Robot-Gripper Profile USD Authoring Guide#

This document describes how to author a USD asset that conforms to the Robot-Gripper profile.

Robot-Gripper is the consolidated gripper profile. It replaces the separate Robot-Gripper-Neutral and Robot-Gripper-Isaac profiles with a single profile whose neutral OpenUSD core is mandatory and whose solver- and runtime-specific behavior is selected through optional features.

Profile definition#

The Robot-Gripper profile includes the following feature set (see robot_gripper.toml and the feature dependency graph). Each feature’s requirements and dependencies are defined in the feature specifications.

[Robot-Gripper]
"2.0.0" = {features = [
    {"FET_001_STANDARD" = {version = "1.0.1"}}, # "Minimal"
    {"FET_003_STANDARD" = {version = "0.2.0"}}, # "RBD Physics"
    {"FET_004_STANDARD" = {version = "0.2.0"}, optional=true}, # "Simulate Multi-Body Physics"
    {"FET_022_STANDARD" = {version = "0.2.0"}, optional=true}, # "Driven Joints"
    {"FET_024_STANDARD" = {version = "0.1.0"}, optional=true}, # "Articulation"
    {"FET_028_STANDARD" = {version = "0.1.0"}, optional=true}, # "Gripper"

    {"FET_004_PHYSX" = {version = "0.4.0"}, optional=true}, # "Simulate Multi-Body Physics (PhysX)"
    {"FET_022_PHYSX" = {version = "0.2.0"}, optional=true}, # "Driven Joints (PhysX)"
    {"FET_024_PHYSX" = {version = "0.1.0"}, optional=true}, # "Articulation (PhysX)"
    {"FET_021_ISAAC" = {version = "0.2.0"}, optional=true}, # "Robot Core (Isaac)"

    {"FET_022_ISAAC" = {version = "0.2.0"}, optional=true}, # "Driven Joints (Isaac)"
    {"FET_028_ISAAC" = {version = "0.1.0"}, optional=true}, # "Gripper (Isaac)"
    {"FET_100_ISAAC" = {version = "0.3.0"}, optional=true}, # "Isaac composition"
]}
"2.1.0" = {features = [ # Add required SimReady packaging + provenance metadata (FET_031_STANDARD, FET_033_STANDARD@0.3.0 / SR.003); add optional Newton/MuJoCo multiphysics runtime features and per-runtime Core scaffolding (FET_000_PHYSX/NEWTON/MUJOCO)
    {"FET_001_STANDARD" = {version = "1.0.1"}}, # "Minimal"
    {"FET_003_STANDARD" = {version = "0.2.0"}}, # "RBD Physics"
    {"FET_004_STANDARD" = {version = "0.2.0"}, optional=true}, # "Simulate Multi-Body Physics"
    {"FET_022_STANDARD" = {version = "0.2.0"}, optional=true}, # "Driven Joints"
    {"FET_024_STANDARD" = {version = "0.1.0"}, optional=true}, # "Articulation"
    {"FET_028_STANDARD" = {version = "0.1.0"}, optional=true}, # "Gripper"

    # SimReady packaging + provenance metadata (required)
    {"FET_031_STANDARD" = {version = "0.1.0"}}, # "Self-contained Package Source"
    {"FET_033_STANDARD" = {version = "0.3.0"}}, # "Metadata (thumbnail + nested provenance metadata)"

    # PhysX runtime core / rbd / multibody / driven joints / articulation
    {"FET_000_PHYSX" = {version = "0.1.0"}, optional=true}, # "Core PhysX runtime variant"
    {"FET_003_PHYSX" = {version = "0.4.0"}, optional=true}, # "RBD Physics (PhysX)"
    {"FET_004_PHYSX" = {version = "0.4.0"}, optional=true}, # "Simulate Multi-Body Physics (PhysX)"
    {"FET_022_PHYSX" = {version = "0.2.0"}, optional=true}, # "Driven Joints (PhysX)"
    {"FET_024_PHYSX" = {version = "0.1.0"}, optional=true}, # "Articulation (PhysX)"
    {"FET_021_ISAAC" = {version = "0.2.0"}, optional=true}, # "Robot Core (Isaac)"

    # Newton runtime core / rbd / multibody / driven joints / articulation
    {"FET_000_NEWTON" = {version = "0.1.0"}, optional=true}, # "Core Newton runtime variant"
    {"FET_003_NEWTON" = {version = "0.1.0"}, optional=true}, # "RBD Physics (Newton)"
    {"FET_004_NEWTON" = {version = "0.1.0"}, optional=true}, # "Simulate Multi-Body Physics (Newton)"
    {"FET_022_NEWTON" = {version = "0.1.0"}, optional=true}, # "Driven Joints (Newton)"
    {"FET_024_NEWTON" = {version = "0.1.0"}, optional=true}, # "Articulation (Newton)"

