The USD primvar reader maps are part of the USD Preview Surface spec. They output primitive attributes from the geometry they are bound to. The maps are separated by the types of data that they read (i.e. float, float2, float3, normal, point, and vector).
default: [ 0, 0, 0 ]
fallback value to be returned if geometry fetch failed.
Name of the primvar to be read from the mesh
Whether or not to issue a warning when the requested attribute is unavailable