Curves I had to leave out, as many other things. I explained my motivations in this other comment: https://news.ycombinator.com/item?id=26020311

Constructive solid geometry I do mention as an extension to the raytracer [0], but it doesn't have a dedicated chapter. Perhaps for the 2nd Edition? :P

[0] https://gabrielgambetta.com/computer-graphics-from-scratch/0...