Did some testing with cloth-sphere collission detection.

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Attachments:
Download 'cloth04test1.mpg' (535 KB)

Hi Apache,

It looks very very good. Are you still using forward Euler? I'm now testing
with backward Euler, in order to increase stability, but I'm having some
problems...

Congratulations, it is high quality work!

Fernando.


"Apache" <apa### [at] yahoocom> wrote in message
news:3c58213a@news.povray.org...
> Did some testing with cloth-sphere collission detection.

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excellent ... but it seams a bit to stiff ...

the first part really looks very well ...

but when it should have come to rest, it's still moving, and trying to find
the optimal postision ...


--
#macro J(N A)#local a=mod(N 3);#local W=<int(mod(A,4)*2)int(-A/4)9>*2;#if
(!mod(a 2))sphere{W,2,2pigment{color rgb<a*5A/2W.x/A*5>}}#if(a<1)sphere{W
+<2,0>2 2pigment{color rgb<a*10A 10>}}#end#end#if(N>3)J(int(N/3)A+1)#end#
end blob{J(29229171 0)threshold 1translate<-6 3>}/******Jan Walzer******/

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What's wrong with that a piece of cloth trying to find the optimal position?
Isn't that what we all should do?


in article 3c585970@news.povray.org, Jan Walzer at jan### [at] lzernet wrote on
30-01-2002 21:37:

> excellent ... but it seams a bit to stiff ...
> 
> the first part really looks very well ...
> 
> but when it should have come to rest, it's still moving, and trying to find
> the optimal postision ...
> 
> 
> --
> #macro J(N A)#local a=mod(N 3);#local W=<int(mod(A,4)*2)int(-A/4)9>*2;#if
> (!mod(a 2))sphere{W,2,2pigment{color rgb<a*5A/2W.x/A*5>}}#if(a<1)sphere{W
> +<2,0>2 2pigment{color rgb<a*10A 10>}}#end#end#if(N>3)J(int(N/3)A+1)#end#
> end blob{J(29229171 0)threshold 1translate<-6 3>}/******Jan Walzer******/
> 
> 
>

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If by "optimal position" you mean its slowly coming to rest where a real cloth
would, then it looks fine to me...quite realistic cloth here...

Jan Walzer wrote:

> excellent ... but it seams a bit to stiff ...
>
> the first part really looks very well ...
>
> but when it should have come to rest, it's still moving, and trying to find
> the optimal postision ...
>
> --
> #macro J(N A)#local a=mod(N 3);#local W=<int(mod(A,4)*2)int(-A/4)9>*2;#if
> (!mod(a 2))sphere{W,2,2pigment{color rgb<a*5A/2W.x/A*5>}}#if(a<1)sphere{W
> +<2,0>2 2pigment{color rgb<a*10A 10>}}#end#end#if(N>3)J(int(N/3)A+1)#end#
> end blob{J(29229171 0)threshold 1translate<-6 3>}/******Jan Walzer******/

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if it's supposed to look that stiff as it does, than OK ...

I'm missing the right words to describe what I mean, but look exactly on the
motion in the second half of the anim ...
especially the right part of it ...
it doesn't try to hang straight down ...

you understand, what I mean ?



--
#macro J(N A)#local a=mod(N 3);#local W=<int(mod(A,4)*2)int(-A/4)9>*2;#if
(!mod(a 2))sphere{W,2,2pigment{color rgb<a*5A/2W.x/A*5>}}#if(a<1)sphere{W
+<2,0>2 2pigment{color rgb<a*10A 10>}}#end#end#if(N>3)J(int(N/3)A+1)#end#
end blob{J(29229171 0)threshold 1translate<-6 3>}/******Jan Walzer******/

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> it doesn't try to hang straight down ...
Believe me, it does try, but it won't hang because of the stiffness of the
material. Try it yourself: fold a piece of stiff material (paper?) and see,
it doesn't hang... :-)
But the slow movements at the end of the animation are caused by the thing
slowly sliding off the sphere. In fact the sphere is too 'sticky' in my
opinion. I have no complete control over the cloth-sphere friction. I should
get that fixed...

I have 3 ways of decreasing the stiffness:
  1. increasing the amount of atoms (now 100x100);
  2. decreasing the amount of atom-atom springs;
  3. combo of 1 and 2.

Using method 1 will increase the time needed to generate the whole thing,
since there are more atoms to work on. Method 2 actually decreases the time
needed.

My todo list:
  1. Adding more collission objects: box, cone, and triangle (mesh)
  2. Speeding up the rendering of .inc files.
  3. cloth-cloth collission detection. I have some ideas how to do it, but I
kind of forgot my C skills a bit, so that takes more time than I'd have
liked  :-(


Regards,
Apache

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"Apache" <apa### [at] yahoocom> wrote:
> > it doesn't try to hang straight down ...
> Believe me, it does try, but it won't hang because of the stiffness of the
> material. Try it yourself: fold a piece of stiff material (paper?) and see,
> it doesn't hang... :-)


Hello ? ... Thats what I said in the other posts ...
I felt, that this thing was to stiff... So whats your point again ?


--
#macro J(N A)#local a=mod(N 3);#local W=<int(mod(A,4)*2)int(-A/4)9>*2;#if
(!mod(a 2))sphere{W,2,2pigment{color rgb<a*5A/2W.x/A*5>}}#if(a<1)sphere{W
+<2,0>2 2pigment{color rgb<a*10A 10>}}#end#end#if(N>3)J(int(N/3)A+1)#end#
end blob{J(29229171 0)threshold 1translate<-6 3>}/******Jan Walzer******/

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