[ODE] Running ODE backwards in time?

[adrianotiger]

If you solve the problem, you will be a hero for this world!
It mean that you solved a big time-problem and you will be someone like 
Einstein!
Maybe, thank your algorithm, we will discover the time machine! Hehe

ODE is a Physic Engine, like the real World, it is not possible to "return 
to the future".


----- Original Message ----- 
From: "Vrej Melkonian" <vmelkon at yahoo.com>
To: <ode at q12.org>
Sent: Monday, November 15, 2004 8:32 PM
Subject: Re: [ODE] Running ODE backwards in time?


>
> Having a residual velocity may not be enough.
> If you have a box on a table that is sliding, then how
> would you know what the original location was?
>
> The box may have been resting somewhere on the table,
> and someone pushed it with their hand.
>
> The box may have been thrown on the table and it hit
> the surface at a certain angle, bounced a bit while
> sliding, then it was in continuous sliding motion.
>
>
>
>
> --- Megan Fox <shalinor at gmail.com> wrote:
>
>> 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
>> <adam.moravanszky at novodex.com> wrote:
>> > 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.
>> >
>> > --Adam
>> >
>> >
>> >
>> > Alen Ladavac wrote:
>> >
>> > >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 -----
>> > >From: "Adam Moravanszky"
>> <adam.moravanszky at novodex.com>
>> > >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.
>> > >>_____________________
>> > >>
>> > >>
>> > >>
>> >
>> > _______________________________________________
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>> > ODE at q12.org
>> > http://q12.org/mailman/listinfo/ode
>> >
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>
>
>
>
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