public UVMeshEdge(UVMesh parentMesh, UVMeshVertex start, UVMeshVertex end, int index)
 {
     _start      = start;
     _end        = end;
     _parentmesh = parentMesh;
     _index      = index;
 }
 public UVMeshFace(int index, UVMesh mesh)
 {
     _index  = index;
     _uvMesh = mesh;
 }