This example shows several aspects of shading.  Specifically, it shows the
differences in appearance between three common basic shading modes: object
shading, flat shading (triangle shading) and Goraud shading (vertex shading).
It also shows that the source of colors for shading is independent of the
shading method, and allows switching between colors generated by lighting, 
and static vertex colors.

The key commands are:

i, k - translate in x
j, l - translate in y
u, o - rotate around z axis
p, ; - uniformly scale
Space - reset transforms
s - cycle shading mode through object, flat shading, and Gouraud shading
c - switch between lit colors and static colors
