[ODE] eliminating all state

Russ Smith russ at q12.org
Thu Nov 21 17:25:02 2002

>  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

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 Smith