Implement BiRefNet and HAT Sharper models with background removal capabilities

- Added validation documentation for AI model tiers.
- Introduced `background.py` for background removal logic, including inference functions for alpha and foreground extraction.
- Created `onnx_birefnet.py` to handle BiRefNet model sessions and alpha inference.
- Developed tests for background models, ensuring proper dispatch and session reuse.
- Added tests for BiRefNet ONNX model to validate alpha output and error handling for invalid values.
- Implemented model export scripts for BiRefNet and HAT Sharper, ensuring proper weight compression and licensing.
- Created `deform_sampling.py` for deformable convolution operations used in BiRefNet.
- Added utility functions for compressing ONNX weights without altering graph arithmetic.
- Introduced a reference plane node for depth field adjustments in geometry processing.

tools/nodes/groups/image_relief_plane.py

@@ -3,7 +3,9 @@
 import bpy
 
 from ..common.nodes import group_input as _group_input, interface_socket as _interface_socket
-from ..common.nodes import prepare_node_group
+from ..common.nodes import prepare_node_group, float_input, vector_input
+from ..common.reference_plane import reference_plane_depth
+from ..common.smoothing import expand_smooth
 
 
 RELIEF_PLANE_NODE_GROUP_NAME = "O Image Relief Plane"
@@ -38,6 +40,8 @@ def build_image_relief_plane_group(image_plane_group):
     depth_scale = _interface_socket(group, "Depth Scale", "INPUT", "NodeSocketFloat")
     depth_scale.default_value = 0.5
     depth_scale.min_value = 0.0
+    smooth = _interface_socket(group, "Smooth", "INPUT", "NodeSocketInt")
+    smooth.default_value, smooth.min_value, smooth.max_value = 0, 0, 20
     options = group.interface.new_panel(name="Options", default_closed=True)
     base_plane_depth = _interface_socket(
         group,
@@ -49,6 +53,8 @@ def build_image_relief_plane_group(image_plane_group):
     base_plane_depth.default_value = 1.0
     base_plane_depth.min_value = 0.0
     base_plane_depth.subtype = "DISTANCE"
+    float_input(group, "Smooth Weight", 1.0, maximum=1, subtype="FACTOR", parent=options)
+    vector_input(group, "Depth Direction", (0, 0, 1), subtype="DIRECTION", parent=options)
     data = group.interface.new_panel(name="Data", default_closed=True)
     uniform_scale = _interface_socket(
         group,
@@ -78,7 +84,7 @@ def build_image_relief_plane_group(image_plane_group):
     )
     shape_input = _group_input(
         nodes,
-        {"Thickness", "Depth Scale", "Reference Depth"},
+        {"Thickness", "Depth Scale"},
     )
     image_input = _group_input(
         nodes,
@@ -114,7 +120,11 @@ def build_image_relief_plane_group(image_plane_group):
     links.new(depth_components.outputs["Z"], metric_depth.inputs[0])
     links.new(image_input.outputs["Uniform Scale"], metric_depth.inputs[1])
     relative_depth = _math(nodes, "SUBTRACT")
-    links.new(shape_input.outputs["Reference Depth"], relative_depth.inputs[0])
+    reference_input = _group_input(nodes, {"Depth Direction", "Reference Depth"})
+    plane_depth = reference_plane_depth(
+        group, reference_input.outputs["Depth Direction"], reference_input.outputs["Reference Depth"],
+    )
+    links.new(plane_depth, relative_depth.inputs[0])
     links.new(metric_depth.outputs[0], relative_depth.inputs[1])
     full_offset = _math(nodes, "MULTIPLY")
     links.new(relative_depth.outputs[0], full_offset.inputs[0])
@@ -167,7 +177,10 @@ def build_image_relief_plane_group(image_plane_group):
     shade_smooth = nodes.new("GeometryNodeSetShadeSmooth")
     shade_smooth.domain = "FACE"
     shade_smooth.inputs["Shade Smooth"].default_value = True
-    links.new(set_position.outputs["Geometry"], shade_smooth.inputs["Geometry"])
+    geometry = expand_smooth(
+        group, set_position.outputs["Geometry"], iterations_name="Smooth", weight_name="Smooth Weight",
+    )
+    links.new(geometry, shade_smooth.inputs["Geometry"])
     links.new(shade_smooth.outputs["Geometry"], group_output.inputs["Geometry"])
     group.color_tag = "GEOMETRY"
     group.description = (