solid tetraeder facet normal 0 0 -5 outer loop vertex 1 2 1 vertex 2 5 1 vertex 3 3 1 endloop endfacet facet normal 6 3 4 outer loop vertex 3 3 1 vertex 2 5 1 vertex 1 3 4 endloop endfacet facet normal -9 3 -1 outer loop vertex 2 5 1 vertex 1 2 1 vertex 1 3 4 endloop endfacet facet normal 3 -6 2 outer loop vertex 1 2 1 vertex 3 3 1 vertex 1 3 4 endloop endfacet endsolid tetraeder