Add tests and implement boundary smoothing and cutout functionality

- Introduced tests for boundary smoothing in `test_boundary_smoothing.py`, verifying that smoothing reduces stair-step artifacts while preserving boundary integrity.
- Added tests for cutout boundary behavior in `test_cutout_boundary.py`, ensuring proper handling of boundary triangles and normal blending.
- Created `test_temporary_attributes.py` to check the cleanup of temporary attributes across depth modifier branches, ensuring no warnings are raised.
- Implemented point culling functionality in `test_validity.py`, confirming that invalid points are removed without affecting adjacent geometry.
- Developed boundary smoothing logic in `boundary_smoothing.py`, allowing for depth smoothing while maintaining edge integrity.
- Added cutout boundary management in `cutout_boundary.py`, including functions for removing boundary triangles and tapering thickness profiles.
- Implemented validity checks in `validity.py` to ensure proper deletion of invalid vertices and associated wire edges.

tests/tools/nodes/test_image_plane.py

@@ -1,4 +1,5 @@
 import bpy
+import pytest
 
 from anyimage.common.object import (
     modifier_input_identifier,
@@ -17,6 +18,46 @@ def evaluated_mesh(obj):
     return evaluated, evaluated.to_mesh()
 
 
+@pytest.mark.parametrize("source_count", [0, 4, 9])
+def test_material_inheritance_removes_only_source_vertices(source_count):
+    from tools.nodes.common.material import inherit_material_slots
+    from tools.nodes.arrangement.arrange import arrange_nodes
+
+    bpy.ops.wm.read_factory_settings(use_empty=True)
+    mesh = bpy.data.meshes.new("Source")
+    mesh.from_pydata([(20 + i % 3, i // 3, 0) for i in range(source_count)], [],
+                     [(0, 1, 3, 2)] if source_count else [])
+    materials = [bpy.data.materials.new(name) for name in ("First", "Second")]
+    for material in materials:
+        mesh.materials.append(material)
+    obj = bpy.data.objects.new("Material Source", mesh)
+    bpy.context.collection.objects.link(obj)
+    group = bpy.data.node_groups.new("Material Inheritance", "GeometryNodeTree")
+    group.interface.new_socket(name="Geometry", in_out="INPUT", socket_type="NodeSocketGeometry")
+    group.interface.new_socket(name="Geometry", in_out="OUTPUT", socket_type="NodeSocketGeometry")
+    source = group.nodes.new("NodeGroupInput")
+    grid = group.nodes.new("GeometryNodeMeshGrid")
+    grid.inputs["Vertices X"].default_value = 3
+    grid.inputs["Vertices Y"].default_value = 2
+    geometry = inherit_material_slots(group, grid.outputs["Mesh"], source.outputs["Geometry"])
+    group.links.new(geometry, group.nodes.new("NodeGroupOutput").inputs["Geometry"])
+    obj.modifiers.new("Material Inheritance", "NODES").node_group = group
+    for arranged in (False, True):
+        if arranged:
+            arrange_nodes(group)
+        obj.update_tag(refresh={"DATA"})
+        ev, result = evaluated_mesh(obj)
+        try:
+            assert len(result.vertices) == 6 and len(result.polygons) == 2
+            assert all(abs(v.co.x) <= 0.5 for v in result.vertices)
+            if source_count:
+                assert [material.original for material in result.materials if material] == materials
+                assert result.materials[0].original == materials[0]
+            assert all(face.material_index == 0 for face in result.polygons)
+        finally:
+            ev.to_mesh_clear()
+
+
 def test_saved_image_plane_evaluation():
     bpy.ops.wm.read_factory_settings(use_empty=True)
     mesh = create_image_plane_mesh("Image Plane", (-1.0, 1.0, -0.5, 0.5))