Physics Determinism

Hey all, I read in the documentation that async physics sims can help with determinism but to what extent? Is it possible for the entirety of physics to be deterministic? And if not, would it be safe to assume I’d have to write a phys engine? I apologize in advance if this question seems silly to more experienced devs.

Interesting question. As far as I am aware there is no way to make Unreal physics simulation deterministic. Physics sub-stepping will improve simulation precision marginally, but the results will vary from device to device, platform to platform, even from run to run on the same device. There are still too many factors, that the calculations depend on. Also, sub-stepping is not supported on the mobile platforms.

Writing your own physics simulation is quite a challenge and a huge project in itself. If high precision and determinism is crucial in your project, I would explore scientific physics simulators that are currently available and are platform agnostic. Whenever they are performant enough for real-time execution is another question.