[Feature] OpenUSD Meshes

genesis/engine/mesh.py

@@ -11,6 +11,7 @@
 import genesis as gs
 import genesis.utils.mesh as mu
 import genesis.utils.particle as pu
+import genesis.utils.usd as uu
 from genesis.ext import fast_simplification
 from genesis.repr_base import RBC
 
@@ -333,6 +334,9 @@ def from_morph_surface(cls, morph, surface=None):
                 else:
                     meshes = mu.parse_mesh_glb(morph.file, morph.group_by_material, morph.scale, surface)
 
+            elif morph.file.endswith(("usd", "usda", "usdc", "usdz")):
+                meshes = uu.parse_mesh_usd(morph.file, morph.group_by_material, morph.scale, surface)
+
             elif hasattr(morph, "files") and len(morph.files) > 0:  # for meshset
                 meshes = morph.files
                 assert all([isinstance(v, trimesh.Trimesh) for v in meshes])

genesis/utils/usd.py

@@ -0,0 +1,312 @@
+import os
+import numpy as np
+import re
+from PIL import Image
+from pxr import Usd, UsdGeom, UsdShade, Gf, Sdf
+
+import genesis as gs
+import genesis.utils.mesh as mu
+
+def parse_mesh_usd(path, group_by_material, scale, surface):
+    """
+    Parse mesh from USD file.
+    This function only supports reading geometries from the default prim of the USD stage.
+    Especially, for NVIDIA's SimReady USD dataset: https://developer.nvidia.com/omniverse/simready-assets
+    Refer to the book for more details: https://www.manning.com/books/universal-scene-description-in-action
+
+    Parameters
+    ----------
+    path : str
+        usd file path.
+    group_by_material : bool
+        Whether to group meshes by material. #TODO: not implemented yet.
+    scale : float
+        Scale factor for the mesh.
+    surface : Surface
+        Surface object to be used for the mesh.
+    """
+
+    def get_world_transform(prim):
+        """Get the world transform of a given prim in the USD stage."""
+        xform = UsdGeom.Xformable(prim)
+        time_code = Usd.TimeCode.Default()
+        world_transform = xform.ComputeLocalToWorldTransform(time_code)
+        return world_transform
+
+    def extract_texture_paths_from_mdl(mdl_file_path):
+        """
+        Extract diffuse and normal map texture paths and diffuse tint (as color_factor)
+        from an MDL file using regex. Since the NVIDIA MDL SDK doesn't have a Python API,
+        we parse the file to extract these values.
+        """
+        with open(mdl_file_path, "r", encoding="utf-8") as f:
+            mdl_content = f.read()
+
+        # Regex patterns to match diffuse and normal map textures
+        diffuse_pattern = re.search(r'diffuse_texture:\s*texture_2d\("([^"]+)"', mdl_content)
+        normal_pattern = re.search(r'normalmap_texture:\s*texture_2d\("([^"]+)"', mdl_content)
+        orm_pattern = re.search(r'ORM_texture:\s*texture_2d\("([^"]+)"', mdl_content)
+
+        # Regex pattern to match diffuse_tint color values
+        # This expects a pattern like: diffuse_tint: color(0.47876447, 0.47875968, 0.47875968)
+        diffuse_tint_pattern = re.search(r"diffuse_tint:\s*color\(([^)]+)\)", mdl_content)
+
+        diffuse_texture = diffuse_pattern.group(1) if diffuse_pattern else None
+        normal_texture = normal_pattern.group(1) if normal_pattern else None
+        orm_texture = orm_pattern.group(1) if orm_pattern else None
+
+        if diffuse_tint_pattern:
+            # Extract the comma-separated color values from inside the parentheses
+            tint_values_str = diffuse_tint_pattern.group(1)
+            # Convert each value to a float and form a tuple
+            diffuse_tint = tuple(float(x.strip()) for x in tint_values_str.split(","))
+        else:
+            diffuse_tint = None
+
+        return diffuse_texture, normal_texture, diffuse_tint, orm_texture
+
+    """parse mesh from USD file"""
+    meshes = list()
+    stage = Usd.Stage.Open(path)
+    default_prim_path = stage.GetDefaultPrim().GetPath().pathString
+    for prim in stage.Traverse():
+        # only load mesh under the default prim
+        if UsdGeom.Mesh(prim) and (default_prim_path in prim.GetPath().pathString):
+            # check surface
+            mesh_surface = gs.surfaces.Default() if surface is None else surface.copy()
+
+            # load mesh basic information
+            mesh = UsdGeom.Mesh(prim)
+            points = mesh.GetPointsAttr().Get()
+            normals = mesh.GetNormalsAttr().Get()
+            face_vertex_counts = mesh.GetFaceVertexCountsAttr().Get()
