VertexNormals specifies that vertex i should have effective normal for purposes of shading by simulated lighting.
The are vectors of the form . Only the directions of these vectors ever matter; the vectors are in effect automatically normalized to unit length.
VertexNormals->None specifies that no explicit vertex normals are being given, and normal directions should be deduced from the actual coordinates specified for vertices. For point and line-like primitives, no shading based on simulated lighting should be done.