A physics engine with incremental rollback for multiplayer games

This looks great - how much of it is open source, could I host it all myself? wouldn't be interested in investing any time learning if I'm locked in to hosting on some else's hardware.

Hi everyone,

I'm making a game engine that uses rollback netcode for its multiplayer architecture. As far as I can tell, no physics engine supports incremental rollback thus far. This means the entire physics engine state has to be snapshotted every frame, which basically means it's infeasible to have large worlds with rollback netcode. I've made a physics engine which only snapshots the changes, and so now I think you can have large worlds, as long as most of the world is static. I think that's true in most cases, like when you're walking around a big spaceship for example, all the walls, tables, control panels etc don't really move. I wrote up a bit of a post to describe some of the cool things I discovered while making my own physics engine.

As a long-time web/app developer getting into game dev, it feels like I'm entering "the big leagues" of software engineering. Tougher problems, more problems, more _interesting_ problems, and problems without prebuilt solutions. Much more fun than making yet another dashboard.

Combining player control, multiplayer, non-player control, and physics is one of the tougher problems. I got it handled (enough) for my project, but I'd be very interested to read the source if Easel's physics engine gets open-sourced.

Fwiw, one case where I've wanted rollback has been input fusion over interface devices with diverse latencies. You might have 10 ms for a keypress, 100 ms for optical tracking, and 1000 ms for speech. So given click+"the red one"(spoken), you might start running click+"the one in front"(default), and almost a second later rollback and rerun with "the red one". Or for real example, keypress event handling might branch on optical "pressed where on the keycap" and "by which finger", which won't become available for several frames.

Does it run Doom?

Is this a demo? A hobby? How long have you been at this?

Can the games only be played on the easel site, or can I upload to e.g. itch.io as well (probably with the limitation of only singleplayer?)