Resolve the base IfcMaterial(s) for a material definition, with a volume
weight per material. Layer sets split by layer thickness, constituent sets by
fraction, profile/list sets equally; a plain IfcMaterial yields a single
leaf with weight 1. Results are memoised per (store, defId) — a type-shared
layer set is resolved once for the whole model.
Resolve the base IfcMaterial(s) for a material definition, with a volume weight per material. Layer sets split by layer thickness, constituent sets by fraction, profile/list sets equally; a plain IfcMaterial yields a single leaf with weight 1. Results are memoised per (store, defId) — a type-shared layer set is resolved once for the whole model.