fix #7537 - Layer thickness correct when slab is rotated and few other features...

- Add dual-rotation support for AXIS3 slabs (IFC angle + object rotation)
- Fix profile editing to display horizontal projection for tilted slabs
- Fix AXIS2 layer slicing to use local extrusion direction for walls
- Fix ChangeExtrusionDepth to refresh geometry after depth changes
- Remove rotation lock on slabs to allow free rotation
- Fix undefined variable bug in add_slab_representation.py

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

@@ -35,7 +35,7 @@ import bonsai.core.geometry
 import bonsai.core.root
 import bonsai.tool as tool
 from bonsai.bim.ifc import IfcStore
-from math import cos, pi
+from math import cos, sin, pi, acos, degrees
 from mathutils import Vector, Matrix
 from bonsai.bim.module.model.decorator import ProfileDecorator, PolylineDecorator, ProductDecorator
 from bonsai.bim.module.model.polyline import PolylineOperator
@@ -296,50 +296,65 @@ class DumbSlabPlaner:
         if representation:
             extrusion = tool.Model.get_extrusion(representation)
             if extrusion:
-                # TODO Right now we don't have a reliable way to calculate the existing x_angle only based solely on the extrusion direction.
-                # For instances, a 30 degrees angled extrusion with positive direction has the same extrusion direction as a
-                # -150 degrees angled extrusion with negative direction. The difference lies in the object's rotation.
-                # This means that things can get messy if the user changes the object x angle somehow. We have to figure out an alternative approach.
-                existing_x_angle = obj.rotation_euler.x
-                existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, 0, tolerance=0.001) else existing_x_angle
-                existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, pi, tolerance=0.001) else existing_x_angle
-                existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, 2 * pi, tolerance=0.001) else existing_x_angle
                 direction_ratios = Vector(extrusion.ExtrudedDirection.DirectionRatios)
-                offset_direction = direction_ratios.copy()
-                perpendicular_depth = thickness * abs(1 / cos(existing_x_angle))
-                perpendicular_offset = layer_offset * abs(1 / cos(existing_x_angle)) / self.unit_scale
-
-                # Check angle and z direction to determine whether the extrusion direction is positive or negative
-                if (abs(existing_x_angle) < (pi / 2) and direction_ratios.z > 0) or (
-                    abs(existing_x_angle) > (pi / 2) and direction_ratios.z < 0
-                ):
-                    # The extrusion direction is positive. If the layer_parameter is set to negative,
-                    # then the we change the extrusion direction.
-                    if layer_params["direction_sense"] == "NEGATIVE":
-                        direction_ratios *= -1
-                elif (abs(existing_x_angle) > (pi / 2) and direction_ratios.z > 0) or (
-                    abs(existing_x_angle) < (pi / 2) and direction_ratios.z < 0
-                ):
-                    # The extrusion direction is negative. If the layer_parameter is set to positive,
-                    # then the we change the extrusion direction. And the offset direction should remain positive
-                    # for either direction sense, so we change it.
-                    offset_direction *= -1
-                    if layer_params["direction_sense"] == "POSITIVE":
-                        direction_ratios *= -1
-
-                extrusion.ExtrudedDirection.DirectionRatios = tuple(direction_ratios)
-                extrusion.Depth = perpendicular_depth
-
-                ifc_position = extrusion.Position
-                position = offset_direction * perpendicular_offset
-                material = ifcopenshell.util.element.get_material(element)
-                if material:
-                    if material.is_a("IfcMaterialLayerSetUsage"):
-                        material.OffsetFromReferenceLine = position.z
-                if ifc_position:
-                    ifc_position.Location.Coordinates = position
+                
+                # Calculate the actual extrusion angle from vertical
+                extrusion_angle = 0
+                if direction_ratios.length > 0:
+                    cos_angle = direction_ratios.normalized().dot(Vector((0, 0, 1)))
+                    extrusion_angle = acos(min(max(cos_angle, -1), 1))
+                
+                # FIX: Only apply 1/cos factor when there's actual extrusion slope
+                if extrusion_angle > 1e-6:
+                    perpendicular_depth = thickness * abs(1 / cos(extrusion_angle))
+                    perpendicular_offset = layer_offset * abs(1 / cos(extrusion_angle)) / self.unit_scale
                 else:
-                    tool.Model.add_extrusion_position(extrusion, position)
+                    perpendicular_depth = thickness
+                    perpendicular_offset = layer_offset / self.unit_scale
+                
+                # Check if direction sense needs to be applied
+                # This should only happen if explicitly requested, not automatically
+                if layer_params.get("apply_direction_sense", False):
+                    # Store current direction before potential change
+                    old_direction = direction_ratios.copy()
+                    
+                    # Apply direction sense logic
+                    existing_x_angle = extrusion_angle
+                    if (abs(existing_x_angle) < (pi / 2) and direction_ratios.z > 0) or (
+                        abs(existing_x_angle) > (pi / 2) and direction_ratios.z < 0
+                    ):
+                        if layer_params["direction_sense"] == "NEGATIVE":
+                            direction_ratios *= -1
+                    elif (abs(existing_x_angle) > (pi / 2) and direction_ratios.z > 0) or (
+                        abs(existing_x_angle) < (pi / 2) and direction_ratios.z < 0
+                    ):
+                        offset_direction = direction_ratios.copy() * -1
+                        if layer_params["direction_sense"] == "POSITIVE":
+                            direction_ratios *= -1
+                    
+                    # If direction changed, update extrusion with rotation compensation
+                    if (direction_ratios.normalized() - old_direction.normalized()).length > 1e-6:
+                        update_extrusion_direction(element, tuple(direction_ratios), obj)
+                        # After updating direction, get the updated extrusion
+                        extrusion = tool.Model.get_extrusion(representation)
+                
+                # Update depth
+                extrusion.Depth = perpendicular_depth
+                
+                # Update position
+                ifc_position = extrusion.Position
+                if direction_ratios.length > 0:
+                    offset_vector = direction_ratios.normalized() * perpendicular_offset
+                    position = offset_vector
+                    
+                    material = ifcopenshell.util.element.get_material(element)
+                    if material and material.is_a("IfcMaterialLayerSetUsage"):
+                        material.OffsetFromReferenceLine = position.z
+                    
+                    if ifc_position:
+                        ifc_position.Location.Coordinates = position
+                    else:
+                        tool.Model.add_extrusion_position(extrusion, position)
 
