mujoco-variant-set#

Code	RV.007
Validator
Compatibility	open-usd
Tags	🔑

Summary#

The asset’s default prim must expose a MuJoCo physics runtime variant set with Disabled and Enabled options, defaulting to Disabled.

Description#

An asset that supports the MuJoCo runtime must declare it on the asset root (the stage defaultPrim) using a USD variant set named exactly MuJoCo. The default prim must:

Declare a variant set named MuJoCo.
Provide at least the options Disabled and Enabled in that variant set.
Select Disabled as the authored default.

The Disabled option represents the neutral/base asset (no MuJoCo payload composed). The Enabled option composes the MuJoCo payload layer (see mujoco-runtime-payload RV.008). Defaulting to Disabled keeps the neutral asset the out-of-the-box state, so a consumer opts into MuJoCo explicitly rather than inheriting MuJoCo schemas by accident.

This requirement covers only the MuJoCo variant set. PhysX and Newton runtime variant sets are covered by their own requirements and features.

Why is it required?#

Lets a single asset serve both neutral and MuJoCo consumers without duplicating the asset.
Keeps MuJoCo-specific schemas and attributes out of the base asset so the neutral form stays portable.
Makes MuJoCo selection explicit and discoverable through a standard USD variant set.
Establishes a predictable variant-set name (MuJoCo) that validators and runtimes can rely on.

Examples#

# Valid: default prim declares a MuJoCo variant set defaulting to Disabled
def Xform "RootNode" (
    kind = "component"
    prepend variantSets = ["MuJoCo"]
    variants = {
        string MuJoCo = "Disabled"
    }
)
{
    variantSet "MuJoCo" = {
        "Disabled" {
        }
        "Enabled" (
            prepend payload = @../runnables/physics/mujoco.usd@
        ) {
        }
    }
}

# Invalid: MuJoCo variant set present but defaults to Enabled
def Xform "RootNode" (
    prepend variantSets = ["MuJoCo"]
    variants = {
        string MuJoCo = "Enabled"
    }
)
{
    # ...
}

# Invalid: missing the Enabled option
    variantSet "MuJoCo" = {
        "Disabled" {
        }
    }

How to comply#

On the stage defaultPrim, add a variant set named exactly MuJoCo.
Give it at least a Disabled and an Enabled variant.
Author the default variant selection as Disabled.
Compose the MuJoCo payload from the Enabled variant (see RV.008), and leave Disabled free of runtime payloads.