Panda Bullet

powerpup118 · February 10, 2012, 8:31pm

enn0x:

Here are a few tips to get as much determinism as possible (not specific to Bullet, but any physics engine we support):
1.) The biggest problem with determinism is that you have to completely decouple the physics simulation from the game loop.
2.) Fixed timesteps are mandatory for determinism!
3.) Never use the computers time - not even if you have a secure time server (e.g. IEEE 1588 Precise Time Protocol) in your network. In other words: feed only constants to BulletWorld.doPhysics, and never variables.
4.) Don’t sync between clients using a timestamp - use the integral count of the simulation frame.

All the samples I have written so far do not care about determinism or decoupling physics from framerate. I even do not bother to some time slip because of user input handling. It’s probably a question of how much determinism you really need.

This is great news to me!

I knew about all of your points (decouple the physics simulation from the game loop… fixed timesteps… no using computer’s time…)

Very good idea about using integral count of the simulation frames vs a timestamp, I would have never thought of that.

Thank you again,
~powerpup118

P.S. will try to get a sample going at some point in case anyone else is interested in the same idea