             else:
                 props = tool.Model.get_model_props()
@@ -383,6 +398,113 @@ class DumbSlabPlaner:
         )
 
 
+    def update_extrusion_direction(element: ifcopenshell.entity_instance, 
+                               new_direction_ratios: tuple,
+                               obj: bpy.types.Object = None) -> None:
+        """
+        Update extrusion direction while preserving overall object orientation.
+        
+        Args:
+            element: The IFC element
+            new_direction_ratios: New extrusion direction ratios (x,y,z)
+            obj: Optional Blender object (will be fetched if not provided)
+        """
+        if not obj:
+            obj = tool.Ifc.get_object(element)
+            if not obj:
+                return
+        
+        representation = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
+        if not representation:
+            return
+        
+        extrusion = tool.Model.get_extrusion(representation)
+        if not extrusion:
+            return
+        
+        # Get current extrusion direction
+        old_direction = Vector(extrusion.ExtrudedDirection.DirectionRatios)
+        if old_direction.length == 0:
+            old_direction = Vector((0, 0, 1))  # Default
+        
+        new_direction = Vector(new_direction_ratios)
+        if new_direction.length == 0:
+            new_direction = Vector((0, 0, 1))  # Default
+        
+        # Normalize both directions
+        old_direction_normalized = old_direction.normalized()
+        new_direction_normalized = new_direction.normalized()
+        
+        # Store current object matrix
+        old_matrix = obj.matrix_world.copy()
+        
+        # Calculate the rotation needed to keep same orientation
+        # When extrusion direction changes from A to B relative to local coordinates,
+        # we need to rotate the object by the inverse of that change
+        
+        # Calculate rotation from old to new direction
+        rotation_axis = old_direction_normalized.cross(new_direction_normalized)
+        if rotation_axis.length > 1e-6:
+            rotation_axis.normalized()
+            dot_product = old_direction_normalized.dot(new_direction_normalized)
+            angle = acos(min(max(dot_product, -1), 1))
+            
+            # Apply INVERSE rotation to object to compensate
+            rotation_matrix = Matrix.Rotation(-angle, 4, rotation_axis)
+            
+            # Update object rotation
+            obj.matrix_world = old_matrix @ rotation_matrix
+            bpy.context.view_layer.update()
+        
+        # Update extrusion direction (keeping magnitude)
+        if old_direction.length > 0:
+            # Preserve the magnitude of the original direction vector
+            magnitude = old_direction.length
+            new_direction = new_direction_normalized * magnitude
+        
+        extrusion.ExtrudedDirection.DirectionRatios = tuple(new_direction)
+        
+        # Update depth based on new extrusion angle
+        extrusion_angle = 0
+        if new_direction.length > 0:
+            cos_angle = new_direction_normalized.dot(Vector((0, 0, 1)))
+            extrusion_angle = acos(min(max(cos_angle, -1), 1))
+        
+        # Get current depth (perpendicular depth)
+        current_perpendicular_depth = extrusion.Depth
+        
+        # If we have material layer info, calculate actual thickness
+        material = ifcopenshell.util.element.get_material(element)
+        actual_thickness = current_perpendicular_depth
+        if material and material.is_a("IfcMaterialLayerSetUsage"):
+            layer_set = material.ForLayerSet
+            actual_thickness = sum([l.LayerThickness for l in layer_set.MaterialLayers])
+            unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
+            actual_thickness *= unit_scale
+        
+        # Convert to perpendicular depth if needed
+        if extrusion_angle > 1e-6:
+            new_perpendicular_depth = actual_thickness * abs(1 / cos(extrusion_angle))
+        else:
+            new_perpendicular_depth = actual_thickness
+        
+        extrusion.Depth = new_perpendicular_depth
+        
+        # Update position offset if needed
+        if extrusion.Position:
+            # Recalculate offset based on new direction
+            material = ifcopenshell.util.element.get_material(element)
+            if material and material.is_a("IfcMaterialLayerSetUsage"):
+                offset = material.OffsetFromReferenceLine
+                if extrusion_angle > 1e-6:
+                    perpendicular_offset = offset * abs(1 / cos(extrusion_angle))
+                else:
+                    perpendicular_offset = offset
+                
+                offset_vector = new_direction_normalized * perpendicular_offset
+                extrusion.Position.Location.Coordinates = tuple(offset_vector)
+
+
 class EnableEditingSketchExtrusionProfile(bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.enable_editing_sketch_extrusion_profile"
     bl_label = "Enable Editing Sketch Extrusion Profile"
@@ -656,6 +778,8 @@ class EnableEditingExtrusionProfile(bpy.types.Operator, tool.Ifc.Operator):
         extrusion = tool.Model.get_extrusion(body)
         existing_x_angle = tool.Model.get_existing_x_angle(extrusion)
         layer_params = tool.Model.get_material_layer_parameters(element)
+        
+        usage_type = tool.Model.get_usage_type(element)
 
