Hi,

I just finished a test with my cloth-cloth collission thing. I included a
divx avi with this message. But if you're not able to view the thing. Check
http://geitenkaas.dns2go.com/experiments/
The cloth06tests are with cloth-cloth collission detection.

(I was actually jumping up and down when I got the first image that showed
me that it actually worked!)



-- too many idle loops? visit http://www.imp.org/ and take care of it! --

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Attachments:
Download 'cloth06test2_640x480.divx.avi.dat' (652 KB)

On Tue, 5 Feb 2002 20:44:47 +0100, Apache wrote:
> I just finished a test with my cloth-cloth collission thing. I included a
> divx avi with this message. But if you're not able to view the thing. Check
> http://geitenkaas.dns2go.com/experiments/
> The cloth06tests are with cloth-cloth collission detection.

I think maybe your universe needs some friction.  But this is very cool.

-- 
#macro R(L P)sphere{L F}cylinder{L P F}#end#macro P(V)merge{R(z+a z)R(-z a-z)R(a
-z-z-z a+z)torus{1F clipped_by{plane{a 0}}}translate V}#end#macro Z(a F T)merge{
P(z+a)P(z-a)R(-z-z-x a)pigment{rgbf 1}hollow interior{media{emission 3-T}}}#end 
Z(-x-x.2x)camera{location z*-10rotate x*90normal{bumps.02scale.05}}

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I've been following your cloth progress, and I just wanted to say:
"Excellent Work!"  What kind of math is behind this?  I assume that it is
well above my head.  The movement is great, but in this last one, the cloth
looks more like silk, because of it's lack of friction; is there someway to
cause it to lose energy?  But whatever comments I have, I really want to say
keep going with this, it is amazing work.

H. David Young

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Nice! There is something odd about the way the fold moves toward the right hand
corner, but I liked the way it pushed the cloth above it  out of the way. What is
the speed decrease when using your internal collision detection?


--
text{ttf"timrom.ttf"concat(#local O=1;#while(O<7)chr(val(substr(concat(#local Q=
1;#while(Q<7)str(asc(substr("???<?>",Q,1))-56,0,0),#local Q=Q+1;#end""),O,2))),#
local O=O+2;#end"").1,0pigment{rgb 9}translate-<1,.3,-2>} // MJL

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Apache wrote:

> Hi,
>
> I just finished a test with my cloth-cloth collission thing. I included a
> divx avi with this message. But if you're not able to view the thing. Check
> http://geitenkaas.dns2go.com/experiments/
> The cloth06tests are with cloth-cloth collission detection.

I like it very much. Like the others I think that you need some friction
to get rid of some energy in order to stop the motion a bit earlier.
I also think that the value for your force that resists the bending between
your elements is too high. Otherwise, brilliant work.

I am also curious what programs you use to compute the motion.


>
> (I was actually jumping up and down when I got the first image that showed
> me that it actually worked!)
>
> -- too many idle loops? visit http://www.imp.org/ and take care of it! --
>

Great idea, I'll give them a call.

>
>                                     Name: cloth06test2_640x480.divx.avi
>    cloth06test2_640x480.divx.avi    Type: WMPLAYER File (video/avi)
>                                 Encoding: x-uuencode

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>Nice!
Thank you!


> There is something odd about the way the fold moves toward the right hand
corner, but I liked the way it pushed the cloth above it  out of the way.

My cloth algorithm works with (very stiff) springs between 'atoms'. That odd
movement at the corner is caused by the fact that at the center side of the
fold there are more pressed (pushing) springs than at the corner side. This
causes some sort of 'imbalance' so the fold is pressed to the corner. I have
some ideas about using a very different cloth model.


> What is the speed decrease when using your internal collision detection?

Not sure what you mean by this. Possibly you're talking about some energy
loss when atoms collide or bounce. Well.. They actually NEVER collide, since
them atoms don't have no volume or width. They're infinitely small like

When 2 atoms come too near eachother I simply put a spring between them that
pushes them apart. That's quite simple in fact. Managing the friction is
something else because the friction depends on the kind of material, the
structure of it. Possibly it depends on the angle of attack too.

(I built some bounding box trick in order to detect near atoms very fast.
I'll start rendering some more animations showing just those boxes and put
them on http://geitenkaas.dns2go.com/experiments/. I'll let you know when
they're up.)

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I'll rerender the thing again then! But this time I'll try making it more
supple. And I'll increase the amount of particles or 'atoms'.

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Bounding box animations:
http://geitenkaas.dns2go.com/experiments/cloth06test2bounds_640x480.divx.avi
and
http://geitenkaas.dns2go.com/experiments/cloth06test2bounds_640x480.mpg .

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Apache wrote:

> My cloth algorithm works with (very stiff) springs between 'atoms'.

Yes, thats it. Reminds me of a stiff rubber sheet.

> > What is the speed decrease when using your internal collision detection?
>
> Not sure what you mean by this.

Sorry, I should have been clearer. I meant to ask about the extra time it takes
to calculate this collision detection.

> When 2 atoms come too near eachother I simply put a spring between them that
> pushes them apart.

Ah... the same method that Clothray (in POVMan) uses. I have some feel over how
much longer this collision detection takes to determine :-) The results, though,
look worth the wait.

> (I built some bounding box trick in order to detect near atoms very fast.
> I'll start rendering some more animations showing just those boxes and put
> them on http://geitenkaas.dns2go.com/experiments/. I'll let you know when
> they're up.)

Is it just me, or do other people enjoy these sort of "show the inner workings"
too? I do it alot with my particle system.

--
text{ttf"timrom.ttf"concat(#local O=1;#while(O<7)chr(val(substr(concat(#local Q=
1;#while(Q<7)str(asc(substr("???<?>",Q,1))-56,0,0),#local Q=Q+1;#end""),O,2))),#
local O=O+2;#end"").1,0pigment{rgb 9}translate-<1,.3,-2>} // MJL

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You're getting very good results!!!

I see that this time you used smooth triangles, am I right? It looks much
better.

I hope I can find some time soon to continue my research! I got a bit
dissappointed with my last experiments, but I think I'm ready to restart.

Congratulations again!

Fernando.

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