Wasn't it Jan Walzer who wrote:

>BTW: how can I to a isosurface from a crackle-pattern, or a
>marble, or some other patterns ??? And with the use of a
>turbulence ???

Do you mean something like this? Declare the basic shape to which you
want to apply the pigment function, declare the pigment function, and
then add them together to create the isosurface.

Note: adding the pigment function to the sphere causes the crackles to
eat into the surface (because the same threshold value is now achieved
for smaller values of x,y,z). If you want the crackles to stand proud of
the sphere you need to subtract it and increase the size of the
contained_by object.


#declare Sphere4=function{"sphere",<4>}
                    
#declare Crackles=function{pigment{
  crackle 
  turbulence 0.1
  color_map { [0 rgb 1] [1 rgb 0] }
  scale 0.5
  }
}

isosurface {
  function { Sphere4(x,y,z) + Crackles(x,y,z)*0.3 }
  method 2
  eval
  accuracy 0.0001
  contained_by{sphere{0,4}}
  pigment {rgb .9}
  finish {phong 0.5 phong_size 10}
}


-- 
Mike Williams
Gentleman of Leisure

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