Closes #7943: Add regenerate_wall_to_underside operator

When extend_walls_to_underside is applied to a wall and the
roof/slab is later moved, pressing Shift+G now re-clips the
wall to the slab's new position.

The IFC relationship created by connect_wall_to_slab
(IfcRelConnectsElements, Description="TOP") is used to look
up which slabs a wall is clipped to. On regeneration, the
existing manual booleans (IfcPolygonalFaceSet operands) are
cleanly removed via remove_representation_item, then
clip_wall_to_slab is re-applied for each connected slab.

Shift+G on a LAYER2 wall that has a TOP connection now calls
bim.regenerate_wall_to_underside; walls without a connection
continue to call bim.recalculate_wall as before.

Generated with the assistance of an AI coding tool.

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

@@ -83,6 +83,7 @@ classes = (
     wall.EnableEditingWall,
     wall.ExtendWallHeightToCursor,
     wall.ExtendWallsToUnderside,
+    wall.RegenerateWallToUnderside,
     wall.ExtendWallsToWall,
     wall.ExtendWallsToPolylinePoint,
     wall.ExtendWallToCursor,

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

@@ -216,6 +216,24 @@ class ExtendWallsToUnderside(bpy.types.Operator, tool.Ifc.Operator):
             self.report({"ERROR"}, "Please select at least one LAYER2 element and an active element")
 
 
+class RegenerateWallToUnderside(bpy.types.Operator, tool.Ifc.Operator):
+    bl_idname = "bim.regenerate_wall_to_underside"
+    bl_label = "Regenerate Wall to Underside"
+    bl_description = "Re-clip selected walls to their connected underside objects after the slab has moved"
+    bl_options = {"REGISTER", "UNDO"}
+
+    def _execute(self, context):
+        wall_objs = [
+            obj
+            for obj in tool.Blender.get_selected_objects()
+            if (element := tool.Ifc.get_entity(obj)) and tool.Model.get_usage_type(element) == "LAYER2"
+        ]
+        if wall_objs:
+            core.regenerate_wall_to_underside(tool.Ifc, tool.Geometry, tool.Model, wall_objs)
+        else:
+            self.report({"ERROR"}, "Please select at least one LAYER2 element")
+
+
 class ExtendWallsToWall(bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.extend_walls_to_wall"
     bl_label = "Extend Walls To Wall"

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

@@ -1300,7 +1300,13 @@ class Hotkey(bpy.types.Operator, tool.Ifc.Operator):
                 bpy.ops.bim.generate_space()
             return
         if self.active_material_usage == "LAYER2":
-            bpy.ops.bim.recalculate_wall()
+            if element and any(
+                rel.is_a("IfcRelConnectsElements") and rel.Description == "TOP"
+                for rel in element.ConnectedFrom
+            ):
+                bpy.ops.bim.regenerate_wall_to_underside()
+            else:
+                bpy.ops.bim.recalculate_wall()
         elif self.active_material_usage == "LAYER3":
             bpy.ops.bim.recalculate_slab()
         elif tool.System.get_ports(element):

src/bonsai/bonsai/core/model.py

@@ -143,6 +143,31 @@ def align_objects(
     model.align_objects(reference_obj, objs, align_type)
 
 
+def regenerate_wall_to_underside(
+    ifc: type[tool.Ifc],
+    geometry: type[tool.Geometry],
+    model: type[tool.Model],
+    wall_objs: list[bpy.types.Object],
+) -> None:
+    """Re-clip walls to their connected underside objects after the slab has moved."""
+    clipped_objs = []
+    for obj in wall_objs:
+        wall = ifc.get_entity(obj)
+        slab_objs = model.get_connected_slab_objs(wall)
+        if not slab_objs:
+            continue
+        if ifc.is_moved(obj):
+            geometry.run_edit_object_placement(obj=obj)
+        model.remove_wall_to_underside_booleans(wall)
+        for slab_obj in slab_objs:
+            clip = model.get_slab_clipping_bmesh(slab_obj)
+            if clip:
+                model.clip_wall_to_slab(wall, clip)
+        clipped_objs.append(obj)
+    if clipped_objs:
+        model.reload_body_representation(clipped_objs)
+
+
 def extend_wall_to_slab(
     ifc: type[tool.Ifc],
     geometry: type[tool.Geometry],

src/bonsai/bonsai/core/tool.py

@@ -668,6 +668,7 @@ class Model:
     def export_profile(cls, obj, position=None): pass
     def generate_occurrence_name(cls, element_type, ifc_class): pass
     def get_extrusion(cls, representation): pass
+    def get_connected_slab_objs(cls, wall): pass
     def get_manual_booleans(cls, element): pass
     def get_material_layer_parameters(cls, element): pass
     def get_slab_clipping_bmesh(cls, obj): pass
@@ -683,6 +684,7 @@ class Model:
     def regenerate_profile(cls, obj): pass
     def regenerate_slab(cls, obj): pass
     def reload_body_representation(cls, obj_or_objects): pass
+    def remove_wall_to_underside_booleans(cls, wall): pass
     def replace_object_ifc_representation(cls, ifc_file, ifc_context, obj, new_representation): pass
 
 

src/bonsai/bonsai/tool/model.py

@@ -811,6 +811,29 @@ class Model(bonsai.core.tool.Model):
                 items.append(item.FirstOperand)
         return booleans
 
+    @classmethod
+    def get_connected_slab_objs(cls, wall: ifcopenshell.entity_instance) -> list[bpy.types.Object]:
+        """Return Blender objects for slabs connected to wall via IfcRelConnectsElements(TOP)."""
+        result = []
+        for rel in wall.ConnectedFrom:
+            if rel.is_a("IfcRelConnectsElements") and rel.Description == "TOP":
+                slab_obj = tool.Ifc.get_object(rel.RelatingElement)
+                if slab_obj:
+                    result.append(slab_obj)
+        return result
+
+    @classmethod
+    def remove_wall_to_underside_booleans(cls, wall: ifcopenshell.entity_instance) -> None:
+        """Remove all IfcBooleanResult items previously added by extend_walls_to_underside."""
+        manual_booleans = cls.get_manual_booleans(wall)
+        if not manual_booleans:
+            return
+        mesh_operands = [
+            b.SecondOperand for b in manual_booleans if b.SecondOperand.is_a("IfcTessellatedFaceSet")
+        ]
+        for mesh in mesh_operands:
+            tool.Geometry.remove_representation_item(mesh, wall)
+
     @classmethod
     def get_manual_booleans(
         cls, element: ifcopenshell.entity_instance, representation: Optional[ifcopenshell.entity_instance] = None