         if extrusion.Position:
             position = Matrix(ifcopenshell.util.placement.get_axis2placement(extrusion.Position).tolist())
@@ -669,22 +793,49 @@ class EnableEditingExtrusionProfile(bpy.types.Operator, tool.Ifc.Operator):
             tranlation_matrix = Matrix.Translation(rot_offset)
             position = position @ tranlation_matrix
 
-            # Restore Object rotation to zero
-            local_rot_mat = obj.rotation_euler.to_matrix()
-            rot_mat = Matrix.Rotation(-existing_x_angle, 4, "X")
-            new_rot_mat = local_rot_mat.to_4x4() @ rot_mat
-            new_rot_euler = new_rot_mat.to_euler()
-            obj.rotation_euler = new_rot_euler
+            # For AXIS3 with dual rotation: Reset rotation to zero so profile is horizontal
+            if usage_type == "LAYER3":
+                # Store original rotation for later restoration
+                original_rotation_x = obj.rotation_euler.x
+                obj["pre_edit_rotation_x"] = original_rotation_x
+                
+                # Reset rotation to zero - profile will be horizontal
+                current_z_rot = obj.rotation_euler.z
+                obj.rotation_euler.x = 0.0
+                obj.rotation_euler.z = current_z_rot
+            else:
+                # Original behavior: Restore Object rotation to zero
+                local_rot_mat = obj.rotation_euler.to_matrix()
+                rot_mat = Matrix.Rotation(-existing_x_angle, 4, "X")
+                new_rot_mat = local_rot_mat.to_4x4() @ rot_mat
+                new_rot_euler = new_rot_mat.to_euler()
+                obj.rotation_euler = new_rot_euler
 
         else:
             position = Matrix()
 
-        tool.Model.import_profile(extrusion.SweptArea, obj=obj, position=position, x_angle=existing_x_angle)
+        # Import profile with correct x_angle
+        if usage_type == "LAYER3":
+            # For LAYER3: Use x_angle=0 and scale by cos(rotation) to get horizontal projection
+            obj_x_rotation = original_rotation_x  # Use stored original rotation
+            scale_factor = abs(cos(obj_x_rotation)) if abs(obj_x_rotation) > 1e-6 else 1.0
+            
+            # Import with x_angle=0
+            tool.Model.import_profile(extrusion.SweptArea, obj=obj, position=position, x_angle=0)
+            
+            # Scale the Y coordinates by cos(rotation) to get horizontal projection
+            bpy.ops.object.mode_set(mode='OBJECT')
+            for vert in obj.data.vertices:
+                vert.co.y *= scale_factor
+        else:
+            # For other types: Use existing_x_angle
+            tool.Model.import_profile(extrusion.SweptArea, obj=obj, position=position, x_angle=existing_x_angle)
 
         bpy.ops.object.mode_set(mode="EDIT")
         ProfileDecorator.install(context, exit_edit_mode_callback=lambda: disable_editing_extrusion_profile(context))
         if not bpy.app.background:
             tool.Blender.set_viewport_tool("bim.cad_tool")
+        
         return {"FINISHED"}
 
 
@@ -706,6 +857,8 @@ class EditExtrusionProfile(bpy.types.Operator, tool.Ifc.Operator):
         extrusion = tool.Model.get_extrusion(body)
         existing_x_angle = tool.Model.get_existing_x_angle(extrusion)
         layer_params = tool.Model.get_material_layer_parameters(element)
+        usage_type = tool.Model.get_usage_type(element)
+        
         if extrusion.Position:
             position = Matrix(ifcopenshell.util.placement.get_axis2placement(extrusion.Position).tolist())
             position.translation *= self.unit_scale
@@ -718,20 +871,40 @@ class EditExtrusionProfile(bpy.types.Operator, tool.Ifc.Operator):
             tranlation_matrix = Matrix.Translation(rot_offset)
             position = position @ tranlation_matrix
 
