How does the replay work?

Just curios about how the replay system works, its awesome, it records the full replay and the file it produces is relatively small. I remember a lively discusion about a replay mode and how it would be super complex or just outright impossible to add, here: https://www.beamng.com/threads/instant-replay-w-video-editor.17281/ but here we have it. So how does it work

 

Press the red circle and drive around. It's very early wip, so you can't edit them or view them outside of the game.
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When finished, press the white square. It will automatically start playing.

 

He is asking how the replay system is stored and read by the game rather than how to use it @BombBoy4

 

I think it might work like the recovery button does. A mix between that and AI. But I seriously have no real ideas...

 

Here's a really cool article about how the Planetary Annihilation replay works. That's an MP game that has to get info to lots of different people as quickly as possible. So, basically, for any given moment, each client just needs to know if anything has changed for a given game object, and if it has, it updates it, and the player sees the change.

BeamNG has a radically different foundation, so it definitely works in an entirely different way. But, hell, this is something interesting to discuss until a dev weighs in.