ply
format ascii 1.0
element vertex 4
property float x
property float y
property float z
property float nx
property float ny
property float nz
element face 2
property list uchar int vertex_indices
end_header
0 0 0 1 0 0 
0 1 0 1 0 0 
0 1 1 1 0 0 
0 0 1 1 0 0 
3 0 1 2 
3 0 2 3