Quaternions are one of those subjects where the community sees a steady stream of tutorial content, which really doesn't seem to be adding much to the discourse to my eyes. It's like a "yet another git tutorial" kind of thing.
In fact Ken Shoemake, who was responsible for originally popularizing quaternions as a robust rotation/orientation representation[1], wrote his own tutorial of this stuff back in the late 80's sometime, and it's really, really great: https://www.ljll.math.upmc.fr/~frey/papers/scientific%20visu...
Folks should start with that one before trying to rewrite it, IMHO.
In fact Ken Shoemake, who was responsible for originally popularizing quaternions as a robust rotation/orientation representation[1], wrote his own tutorial of this stuff back in the late 80's sometime, and it's really, really great: https://www.ljll.math.upmc.fr/~frey/papers/scientific%20visu...
Folks should start with that one before trying to rewrite it, IMHO.
[1] Here's a copy of the 1985 paper: https://www.cs.cmu.edu/~kiranb/animation/p245-shoemake.pdf