material group

import hou
from pxr import Usd, UsdGeom, Sdf, UsdShade

# Access the USD stage from the LOPS context
stage = hou.pwd().editableStage()

def gather_mesh_prims(prim):
    """Recursively gather all mesh prims under the given prim."""
    mesh_prims = []
    if prim.IsA(UsdGeom.Mesh):
        mesh_prims.append(prim)

    for child in prim.GetAllChildren():
        mesh_prims.extend(gather_mesh_prims(child))

    return mesh_prims

def get_bound_material(mesh_prim):
    """Get the material bound to the given mesh prim."""
    bindings = UsdShade.MaterialBindingAPI(mesh_prim)
    bound_material = bindings.ComputeBoundMaterial()[0]
    return bound_material

def group_mesh_prims_by_material(root_prim):
    """Return a dictionary of mesh prims grouped by their bound materials."""
    all_mesh_prims = gather_mesh_prims(root_prim)
    mesh_prims_by_material = {}

    for mesh_prim in all_mesh_prims:
        bound_material = get_bound_material(mesh_prim)
        material_path = bound_material.GetPath() if bound_material else Sdf.Path.emptyPath
        if material_path not in mesh_prims_by_material:
            mesh_prims_by_material[material_path] = []
        mesh_prims_by_material[material_path].append(mesh_prim)

    return mesh_prims_by_material

# Test with a root prim
root_prim_path = "/geo"
root_prim = stage.GetPrimAtPath(root_prim_path)

# Get the mesh prims grouped by their bound materials
mesh_prims_by_material = group_mesh_prims_by_material(root_prim)

# Print the results
for material_path, mesh_prims in mesh_prims_by_material.items():
    material_path_str = str(material_path) if material_path != Sdf.Path.emptyPath else "No Material"
    print(f"Material: {material_path_str}")
    for mesh_prim in mesh_prims:
        print(f"  Mesh Prim: {mesh_prim.GetPath()}")