[ODE] CFM and timesteps

[amundbørsand]

"gl" <gl@ntlworld.com> skreiv:

> > Yes, but you're not really supposed to do that, are you? And I thought
> > ODE finds out where the intersection/collision occurs ahead of time, and
> > applies forces accordingly, not waiting until *after* objects have
> > intersected, it's not using penalty methods. The way I see it your
> > example is an error in the simulation and shouldn't happen.
> 
> Can't answer that as I'm not clued up on that side of it yet.  I did some
> tests with box stacking early on though, and larger timesteps resulted in
> deeper penetration, so again you will get different results - but if you
> don't have any of those requirements and it looks fine in your app, then
> you're obviously OK : ).

If I remember correctly, the boxstack example uses CFM, and CFM and ERP
is stepsize dependent! =) But of course errors will sneak in more
frequently and in a larger scale with larger time steps, and roundoffs
and inaccuracies will be more significant and/or cause different
solutions. But in my case it seems to work fine, which is what I hope
for as well, because running smooth graphics at an optimal framerate is
not easily crossed with constant time steps (unless your're running on
75 fps refresh rate, but then you'll get such a drastic decrease if the
computer can't keep up and drops to 35).