Fix clipped space top reaching sloped planes

The extrusion height was capped at the top/bottom plane anchor z (the mean
of the ray-cast hits, near the footprint centre), so a sloped ceiling's
high side stopped short of the plane (e.g. 5.5 m instead of 6.88 m for the
shed roof test). Extend the extrusion to the plane's z at every footprint
vertex before clipping, falling back to the base z as before. Also correct
the mirrored profile-to-world mapping comment in the shed roof test helper
(the ridge is at world y=-5, not y=+5).

Generated with the assistance of an AI coding tool.

src/bonsai/test/tool/test_spatial.py

@@ -511,9 +511,12 @@ class TestGenerateSpaceSlopedRoof(NewFile):
 
         Triangular prism: vertical profile (in the y-z plane) extruded along +x.
         Profile points (u, v) with placement loc=(-5, 0, z), axis=(1,0,0),
-        ref=(0,0,1):  (0,-5) -> world (-5,-5,z)      eave bottom
-                       (rise,-5) -> world (-5,-5,z+rise) eave top
-                       (rise,5)  -> world (-5,5,z+rise)  ridge
+        ref=(0,0,1). The local frame maps u to world +z (u=0 -> z, u=rise ->
+        z+rise) and v to world -y (v=-5 -> y=+5, v=+5 -> y=-5):
+                       (0,-5)    -> world (-5, +5, z)      eave (low) at north
+                       (rise,-5) -> world (-5, +5, z+rise) vertical edge
+                       (rise,5)  -> world (-5, -5, z+rise) ridge at south
+        The underside is the sloped face from (y=+5, z) to (y=-5, z+rise).
         ExtrudedDirection (0,0,1) is local, mapping to world +x; depth 10 spans
         x in [-5, 5].
         """

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

@@ -410,6 +410,13 @@ def detect_space_volume_strategy(
     return "EXTRUDE_CLIP", top_planes, bottom_planes
 
 
+def _footprint_coords(space_polygon: shapely.Polygon):
+    """Yield (x, y) boundary coordinates of a footprint polygon (exterior then holes)."""
+    for coords in [space_polygon.exterior.coords, *[ring.coords for ring in space_polygon.interiors]]:
+        for point in coords:
+            yield point[0], point[1]
+
+
 def build_extruded_clipped_space(
     ifc_file: ifcopenshell.file,
     space_polygon: shapely.Polygon,
@@ -447,8 +454,17 @@ def build_extruded_clipped_space(
     profile = builder.profile(outer_curve, inner_curves=inner_curves)
 
     all_z = [base_z]
-    for point, _ in top_planes + bottom_planes:
+    for point, normal in top_planes + bottom_planes:
         all_z.append(float(point[2]))
+        for x, y in _footprint_coords(space_polygon):
+            # A sloped plane's height varies across the footprint. The anchor
+            # point is near the centre, so also cover the plane at the polygon
+            # vertices, otherwise the high side of a sloped ceiling is capped
+            # below the plane it should reach.
+            if abs(normal[2]) < 1e-6:
+                continue
+            plane_z = (float(np.dot(normal, point)) - float(normal[0]) * x - float(normal[1]) * y) / float(normal[2])
+            all_z.append(plane_z)
     min_z = min(all_z)
     max_z = max(all_z)
     height = max_z - min_z

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

@@ -297,6 +297,19 @@ class TestBuildExtrudedClippedSpace(test.bootstrap.IFC4):
         assert item.FirstOperand.is_a("IfcBooleanClippingResult")
         assert item.FirstOperand.FirstOperand.is_a("IfcExtrudedAreaSolid")
 
+    def test_sloped_top_plane_reaches_footprint_max(self):
+        # A sloped ceiling's high side must reach the plane at the footprint
+        # edge (z=7.0 at y=-5), not be capped at the plane anchor z=5.5.
+        # 3D coords guard against the polygon carrying Z from the bisection.
+        space_polygon = shapely.Polygon([(-5, -5, 0), (5, -5, 0), (5, 5, 0), (-5, 5, 0)])
+        top_plane = (np.array([0.0, 0.0, 5.5]), np.array([0.0, 0.287, 0.958]))
+        bottom_plane = (np.array([0.0, 0.0, 0.0]), np.array([0.0, 0.0, -1.0]))
+        item = subject.build_extruded_clipped_space(self.file, space_polygon, 0.0, [top_plane], [bottom_plane])
+        shape = ifcopenshell.geom.create_shape(ifcopenshell.geom.settings(), item)
+        verts = ifcopenshell.util.shape.get_vertices(shape)
+        assert verts[:, 2].min() == pytest.approx(0.0, abs=0.1)
+        assert verts[:, 2].max() == pytest.approx(7.0, abs=0.1)
+
 
 class TestBuildBrepSpace(test.bootstrap.IFC4):
     def test_sloped_wall_brep_has_faces(self):