-            # Restore Object rotation to x_angle
-            local_rot_mat = obj.rotation_euler.to_matrix()
-            rot_mat = Matrix.Rotation(existing_x_angle, 4, "X")
-            new_rot_mat = local_rot_mat.to_4x4() @ rot_mat
-            new_rot_euler = new_rot_mat.to_euler()
-            obj.rotation_euler = new_rot_euler
+            # Restore rotation
+            if usage_type == "LAYER3":
+                # Restore original rotation from before editing
+                if "pre_edit_rotation_x" in obj:
+                    current_z_rot = obj.rotation_euler.z
+                    obj.rotation_euler.x = obj["pre_edit_rotation_x"]
+                    obj.rotation_euler.z = current_z_rot
+                    del obj["pre_edit_rotation_x"]
+            else:
+                # Original behavior
+                local_rot_mat = obj.rotation_euler.to_matrix()
+                rot_mat = Matrix.Rotation(existing_x_angle, 4, "X")
+                new_rot_mat = local_rot_mat.to_4x4() @ rot_mat
+                new_rot_euler = new_rot_mat.to_euler()
+                obj.rotation_euler = new_rot_euler
 
         else:
             position = Matrix()
 
-        profile = tool.Model.export_profile(obj, position=position, x_angle=existing_x_angle)
+        # Export profile with correct x_angle
+        if usage_type == "LAYER3":
+            # Scale Y coordinates back up before exporting
+            obj_x_rotation = obj.rotation_euler.x
+            scale_factor = abs(cos(obj_x_rotation)) if abs(obj_x_rotation) > 1e-6 else 1.0
+            
+            # Un-scale the profile before exporting
+            for vert in obj.data.vertices:
+                vert.co.y /= scale_factor  # Inverse of import scaling
+            
+            profile = tool.Model.export_profile(obj, position=position, x_angle=0)
+        else:
+            profile = tool.Model.export_profile(obj, position=position, x_angle=existing_x_angle)
 
         if not profile:
-
             def msg(self, context):
                 self.layout.label(text="INVALID PROFILE")
 
@@ -781,6 +954,29 @@ class EditExtrusionProfile(bpy.types.Operator, tool.Ifc.Operator):
             )
 
 
+        footprint_context = ifcopenshell.util.representation.get_context(
+            tool.Ifc.get(), "Plan", "FootPrint", "SKETCH_VIEW"
+        )
+        if not footprint_context:
+            return
+
+        curves = [profile.OuterCurve]
+        if profile.is_a("IfcArbitraryProfileDefWithVoids"):
+            curves.extend(profile.InnerCurves)
+        new_footprint = ifcopenshell.api.geometry.add_footprint_representation(
+            tool.Ifc.get(), context=footprint_context, curves=curves
+        )
+        old_footprint = ifcopenshell.util.representation.get_representation(element, "Plan", "FootPrint", "SKETCH_VIEW")
+        if old_footprint:
+            for inverse in tool.Ifc.get().get_inverse(old_footprint):
+                ifcopenshell.util.element.replace_attribute(inverse, old_footprint, new_footprint)
+            bonsai.core.geometry.remove_representation(tool.Ifc, tool.Geometry, obj=obj, representation=old_footprint)
+        else:
+            ifcopenshell.api.geometry.assign_representation(
+                tool.Ifc.get(), product=element, representation=new_footprint
+            )
+
+
 class ResetVertex(bpy.types.Operator):
     bl_idname = "bim.reset_vertex"
     bl_label = "Reset Vertex"

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

@@ -43,7 +43,7 @@ import bonsai.core.geometry
 import bonsai.core.model as core
 import bonsai.tool as tool
 from bonsai.bim.ifc import IfcStore
-from math import pi, sin, cos, degrees, atan2
+from math import pi, sin, cos, degrees, atan2, acos
 from mathutils import Vector, Matrix
 from bonsai.bim.module.model.opening import FilledOpeningGenerator
 from bonsai.bim.module.model.decorator import PolylineDecorator, ProductDecorator
@@ -397,27 +397,46 @@ class ChangeExtrusionDepth(bpy.types.Operator, tool.Ifc.Operator):
         for obj in selected_objs:
             element = tool.Ifc.get_entity(obj)
             assert element
+            
             representation = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
             if not representation:
                 continue
+                
             extrusion = tool.Model.get_extrusion(representation)
             if not extrusion:
                 continue
+            
+            # Get extrusion direction
             x, y, z = extrusion.ExtrudedDirection.DirectionRatios
+            
+            # Calculate angle from vertical
             x_angle = Vector((0, 1)).angle_signed(Vector((y, z)))
-            extrusion.Depth = self.depth / si_conversion * (1 / cos(x_angle))
+            
+            # For sloped walls, compensate so VERTICAL height = target depth
+            cos_angle = cos(x_angle)
+            compensation_factor = abs(1 / cos_angle) if abs(cos_angle) > 1e-6 else 1.0
+            new_depth_ifc = (self.depth / si_conversion) * compensation_factor
+            
+            extrusion.Depth = new_depth_ifc
+            
+            # IMPORTANT: Refresh the geometry to reflect the IFC changes
+            bonsai.core.geometry.switch_representation(
+                tool.Ifc,
+                tool.Geometry,
+                obj=obj,
+                representation=representation,
+            )
+            
             if tool.Model.get_usage_type(element) == "LAYER2":
                 for rel in element.ConnectedFrom:
                     if rel.is_a() == "IfcRelConnectsElements":
-                        ifcopenshell.api.geometry.disconnect_element(
-                            ifc_file,
-                            relating_element=rel.RelatingElement,
-                            related_element=element,
-                        )
-                layer2_objs.append(obj)
+                        related_element = rel.RelatedElement
+                        if related_element.is_a() == "IfcWall":
+                            layer2_objs.append(tool.Ifc.get_object(related_element))
 
         if layer2_objs:
             tool.Model.recalculate_walls(layer2_objs)
+        
         return {"FINISHED"}
 
