FixRevitTINs patch now also flips normals for surface TINs instead of solid TINs.

Minor fixes to use view_layer.object.active etc instead of context.active_object when running via Blender UI (it seems when you run the patch recipe from the Blender UI at least in later versions, context does not have an "active_object" property.

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

@@ -275,7 +275,7 @@ class UpdateRepresentation(bpy.types.Operator, Operator):
     ifc_representation_class: bpy.props.StringProperty()
 
     def _execute(self, context):
-        if context.active_object and context.active_object.mode != "OBJECT":
+        if context.view_layer.objects.active and context.view_layer.objects.active.mode != "OBJECT":
             # Ensure mode is object to prevent invalid mesh data causing CTD
             bpy.ops.object.mode_set(mode="OBJECT", toggle=False)
 

src/blenderbim/blenderbim/bim/module/patch/operator.py

@@ -87,6 +87,9 @@ class ExecuteIfcPatch(bpy.types.Operator):
             input_file = props.ifc_patch_input
             file = ifcopenshell.open(props.ifc_patch_input)
 
+        # Store this in case the patch recipe resets the Blender session, such as by loading a new project.
+        ifc_patch_output = props.ifc_patch_output
+
         output = ifcpatch.execute(
             {
                 "input": input_file,
@@ -96,7 +99,7 @@ class ExecuteIfcPatch(bpy.types.Operator):
                 "log": os.path.join(context.scene.BIMProperties.data_dir, "process.log"),
             }
         )
-        ifcpatch.write(output, props.ifc_patch_output)
+        ifcpatch.write(output, ifc_patch_output)
         return {"FINISHED"}
 
 

src/ifcpatch/ifcpatch/recipes/FixRevitTINs.py

@@ -18,7 +18,7 @@
 
 
 class Patcher:
-    def __init__(self, src, file, logger):
+    def __init__(self, src, file, logger, is_solid=True):
         """Fix missing or spot-coordinate bugged TINs loading in Revit
 
         TINs exported from 12D or Civil 3D may contain dense or highly obtuse
@@ -27,11 +27,19 @@ class Patcher:
 
         See bug: https://github.com/Autodesk/revit-ifc/issues/511
 
-        The solution will delete any faces with a Z normal less than 0.5. In
-        case the mesh has any side faces or thickness, this should leave only
-        the top surface which is relevant for spot coordinates and elevations.
-        (e.g. I have come across surfaces which are extruded by 1mm from Civil
-        3D).  Vertices closer than 10mm will also be merged to prevent dense
+        If `is_solid` is enabled, we assume the surface is represented as a
+        solid (e.g. I have come across surfaces which are extruded by 1mm from
+        Civil 3D). The solution will delete any faces with a Z normal less
+        than 0.5. In case the mesh has any side faces or thickness, this should
+        leave only the top surface which is relevant for spot coordinates and
+        elevations.
+
+        If `is_solid` is disabled, then we assume the surface has no thickness.
+        In this scenario, all faces with any normals pointing in a negative
+        global Z direction will be flipped. This is because Revit cannot
+        annotate backfaces.
+
+        Vertices closer than 10mm will also be merged to prevent dense
         portions of the TIN at a minor sacrifice of surveying accuracy. It will
         also triangulate all meshes to prevent non-coplanar surfaces, and
         delete any obtuse triangles where one of their XY angles is less than
@@ -52,11 +60,12 @@ class Patcher:
 
         .. code:: python
 
-            ifcpatch.execute({"input": "input.ifc", "file": model, "recipe": "Fix12DToRevitTINs", "arguments": []})
+            ifcpatch.execute({"input": "input.ifc", "file": model, "recipe": "FixRevitTINs", "arguments": []})
         """
         self.src = src
         self.file = file
         self.logger = logger
+        self.is_solid = is_solid
 
     def patch(self):
         import bpy
@@ -77,30 +86,46 @@ class Patcher:
         for obj in bpy.data.objects:
             if not obj.BIMObjectProperties.ifc_definition_id or not obj.data:
                 continue
+            if not obj.data.polygons:
+                continue
             data = obj.data
             bm = bmesh.new()
             bm.from_mesh(data)
 
             bm.faces.ensure_lookup_table()
             faces_to_delete = []
-            for face in bm.faces:
-                if face.normal.z < 0.5:
-                    faces_to_delete.append(face)
+
+            if self.is_solid:
+                for face in bm.faces:
+                    if face.normal.z < 0.5:
+                        faces_to_delete.append(face)
+
             bmesh.ops.delete(bm, geom=faces_to_delete, context='FACES_ONLY')
 
             bmesh.ops.remove_doubles(bm, verts=bm.verts, dist=0.01)
             bmesh.ops.triangulate(bm, faces=bm.faces[:], quad_method="BEAUTY", ngon_method="BEAUTY")
             bm.faces.ensure_lookup_table()
             for polygon in bm.faces:
-                v1, v2, v3 = [v.co.to_2d() for v in polygon.verts]
-                d1 = degrees((v2 - v1).angle(v3 - v1))
-                d2 = degrees((v3 - v2).angle(v1 - v2))
-                d3 = degrees((v1 - v3).angle(v2 - v3))
-                if d1 < angle_threshold or d2 < angle_threshold or d3 < angle_threshold:
+                try:
+                    v1, v2, v3 = [v.co.to_2d() for v in polygon.verts]
+                    d1 = degrees((v2 - v1).angle(v3 - v1))
+                    d2 = degrees((v3 - v2).angle(v1 - v2))
+                    d3 = degrees((v1 - v3).angle(v2 - v3))
+                    if d1 < angle_threshold or d2 < angle_threshold or d3 < angle_threshold:
+                        bm.faces.remove(polygon)
+                except:
                     bm.faces.remove(polygon)
-            bm.to_mesh(data)
-            bm.free()
-            bpy.ops.bim.update_representation(obj=obj.name, ifc_representation_class="")
+            if bm.faces:
+                if not self.is_solid:
+                    bmesh.ops.recalc_face_normals(bm, faces=bm.faces)
+                    for face in bm.faces:
+                        global_normal = obj.matrix_world.to_3x3() @ face.normal
+                        if global_normal.z < 0:
+                            face.normal_flip()
+
+                bm.to_mesh(data)
+                bm.free()
+                bpy.ops.bim.update_representation(obj=obj.name, ifc_representation_class="")
 
         tool.Ifc.get().history_size = old_history_size
         bpy.context.preferences.edit.undo_steps = old_undo_steps