Optimize coplanar face reconstruction and add tests

Vectorize the coplanarity prefilter in _union_coplanar_face_polygon and
compute per-triangle normals once instead of per space face. Add
regression tests for the SmallHouse and Triangle boundary test models.

Generated with the assistance of an AI coding tool.

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

@@ -64,6 +64,7 @@ FULL_FACE_OFFSET_TOL = 0.25
 def _union_coplanar_face_polygon(
     space_verts_local,
     space_triangles,
+    space_triangle_normals,
     face_origin,
     face_normal,
     face_matrix_inv,
@@ -76,14 +77,15 @@ def _union_coplanar_face_polygon(
     or an opening. Unioning the raw triangles coplanar with the face restores
     those holes.
     """
+    # Vectorized coplanarity prefilter: keep only triangles whose vertices all
+    # lie within 1e-4 m (0.1 mm) of the face plane.
+    triangle_points = space_verts_local[space_triangles]
+    plane_offsets = np.abs(np.tensordot(triangle_points - face_origin, face_normal, axes=(2, 0))).max(axis=1)
     polygons = []
-    for triangle in space_triangles:
-        points = space_verts_local[triangle]
-        if _face_normal(points) is None:
+    for triangle in np.flatnonzero(plane_offsets <= 1e-4):
+        if space_triangle_normals[triangle] is None:
             continue
-        if np.abs(np.dot(points - face_origin, face_normal)).max() > 1e-4:
-            continue
-        polygon = _verts_to_polygon(points, face_matrix_inv, snap=1e-6)
+        polygon = _verts_to_polygon(space_verts_local[space_triangles[triangle]], face_matrix_inv, snap=1e-6)
         if not polygon.is_valid:
             polygon = polygon.buffer(0)
         if polygon.is_empty:
@@ -159,6 +161,11 @@ def auto_generate_boundaries(
         space_verts_local, space_shape["faces"], space_shape["edges"], merge_coplanar=True
     )
 
+    # Per-triangle normals used to reconstruct space faces from their raw
+    # triangles (see _union_coplanar_face_polygon). Computed once instead of
+    # once per space face.
+    space_triangle_normals = [_face_normal(space_verts_local[tri]) for tri in space_shape["faces"]]
+
     # Dissolve building element meshes — verts are in element-local coords
     element_ngons = {}
     for element in building_elements:
@@ -262,6 +269,7 @@ def auto_generate_boundaries(
         space_face_polygon = _union_coplanar_face_polygon(
             space_verts_local,
             space_shape["faces"],
+            space_triangle_normals,
             space_verts_l[0],
             space_face_normal_local,
             face_matrix_inv,
@@ -317,7 +325,9 @@ def auto_generate_boundaries(
         # candidates are kept in order of increasing plane offset (ties broken
         # by polygon area). A candidate whose polygon is entirely covered by
         # the candidates already kept is redundant and is absorbed into the
-        # larger boundary.
+        # larger boundary. This includes coplanar candidates: e.g. wall end
+        # caps that are coplanar with the ceiling and fully covered by the
+        # slab above do not get their own boundary in the reference output.
         surviving_candidates = []
         kept_union = None
         for element, dist_min, plane_offset_min, gross_boundary_polygon, matched_elem_normal in sorted(

src/ifcopenshell-python/test/util/test_boundary.py

@@ -208,6 +208,26 @@ def _over_splitted_ifc():
     )
 
 
+def _small_house_ifczip():
+    return os.path.join(
+        os.path.dirname(__file__),
+        "..",
+        "IfcRelSpaceBoundary_TestFiles",
+        "IfcRelSpaceBoundary2ndLevel",
+        "SmallHouse_BB_IFC4.ifczip",
+    )
+
+
+def _triangle_ifczip():
+    return os.path.join(
+        os.path.dirname(__file__),
+        "..",
+        "IfcRelSpaceBoundary_TestFiles",
+        "IfcRelSpaceBoundary2ndLevel",
+        "Triangle_BB_IFC4.ifczip",
+    )
+
+
 def _boundary_element_counts(ifc_file, space_id):
     space = ifc_file.by_id(space_id)
     counts = Counter()
@@ -332,6 +352,10 @@ class TestAutoGenerateBoundaries(test.bootstrap.IFC4):
                 assert skylight[0].ParentBoundary == roof_boundaries[0]
 
     def test_over_splitted_roof_keeps_shaft_opening(self):
+        # Space 251 of OverSplitted_R20_IFC2X3.ifc has an L-shaped ceiling
+        # pierced by a shaft opening. The ceiling boundary must keep the
+        # opening as an inner boundary, and each shaft wall must get exactly
+        # one boundary instead of fragmented partial + gap boundaries.
         ifc_path = _over_splitted_ifc()
         if not os.path.exists(ifc_path):
             pytest.skip("IfcRelSpaceBoundary_TestFiles submodule is not checked out")
@@ -352,3 +376,28 @@ class TestAutoGenerateBoundaries(test.bootstrap.IFC4):
         assert shapely.Polygon(outer, inner).area == pytest.approx(9.962, abs=1e-3)
         for wall_id in (5832, 5877, 5922, 5967):
             assert len(_boundaries_for(result, copy.by_id(wall_id))) == 1
+
+    def test_small_house_boundaries(self):
+        ifc_path = _small_house_ifczip()
+        if not os.path.exists(ifc_path):
+            pytest.skip("IfcRelSpaceBoundary_TestFiles submodule is not checked out")
+        ifc_file = ifcopenshell.open(ifc_path)
+        shapes = _build_shapes_dict_from_iterator(ifc_file)
+        for space_id, expected_total in [(1692, 8), (4356, 8), (4380, 13), (6185, 1)]:
+            copy = ifcopenshell.file.from_string(ifc_file.wrapped_data.to_string())
+            result = subject.auto_generate_boundaries(
+                copy, copy.by_id(space_id), shapes=shapes, boundary_class="IfcRelSpaceBoundary2ndLevel"
+            )
+            assert len(result) == expected_total
+
+    def test_triangle_boundaries(self):
+        ifc_path = _triangle_ifczip()
+        if not os.path.exists(ifc_path):
+            pytest.skip("IfcRelSpaceBoundary_TestFiles submodule is not checked out")
+        ifc_file = ifcopenshell.open(ifc_path)
+        shapes = _build_shapes_dict_from_iterator(ifc_file)
+        copy = ifcopenshell.file.from_string(ifc_file.wrapped_data.to_string())
+        result = subject.auto_generate_boundaries(
+            copy, copy.by_id(1573), shapes=shapes, boundary_class="IfcRelSpaceBoundary2ndLevel"
+        )
+        assert len(result) == 6