PhysxSplinesSurfaceVelocityAPI

Surface velocity that follows a BasisCurves prim under the body instead of a constant vector. Read only on dynamic bodies and articulation links. Silently disables itself when its curve target does not validate.

• Applies to: Xformable

• Requires on the same prim: PhysicsRigidBodyAPI

• Read only when listed in usd-schemas.

What USD population writes

Every declared attribute is published at its resolved value; the curve relationship only when authored.

Columns

Raw fallback is the USD schema value. Producer writes is what ovstage population puts in the column for a USD stage. Parser default applies on the consumer when the column is absent, in stage units. diverges means writing the raw fallback literally parses differently from omitting the column (the parser default): USD population may well publish that very value for an unauthored attribute, so the marker is about the column being present, not about its value.

Column	Type	Units	Raw fallback	Producer writes	Parser default	If absent
physxSplinesSurfaceVelocity:surfaceVelocityEnabled	bool8	none	true	resolved USD value (authored, else raw fallback)	true	On, but forced off when PhysxSurfaceVelocityAPI is enabled on the same body, when surfaceVelocityCurve is empty, or when its first target is not a BasisCurves prim that is a descendant of the body.
physxSplinesSurfaceVelocity:surfaceVelocityMagnitude	float32	length/s	0.0	resolved USD value (authored, else raw fallback)	0.0	0: the surface does not move along the curve.
physxSplinesSurfaceVelocity:surfaceVelocityCurve	uint64 array, RELATIONSHIP_PATH_ID			not written		Feature disabled. Only the first target is used; it must be a prim of concrete type BasisCurves (an isA check, not an applied-schema check) and a descendant of the body, otherwise the feature is disabled silently on the parse side (the runtime re-emits a warning on the USD path only).

Interactions

• PhysxSurfaceVelocityAPI: Mutually exclusive; the constant-vector API wins when both are enabled.

Notes

• physxSplinesSurfaceVelocity:surfaceVelocityForceBased (bool, fallback true) is declared by the schema but not read by the consumer; it is not a column of this contract.