I've been wondering about how to make these, either as a pigment
pattern, or at least as a function enabling to position and scale
objects. Basically, it looks like crackle, but with zones of increasing
or decreasing cell sizes. I've made  experiments using a blob density
function that attracts/repels the elements (spheres) according to their
proximity to centres. The size (radius) of each object is afterwards
calculated as the minimum distance from its 8 neighbours (it's in 2D).
It works, but it's very difficult to control to obtain a desired effect
(like a pinching or bulging at a particular place). Anyone would have
pointers to algorithms, or ideas ???

G.

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Bozo and Crackle? how about something like this, which I adapted from
Rune's incredible pigment:

#declare MyPigment =
   pigment {
      bozo
      scale 2 triangle_wave
      pigment_map {
         #declare X = 0;
         #declare Y = 255;
         #while (X<Y)
            #declare V = X/Y;
            #declare A = pow(V,3);
            [V,
               crackle triangle_wave scale 0.1 // rotate 30*z
               warp {turbulence 0.5 octaves 1}
               color_map {
                  [A, color rgb <1,1,1>]
                  [A, color rgb <0,0,0>]
               }
            ]
            #declare X = X+1;
         #end
      }
   }


Just a thought. I really like the effect.

Josh

Gilles Tran wrote:

> I've been wondering about how to make these, either as a pigment
> pattern, or at least as a function enabling to position and scale
> objects. Basically, it looks like crackle, but with zones of increasing
> or decreasing cell sizes. I've made  experiments using a blob density
> function that attracts/repels the elements (spheres) according to their
> proximity to centres. The size (radius) of each object is afterwards
> calculated as the minimum distance from its 8 neighbours (it's in 2D).
> It works, but it's very difficult to control to obtain a desired effect
> (like a pinching or bulging at a particular place). Anyone would have
> pointers to algorithms, or ideas ???
>
> G.

--
Josh English -- Lexiphanic Lethomaniac
eng### [at] spiritonecom
The POV-Ray Cyclopedia http://www.spiritone.com/~english/cyclopedia/

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Josh English wrote:

> Bozo and Crackle? how about something like this, which I adapted from
> Rune's incredible pigment:

Interesting... Not exactly what I'm looking for but this could be useful.
Here is another version  (try the different patterns) :
#version 3.1
#include "colors.inc"
global_settings{  assumed_gamma 1.0}
camera{ location  <0.0, 0.5, -4.0>  direction 1.5*z  right     4/3*x
look_at   <0.0, 0.0,  0.0>}
light_source{  0*x   color red 1.0  green 1.0  blue 1.0    translate <-30,
30, -30>}
#declare MyPigment =
   pigment {
      granite scale 5
//      bozo scale 1
//      wrinkles scale 1.2
//      agate scale 2
//      crackle scale 1.2
//      dents scale 1.5
//      wood triangle_wave rotate <60,40,0> scale 2

      pigment_map {
         #declare X = 0;
         #declare Y = 255;
         #declare rd=seed(0);
         #while (X<Y)
            #declare V = X/Y;
            [V,
               crackle scale (0.3*V+0.2)*0.4 // rotate 30*z
               color_map {
                  [0, color rgb Black]
                  [1, color rgb <rand(rd),1,rand(rd)+0.5>*1.5]
               }
            ]
            #declare X = X+1;
         #end
      }

      scale 0.4
   }

sphere { 0.0, 1 texture {pigment{MyPigment}  finish{specular 0.5 roughness
0.001}} }
plane{z,0 texture {pigment{MyPigment}  finish{specular 0.5 roughness 0.001}}
}

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Oh wow. You and Rune are truly pigment masters.

Josh

Gilles Tran wrote:

> Josh English wrote:
>
> > Bozo and Crackle? how about something like this, which I adapted from
> > Rune's incredible pigment:
>
> Interesting... Not exactly what I'm looking for but this could be useful.
> Here is another version  (try the different patterns) :
> #version 3.1
> #include "colors.inc"
> global_settings{  assumed_gamma 1.0}
> camera{ location  <0.0, 0.5, -4.0>  direction 1.5*z  right     4/3*x
> look_at   <0.0, 0.0,  0.0>}
> light_source{  0*x   color red 1.0  green 1.0  blue 1.0    translate <-30,
> 30, -30>}
> #declare MyPigment =
>    pigment {
>       granite scale 5
> //      bozo scale 1
> //      wrinkles scale 1.2
> //      agate scale 2
> //      crackle scale 1.2
> //      dents scale 1.5
> //      wood triangle_wave rotate <60,40,0> scale 2
>
>       pigment_map {
>          #declare X = 0;
>          #declare Y = 255;
>          #declare rd=seed(0);
>          #while (X<Y)
>             #declare V = X/Y;
>             [V,
>                crackle scale (0.3*V+0.2)*0.4 // rotate 30*z
>                color_map {
>                   [0, color rgb Black]
>                   [1, color rgb <rand(rd),1,rand(rd)+0.5>*1.5]
>                }
>             ]
>             #declare X = X+1;
>          #end
>       }
>
>       scale 0.4
>    }
>
> sphere { 0.0, 1 texture {pigment{MyPigment}  finish{specular 0.5 roughness
> 0.001}} }
> plane{z,0 texture {pigment{MyPigment}  finish{specular 0.5 roughness 0.001}}
> }

--
Josh English -- Lexiphanic Lethomaniac
eng### [at] spiritonecom
The POV-Ray Cyclopedia http://www.spiritone.com/~english/cyclopedia/

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Hi Gilles the only things I can think of that might help are blackhole warps
and perhaps as a last resort image maps!

