[larrry]

The core of my multiplayer arena game is in fixed point

I wanted absolute certainty that the rollback netcode would result in identical simulations on any platform, and integer math provides that. With set of wrapper functions and look up tables for trig it’s not that much worse than using regular floats

I am still uncertain if I actually would have been fine with floats, being diligent to round frequently and staying within true integer representable range… but now at least I’m far less afraid of game desyncs and it wasn’t that much work

Cross platform, cross USA games have been stable and fun to play, no fixed point complaints here

[AlotOfReading]

Floating point determinism has been a personal bugbear of mine for a number of years. You still have to be careful, but it's at the point where it's less work than switching to fixed point (cheap as that may be). There are even libraries [0] [1] that implement full reproducibility with negligible overhead. Compilers shipping incorrectly rounded stdlib functions remains an issue, but they're slowly improving. Language level support for float reproducibility is in the C++ pipeline, and already a design consideration on the Rust side. In a decade or so determinism issues might be a distant memory once you've ensured same inputs to the same instructions in the same order.

[0] https://github.com/J-Montgomery/rfloat

[1] https://github.com/sixitbb/sixit-dmath