[ODE] air friction

[DjArcas]

Have a look at some of the auto disable posts that have been here recently,
or simply say

when angvel < 0.0001 angvel = 0

Or similar.


From: "Ivan Bolcina" <ivan.bolcina at snt.si>
To: <ode at q12.org>
Sent: Wednesday, April 21, 2004 3:25 PM
Subject: Re: [ODE] air friction


> Actually I have a question on this to.
> If you want to simulate drag of friction, than you put some force. The
> problem is, the force will work fore some ammount of time, giving the
> object certain  amount of dV.
> The problem is,that by doing this, the object never stops (or it stops,
> but only because float numbers have limited range).  This is also true
> for air friction, I think.
> The object in realitiy would never completly stop, since friction force
> would alwasy produce smaller dV for current velocity. But this would
> only be true, if we could operate with smaller and smaller dt.  If we
> operate with fixed dt, I am not sure the results are accurate.
>
> The sistem doesn't seem stable. During some point, the ODE should decide
> that object is moving so slowly, that it is actually stoped.
> BTW, friction and drag are actually sum of forces of molecules hitting
> the object, or some other micro events, and we have to simulate this in
> one way or another. The question is how?
>
>
> DjArcas wrote:
>
> >Uhm, you could read the FAQ.
> >
> >Q How do I stop things from rolling off into infinity, or pendulums from
> >swinging forever?
> >A ODE models a universe with frictionless hinges and no rolling friction,
so
> >problems like those are fairly common. The solution is to apply a force
to
> >simulate RollingFrictionOrAerodynamicDrag.
> >
> >http://q12.org/cgi-bin/wiki.pl?RollingFrictionOrAerodynamicDrag
> >
> >
> >----- Original Message ----- 
> >From: <barbara.yersin at urbanet.ch>
> >To: <ode at q12.org>
> >Sent: Wednesday, April 21, 2004 10:58 AM
> >Subject: [ODE] air friction
> >
> >
> >
> >
> >>Hi guys!
> >>I now have a ball  on which I apply a force once (only once => no
> >>
> >>
> >acceleration, constant speed)
> >
> >
> >>Then the ball starts rolling, but it never stops. How can I create the
air
> >>
> >>
> >friction effect? How can I stop the ball ?
> >
> >
> >>Thanks!
> >>
> >>Barbara
> >>
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> >>
> >>
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