Does any one have ideas for a compressible spring for an animation. I've tried a
sphere_sweep but the rendering times are too long for me?

Regards
        Stephen

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McA### [at] aolcom news:c1j0nvccpb4or0qvk6kcm10o73j08mfikq@4ax.com

> Does any one have ideas for a compressible spring for an animation.
> I've tried a sphere_sweep but the rendering times are too long for me?

Maybe union of sphere+cones would be faster?

-- 
#macro g(U,V)(.4*abs(sin(9*sqrt(pow(x-U,2)+pow(y-V,2))))*pow(1-min(1,(sqrt(
pow(x-U,2)+pow(y-V,2))*.3)),2)+.9)#end#macro p(c)#if(c>1)#local l=mod(c,100
);g(2*div(l,10)-8,2*mod(l,10)-8)*p(div(c,100))#else 1#end#end light_source{
y 2}sphere{z*20 9pigment{function{p(26252423)*p(36455644)*p(66656463)}}}//M

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On 23 Sep 2003 10:24:30 -0400, "Rafal 'Raf256' Maj" <spa### [at] raf256com> wrote:

>
>Maybe union of sphere+cones would be faster?

I don't know what you mean. I can't visualise a helix made out of spheres and
cones :-{
 

Regards
        Stephen

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Stephen McAvoy wrote:
> Does any one have ideas for a compressible spring for an animation. I've tried a
> sphere_sweep but the rendering times are too long for me?

Have a look at the f_helix* functions in functions.inc:

http://www.povray.org/documentation/view/244/

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 2 Sep. 2003 _____./\/^>_*_<^\/\.______

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On Tue, 23 Sep 2003 15:37:29 +0100, Stephen McAvoy <McA### [at] aolcom> wrote:
> > Maybe union of sphere+cones would be faster?
>
> I don't know what you mean. I can't visualise a helix made out of spheres and
> cones :-{

You said you tried sphere_sweep. So you had centers and radiuses for it. Now
instead of sphere_sweep use macro Connect_Spheres() from shapes.inc with those
centers and radiuses.

ABX

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chr### [at] gmxde news:ic2### [at] tritonschunteretctu-bsde

> Have a look at the f_helix* functions in functions.inc:
> http://www.povray.org/documentation/view/244/
> Christoph

Hmm is this isosurface actualy *faster* then spheresweep ;) ?

-- 
#macro g(U,V)(.4*abs(sin(9*sqrt(pow(x-U,2)+pow(y-V,2))))*pow(1-min(1,(sqrt(
pow(x-U,2)+pow(y-V,2))*.3)),2)+.9)#end#macro p(c)#if(c>1)#local l=mod(c,100
);g(2*div(l,10)-8,2*mod(l,10)-8)*p(div(c,100))#else 1#end#end light_source{
y 2}sphere{z*20 9pigment{function{p(26252423)*p(36455644)*p(66656463)}}}//M

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"Christoph Hormann" <chr### [at] gmxde> wrote in message
news:ic2### [at] tritonschunteretctu-bsde...

> Have a look at the f_helix* functions in functions.inc:

Do you know what the (simple - i.e. I don't need no steenkin parameters)
roll-your-own function for a helix would be?

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"Stephen McAvoy" <McA### [at] aolcom> wrote in message
news:c1j0nvccpb4or0qvk6kcm10o73j08mfikq@4ax.com...
> Does any one have ideas for a compressible spring for an animation. I've tried
a
> sphere_sweep but the rendering times are too long for me?

Hmm, well I googled for helix function
which got me http://www.ric.edu/mrodrigues/math411/TheHelix.doc
which got me
#declare fn_X = function(x,y,z) {(x-cos(3*z))*(x-cos(3*z)) + (y -
sin(2*z))*(y-sin(2*z)) - 0.5}

which is fine if you want to model a slinky after a 4yr old with tourette's has
got hold of it.... :(

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Stephen McAvoy <McA### [at] aolcom> wrote:
> Does any one have ideas for a compressible spring for an animation. I've tried a
> sphere_sweep but the rendering times are too long for me?

  There are basically to ways of making this (so that it will render with
an acceptable speed):

  1. Construct the spring with cylinders joined by spheres. Here is an
example of how it can be done:

camera { location -z*20 look_at 0 angle 35 }
light_source { -z*10, 1 }

#declare SpringHeight = 8;
#declare SpringMajorRadius = 1;
#declare SpringMinorRadius = .1;
#declare SpringRevolutions = 10;
#declare SpringSegments = 1000;

union
{
  #declare Ind = 0;
  #while(Ind <= SpringSegments)
    #declare Pos2 =
      vrotate(<SpringMajorRadius, SpringHeight*Ind/SpringSegments, 0>,
              y*360*SpringRevolutions*Ind/SpringSegments);
    #if(Ind > 0)
      cylinder { Pos1, Pos2, SpringMinorRadius }
      sphere { Pos2, SpringMinorRadius }
    #end
    #declare Pos1 = Pos2;
    #declare Ind = Ind+1;
  #end

  pigment { rgb 1 } finish { specular .5 }
  translate -y*4
}

box { <-2,-4,-2><2,-4.1,2> pigment { rgb <.8,.4,.2> } }


     The main problem is that you need a lot of segments to get a smooth
look.

  2. Construct the spring as a mesh. The advantage is that it renders
fast and it will look smooth even with fewer segments (because of
smooth triangles). The problem is that constructing it is a lot
more complicated (so complicated I'm not bothering doing it right now).

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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On 23 Sep 2003 10:50:22 -0400, "Rafal 'Raf256' Maj" <spa### [at] raf256com> wrote:
> > Have a look at the f_helix* functions in functions.inc:
> > http://www.povray.org/documentation/view/244/
> > Christoph
>
> Hmm is this isosurface actualy *faster* then spheresweep ;) ?

Why do you think it is not ? Not that I think it is faster or slower but I'm
sure there are reasons why Gilles Tran used so many isosurfaces instead of
rounded boxes in http://www.irtc.org/ftp/pub/stills/2001-12-31/gt_asia.jpg .
Internal functions are not that slow.

ABX

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