[ODE] Buffered World

[Will Thimbleby]

Hi again - thanks for all your help.

I'm trying to use ODE in a thread separate to my drawing. It almost 
works, I was using mutexes to keep them apart, but I get lots of jerks 
and frames dropping.

I am thinking that the best way to do this is to use a buffered physics 
sim. One which runs in a separate thread to the drawing, and runs 
accurately with a fixed timestep. And a buffered sim that runs on-top 
that runs very fast and inaccurately: this is used to draw. Every frame 
the accurate version can update the buffered.

The syncing is then the only thing that needs to be mutexed. This 
hopefully should stop my problems, it will be much much faster than a 
full physics step, and it is also not critical if it is missed for a 
frame or two.

This buffered version needs no contacts or forces or physics other than 
a simple linear interpolation of positions, which can be processed in 
the graphics update thread using a variable timestep (VBL).

What is the best way to do this and is it a good idea? What is the best 
way to create a world and do as little calculation as possible in the 
physics step. Or is it best for me to buffer the objects myself, and 
write the linear interpolation?

many thanks --Will