public MeshEntityViewModel(MainWindow wnd, MeshEntity entity, bool is_expanded)
        {
            wnd_         = wnd;
            entity_      = entity;
            is_expanded_ = is_expanded;

            foreach (var child in entity_.Children)
            {
                children_.Add(new MeshEntityViewModel(wnd, child, false));
            }
        }
 public MeshEntityViewModel(MainWindow wnd, MeshEntity entity)
     : this(wnd, entity, true)
 {
 }