OvPhysX Backend

OvPhysX Backend#

Warning

OvPhysX is highly experimental and is not recommended for general use yet. The public surface is changing rapidly while the backend is under active development. Expect feature coverage and test commands to change between Isaac Lab 3.0 beta releases.

Warning

Do not combine OvPhysX with the Kit visualizer. Commands such as physics=ovphysx --visualizer kit are unsupported because ovphysx loads USD-dependent PhysX plugins from its own package, while Kit already owns a separate USD/plugin stack in the same process. Use --visualizer newton, --visualizer rerun, --visualizer viser, or omit --visualizer for headless execution.

OvPhysX is a kit-less variant of the PhysX backend. It drives PhysX directly (without the Omniverse Kit runtime) and reads scene-level solver parameters from the USD PhysicsScene prim rather than from a Python config. The Python config OvPhysxCfg only exposes the handful of GPU buffer sizes that are not represented on the USD schema.

OvPhysX is selected through OvPhysxCfg:

from isaaclab.sim import SimulationCfg
from isaaclab_ov.physics import OvPhysxCfg

sim_cfg = SimulationCfg(physics=OvPhysxCfg())

Why use OvPhysX?#

  • Kit-less execution. OvPhysX avoids Omniverse Kit, which makes it a useful experimental path for headless deployments and for backends that don’t need the Kit runtime stack.

  • USD-as-source-of-truth. Solver parameters are taken from the PhysicsScene USD prim, so authoring tools that already manage USD scenes do not need a parallel Python config.

What works today#

The asset and sensor surface tracks PhysX, but only a subset is implemented and validated at the time of writing. The following pieces are available on develop:

  • RigidObject — merged via PR #5426.

  • Articulation — merged via PR #5459.

  • RigidObjectCollection — merged via PR #5570.

  • Contact Sensor — merged via PR #5422.

  • SceneDataProvider — merged via PR #5589.

  • FrameView — merged via PR #5678.

  • DeformableObject — experimental volume- and surface-deformable support on CUDA simulation devices.

Additional OvPhysX work remains in flight. IMU, Frame Transformer, Joint Wrench, PVA, Ray Caster, and rendering support are not documented as supported here until their implementations land on develop and pass the backend smoke tests.

Deformable limitations#

OvPhysX deformables currently require every body matched by one DeformableObject to have the same number of simulation nodes. Initialization raises an error for mixed node counts instead of exposing padded state that would produce incorrect reductions.

Deformable scenes also require full-stage materialization. Startup cost therefore grows with the number of authored environments. Use this path for small validation scenes; training-scale workloads with thousands of environments are not currently supported.

Installation#

The public ovphysx extra remains pinned to OvPhysX 0.5.11. Install it from the repository root with:

uv sync --inexact --extra ovphysx

The --inexact flag preserves packages installed through other extras. Use --extra ov to install both public OvPhysX and OVRTX runtimes. The legacy Isaac Lab installer also supports ./isaaclab.sh -i 'ov[ovphysx]' and ./isaaclab.sh -i 'ov[all]'.

Testing the Installation#

First check that the Python package and runtime wheel import correctly:

uv run --extra ovphysx --extra test python -c "import ovphysx.types; from isaaclab_ov.physics import OvPhysxCfg; print('OvPhysX runtime OK')"

./isaaclab.sh -p -c "import ovphysx.types; from isaaclab_ov.physics import OvPhysxCfg; print('OvPhysX runtime OK')"

Then run a small backend smoke test:

uv run --extra ovphysx --extra test python -m pytest source/isaaclab_ov/test/assets/test_rigid_object.py::test_initialization -k cpu

./isaaclab.sh -p -m pytest source/isaaclab_ov/test/assets/test_rigid_object.py::test_initialization -k cpu

To try a task that declares an OvPhysX physics preset, use the same preset CLI syntax as the other backends:

uv run --extra ovphysx isaaclab zero_agent --task Isaac-Cartpole-Direct \
    --num_envs 128 --max_steps 64 --viz none physics=ovphysx

./isaaclab.sh -p scripts/environments/zero_agent.py --task Isaac-Cartpole-Direct \
    --num_envs 128 --max_steps 64 --viz none physics=ovphysx

This command runs a 64-step headless zero-action rollout and then exits.

Supported locomotion environments#

The following locomotion training environments declare an ovphysx physics preset. Their corresponding -Play variants support the same backend where available.

  • Isaac-Ant-Direct

  • Isaac-Humanoid-Direct

  • IsaacContrib-Velocity-Rough-AnymalB

  • IsaacContrib-Velocity-Rough-AnymalC

  • Isaac-Velocity-Flat-AnymalD

  • Isaac-Velocity-Rough-AnymalD

  • IsaacContrib-Velocity-Rough-UnitreeA1

  • IsaacContrib-Velocity-Rough-UnitreeGo1

  • Isaac-Velocity-Rough-UnitreeGo2

  • Isaac-Velocity-Rough-Cassie

  • Isaac-Velocity-Rough-G1

  • Isaac-Velocity-Rough-H1

Status and follow-up#

OvPhysX is still experimental, so the feature list above is intentionally conservative. Broader feature coverage and documentation parity are tracked in issue #5634.

For architectural context, see Backend Architecture.

For raw TensorBinding access and OvPhysxView, see OvPhysX Tensor Bindings.