A sparse mapping from selector to pc-material id, as carried by the material-overrides
attribute and materialOverrides property. A name:X key selects every mesh instance of the
bound node's render component whose baseline material is named X; an index:N key selects
mesh instance N and wins over a name rule for the same instance.
A sparse mapping from selector to
pc-materialid, as carried by thematerial-overridesattribute andmaterialOverridesproperty. Aname:Xkey selects every mesh instance of the bound node's render component whose baseline material is namedX; anindex:Nkey selects mesh instanceNand wins over a name rule for the same instance.