feat: Implement depth cutout symmetry and associated functionalities

- Introduced a new proposal for depth cutout symmetry, allowing for the reuse of depth replacement and geometry operations.
- Added requirements for maintaining default thickness values for cutout nodes and ensuring proper initialization during object creation.
- Enhanced symmetry node to handle existing geometry, including alignment, mirroring, and boundary filling.
- Implemented fill smoothing to control the geometry of generated walls while preserving original surfaces.
- Created tests to validate the functionality of the new symmetry features against baseline geometry.
- Updated existing assets and node groups to support the new symmetry capabilities without introducing additional dependencies.

tools/nodes/groups/image_depth_cutout.py

@@ -15,15 +15,13 @@ NODE_GROUP_NAME = "O Image Depth Cutout"
 
 
 def build_normal_weight(group, is_shell):
-    """Scale normal smoothing by the active mode's relative thickness."""
-    control = group_input(group.nodes, {"Thickness", "Shell Thickness", "Reference Depth"})
+    """Use full shell smoothing and thickness-weighted balloon smoothing."""
+    control = group_input(group.nodes, {"Thickness"})
     amount = group.nodes.new("GeometryNodeSwitch")
     amount.input_type = "FLOAT"
     group.links.new(is_shell, amount.inputs["Switch"])
     group.links.new(control.outputs["Thickness"], amount.inputs["False"])
-    ratio = _math(group, "DIVIDE", control.outputs["Shell Thickness"],
-                  _math(group, "MAXIMUM", control.outputs["Reference Depth"], 1e-8))
-    group.links.new(ratio, amount.inputs["True"])
+    amount.inputs["True"].default_value = 1
     ramp = group.nodes.new("ShaderNodeMapRange")
     ramp.interpolation_type = "SMOOTHSTEP"
     ramp.clamp = True
@@ -343,8 +341,8 @@ def build_image_depth_cutout_group():
     group.color_tag = 'GEOMETRY'
     interface_socket(group, 'Geometry', 'INPUT', 'NodeSocketGeometry')
     interface_socket(group, 'Mode', 'INPUT', 'NodeSocketMenu')
-    float_input(group, 'Thickness', 1.0).description = 'Control how much the surface bulges in Balloon mode. Zero removes the bulge.'
-    float_input(group, 'Shell Thickness', 0.5, subtype='DISTANCE').description = 'Add thickness behind the original surface while keeping the front surface in place.'
+    float_input(group, 'Thickness', 0.0).description = 'Control how much the surface bulges in Balloon mode. Zero removes the bulge.'
+    float_input(group, 'Shell Thickness', 0.0, subtype='DISTANCE').description = 'Add thickness behind the original surface while keeping the front surface in place.'
     float_input(group, 'Depth Scale', 1.0)
     float_input(group, 'Depth Split', 0.1, maximum=1, subtype='FACTOR').description = 'Split the mesh where depth changes abruptly. Higher values detect smaller depth jumps. Zero disables splitting.'
     iterations = interface_socket(group, 'Smooth', 'INPUT', 'NodeSocketInt')