Does anybody know how it is implemented or has any advice how to do it?
I'm especially interested in how to avoid that a player dies right after a checkpoint. How does the game evaluate when it's save to do one. Of course there seem to be "simple" triggers based on passing through a position in the map or achieving certain objectives, but I'm pretty sure they avoid that the game saves while a bullet is in flight killing you.
I have the feeling that the game shows you something slightly different on every reload, like if it would save the game at one point and maybe do a little replay. If it reloads and you die quickly, the next reload will be slightly different, I feel.
Could it be that once a trigger for a checkpoint is passed, the game saves it's whole state to a new file. Then it waits for maybe 2s whether you die. Only if you don't die it saves the game. Is that all?
Maybe it even freezes it's random number generator and stores the next player actions, too. So when the checkpoint loads, it can fast forward a little bit and a different amount of time each load?