ShadedGeometry-PerVertexLighting
lab11-GeometryPositionNormalPerVertexLighting
http://en.wikibooks.org/wiki/GLSL_Programming/GLUT/Diffuse_Reflection
http://en.wikibooks.org/wiki/GLSL_Programming/GLUT/Specular_Highlights
ShadedGeometry-PerPixelLighting
lab11-GeometryPositionNormalPerPixelLighting
http://en.wikibooks.org/wiki/GLSL_Programming/GLUT/Smooth_Specular_Highlights