 
@@ -437,80 +456,126 @@ class ChangeExtrusionXAngle(bpy.types.Operator, tool.Ifc.Operator):
 
     def _execute(self, context):
         layer2_objs: list[bpy.types.Object] = []
-        x_angle = 0 if tool.Cad.is_x(self.x_angle, 0, tolerance=0.001) else self.x_angle
-        x_angle = 0 if tool.Cad.is_x(self.x_angle, pi, tolerance=0.001) else self.x_angle
-        unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
-        selected_objs = tool.Model.get_selected_mesh_ifc_objects()
         builder = ifcopenshell.util.shape_builder.ShapeBuilder(tool.Ifc.get())
+        unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
+        x_angle = self.x_angle
 
-        for obj in selected_objs:
+        for obj in context.selected_objects:
             element = tool.Ifc.get_entity(obj)
-            assert element
+            if not element:
+                continue
+
             representation = ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW")
             if not representation:
                 continue
             extrusion = tool.Model.get_extrusion(representation)
             if not extrusion:
                 continue
+            
+            # Get current object rotation matrix
+            obj_rotation = obj.matrix_world.to_3x3()
+            
+            # Get current extrusion direction in LOCAL coordinates
+            current_local_direction = Vector(extrusion.ExtrudedDirection.DirectionRatios)
+            if current_local_direction.length == 0:
+                current_local_direction = Vector((0, 0, 1))
+            current_local_direction_normalized = current_local_direction.normalized()
+            
+            # Calculate what the current extrusion direction is in WORLD coordinates
+            current_world_direction = obj_rotation @ current_local_direction_normalized
+            
             existing_x_angle = tool.Model.get_existing_x_angle(extrusion)
             existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, 0, tolerance=0.001) else existing_x_angle
             existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, pi, tolerance=0.001) else existing_x_angle
+            
+            # Calculate the NEW local extrusion direction based on x_angle
+            new_local_direction = Vector((0.0, sin(x_angle), cos(x_angle)))
+            
+            # Check if extrusion direction is actually changing
+            current_local_norm = current_local_direction_normalized
+            new_local_norm = new_local_direction.normalized()
+            
+            # Compare the LOCAL directions
+            local_direction_changed = (new_local_norm - current_local_norm).length > 1e-6
+            
             if tool.Model.get_usage_type(element) == "LAYER2":
-                x, y, z = extrusion.ExtrudedDirection.DirectionRatios
                 depth = extrusion.Depth / abs(1 / cos(existing_x_angle))
                 perpendicular_depth = depth * abs(1 / cos(x_angle))
-                extrusion.ExtrudedDirection.DirectionRatios = (0.0, sin(x_angle), cos(x_angle))
-                layer2_objs.append(obj)
+                
+                # Update extrusion direction
+                if local_direction_changed:
+                    extrusion.ExtrudedDirection.DirectionRatios = tuple(new_local_direction)
+                
+                # Always update depth
                 extrusion.Depth = perpendicular_depth
+                layer2_objs.append(obj)
+                
             else:
                 if tool.Model.get_usage_type(element) == "LAYER3":
-                    existing_x_angle = obj.rotation_euler.x
-                    existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, 0, tolerance=0.001) else existing_x_angle
-                    existing_x_angle = 0 if tool.Cad.is_x(existing_x_angle, pi, tolerance=0.001) else existing_x_angle
+                    # For slabs, handle polyline scaling
+                    existing_obj_x_angle = obj.rotation_euler.x
+                    existing_obj_x_angle = 0 if tool.Cad.is_x(existing_obj_x_angle, 0, tolerance=0.001) else existing_obj_x_angle
+                    existing_obj_x_angle = 0 if tool.Cad.is_x(existing_obj_x_angle, pi, tolerance=0.001) else existing_obj_x_angle
 
+                    # Scale the polyline coordinates
                     coord_list = builder.get_polyline_coords(extrusion.SweptArea.OuterCurve)
                     coord_list = [
                         (p[0], p[1] * abs(cos(existing_x_angle))) for p in coord_list
-                    ]  # Reset the transformation and returns to the original points with 0 degrees
+                    ]  # Reset the transformation
                     coord_list = [
                         (p[0], p[1] * abs(1 / cos(x_angle))) for p in coord_list
                     ]  # Apply the transformation for the new x_angle
                     builder.set_polyline_coords(extrusion.SweptArea.OuterCurve, coord_list)
 
