---

name: scene-simulation-assets description: "Compose mjlab scenes, entities, variants, simulation configs, asset-zoo robots, and exportable MuJoCo packages." disable-model-invocation: true metadata: disco-role: operating license: Apache 2.0

Scene, Simulation, and Assets

Use this sub-skill when the task is about mjlab scene assembly or the MuJoCo asset layer: EntityCfg, VariantEntityCfg, SceneCfg, TerrainEntityCfg, entity-level actuator attachment, SimulationCfg / MujocoCfg, asset-zoo robots, scene export, or direct mujoco.MjSpec / MuJoCo Warp model-data access.

Start Here

• For the scene/entity/simulation object model, lifecycle order, namespacing, data access, and graph constraints, read scene-entity-simulation.md.
• For asset-zoo robot factories, export targets, Scene.write(...), and heterogeneous mesh variants, read assets-export-variants.md.
• For texture, material, mesh, geom, collision, light, camera, and cross-entity spec editing, read spec-editors.md.
• For common MJCF, keyframe, mocap, namespacing, variant, export, and CUDA graph failures, read troubleshooting.md.
• For a safe scene-export smoke check, use scripts/export_scene_smoke.py.

Core Runtime Contract

When manually constructing the runtime, follow the same order used by mjlab's manager-based environment:

from mjlab.scene import Scene
from mjlab.sim import Simulation, SimulationCfg

scene = Scene(scene_cfg, device="cpu")
sim = Simulation(
    scene.num_envs,
    SimulationCfg(),
    spec=scene.spec,
    variant_info=scene.collect_variant_info(),
    device="cpu",
)
scene.initialize(sim.mj_model, sim.model, sim.data)
if scene.sensor_context is not None:
    sim.set_sensor_context(scene.sensor_context)

Use scene.write(output_dir, zip=False) or scene.write(output_dir, zip=True) for exportable packages. For direct runtime reads, prefer entity.data and use sim.model / sim.data only when a task needs global MuJoCo IDs or fields.

Boundary Routing

• Route action-term selection, policy-output scaling, reward/action wiring, and detailed actuator type tradeoffs to ../mdp-components/. This sub-skill only covers how actuator configs attach to an entity spec.
• Route camera/raycast/contact sensor configuration, terrain generation presets, flat-patch sampling, and domain-randomization recipes to ../perception-terrain-randomization/. This sub-skill covers only how those objects connect to SceneCfg and Simulation.
• Route installed export-scene CLI usage, task-registry command workflows, training, playback, and debug CLI flags to ../training-evaluation-cli/. This sub-skill is the API-internals reference for what that export command builds.