[ODE] Running ODE backwards in time?

Megan Fox shalinor at gmail.com
Mon Nov 15 10:32:26 MST 2004

```This is probably a ridiculous question, but I'm assuming you would
have physics turned completely off for the replay (and have a movement
vector/orientation vector saved out for each keyframe) - not plugging
in the keyframe'd reverse velocities and so on.

-Megan Fox

On Mon, 15 Nov 2004 13:16:34 +0100, Adam Moravanszky
> Good point.  You would have to make sure that you never completely stop
> -- you would have to maintain a tiny residual velocity.  Of course with
> float rather than real numbers you would have data loss anyway as values
> get truncated.  Anyway, this discussion is only theoretical anyway, in
> practice there is no way you could pull this off.  In the real world you
> would have to record motion keyframes when simulating forward and
> interpolate backwards -- just like in games that have a rewindable
> instant replay feature.
>
>
>
>
>
> >I'd say that this is insolvable for general case with dynamic friction. If a
> >box slides on a horizontal plane and comes to rest, how do you calculate
> >where it was supposed to come from, from its position only? ;)
> >
> >
> >----- Original Message -----
> >To: <mtoussai at inf.ed.ac.uk>
> >Cc: <ode at q12.org>
> >Sent: Monday, November 15, 2004 10:36
> >Subject: Re: [ODE] Running ODE backwards in time?
> >
> >
> >
> >
> >>    mtoussai at inf.ed.ac.uk wrote:
> >>
> >>Hi there!
> >>
> >>I need to run some simulations backwards in time (for some planning
> >>algorithms..). I know I could do this by inverting all dynamic properties
> >>((angular) velocities, accelerations, etc.) of the system and running ODE
> >>forwards. But is there a simpler way? Just setting a negative time
> >>
> >>
> >interval in
> >
> >
> >>a step function doesn't work.
> >>
> >>Thanks!
> >>Marc.
> >>_____________________
> >>
> >>
> >>
>
> _______________________________________________
> ODE mailing list
> ODE at q12.org
> http://q12.org/mailman/listinfo/ode
>
```