Instead of trying to replicate and reproduce the physics in my replay, i think i will go with the keyframe system as you mentioned.
It just looks to be so less pain..
I have more questions though, i hope you can help me to clear my mind.
If during the game, i record something like this :
0.0 ==> carPosition.x = 0;
1.0 ==> carPosition.x = 10;
2.0 ==> carPosition.x = 20;
Because my game has no fixed time step, the framerate is every-time different. So if during the replay my camera angle is different, with more objects displayed on screen, i will never be able to reproduce the action at the exact same timing i recorded them..
Instead of being 0.0, 1.0, and 2.0 seconds it will probably play 0.03, 1.023, 2.054 etc...
Does that mean that i need to calculate the position of my car related to these value ?
For example if at recorded time 1.0 my car position is 10, when replayed at 1.023 it should be :