Unreal Engine 5 plugin that adds jolt

[Yadhu-S]

Hello everyone,

I'd like to share a plugin which brings jolt into UE5. All started when I wanted to bring deterministic physics for client side prediction, rollback and corrections, for which jolt seemed like the perfect candidate. The plugin's development is tied to my side project of course, and it may not be as generic (or polished) as it needs to be. Still I believe it is at a stage where it can be used for other projects (With some work probably) .

Follows the same ideas as mentioned in this blog but I am using a subsystem instead of an actor

If anyone is interested, feel free to check it out here --> https://github.com/Yadhu-S/UnrealJolt

[AnuraDev]

cool thanks for sharing!

[jrouwe]

This is a very cool project! I'll add it to the 'projects using Jolt' page so that people can hopefully find it easier.

[Yadhu-S]

@jrouwe Thanks, that would be amazing! 😃
In the mean time, I'll work towards improving the documentation and polish the rough edges.

[jrouwe]

See 8399da3

[AnuraDev]

btw does your plugin disable chaos in some way? cause it's actually one of the major sources of performance degradation in unreal engine (in a row with the actor system itself, idk how they did design such a dumpster, kind a obvious you can't have heavy objects as your primitive class, actor is like 2K+ bytes rofl. jolt body on the other hand afaik fits into 128bytes (2 cache lines)? (even bit less but it's rounded) thats chad design).

i made a pathing/local avoidance system and the heaviest part in it was to manually move actors (update their position) in the scene ))) i cringed so hard. out of the box unreal is poorly optimized (maybe in some areas it is, but the actor system ruins it anyway). maybe in like 3-4 years it will be better (thanks to CDPR).

[Yadhu-S]

@AnuraDev

btw does your plugin disable chaos in some way?

No, it does not. I really did not want to mess with the unreal engine source, and manage my own fork 😵 . I think we should be okay, as long as there are no bodies simulating using chaos. I have added an error log to warn if a body is simulating using jolt and chaos for now.

manually move actors (update their position) in the scene ))) i cringed so hard

Have to cringe here as well because this is what UnrealJolt does 😅 . For my specific project, I can get away with it because the amount of dynamic bodies is really low (worst case would be ~20). Maybe using the new Mass Entity System would be good choice if we want to simulate many bodies? I have no experience with it, but ECS seems like the way to reduce size. Worth looking into later I guess.

maybe in like 3-4 years it will be better (thanks to CDPR)

Yeah, hoping for the best.

[hollsteinm]

@jrouwe @Yadhu-S are you aware of any UE5 source mods that DO swap out the physics interfaces with Jolt? I understand it is a surgical effort, but Havok has a fork/branch that does so.

If so, what is the link?

[jrouwe]

No, I'm not aware of anyone doing it like that.