Newton¶

The Newton backend: NVIDIA Warp and MuJoCo-Warp GPU physics on the same MJCF assets, with ray-traced tiled cameras.

By the end of this page you know what the newton backend is, which solver names it accepts, and what it needs from your machine.

pip install 'strands-robots[sim-newton]'   # newton 1.5, warp-lang, mujoco 3.11, mujoco-warp, trimesh, plus [sim-mujoco]

What it is¶

NewtonSimEngine (strands_robots/simulation/newton/simulation.py) implements SimEngine on newton-physics/newton, NVIDIA Warp plus MuJoCo-Warp. It ingests the MuJoCo backend's MJCF assets, builds a GPU model, and steps it with one of Newton's rigid-body solvers. Rendering is headless through Newton's ray-traced SensorTiledCamera. Policy orchestration (run_policy, eval_policy, replay_episode, recording in newton/recording.py) is inherited from the base class.

from strands_robots.simulation import create_simulation

sim = create_simulation("newton", solver="mujoco")
sim.create_world()
sim.add_robot("so100")
sim.send_action({"Rotation": 0.5}, robot_name="so100")
out = sim.render(width=320, height=240)
print(out["status"])
print(sim.run_policy(robot_name="so100", policy_provider="mock", n_steps=200)["status"])
sim.destroy()

slow motion: so100 on Newton's mujoco solver runs the mock policy for 200 steps

Constructor keywords¶

keyword	default	meaning
`solver`	`"mujoco"`	Newton solver by friendly name; see below
`default_timestep`	backend default	physics step in seconds
`substeps`	`10`	solver substeps per physics step
`device`	`None`	Warp device, auto-selected when `None`
`default_width`, `default_height`	`640`, `480`	camera resolution when a call gives none

Solvers¶

strands_robots.simulation.newton.backend.solver_registry() maps friendly names to Newton classes: mujoco, featherstone, xpbd, semi_implicit, vbd, style3d, mpm, kamino. articulated_solvers() returns the subset that can drive a robot: mujoco, featherstone and kamino. The rest are refused with the reason: xpbd and semi_implicit never integrate rigid bodies (the world freezes), vbd needs per-body colouring the build does not apply, style3d is a cloth solver, mpm needs a config object this backend does not build.

Same API, same rules¶

add_camera(parent_body=...) works here as on MuJoCo; a policy declaring requires_action_controller (the WBC torque shim) is refused rather than rolled out without it. On Newton a mesh size scales the mesh per axis (default [1, 1, 1]); MuJoCo and Isaac ignore it and still report success (#2300). set_obs_noise mirrors the MuJoCo signature and behaves the same. Terrain, task objects and the predicate DSL read the same observation surface. The wbc torque shim is MuJoCo-only, so a WBC rollout on Newton refuses unless wbc_install_torque_control=False against a torque-actuated scene.

Limits¶

NVIDIA GPU and CUDA-capable Warp. No CPU device runs the articulated solvers at useful speed.
Pinned to mujoco>=3.11,<3.12 and mujoco-warp of the same series, while [sim-mujoco] allows any 3.5+. Install [sim-newton] in its own environment if you want the newest MuJoCo.
Rendering is ray-traced and tiled: per-frame cost above MuJoCo's rasteriser, per-batch cost below.

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