-                    # The extrusion direction calculated previously default to the positive direction
-                    # Here we set the extrusion direction to negative if that's the case
-                    direction_ratios = Vector((0.0, sin(x_angle), cos(x_angle)))
-                    # direction_ratios = Vector(extrusion.ExtrudedDirection.DirectionRatios)
+                    # Calculate new extrusion direction with direction sense
+                    base_local_direction = Vector((0.0, sin(x_angle), cos(x_angle)))
                     layer_params = tool.Model.get_material_layer_parameters(element)
                     perpendicular_depth = layer_params["thickness"] * abs(1 / cos(x_angle)) / unit_scale
                     perpendicular_offset = layer_params["offset"] * abs(1 / cos(x_angle)) / unit_scale
-                    offset_direction = direction_ratios.copy()
+                    offset_direction = base_local_direction.copy()
 
-                    # Check angle and z direction to determine whether the extrusion direction is positive or negative
-                    if (abs(x_angle) < (pi / 2) and direction_ratios.z > 0) or (
-                        abs(x_angle) > (pi / 2) and direction_ratios.z < 0
+                    # Apply direction sense
+                    final_local_direction = base_local_direction.copy()
+                    if (abs(x_angle) < (pi / 2) and base_local_direction.z > 0) or (
+                        abs(x_angle) > (pi / 2) and base_local_direction.z < 0
                     ):
-                        # The extrusion direction is positive. If the layer_parameter is set to negative,
-                        # then the we change the extrusion direction.
                         if layer_params["direction_sense"] == "NEGATIVE":
-                            direction_ratios *= -1
-                    elif ((x_angle) > (pi / 2) and direction_ratios.z > 0) or (
-                        (x_angle) < (pi / 2) and direction_ratios.z < 0
+                            final_local_direction *= -1
+                    elif (x_angle > (pi / 2) and base_local_direction.z > 0) or (
+                        x_angle < (pi / 2) and base_local_direction.z < 0
                     ):
-                        # The extrusion direction is negative. If the layer_parameter is set to positive,
-                        # then the we change the extrusion direction.
-                        # then the we change the extrusion direction. And the offset direction should remain positive
-                        # for either direction sense, so we change it.
                         offset_direction *= -1
                         if layer_params["direction_sense"] == "POSITIVE":
-                            direction_ratios *= -1
-
-                    extrusion.ExtrudedDirection.DirectionRatios = tuple(direction_ratios)
+                            final_local_direction *= -1
+                    
+                    # Check if extrusion direction actually changed
+                    final_local_norm = final_local_direction.normalized()
+                    local_direction_changed = (final_local_norm - current_local_norm).length > 1e-6
+                    
+                    # Update extrusion properties
+                    extrusion.ExtrudedDirection.DirectionRatios = tuple(final_local_direction)
                     extrusion.Depth = perpendicular_depth
 
                     if extrusion.Position or perpendicular_offset != 0:
                         position = offset_direction * perpendicular_offset
                         tool.Model.add_extrusion_position(extrusion, position)
+                    
+                    # Adjust object rotation if extrusion direction changed
+                    if local_direction_changed:
+                        # Calculate what the NEW world direction would be with current object rotation
+                        expected_new_world_direction = obj_rotation @ final_local_norm
+                        
+                        # The rotation needed is from expected_new_world_direction to current_world_direction
+                        rotation_axis = expected_new_world_direction.cross(current_world_direction)
+                        if rotation_axis.length > 1e-6:
+                            rotation_axis.normalize()
+                            dot_product = expected_new_world_direction.dot(current_world_direction)
+                            angle = acos(min(max(dot_product, -1), 1))
+                            
+                            # Create and apply rotation matrix
+                            rotation_matrix = Matrix.Rotation(angle, 4, rotation_axis)
+                            obj.matrix_world = rotation_matrix @ obj.matrix_world
+                            bpy.context.view_layer.update()
 
                 bonsai.core.geometry.switch_representation(
                     tool.Ifc,
@@ -519,12 +584,6 @@ class ChangeExtrusionXAngle(bpy.types.Operator, tool.Ifc.Operator):
                     representation=representation,
                 )
 
-                # Object rotation
-                current_z_rot = obj.rotation_euler.z
-                rot_mat = mathutils.Matrix.Rotation(x_angle, 4, "X")
-                obj.rotation_euler = rot_mat.to_euler()
-                obj.rotation_euler.z = current_z_rot
-
         if layer2_objs:
             tool.Model.recalculate_walls(layer2_objs)
         return {"FINISHED"}
@@ -1022,6 +1081,7 @@ class DumbWallGenerator:
             obj=obj,
             representation=representation,
         )
+        
         pset = ifcopenshell.api.pset.add_pset(self.file, product=element, name="EPset_Parametric")
         ifcopenshell.api.pset.edit_pset(self.file, pset=pset, properties={"Engine": "Bonsai.DumbLayer2"})
         material = ifcopenshell.util.element.get_material(element)

