Yeah but here's the thing: if your math skills are good enough to write and maintain a 3D engine, quaternions are not the problem. They are super easy to work w

Yeah but here's the thing: if your math skills are good enough to write and maintain a 3D engine, quaternions are not the problem. They are super easy to work with, and material that explains how to use them is readily available. Is "what they do" unintuitive? Sure, but I couldn't care less about whether someone can conceptualise _why_ they do what they do, I care about _that_ they do what they do, and that I can trust them to do that. If someone can't understand what geometric operation an non-geometric transformation might map to "in between the start state and the end state" then that someone is focussing on the wrong thing twice: 1. quaternion maths is not geometry, it's algebra. It has some nice geometric analogies when performing specific operations, but trying to understand them _as_ geometry and expecting them to make sense across the board is ridiculous, and 2. if you feel you need to understand the "intermediary" results of a 4 dimensional algebra before you're willing to write or maintain code that uses it, maybe you're putting your foot down in the wrong spot: this is a 3D engine. It's not "easy code that we over-complicated by using quaternions", it's stupidly complex code that we simplified by working with quaternions.