newton-variant-set#

Code	RV.004
Validator
Compatibility	open-usd
Tags	🔑

Summary#

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

Description#

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

Declare a variant set named Newton.
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 Newton payload composed). The Enabled option composes the Newton payload layer (see newton-runtime-payload RV.005). Defaulting to Disabled keeps the neutral asset the out-of-the-box state, so a consumer opts into Newton explicitly rather than inheriting Newton schemas by accident.

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

Why is it required?#

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

Examples#

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

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

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

How to comply#

On the stage defaultPrim, add a variant set named exactly Newton.
Give it at least a Disabled and an Enabled variant.
Author the default variant selection as Disabled.
Compose the Newton payload from the Enabled variant (see RV.005), and leave Disabled free of runtime payloads.