+            face_vertex_indices = mesh.GetFaceVertexIndicesAttr().Get()
+            sts = mesh.GetPrim().GetAttribute("primvars:st").Get()
+            st_indices = mesh.GetPrim().GetAttribute("primvars:st:indices").Get()
+
+            # calculate transform
+            transform = np.array(get_world_transform(mesh.GetPrim()))
+            points_homogeneous = np.hstack([points, np.ones((len(points), 1))])
+
+            verts = (points_homogeneous @ transform)[:, :3]
+            normals = np.array(normals, dtype=float)
+            indices = np.array(face_vertex_indices, dtype=int)
+
+            faces = []
+            index_offset = 0
+            face_count = {}
+
+            for count in face_vertex_counts:
+                face_count[count] = face_count.get(count, 0) + 1
+                face = indices[index_offset : index_offset + count].tolist()
+
+                # If the face is a triangle, keep it as is
+                if count == 3:
+                    faces.append(face)
+                # If the face is a quad or more, triangulate it
+                elif count > 3:
+                    for i in range(1, count - 1):
+                        faces.append([face[0], face[i], face[i + 1]])  # Fan triangulation
+
+                index_offset += count  # Move to the next set of indices
+
+            # if face count is not 3, means it is not all triangle faces
+            if len(face_count) >= 2 or (3 not in face_count):
+                gs.logger.warning(f"Mesh {mesh} has non-triangle faces. Face count {face_count}")
+
+            faces = np.array(faces, dtype=int)
+
+            # load uvs
+            if sts is not None:
+                uvs = []
+                gs.logger.info("Parsing OpenUSD Face st into Vertex uv")
+                # Create a mapping of face vertex indices to their UV
+                if st_indices:
+                    assert len(face_vertex_indices) == len(
+                        st_indices
+                    ), "face vertice count should be the same as st indices"
+                    index_to_uv = {fv_idx: sts[st_indices[idx]] for idx, fv_idx in enumerate(face_vertex_indices)}
+                else:
+                    assert len(sts) == len(face_vertex_indices), "face vertice count should be the same as st"
+                    index_to_uv = {fv_idx: sts[idx] for idx, fv_idx in enumerate(face_vertex_indices)}
+
+                # Collect the UVs using the mapping
+                uvs = [index_to_uv[i] for i in range(len(points)) if i in index_to_uv]
+                uvs = np.array(uvs)
+                uvs[:, 1] = 1.0 - uvs[:, 1]  # flip y axis for trimesh
+            else:
+                uvs = None
+
+            # load material
+            material_binding = UsdShade.MaterialBindingAPI(mesh.GetPrim())
+            material, relation = material_binding.ComputeBoundMaterial()
+
+            # if has material
+            if material.GetPrim().IsValid():
+                # normal usd shader
+                shader, _, _ = material.ComputeSurfaceSource()
+                # compatible with NVIDIA mdl: https://github.com/NVIDIA/MDL-SDK
+                if not shader:
+                    shader, _, _ = material.ComputeSurfaceSource("mdl")
+
+                if shader:
+                    diffuse_texture_attr = shader.GetPrim().GetAttribute("inputs:diffuse_texture").Get()
+
+                    # handle the diffuse map texture from USD attribute
+                    if diffuse_texture_attr:
+                        diffuse_texture_path = diffuse_texture_attr.resolvedPath
+                        diffuse_image = mu.PIL_to_array(Image.open(diffuse_texture_path).convert("RGB"))
+
+                        # get diffuse tint color
+                        diffuse_tint = shader.GetPrim().GetAttribute("inputs:diffuse_tint").Get()
+                        if diffuse_tint:
+                            diffuse_tint = np.array(list(diffuse_tint) + [1.0], dtype=float)
+                        else:
+                            diffuse_tint = np.ones(4, dtype=float)
+
+                        color_texture = None
+                        opacity_texture = None
+                        roughness_texture = None
+                        metallic_texture = None
+                        normal_texture_path = None
+
+                        # handle the diffuse map texture from USD attribute
+                        if diffuse_image.ndim == 2:
+                            diffuse_image = diffuse_image[:, :, np.newaxis]