src/bonsai/bonsai/tool/collector.py

@@ -44,8 +44,6 @@ class Collector(bonsai.core.tool.Collector):
         # Note that tool.Geometry.is_locked is only checked within the if
         # statements for efficiency as it is a slow check.
         tool.Geometry.lock_scale(obj)
-        if element.is_a("IfcSlab"):
-            tool.Geometry.lock_rotation(obj, x=True)
 
         if element.is_a("IfcGridAxis"):
             if tool.Geometry.is_locked(element):

src/bonsai/bonsai/tool/loader.py

@@ -1030,28 +1030,57 @@ class Loader(bonsai.core.tool.Loader):
             sense_factor = 1
         else:
             return mesh
+        
         if len(layer_set.MaterialLayers) == 1:
             return mesh
+        
         bm = bmesh.new()
         bm.from_mesh(mesh)
+        
         prev_co = None
+        advance_direction = None  # Will store direction to advance planes
+        
         if not usage:
-            sense_factor = 1  # Assume the extrusion vector points in the direction sense
+            sense_factor = 1
             no = cls.get_extrusion_vector(element).normalized()
             co = Vector((0.0, 0.0, offset))
+            advance_direction = no
         elif usage.LayerSetDirection == "AXIS2":
             co = Vector((0.0, offset, 0.0))
-            no = cls.get_extrusion_vector(element).normalized()
-            no = no.cross(Vector([1.0, 0.0, 0.0]))
+            
+            # Get LOCAL extrusion direction
+            local_extrusion = Vector([0.0, 0.0, 1.0])
+            if body := ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW"):
+                for item in ifcopenshell.util.representation.resolve_representation(body).Items:
+                    while item.is_a("IfcBooleanResult"):
+                        item = item.FirstOperand
+                    if item.is_a("IfcExtrudedAreaSolid"):
+                        local_extrusion = Vector(item.ExtrudedDirection.DirectionRatios).normalized()
+                        break
+            
+            # Thickness direction: perpendicular to extrusion and length
+            thickness_dir = local_extrusion.cross(Vector([1.0, 0.0, 0.0])).normalized()
+            
+            # Ensure it points in POSITIVE Y (through wall thickness, not backwards)
+            if thickness_dir.y < 0:
+                thickness_dir = -thickness_dir
+            
+            no = thickness_dir
+            advance_direction = thickness_dir
         elif usage.LayerSetDirection == "AXIS3":
             co = Vector((0.0, 0.0, offset))
             no = cls.get_extrusion_vector(element).normalized()
             no = Vector([0.0, 0.0, 1.0])
+            advance_direction = no
         elif usage.LayerSetDirection == "AXIS1":
             co = Vector((0.0, 0.0, offset))
             no = cls.get_extrusion_vector(element).normalized()
             no = Vector([1.0, 0.0, 0.0])
+            advance_direction = no
+        
         no *= sense_factor
+        advance_direction *= sense_factor
+        
         # Cache this
         body = ifcopenshell.util.representation.get_context(tool.Ifc.get(), "Model", "Body", "MODEL_VIEW")
         styles = {}
@@ -1059,20 +1088,25 @@ class Loader(bonsai.core.tool.Loader):
         for i, material in enumerate(mesh.materials):
             if style := tool.Ifc.get_entity(material):
                 styles[style] = i
+        
         last_i = len(layer_set.MaterialLayers) - 1
         for i, layer in enumerate(layer_set.MaterialLayers):
             if i != last_i:
                 prev_co = co.copy()
-                co += no * layer.LayerThickness * cls.unit_scale
+                # Use advance_direction (not no) to move planes!
+                co += advance_direction * layer.LayerThickness * cls.unit_scale
+                
                 bisect_geom = bmesh.ops.bisect_plane(
                     bm, geom=bm.verts[:] + bm.edges[:] + bm.faces[:], dist=0.0001, plane_co=co, plane_no=no
                 )
                 bmesh.ops.duplicate(bm, geom=bisect_geom["geom_cut"])
+            
             if not (style := ifcopenshell.util.representation.get_material_style(layer.Material, body)):
                 continue
             if (material_index := styles.get(style, None)) is None:
                 material_index = len(mesh.materials)
                 mesh.materials.append(tool.Ifc.get_object(style))
+            
             if i == last_i:
                 for face in bisect_geom["geom"]:
                     if isinstance(face, bmesh.types.BMFace):
@@ -1097,13 +1131,35 @@ class Loader(bonsai.core.tool.Loader):
         return mesh
 
