When I was working on this project, I was trying to restrict myself to the architecture of the original Ray Tracing in One Weekend book series. I am aware that things are not as SIMD friendly and that becomes a major bottle neck. While I am confident that an architectural change could yield a massive performance boost, it's something I don't want to spend my time on.

I think it's also more fun sometimes to take existing systems and to try to optimize them given whatever constraints exist. I've had to do that a lot in my day job already.

I can relate to setting an arbitrary challenge for myself. fwiw, don't know where you draw the line of an architectural change, but I think that switching AoS -> SoA may actually be an approachably-sized mechanical refactor, and then taking advantage of it to SIMDify object lists can be done incrementally.

The value of course is contingent on there being a decent number of objects of a given type in the list rather than just a huge number of rays being sent to a small number of objects; I didn't evaluate that. If it's the other way around, the structure would be better flipped, and I don't know how reasonable that is with bounces (that maybe then aren't all being evaluated against the same objects?).