    # MuJoCo runtime core / rbd / multibody / driven joints / articulation / gripper
    {"FET_000_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Core MuJoCo runtime variant"
    {"FET_003_MUJOCO" = {version = "0.1.0"}, optional=true}, # "RBD Physics (MuJoCo)"
    {"FET_004_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Simulate Multi-Body Physics (MuJoCo)"
    {"FET_022_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Driven Joints (MuJoCo)"
    {"FET_024_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Articulation (MuJoCo)"
    {"FET_028_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Gripper (MuJoCo)"

    {"FET_022_ISAAC" = {version = "0.2.0"}, optional=true}, # "Driven Joints (Isaac)"
    {"FET_028_ISAAC" = {version = "0.1.0"}, optional=true}, # "Gripper (Isaac)"
    {"FET_100_ISAAC" = {version = "0.3.0"}, optional=true}, # "Isaac composition"
]}
"2.2.0" = {features = [ # Adopt FET_033_STANDARD@0.4.0 (SR.004 USD/sidecar union)
    {"FET_001_STANDARD" = {version = "1.0.1"}}, # "Minimal"
    {"FET_003_STANDARD" = {version = "0.2.0"}}, # "RBD Physics"
    {"FET_004_STANDARD" = {version = "0.2.0"}, optional=true}, # "Simulate Multi-Body Physics"
    {"FET_022_STANDARD" = {version = "0.2.0"}, optional=true}, # "Driven Joints"
    {"FET_024_STANDARD" = {version = "0.1.0"}, optional=true}, # "Articulation"
    {"FET_028_STANDARD" = {version = "0.1.0"}, optional=true}, # "Gripper"

    # SimReady packaging + provenance metadata (required)
    {"FET_031_STANDARD" = {version = "0.1.0"}}, # "Self-contained Package Source"
    {"FET_033_STANDARD" = {version = "0.4.0"}}, # "Metadata (thumbnail + USD/sidecar provenance union / SR.004)"

    # PhysX runtime core / rbd / multibody / driven joints / articulation
    {"FET_000_PHYSX" = {version = "0.1.0"}, optional=true}, # "Core PhysX runtime variant"
    {"FET_003_PHYSX" = {version = "0.4.0"}, optional=true}, # "RBD Physics (PhysX)"
    {"FET_004_PHYSX" = {version = "0.4.0"}, optional=true}, # "Simulate Multi-Body Physics (PhysX)"
    {"FET_022_PHYSX" = {version = "0.2.0"}, optional=true}, # "Driven Joints (PhysX)"
    {"FET_024_PHYSX" = {version = "0.1.0"}, optional=true}, # "Articulation (PhysX)"
    {"FET_021_ISAAC" = {version = "0.2.0"}, optional=true}, # "Robot Core (Isaac)"

    # Newton runtime core / rbd / multibody / driven joints / articulation
    {"FET_000_NEWTON" = {version = "0.1.0"}, optional=true}, # "Core Newton runtime variant"
    {"FET_003_NEWTON" = {version = "0.1.0"}, optional=true}, # "RBD Physics (Newton)"
    {"FET_004_NEWTON" = {version = "0.1.0"}, optional=true}, # "Simulate Multi-Body Physics (Newton)"
    {"FET_022_NEWTON" = {version = "0.1.0"}, optional=true}, # "Driven Joints (Newton)"
    {"FET_024_NEWTON" = {version = "0.1.0"}, optional=true}, # "Articulation (Newton)"

    # MuJoCo runtime core / rbd / multibody / driven joints / articulation / gripper
    {"FET_000_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Core MuJoCo runtime variant"
    {"FET_003_MUJOCO" = {version = "0.1.0"}, optional=true}, # "RBD Physics (MuJoCo)"
    {"FET_004_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Simulate Multi-Body Physics (MuJoCo)"
    {"FET_022_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Driven Joints (MuJoCo)"
    {"FET_024_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Articulation (MuJoCo)"
    {"FET_028_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Gripper (MuJoCo)"