     @classmethod
-    def get_extrusion_vector(cls, wall):
-        if body := ifcopenshell.util.representation.get_representation(wall, "Model", "Body", "MODEL_VIEW"):
+    def get_extrusion_vector(cls, element):
+        """Get the extrusion direction in WORLD coordinates (accounting for object rotation)"""
+        if body := ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW"):
             for item in ifcopenshell.util.representation.resolve_representation(body).Items:
                 while item.is_a("IfcBooleanResult"):
                     item = item.FirstOperand
                 if item.is_a("IfcExtrudedAreaSolid"):
-                    return Vector(item.ExtrudedDirection.DirectionRatios)
+                    local_direction = Vector(item.ExtrudedDirection.DirectionRatios)
+                    
+                    # Transform to world coordinates using object rotation
+                    obj = tool.Ifc.get_object(element)
+                    if obj:
+                        # Apply object rotation to get actual world direction
+                        world_direction = obj.matrix_world.to_3x3() @ local_direction
+                        return world_direction
+                    
+                    return local_direction
+        return Vector([0.0, 0.0, 1.0])
+
+    @classmethod
+    def get_local_extrusion_vector(cls, element):
+        """Get the extrusion direction in LOCAL coordinates (from IFC, no object rotation)"""
+        if body := ifcopenshell.util.representation.get_representation(element, "Model", "Body", "MODEL_VIEW"):
+            for item in ifcopenshell.util.representation.resolve_representation(body).Items:
+                while item.is_a("IfcBooleanResult"):
+                    item = item.FirstOperand
+                if item.is_a("IfcExtrudedAreaSolid"):
+                    local_direction = Vector(item.ExtrudedDirection.DirectionRatios)
+                    return local_direction
         return Vector([0.0, 0.0, 1.0])
 
     @classmethod

src/ifcopenshell-python/ifcopenshell/api/geometry/add_slab_representation.py

@@ -100,35 +100,45 @@ class Usecase:
         size = self.convert_si_to_unit(1)
         points = ((0.0, 0.0), (size, 0.0), (size, size), (0.0, size), (0.0, 0.0))
         if self.polyline:
-            points = [
-                (self.convert_si_to_unit(p[0]), self.convert_si_to_unit(p[1] * abs(1 / cos(self.x_angle))))
-                for p in self.polyline
-            ]
+            # Only scale polyline if we have actual slope
+            if self.x_angle and abs(self.x_angle) > 1e-6:
+                points = [
+                    (self.convert_si_to_unit(p[0]), self.convert_si_to_unit(p[1] * abs(1 / cos(self.x_angle))))
+                    for p in self.polyline
+                ]
+            else:
+                points = [
+                    (self.convert_si_to_unit(p[0]), self.convert_si_to_unit(p[1]))
+                    for p in self.polyline
+                ]
+        
         if self.file.schema == "IFC2X3":
             curve = self.file.createIfcPolyline([self.file.createIfcCartesianPoint(p) for p in points])
         else:
             curve = self.file.createIfcIndexedPolyCurve(self.file.createIfcCartesianPointList2D(points))
-
+        
         if self.x_angle:
             direction_ratios = (0.0, sin(self.x_angle), cos(self.x_angle))
         else:
             direction_ratios = (0.0, 0.0, 1.0)
 
-        offset_direction = direction_ratios  # offset direction doesn't change if direction_sense is negative
         extrusion_direction = self.file.createIfcDirection(direction_ratios)
-        if self.direction_sense == "NEGATIVE":
-            direction_ratios = tuple(-n for n in direction_ratios)
-            extrusion_direction = self.file.createIfcDirection(direction_ratios)
-
-        perpendicular_offset = self.convert_si_to_unit(self.offset) * abs(1 / cos(self.x_angle))
-        perpendicular_depth = self.convert_si_to_unit(self.depth) * abs(1 / cos(self.x_angle))
+        
+        # Calculate depth based on extrusion angle
+        extrusion_angle = abs(self.x_angle) if self.x_angle else 0
+        if extrusion_angle > 1e-6:
+            perpendicular_depth = self.convert_si_to_unit(self.depth) * abs(1 / cos(extrusion_angle))
+            perpendicular_offset = self.convert_si_to_unit(self.offset) * abs(1 / cos(extrusion_angle))
+        else:
+            perpendicular_depth = self.convert_si_to_unit(self.depth)
+            perpendicular_offset = self.convert_si_to_unit(self.offset)
+            
         position = None
-        # default position for IFC2X3 where .Position is not optional
         if self.file.schema == "IFC2X3" or self.offset != 0:
             position_vector = (
-                offset_direction[0] * perpendicular_offset,
-                offset_direction[1] * perpendicular_offset,
-                offset_direction[2] * perpendicular_offset,
+                direction_ratios[0] * perpendicular_offset,
+                direction_ratios[1] * perpendicular_offset,
+                direction_ratios[2] * perpendicular_offset,
             )
             position = self.file.createIfcAxis2Placement3D(
                 self.file.createIfcCartesianPoint(position_vector),

src/ifcopenshell-python/ifcopenshell/api/geometry/add_wall_representation.py

@@ -85,7 +85,6 @@ class Usecase:
     def create_item(self) -> ifcopenshell.entity_instance:
         length = self.convert_si_to_unit(self.settings["length"])
         thickness = self.convert_si_to_unit(self.settings["thickness"])
-        thickness *= 1 / cos(self.settings["x_angle"])
         if self.settings["direction_sense"] == "NEGATIVE":
             thickness *= -1
         points = (
@@ -113,7 +112,7 @@ class Usecase:
                 self.file.createIfcDirection((1.0, 0.0, 0.0)),
             ),
             extrusion_direction,
-            self.convert_si_to_unit(self.settings["height"]) * abs(1 / cos(self.settings["x_angle"])),
+            self.convert_si_to_unit(self.settings["height"]),
         )
         if self.settings["booleans"]:
             extrusion = self.apply_booleans(extrusion)