Physically Based Rendering[0] Graphics Pipeline[1]

I'd also add Real Time Rendering [2] to that list.

[0] http://www.pbrt.org/ [1] https://fgiesen.wordpress.com/2011/07/09/a-trip-through-the-... [2] http://www.realtimerendering.com/book.html

Yup RTR is a great addition. It's so foundational it keeps slipping my mind to recommend.

I think he was referring to Pharr's book on PBR:

http://www.pbrt.org/

It is an absolute beast of a book, and not for beginners. Nor is it written as such; After Ch. 1 the book acts less like a sequential book, and more like an extensive reference guide for anything you'd need to really understand what goes on in a Ray Tracer.

As for "A trip down the Graphics Pipeline", I found it fairly easily:

https://fgiesen.wordpress.com/2011/07/09/a-trip-through-the-...

For a gentle intro to Ray tracing that is specifically geared for beginners, and lays a simple foundation for physically based rendering, I'll recommend Pete Shirley's mini-book Ray Tracing in One Weekend. http://in1weekend.blogspot.com/2016/01/ray-tracing-in-one-we...

Not to be pedantic but "ray tracer" evokes a concept that is a fair bit narrower than a "path tracer." The latter has concepts of sampling multiple directions and attempts to do things like conserve energy, respect the statistical properties of the surfaces it interacts with etc. A perfect ray tracer is easy to write but untenable for most real-world usage so PBRT is written more to the tune of all the various things you can do to improve performance without introducing statistical bias.

What would you recommend as prerequisites for PBR?

All that's "really" required is patience and some mathematical maturity. It is a complete book for the most part, but if you already are familiar with concepts like sampling theory, calculus, and concepts like convolutions and signal processing you'll be better off.