This is just another cloth animation... my apologies    :-)

I lowered the stiffness to a minimum of 1. This rubber sheet consists of
150x150 atoms (149x149x2 triangles). The total atom-atom spring amount is
221710. I put three spheres in the scene, since I haven't found the time to
work more on the system today. The higher quality animations are available
at http://geitenkaas.dns2go.com/experiments/. (Cloth06test3)

As you can see in the higher quality animations the sheet is trembling a
bit. This is caused by the inherent instability of the forward-Euler
algorithm that my system uses.
There are a few different ways to minimize this instability:
 1. Smaller timesteps (now: 0.0001)--> more steps needed per animation frame
(now: 80).
 2. More force dampening (now: 0.997). Each timestep the velocities of the
atoms are multiplied by a value to simulate energy loss (by internal
friction). The lower the DAMPING value, the more stable the system becomes
and the less interesting the movements become.
 3. Using another algorithm instead of Forward-Euler like Inherent Euler or
Leap-Frog.

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Attachments:
Download 'cloth06test3_small.mpg' (439 KB)

"Apache" <apa### [at] yahoocom> wrote in message
news:3c61d8f1@news.povray.org...
> This is just another cloth animation... my apologies    :-)

    Doesn't the cloth exert any force on the ball? It just sits there.

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The balls are VERY HEAVY. In fact, their mass is infinite. And since the
cloth is infinitely thing, it's weight is infinitely small  ;-)

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oooooooooooo :)


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Very impressive anim!
Would it be possible to move the spheres while the cloth is falling? Like
adding some friction so that the cloth is influenced by the sphere's
rotation?
Or am I asking for too much? .-)

congratulations!
regards
SY

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I think the animation you posted was too small to really appreciat it. I
downloaded the higher quality DIVX animation and I must say I liked it a
lot.

You're right about the trembling... I think it would be great if you could
be able to implement a better algorithm instead of Forward Euler. I didn't
have luck in that attempt, but I hope you will succeed.

Congratulations!

Fernando.



"Apache" <apa### [at] yahoocom> wrote in message
news:3c61d8f1@news.povray.org...
> This is just another cloth animation... my apologies    :-)
>
> I lowered the stiffness to a minimum of 1. This rubber sheet consists of
> 150x150 atoms (149x149x2 triangles). The total atom-atom spring amount is
> 221710. I put three spheres in the scene, since I haven't found the time
to
> work more on the system today. The higher quality animations are available
> at http://geitenkaas.dns2go.com/experiments/. (Cloth06test3)
>
> As you can see in the higher quality animations the sheet is trembling a
> bit. This is caused by the inherent instability of the forward-Euler
> algorithm that my system uses.
> There are a few different ways to minimize this instability:
>  1. Smaller timesteps (now: 0.0001)--> more steps needed per animation
frame
> (now: 80).
>  2. More force dampening (now: 0.997). Each timestep the velocities of the
> atoms are multiplied by a value to simulate energy loss (by internal
> friction). The lower the DAMPING value, the more stable the system becomes
> and the less interesting the movements become.
>  3. Using another algorithm instead of Forward-Euler like Inherent Euler
or
> Leap-Frog.

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"Cloth on sphere family"

Heh... "Who's been sleeping in MY indentation?"

Sorry, it's getting late over here and I'm tired.

-- 
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}

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I'm tired too!  ;-)

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"Apache" <apa### [at] yahoocom> wrote in message
news:3c621b8c@news.povray.org...
> The balls are VERY HEAVY. In fact, their mass is infinite. And since the
> cloth is infinitely thing, it's weight is infinitely small  ;-)
>
>

If their mass was infinite, the cloth would be drawn towards the spheres and
not the ground.

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Chaz wrote:

> "Apache" <apa### [at] yahoocom> wrote in message
> news:3c621b8c@news.povray.org...
> > The balls are VERY HEAVY. In fact, their mass is infinite. And since the
> > cloth is infinitely thing, it's weight is infinitely small  ;-)
> >
> >
>
> If their mass was infinite, the cloth would be drawn towards the spheres and
> not the ground.

But if the weight of the cloth was infinitely small, it would not be attracted
at
all, not even by the ground.

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