[ODE] eliminating all state

[Russ Smith]

>  Russ, you mentioned that ODE uses the correction at one timestep to
> estimate the size of the correction at the next timestep.  Is there any
> way I can reset this between evaluations?  Is there anywhere else state is
> stored?

i hope i didn't mention this, because its not true. each time step is
completely independent from the last ... the only information that flows
between time steps is the position, orientation and linear/angular
velocity of the bodies. but of course all the ODE parameters will have
effects that spread throughout time precisely because they affect the
positions/velocities.

if you're trying to reproduce exact behavior, there's one thing
to watch out for when saving and restoring state: save and restore the
quaternion, not the rotation matrix, as R is generated from Q not the
other way around. saving and restoring R will result in some
least-significants-bits errors in the restored state.

russ.

--
Russ Smith
http://www.q12.org/