    {"FET_022_ISAAC" = {version = "0.2.0"}, optional=true}, # "Driven Joints (Isaac)"
    {"FET_028_ISAAC" = {version = "0.1.0"}, optional=true}, # "Gripper (Isaac)"
    {"FET_100_ISAAC" = {version = "0.3.0"}, optional=true}, # "Isaac composition"
]}
"3.0.0" = {features = [ # Require UsdPreviewSurface; display colour, OpenPBR and MDL stay optional
    {"FET_001_STANDARD" = {version = "1.0.1"}}, # "Minimal"
    {"FET_003_STANDARD" = {version = "0.2.0"}}, # "RBD Physics"
    {"FET_004_STANDARD" = {version = "0.2.0"}, optional=true}, # "Simulate Multi-Body Physics"
    {"FET_022_STANDARD" = {version = "0.2.0"}, optional=true}, # "Driven Joints"
    {"FET_024_STANDARD" = {version = "0.1.0"}, optional=true}, # "Articulation"
    {"FET_028_STANDARD" = {version = "0.1.0"}, optional=true}, # "Gripper"
    {"FET_006_STANDARD" = {version = "0.2.0"}}, # "Materials - UsdPreviewSurface (required)"
    {"FET_006_OPENPBR" = {version = "0.1.0"}, optional=true}, # "Materials - OpenPBR (optional)"
    {"FET_006_MDL" = {version = "0.2.0"}, optional=true}, # "Materials - MDL (optional)"
    {"FET_010_STANDARD" = {version = "0.1.0"}, optional=true}, # "Display Color (optional)"

    # SimReady packaging + provenance metadata (required)
    {"FET_031_STANDARD" = {version = "0.1.0"}}, # "Self-contained Package Source"
    {"FET_033_STANDARD" = {version = "0.4.0"}}, # "Metadata (thumbnail + USD/sidecar provenance union / SR.004)"

    # PhysX runtime core / rbd / multibody / driven joints / articulation
    {"FET_000_PHYSX" = {version = "0.1.0"}, optional=true}, # "Core PhysX runtime variant"
    {"FET_003_PHYSX" = {version = "0.4.0"}, optional=true}, # "RBD Physics (PhysX)"
    {"FET_004_PHYSX" = {version = "0.4.0"}, optional=true}, # "Simulate Multi-Body Physics (PhysX)"
    {"FET_022_PHYSX" = {version = "0.2.0"}, optional=true}, # "Driven Joints (PhysX)"
    {"FET_024_PHYSX" = {version = "0.1.0"}, optional=true}, # "Articulation (PhysX)"
    {"FET_021_ISAAC" = {version = "0.2.0"}, optional=true}, # "Robot Core (Isaac)"

    # Newton runtime core / rbd / multibody / driven joints / articulation
    {"FET_000_NEWTON" = {version = "0.1.0"}, optional=true}, # "Core Newton runtime variant"
    {"FET_003_NEWTON" = {version = "0.1.0"}, optional=true}, # "RBD Physics (Newton)"
    {"FET_004_NEWTON" = {version = "0.1.0"}, optional=true}, # "Simulate Multi-Body Physics (Newton)"
    {"FET_022_NEWTON" = {version = "0.1.0"}, optional=true}, # "Driven Joints (Newton)"
    {"FET_024_NEWTON" = {version = "0.1.0"}, optional=true}, # "Articulation (Newton)"

    # MuJoCo runtime core / rbd / multibody / driven joints / articulation / gripper
    {"FET_000_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Core MuJoCo runtime variant"
    {"FET_003_MUJOCO" = {version = "0.1.0"}, optional=true}, # "RBD Physics (MuJoCo)"
    {"FET_004_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Simulate Multi-Body Physics (MuJoCo)"
    {"FET_022_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Driven Joints (MuJoCo)"
    {"FET_024_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Articulation (MuJoCo)"
    {"FET_028_MUJOCO" = {version = "0.1.0"}, optional=true}, # "Gripper (MuJoCo)"

    {"FET_022_ISAAC" = {version = "0.2.0"}, optional=true}, # "Driven Joints (Isaac)"
    {"FET_028_ISAAC" = {version = "0.1.0"}, optional=true}, # "Gripper (Isaac)"
    {"FET_100_ISAAC" = {version = "0.3.0"}, optional=true}, # "Isaac composition"
]}

Required versus optional features#

Two features are required in version 2.0.0; packaging and provenance join them from 2.1.0. Version 3.0.0 also requires the baseline visual-material feature FET_006_STANDARD; every gripper-specific or alternative visual feature stays optional and is validated only when the asset selects it.

