urdf2any

CI PyPI Python License

Convert URDF robot descriptions to USD (OpenUSD / Isaac Sim) and MJCF (MuJoCo) — in pure Python, with no Isaac Sim, Omniverse, or GPU required.

  • Self-contained — runs anywhere pip works (usd-core, trimesh, numpy)
  • One source of truth — a single simulator-agnostic intermediate representation drives both backends, so USD and MJCF describe the same physical robot
  • Verified — output is checked in CI against the real reference implementations: the IsaacLab URDF importer (golden comparison) and MuJoCo's native URDF loader (live comparison)

Installation

pip install urdf2any

Quick start

The output format is inferred from the file extension:

urdf2any robot.urdf -o robot.usd   # USD (UsdPhysics articulation)
urdf2any robot.urdf -o robot.xml   # MJCF (with actuators)

Or from Python:

from urdf2any import convert, ConvertConfig, JointDriveCfg

convert(
    "robot.urdf",
    "robot.usd",
    ConvertConfig(joint_drive=JointDriveCfg(stiffness=100.0, damping=1.0)),
)

By default every URDF link becomes one body and no lossy transformation is applied — the same config yields the same robot in both formats.

Compatibility presets

To reproduce the behavior of an existing converter, start from a preset; individual flags still override it:

urdf2any robot.urdf -o robot.usd --preset isaaclab   # IsaacLab URDF importer defaults
urdf2any robot.urdf -o robot.xml --preset mujoco     # MuJoCo native URDF conversion
Preset Matches Effect
isaaclab IsaacLab UrdfConverter defaults merges all fixed-joint links
mujoco MuJoCo's built-in URDF loader merges fixed-joint links and derives missing link masses from collision geometry (needs pip install "urdf2any[mjcf-validate]")

The same presets are available in Python as ConvertConfig.isaaclab() / ConvertConfig.mujoco(), and their definitions are what the parity test suites validate against the real implementations.

Feature support
Joints revolute, continuous, prismatic, fixed (optional merging with inertia composition)
Geometry box, sphere, cylinder, capsule, mesh (STL / OBJ / DAE via trimesh)
Inertials authored mass/inertia/COM; optional geometry-derived backfill via MuJoCo
Drives position / velocity PD gains → USD DriveAPI / MJCF actuators
Materials URDF colors → UsdPreviewSurface / MJCF materials
Skins skinned Collada (DAE) → MuJoCo <skin> assets, bone weights rebound to link frames (pip install "urdf2any[skin]")
Not yet mimic joints, sensors, UsdSkel skins, package:// ROS package resolution beyond a search root

Robot-specific preprocessing (renaming links, removing parts) is deliberately out of scope: parse with parse_urdf, mutate the IR, then emit with convert_robot.

Development

uv sync
uv run pytest        # includes the parity suites (CPU only)
uv run ruff check .

Releases are published to PyPI by pushing a vX.Y.Z tag (Trusted Publishing via .github/workflows/release.yml).

Parity testing

  • USD vs IsaacLab importer — tests/test_golden_parity.py diffs urdf2any's output against committed golden summaries (tests/golden/) generated by the real importer. Regenerate them inside an IsaacLab container with scripts/generate_reference.py (the import itself needs no GPU).
  • MJCF vs MuJoCo — tests/test_mjcf_parity.py compiles both urdf2any's MJCF and the source URDF with MuJoCo and compares the resulting models live; no golden files needed.

Sample robots under tests/assets/ are vendored from IsaacLab (BSD-3-Clause) and Isaac Sim (Apache-2.0); see the NOTICE file next to each.

License

Apache-2.0

Project links

Data verified by PyPI on Aug 11, 2026
Data provided by the project maintainers, verified at the time the release was uploaded to PyPI.

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1 maintainer

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Avatar for ksyundo from gravatar.com ksyundo

Credits

Author: Shundo Kishi

GitHub Statistics

Data verified by PyPI on Aug 11, 2026
The GitHub source repository was provided by the project maintainers and verified by PyPI at the time of upload. Stars, forks, and open issues/PRs are derived from that repository and have not been independently verified.

License expression

Apache-2.0
View SPDX License List

Requires

Python >=3.11

Provides Extra

mjcf-validate skin

Tags

mjcf mujoco openusd robotics simulation urdf usd

Classifiers

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