[ODE] Re: Inside ODE

[François Beaune]

If I create a wall made of several independant bricks, wouldn't
the wall slightly "vibrate" then eventually collapse ? I guess it
will only if at the beginning of the simulation, bodies are already
interpenetrating each others...

But I understand that on the other hand, allowing bodies to slightly
penetrate each others should make simulations more robust and more
resistant to explosion...

Cheers,
François

PS : Fred, c'est quoi ton projet ?

----- Original Message -----
From: "Nate W" <coding@natew.com>
To: <ode@q12.org>
Sent: Tuesday, March 12, 2002 3:41 AM
Subject: Re: [ODE] Re: Inside ODE


> On Tue, 12 Mar 2002, [iso-8859-1] François Beaune wrote:
>
> > Hmmm, on second thoughts, I suppose it should not be a problem
> > since in most cases relaxation (error reduction) is involved because
> > of penetrating (thus moving) bodies. However, if you create a stable
> > assembly of bodies (a wall made of bricks) which interpenetrate
> > slightly each other and then run the simulation, the wall may crash,
> > am I wrong ?
>
> If you create interpenetrating objects, they behave as if they were made
> of rubber and pressed together tightly.  When the simulation begins, they
> just bounce apart, but it does not necessarily cause a simulation crash
> (you don't get division by zero or not_a_number values).  With a bit of
> trial and error, I found global CFM values that worked well for what I'm
> doing, and I haven't seen a simulation explosion in a long time, even when
> deliberately creating interpenetrating systems.
>
> If this system has a flaw, it may be that it is too easy to make it
> tolerate errors.  It's easy to make simulations where all of the joints
> are slightly elastic.  They're very resistant to explosion, but if you
> look closely sometimes the bodies don't line up perfectly with the
> joints.  On the other hand, by changing the CFM you can make everything
> line up perfectly but with increased risk of binding or explosion.
>
> What kinds of systems are you intersted in simulating, if I may ask?
>
> --
>
> Nate Waddoups
> Redmond WA USA
> http://www.natew.com
>
>
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