Chapter 4 is vague
I can't understand this chapter. Thats all just mixed with no enough explanations. The one certain issue I can't solve is this equation: http://www.arcsynthesis.org/gltut/Positioning/ZValueFunc.svg It's put there like its to be taken for granted.
I think that if You try to explain the math behind all this - it has to be done in every point or not at all.