Prop-Robotics-Physx Profile USD Authoring Guide#

This document describes how to author a USD asset that conforms to the Prop-Robotics-Physx profile. It consolidates the required feature set, USD properties, naming conventions, and composition expectations.

Profile definition#

The Prop-Robotics-Physx profile includes the following feature sets (see profiles.toml and the feature dependency graph). Each feature’s requirements and dependencies are defined in the feature specifications.

[Prop-Robotics-Physx]
"1.0.0" = {features = [
    {"FET000_CORE" = {version = "0.1.0"}}, # Core
    {"FET001_BASE_NEUTRAL" = {version = "0.1.0"}}, # Minimal
    {"FET003_BASE_PHYSX" = {version = "0.1.0"}}, # RBD Physics (PhysX)
    {"FET004_BASE_PHYSX" = {version = "0.1.0"}}, # Multi-Body Physics (PhysX)
    {"FET005_BASE_NEUTRAL" = {version = "0.1.0"}}, # Grasp Physics
    {"FET006_BASE_MDL" = {version = "0.1.0"}}, # Materials (MDL)
]}
"2.0.0" = {features = [
    {"FET000_CORE" = {version = "0.1.0"}}, # Core
    {"FET001_BASE_NEUTRAL" = {version = "1.0.0"}}, # Minimal
    {"FET003_BASE_PHYSX" = {version = "0.1.0"}}, # RBD Physics (PhysX)
    {"FET004_BASE_PHYSX" = {version = "0.1.0"}}, # Multi-Body Physics (PhysX)
    {"FET005_BASE_NEUTRAL" = {version = "0.1.0"}}, # Grasp Physics
    {"FET006_BASE_MDL" = {version = "0.1.0"}}, # Materials (MDL)
]}

Required USD properties and schemas#

Stage metadata (required)#

  • defaultPrim must be set on every layer.

  • upAxis = "Z" and metersPerUnit = 1 must be set on every stage.

PhysX rigid bodies and colliders (required)#

  • Apply PhysicsRigidBodyAPI to any simulated rigid body prim.

  • Apply PhysicsCollisionAPI to collision-enabled prims.

  • Author physics:approximation = "sdf" for PhysX collider approximation.

  • Rigid body prims must be UsdGeomXformable.

Multi-body joints (required)#

  • Use UsdPhysicsJoint prims (or subtypes) to connect rigid bodies.

  • Author rel physics:body0 and rel physics:body1 relationships.

  • Apply PhysxJointAPI when authoring PhysX-specific joint properties.

Grasp physics (required)#

  • Author grasp data according to FET005_BASE_NEUTRAL requirements.

Materials (required)#

  • Author MDL materials per FET006_BASE_MDL requirements.

  • Ensure all material and MDL asset paths are relative and exist.

  • Bind materials to all non-guide meshes.

Stage composition requirements#

This profile does not require Isaac Sim composition. A single-layer USD is acceptable. If you choose to split layers, keep all references and payloads relative and consistent.

Naming conventions#

Prim naming#

  • Choose either camelCase or snake_case and use it consistently.

  • Avoid spaces, special characters, and reserved keywords.

  • Use descriptive, purpose-driven names.

  • Use prefixes by prim type when appropriate (e.g., mesh_, material_).

File naming#

  • Use lowercase file names.

  • Use .usd, .usda, .usdc, or .usdz as appropriate.

  • Use underscores or hyphens; avoid spaces and special characters.

  • Avoid reserved names (e.g., CON, PRN, AUX, NUL).

  • Use version numbers when appropriate (e.g., _v1.0).

References#

  • Feature dependency graph — requirements and dependencies for all features

  • nv_core/sr_specs/docs/profiles/profiles.toml

  • nv_core/sr_specs/docs/features/FET_001-minimal.md

  • nv_core/sr_specs/docs/features/FET_003-rigid_body_physics.md

  • nv_core/sr_specs/docs/features/FET_004-simulate_multi_body_physics.md

  • nv_core/sr_specs/docs/features/FET_005-simulate_grasp_physics.md

  • nv_core/sr_specs/docs/features/FET_006-materials.md

  • nv_core/sr_specs/docs/capabilities/core/naming_paths/requirements/prim-naming-convention.md

  • nv_core/sr_specs/docs/capabilities/core/naming_paths/requirements/file-naming-convention.md