copy method
Implementation
@override
MeshMatcapMaterial copy(Material source) {
super.copy(source);
defines = {'MATCAP': ''};
color.copy(source.color);
matcap = source.matcap;
map = source.map;
bumpMap = source.bumpMap;
bumpScale = source.bumpScale;
normalMap = source.normalMap;
normalMapType = source.normalMapType;
normalScale!.copy(source.normalScale!);
displacementMap = source.displacementMap;
displacementScale = source.displacementScale;
displacementBias = source.displacementBias;
alphaMap = source.alphaMap;
flatShading = source.flatShading;
fog = source.fog;
return this;
}