copy method
Implementation
@override
SkinnedMesh copy(Object3D source, [bool? recursive]) {
super.copy(source);
SkinnedMesh source1 = source as SkinnedMesh;
bindMode = source1.bindMode;
bindMatrix!.copy(source1.bindMatrix!);
bindMatrixInverse.copy(source1.bindMatrixInverse);
skeleton = source1.skeleton;
return this;
}