+                        elif diffuse_image.shape[2] == 4:
+                            # get opacity texture from alpha channel
+                            opacity_texture = mu.create_texture(diffuse_image[:, :, 3], None, "linear")
+
+                            # remove alpha channel
+                            diffuse_image = diffuse_image[:, :, :3]
+
+                        color_texture = mu.create_texture(diffuse_image, diffuse_tint, "srgb")
+                        gs.logger.info(f"Loading Diffuse texture: {diffuse_texture_path}")
+
+                        # handle the normal map texture from USD attribute
+                        normal_texture_attr = shader.GetPrim().GetAttribute("inputs:normal_texture").Get()
+                        if normal_texture_attr:
+                            normal_texture_path = normal_texture_attr.resolvedPath
+                            normal_image = mu.PIL_to_array(Image.open(normal_texture_path))
+                            normal_texture_path = mu.create_texture(normal_image, None, "linear")
+                            gs.logger.info(f"Loading Normal texture: {normal_texture_path}")
+
+                        # handle ORM texture from USD attribute
+                        orm_texture_attr = shader.GetPrim().GetAttribute("inputs:ORM_texture").Get()
+                        if orm_texture_attr:
+                            orm_texture_path = orm_texture_attr.resolvedPath
+                            orm_image = mu.PIL_to_array(Image.open(orm_texture_path))
+                            # Split ORM image into separate textures
+                            opacity_texture = mu.create_texture(orm_image[:, :, 0], None, "linear")
+                            roughness_texture = mu.create_texture(orm_image[:, :, 1], None, "linear")
+                            metallic_texture = mu.create_texture(orm_image[:, :, 2], None, "linear")
+                            gs.logger.info(f"Loading ORM texture: {orm_texture_path}")
+                        else:
+                            # no ORM texture， handle roughness and metallic texture from USD attribute
+                            opacity_texture_attr = shader.GetPrim().GetAttribute("inputs:opacity_texture").Get()
+                            if opacity_texture_attr:
+                                opacity_texture_path = opacity_texture_attr.resolvedPath
+                                opacity_image = mu.PIL_to_array(Image.open(opacity_texture_path))
+                                opacity_texture = mu.create_texture(opacity_image, None, "linear")
+                                gs.logger.info(f"Loading Opacity texture: {opacity_texture_path}")
+
+                            roughness_texture_attr = (
+                                shader.GetPrim().GetAttribute("inputs:reflectionroughness_texture").Get()
+                            )
+                            if roughness_texture_attr:
+                                roughness_texture_path = roughness_texture_attr.resolvedPath
+                                roughness_image = mu.PIL_to_array(Image.open(roughness_texture_path))
+                                roughness_texture = mu.create_texture(roughness_image, None, "linear")
+                                gs.logger.info(f"Loading Roughness texture: {roughness_texture_path}")
+
+                            metallic_texture_attr = shader.GetPrim().GetAttribute("inputs:metallic_texture").Get()
+                            if metallic_texture_attr:
+                                metallic_texture_path = metallic_texture_attr.resolvedPath
+                                metallic_image = mu.PIL_to_array(Image.open(metallic_texture_path))
+                                metallic_texture = mu.create_texture(metallic_image, None, "linear")
+                                gs.logger.info(f"Loading Metallic texture: {metallic_texture_path}")
+
+                        # update surface texture
+                        mesh_surface.update_texture(
+                            color_texture=color_texture,
+                            normal_texture=normal_texture_path,
+                            opacity_texture=opacity_texture,
+                            roughness_texture=roughness_texture,
+                            metallic_texture=metallic_texture,
+                        )
+
+                    else:  # load from .mdl description
+                        source = shader.GetImplementationSource()
+                        # handle the mdl shader source from asset
