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lightusd

Lightweight, dependency-free USD (Universal Scene Description) library for Python: load and author USDA / USDC / USDZ, resolve composition, and extract GPU-ready render data — with zero-copy NumPy interop.

Built on the LightUSD next core + tydra-next (no pxrUSD install required, no legacy core in the wheel; native cmake -S . and WASM still provide the legacy path via web/binding.cc). v1.0.0, npm preview dist-tag. Wheels:

  • cp310-abi3 — one stable-ABI wheel covers CPython 3.10+
  • cp314t — native free-threaded (GIL-less) CPython 3.14 wheel
pip install lightusd

Reading

import numpy as np
import lightusd

stage = lightusd.load("scene.usdz")          # usda / usdc / usdz, composed
for prim in stage:                            # depth-first traversal
    print(prim.path, prim.type_name)

mesh = stage.prim_at("/World/Mesh")
points = np.asarray(mesh["points"])           # zero-copy (N, 3) float32
attr = mesh.attribute("xformOp:translate")
if attr.has_timesamples:
    value = attr.get(time=12.0)               # linear interpolation
print(mesh.relationship("material:binding").targets)

Authoring

st = lightusd.Stage.create()
st.up_axis = "Y"
grid = st.define_prim("/World/Grid", "Mesh")
grid.set("points", np.zeros((64, 3), np.float32), type="point3f[]")
grid.set("purpose", "render", uniform=True)
grid.set("xformOp:translate", (0.0, 1.0, 0.0), time=0.0)
st.set_default_prim("World")
st.save("out.usdc")                           # or .usda / .usdz

Render extraction (tydra)

from lightusd import tydra

scene = tydra.to_render_scene(stage)          # triangulated, GPU-friendly
for mesh in scene.meshes:
    vertices = np.asarray(mesh.points)                # (N, 3) float32
    indices = np.asarray(mesh.triangulated_indices)   # (T,) uint32
    material = scene.materials[mesh.material_id]
    base_color = material.param("diffuse_color")      # tuple or RenderTexture

Notes

  • NumPy is optional (interop only, not a dependency).
  • lightusd.flatten_file(src, dst) runs a low-memory compose+flatten pipeline that streams large arrays through without decoding them.
  • Free-threaded CPython: concurrent reads of one Stage are safe; do not author to a stage while other threads read it.

Apache 2.0. Part of LightUSD.