cls, obj: bpy.types.Object) -> List[bpy.types.Mesh]:
+        dup_obj = obj.copy()
+        dup_obj.data = obj.data.copy()
+        bpy.context.scene.collection.objects.link(dup_obj)
+
+        tool.Blender.select_and_activate_single_object(bpy.context, dup_obj)
+
+        bpy.ops.object.mode_set(mode="EDIT")
+        bpy.ops.mesh.select_all(action="SELECT")
+        bpy.ops.mesh.separate(type="LOOSE")
+        bpy.ops.object.mode_set(mode="OBJECT")
+
+        results = []
+        for obj in bpy.context.selected_objects:
+            results.append(obj.data)
+            bpy.data.objects.remove(obj)
+
+        return results