+                        if source == UsdShade.Tokens.sourceAsset:
+                            mdl_asset_attr = shader.GetPrim().GetAttribute("info:mdl:sourceAsset")
+                            mdl_sub_identifier_attr = shader.GetPrim().GetAttribute(
+                                "info:mdl:sourceAsset:subIdentifier"
+                            )
+
+                            if mdl_asset_attr and mdl_sub_identifier_attr:
+                                mdl_asset_path = mdl_asset_attr.Get().resolvedPath  # absolute path
+                                mdl_material_name = mdl_sub_identifier_attr.Get()
+                                diffuse_texture_path, normal_texture_path, diffuse_tint, orm_texture_path = (
+                                    extract_texture_paths_from_mdl(mdl_asset_path)
+                                )
+
+                                if diffuse_tint:
+                                    diffuse_tint = np.array(list(diffuse_tint) + [1.0], dtype=float)  # RGB + A
+                                else:
+                                    diffuse_tint = np.ones(4, dtype=float)
+
+                                color_texture = None
+                                normal_texture = None
+                                opacity_texture = None
+                                roughness_texture = None
+                                metallic_texture = None
+
+                                if diffuse_texture_path:
+                                    diffuse_texture_path = os.path.normpath(
+                                        os.path.join(os.path.dirname(mdl_asset_path), diffuse_texture_path)
+                                    )
+                                    diffuse_image = mu.PIL_to_array(Image.open(diffuse_texture_path))
+                                    color_texture = mu.create_texture(diffuse_image, diffuse_tint, "srgb")
+                                    gs.logger.info(f"Get Diffuse texture: {diffuse_texture_path}")
+
+                                if normal_texture_path:
+                                    normal_texture_path = os.path.normpath(
+                                        os.path.join(os.path.dirname(mdl_asset_path), normal_texture_path)
+                                    )
+                                    normal_image = mu.PIL_to_array(Image.open(normal_texture_path))
+                                    normal_texture = mu.create_texture(normal_image, None, "linear")
+                                    gs.logger.info(f"Get Normal texture: {normal_texture_path}")
+
+                                if orm_texture_path:
+                                    orm_texture_path = os.path.normpath(
+                                        os.path.join(os.path.dirname(mdl_asset_path), orm_texture_path)
+                                    )
+                                    orm_image = mu.PIL_to_array(Image.open(orm_texture_path))
+                                    # Split ORM image into separate textures
+                                    opacity_texture = mu.create_texture(orm_image[:, :, 0], None, "linear")
+                                    roughness_texture = mu.create_texture(orm_image[:, :, 1], None, "linear")
+                                    metallic_texture = mu.create_texture(orm_image[:, :, 2], None, "linear")
+                                    gs.logger.info(f"Get ORM texture: {orm_texture_path}")
+
+                                mesh_surface.update_texture(
+                                    color_texture=color_texture,
+                                    normal_texture=normal_texture,
+                                    opacity_texture=opacity_texture,
+                                    roughness_texture=roughness_texture,
+                                    metallic_texture=metallic_texture,
+                                )
+
+            meshes.append(
+                gs.Mesh.from_attrs(
+                    verts=verts,
+                    faces=faces,
+                    normals=normals,
+                    surface=mesh_surface,
+                    uvs=uvs,
+                    scale=scale,
+                )
+            )
+
+    del stage
+    return meshes

pyproject.toml

@@ -48,6 +48,8 @@ dependencies = [
     "coacd",
     # Used for loading raytracing special texture images used by LuisaRender
     "OpenEXR",
+    # OpenUSD support
+    "usd-core",
 ]
 
 [tool.setuptools.packages.find]