Normals of the mesh For a triangle mesh, each triangle (or facet) defines a plane and the vector perpendicular to the plane given by the cross product of two edges of that triangle is what we call the facet normal (because the normal is the same for the entire facet, regardless of the point you pick on that facet). But the normals of triangle meshes can also be defined to the nodes, in which case we call these normals node normals. All meshes have facet normals, but do not have always node normals.