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From: Fernando González del Cueto
Subject: New ideas that yield nothing but frustration... DIVX
Date: 31 Jan 2002 19:01:11
Message: <3c59dac7@news.povray.org>
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In the past week, I've been doing a lot of thoughts and experiments trying
to implement a more robust cloth algorithm, but I think I'm getting worse
results than before.
I've been implementing the Backward Euler method, which is supposed to be
much more stable in stiff equations (like those which arise in cloth
simulations). It has not been very easy, mainly because, in contrast with
forward Euler, one has to find the derivatives of the force functions, and
solve a linear system.
Even though it takes much more time per iteration, in theory, one can take
much larger time steps, and it's faster in the long run.
However, I'm still having to take rather small steps, because if not, I have
stability problems.
This is an example in which the system does not explode, but display a
rather exotic behaviour. See how the cloth "contracts" when it touches the
floor, it is very bizarre.
Well, I just wanted to report my latest advances (?) in cloth simulation.
I'm still trying :)
Fernando.
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Attachments:
Download 'clothtest_divx.avi.dat' (106 KB)
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From: Fernando González del Cueto
Subject: Re: New ideas that yield nothing but frustration... DIVX
Date: 31 Jan 2002 19:35:13
Message: <3c59e2c1$1@news.povray.org>
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I forgot to say that one of the vertices of the cloth is fixed, to "hang"
the cloth from it. It may seem that it is an error, but it isn't :)
Fernando
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From:
Subject: Re: New ideas that yield nothing but frustration... DIVX
Date: 1 Feb 2002 12:46:23
Message: <3c5ad46f@news.povray.org>
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For me it looks as the cloth would fall onto an invisible string which then
teares off and drops down together with the cloth.
Is this your personal string-theory? :-)
Anyway, it looks nice. Really. It's fun to watch.
regards
SY
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From: Fernando Gonzalez del Cueto
Subject: Re: New ideas that yield nothing but frustration... DIVX
Date: 2 Feb 2002 02:39:16
Message: <3c5b979c@news.povray.org>
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> For me it looks as the cloth would fall onto an invisible string which
> then teares off and drops down together with the cloth.
> Is this your personal string-theory? :-)
>
> Anyway, it looks nice. Really. It's fun to watch.
> regards
> SY
I slept until late, implementing an idea which hopefully would fix this
aberration, and left it all night making the animation...
Unfortunately, it didn't help a lot. It seems I will have to return to the
old trusty Forward Euler method :/
Anyway, I'm glad you found it fun to watch :)
Fernando.
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From: Simen Kvaal
Subject: Re: New ideas that yield nothing but frustration... DIVX
Date: 3 Feb 2002 05:58:33
Message: <3c5d17d9$1@news.povray.org>
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What about using a Runge-Kutta integration scheme? I haven't studied
cloth-simulation in any extent, bu I suppose one has a (poosibly) huge set
of ODEs to solve. Euler is intrisicly unstable, but 4th order Runge-Kutta is
very stable, even with high force gradients in newtonian systems.
regards
Simen Kvaal.
> I've been implementing the Backward Euler method, which is supposed to be
> much more stable in stiff equations (like those which arise in cloth
> simulations). It has not been very easy, mainly because, in contrast with
> forward Euler, one has to find the derivatives of the force functions, and
> solve a linear system.
>
> Even though it takes much more time per iteration, in theory, one can take
> much larger time steps, and it's faster in the long run.
>
> However, I'm still having to take rather small steps, because if not, I
have
> stability problems.
>
Post a reply to this message
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