For anyone interested in computer graphics, I find Inigo Quilez's site (https://iquilezles.org/www/index.htm) more helpful than most of the textbooks on my shelf.
* https://web.archive.org/web/20160519071801/http://freespace....
The source is available here: https://github.com/mmp/pbrt-v3/
The latest text has an additional author: Wenzel Jakob