As with almost everything that comes out of Wenzel Jakob's lab at EPFL, the documentation for Mitsuba 3 is _incredible_. Check out this writeup of how polarization is handled in Mitsuba 3 (complete with animated diagrams): https://mitsuba.readthedocs.io/en/latest/src/key_topics/pola...
That writeup is PhD Thesis material in terms of scope and detail, but the student that wrote it, Tizian Zeltner, actually wrote his PhD on another topic entirely. This is just the level of stuff that routinely comes out of that lab.
This is a result of a group in harmony with people who are in love with what they are doing. When you like the subject, and pour what you have into it, this is what comes out. I'm sure this wasn't tiring for them.
Make no mistake, this is a very high achievement, and is very rare in both private companies and research labs. It's a very hard point to reach if you don't like or care about what you are doing.
Agree on the quality. I have several documents from the Mitsuba 2 era that are of the absolute highest quality. And for anyone wondering, this counts both the quality of content and the actual success of communicating complex and varied ideas in commendable fashion.
That writeup is PhD Thesis material in terms of scope and detail, but the student that wrote it, Tizian Zeltner, actually wrote his PhD on another topic entirely. This is just the level of stuff that routinely comes out of that lab.