Feature	Version	Status	Purpose
`FET_001_STANDARD`	1.0.1	Required	Minimal OpenUSD asset: units, hierarchy, mesh geometry
`FET_003_STANDARD`	0.2.0	Required	Neutral rigid-body physics and colliders
`FET_006_STANDARD`	0.2.0 (from profile `3.0.0`)	Required	`UsdPreviewSurface` materials
`FET_010_STANDARD`	0.1.0 (from profile `3.0.0`)	Optional	Display colour and opacity
`FET_006_OPENPBR`	0.1.0 (from profile `3.0.0`)	Optional	OpenPBR materials
`FET_006_MDL`	0.2.0 (from profile `3.0.0`)	Optional	MDL materials
`FET_004_STANDARD`	0.2.0	Optional	Neutral multibody joints
`FET_022_STANDARD`	0.2.0	Optional	Neutral driven joints
`FET_024_STANDARD`	0.1.0	Optional	Single articulation root
`FET_028_STANDARD`	0.1.0	Optional	Gripper site: socket type, forward axis, grip line, max opening
`FET_004_PHYSX`	0.4.0	Optional	PhysX multibody, mass, and nesting rules
`FET_022_PHYSX`	0.2.0	Optional	PhysX drives and mimic joints
`FET_024_PHYSX`	0.1.0	Optional	PhysX collision clearance between links
`FET_021_ISAAC`	0.2.0	Optional	Robot identity: robot schema, robot type, root joint
`FET_022_ISAAC`	0.2.0	Optional	Isaac link and joint APIs
`FET_028_ISAAC`	0.1.0	Optional	Isaac gripper site
`FET_100_ISAAC`	0.3.0	Optional	Isaac Sim composition

A practical end-effector selects at least FET_004_STANDARD, FET_022_STANDARD, FET_024_STANDARD, and FET_028_STANDARD. Add the PhysX features for a runnable PhysX gripper, and the Isaac features for an Isaac Sim deliverable.

Version 3.0.0 makes the baseline appearance mandatory: every conforming gripper carries a UsdPreviewSurface material (FET_006_STANDARD). Display colour (FET_010_STANDARD), OpenPBR and MDL remain optional, so an asset picks whichever final surface its runtime needs and DISP.001 to DISP.003 are validated only on an asset that selects display colour. Requirements shared between a required and an optional feature stay required: VM.MAT.001, VM.TEX.001, com.nvidia.usd.VM.BIND.001, and com.nvidia.usd.VM.PS.001 are mandatory from 3.0.0. VM.PBR.* (OpenPBR) and VM.BIND.002, VM.MDL.001, com.nvidia.usd.VM.MDL.002, VM.TEX.002 (MDL) stay optional.

Required USD properties and schemas#

Stage metadata and hierarchy (`FET_001_STANDARD`)#

Set defaultPrim on every layer, and upAxis = "Z" with metersPerUnit = 1 on every stage.
Keep the prim hierarchy anchored under the default prim.

Rigid bodies and colliders (`FET_003_STANDARD`)#

Apply PhysicsRigidBodyAPI to any simulated rigid body prim, which must be UsdGeomXformable.
Apply PhysicsCollisionAPI to collision-enabled prims.

Materials (`FET_006_STANDARD`, `FET_010_STANDARD`, `FET_006_OPENPBR`, and `FET_006_MDL`)#

Required from version 3.0.0. The material requirements are identical to those in the Robotics-Prop guide, which describes each requirement in full.

Optional feature requirements#

Gripper site (`FET_028_STANDARD`)#

Every gripper interaction point must be an Xform prim carrying:

token simready:attactment:socketType = "Gripper" — discovery attribute.
float custom:maxOpening — maximum jaw separation in meters, strictly positive.
A BasisCurves child named forward_axis with at least 2 points encoding the approach direction.
A BasisCurves child named grip_line with at least 2 points encoding the graspable-tube axis, whose segment length equals the physical width of the grip pads.

The gripper site prim may have any name, and multiple sites on one end-effector are supported.

Multibody joints, driven joints, and articulation#

FET_004_*, FET_022_*, and FET_024_* carry the same requirements as in the Robot-Body guide.

Validation metadata (recommended)#

Include profile metadata in customLayerData to simplify validation workflows:

customLayerData = {
    dictionary SimReady_Metadata = {
        dictionary validation = {
            string profile = "Robot-Gripper"
            string profile_version = "3.0.0"
        }
    }
}

References#

docs/profiles/robot_gripper.toml
docs/features/FET_028_STANDARD.md
docs/features/FET_006_STANDARD.md
docs/features/FET_010_STANDARD.md
docs/capabilities/physics_bodies/physics_grippers/requirements/gripper-socket-type.md
docs/capabilities/physics_bodies/physics_grippers/requirements/gripper-forward-axis.md
docs/capabilities/physics_bodies/physics_grippers/requirements/gripper-grip-line.md
docs/capabilities/physics_bodies/physics_grippers/requirements/gripper-max-opening.md