Gouraud Shading

We can approximate the correct shading by using the information at each vertex, since the normals are specified there, and then interpolate colors between vertices as the polygon is shaded.

This approach is called Gouraud Shading.

Gouraud shading works reasonably well, and fits very nicely into the rendering pipeline because the Phong model parameters need only be known at the vertices.

This approach does have one serious flaw, however...