The summary of this chapter is "Just say NO!" to the traditional computer graphics lighting model." Now that programmable graphics hardware has freed us from the shackles of the traditional hardware lighting equations, we are free to implement and experiment with a variety of new techniques. Some of the techniques we explored are both faster and more realistic than the traditional methods.
Hemisphere lighting is a simple way to approximate global illumination in a scene. Environment maps are very useful tools for simulating complex lighting environments. It is neither expensive nor difficult to capture images of real-world lighting conditions. Such light probe images can either be preprocessed and used to perform image-based lighting directly, or they can be preprocessed to compute spherical harmonic basis function coefficients that can be used for simple and high-performance lighting.
We've also seen that the traditional OpenGL fixed functionality lighting model leaves a lot to be desired in terms of flexibility and ease of use. Lighting models such as the one defined by the überlight shader are much more versatile and easier for artists to use.