Fix normals for generic parametric stairs #4020

Also made concrete stair normals defined more explicitly.

src/blenderbim/blenderbim/tool/model.py

@@ -1109,6 +1109,9 @@ class Model(blenderbim.core.tool.Model):
             vertices.append(vertices[-1] * V(1, 0))
             edges.extend([(last_vert_i - 1, last_vert_i), (last_vert_i, 0)])
 
+            # flip edges direction for ccw polygon winding order
+            edges = [e[::-1] for e in edges]
+
         elif stair_type == "CONCRETE":
             define_generic_stair_treads()
 
@@ -1158,19 +1161,22 @@ class Model(blenderbim.core.tool.Model):
             if base_point.y > -base_slab_depth:
                 # stair doesn't meet the slab
                 vertices.append(base_point)
-                edges.append((0, len(vertices) - 1))
+                edges.append((len(vertices) - 1, 0))
                 bottom_nib_end = len(vertices) - 1
             else:
                 # slab overlaps stair
                 vertices.append(get_point_on_2d_line(y=start_vert.y - base_slab_depth))
                 vertices.append(start_vert + Vector((0, -base_slab_depth)))
                 last_vertex_i = len(vertices) - 1
-                edges.append((0, last_vertex_i))
+                edges.append((last_vertex_i, 0))
                 edges.append((last_vertex_i - 1, last_vertex_i))
                 bottom_nib_end = len(vertices) - 2
 
             # close the shape
-            edges.append((bottom_nib_end, top_nib_end))
+            edges.append((top_nib_end, bottom_nib_end))
+
+            # flip edges direction for ccw polygon winding order
+            edges = [e[::-1] for e in edges]
         else:
             raise Exception(f"Unsupported stair type: {stair_type}")
 

src/blenderbim/test/tool/test_model.py

@@ -199,10 +199,11 @@ class TestGenerateStair2DProfile(NewFile):
             (6, 7),
             (7, 8),
             (8, 9),
-            (0, 11),
+            (11, 0),
             (10, 11),
-            (10, 9),
+            (9, 10),
         )
+        edges_data = [e[::-1] for e in edges_data]
         faces_data = ()
         expected_profile = (verts_data, edges_data, faces_data)
         generated_profile = subject.generate_stair_2d_profile(**kwargs)
@@ -235,7 +236,6 @@ class TestGenerateStair2DProfile(NewFile):
             V(0.1, 0, -0.25),
             V(0.0, 0, -0.25),
         )
-
         edges_data = (
             (0, 1),
             (1, 2),
@@ -247,10 +247,11 @@ class TestGenerateStair2DProfile(NewFile):
             (7, 8),
             (8, 9),
             (9, 10),
-            (0, 12),
+            (12, 0),
             (11, 12),
-            (11, 10),
+            (10, 11),
         )
+        edges_data = [e[::-1] for e in edges_data]
 
         faces_data = ()
         expected_profile = (verts_data, edges_data, faces_data)
@@ -284,7 +285,6 @@ class TestGenerateStair2DProfile(NewFile):
             V(1.2, 0, 1.0),
             V(0.9, 0, 1.0),
         )
-
         edges_data = (
             (0, 1),
             (1, 2),
@@ -324,7 +324,6 @@ class TestGenerateStair2DProfile(NewFile):
             V(1.2, 0, 1.0),
             V(1.2, 0, 0.0),
         )
-
         edges_data = (
             (0, 1),
             (1, 2),
@@ -337,6 +336,7 @@ class TestGenerateStair2DProfile(NewFile):
             (8, 9),
             (9, 0),
         )
+        edges_data = [e[::-1] for e in edges_data]
 
         faces_data = ()
         expected_profile = (verts_data, edges_data, faces_data)