Mick

"Gilles Tran" <tra### [at] inapginrafr> wrote in message
news:39B7C8C8.3D5EB9D4@inapg.inra.fr...
> I've been wondering about how to make these, either as a pigment
> pattern, or at least as a function enabling to position and scale
> objects. Basically, it looks like crackle, but with zones of increasing
> or decreasing cell sizes. I've made  experiments using a blob density
> function that attracts/repels the elements (spheres) according to their
> proximity to centres. The size (radius) of each object is afterwards
> calculated as the minimum distance from its 8 neighbours (it's in 2D).
> It works, but it's very difficult to control to obtain a desired effect
> (like a pinching or bulging at a particular place). Anyone would have
> pointers to algorithms, or ideas ???
>
> G.
>

Post a reply to this message

Josh English wrote:

> Oh wow. You and Rune are truly pigment masters.

No, no, I just took your code and replaced the color_map shift by scaling,
something I had done before, but much more clumsily. Other transformations could
be interesting and I'm sure other people have been there.
But the results are pleasantly weird.

G.

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Mick Hazelgrove wrote:

> Hi Gilles the only things I can think of that might help are blackhole warps
> and perhaps as a last resort image maps!

To be more precise, I'd like to find a way to position droplets of water on a
surface. From real-life observation, condensation droplets are not positionned
at random, but follow a pattern that looks like reptilian scales. So I thought
that the solution could be in a "reptilian scale" pattern algorithm, something
like a voronoi diagram but with some weight added to some of the points. My
investigations so far are good enough for my current projet, but I'd like a
better and more general solution.
For a texture, though, black holes are something worth investigating.

G.

Post a reply to this message

I wrote a simple scene for waterdrops..
placing every single drop makes it quite memoryextensive

I think you should be able to tweek the txture of the drops to
your needs,
I'm not such a master in texturing like you are ...

I'm not sure it's what you wanted but an idea I had when reading
your Post ...
look in p.t.scene-files and p.b.images ...

--

 ,',    Jan Walzer      \V/  http://wa.lzer.net     ,',
',','   student of      >|<  mailto:jan### [at] lzernet ',','
  '   ComputerScience   /A\  +49-177-7403863         '

Gilles Tran <tra### [at] inapginrafr> schrieb in im Newsbeitrag:
39B7C8C8.3D5EB9D4@inapg.inra.fr...
> I've been wondering about how to make these, either as a
pigment
> pattern, or at least as a function enabling to position and
scale
> objects. Basically, it looks like crackle, but with zones of
increasing
> or decreasing cell sizes. I've made  experiments using a blob
density
> function that attracts/repels the elements (spheres) according
to their
> proximity to centres. The size (radius) of each object is
afterwards
> calculated as the minimum distance from its 8 neighbours (it's
in 2D).
> It works, but it's very difficult to control to obtain a
desired effect
> (like a pinching or bulging at a particular place). Anyone
would have
> pointers to algorithms, or ideas ???
>
> G.
>

Post a reply to this message

Gilles Tran <tra### [at] inapginrafr> wrote:
> Mick Hazelgrove wrote:

>> Hi Gilles the only things I can think of that might help are blackhole warps
>> and perhaps as a last resort image maps!

> To be more precise, I'd like to find a way to position droplets of water on a
> surface. From real-life observation, condensation droplets are not positionned
> at random, but follow a pattern that looks like reptilian scales. So I thought
> that the solution could be in a "reptilian scale" pattern algorithm, something
> like a voronoi diagram but with some weight added to some of the points. My
> investigations so far are good enough for my current projet, but I'd like a
> better and more general solution.
> For a texture, though, black holes are something worth investigating.

Hmm, from a physical standpoint, it seems the droplets form based upon the
surface tension and the amount of water available.  I don't know how true
this is to real life, but I'd try something like scattering points on the
surface.  Those are the drop points.  Then, for any other point on the
surface, add it's strength (assume all points have uniform strength) to the
point closest to it.  Once you've simulated long enough (where long enough
is probably on the range of 10 - 1000 * number of drops), each drop can be
formed based on its weight.  Other statistics (direction?) could be kept to
shape the drop rather than having them all spherical.  You should get
something approximating the right pattern, I'd think.

But that's all idle speculation.  I dunno if it'd work.

Geoff

Post a reply to this message

Geoff Wedig wrote:

> Hmm, from a physical standpoint, it seems the droplets form based upon the
> surface tension and the amount of water available.  I don't know how true
> this is to real life, but I'd try something like scattering points on the
> surface.  Those are the drop points.  Then, for any other point on the
> surface, add it's strength (assume all points have uniform strength) to the
> point closest to it.  Once you've simulated long enough (where long enough
> is probably on the range of 10 - 1000 * number of drops), each drop can be
> formed based on its weight.  Other statistics (direction?) could be kept to
> shape the drop rather than having them all spherical.  You should get
> something approximating the right pattern, I'd think.
>
> But that's all idle speculation.  I dunno if it'd work.

Not that idle. I like the idea. I'll give it a try if I find the time (the potential
parsing time is scary).
Thanks

G.

>
>
> Geoff

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