with 2 very good demos inside~
http://blog.yoz.sk/2010/03/fixing-z-sorting-in-papervision-3d/
another tutorial, it also mention cube.meshSort = DisplayObject3D.MESH_SORT_FAR; // before line 50
http://www.bukisa.com/articles/37044_papervision-3d-programming-tutorial-quadtree-renderer
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