Wasn't it Tim Nikias who wrote:
>> SNIPPED Function-Pigment/Pattern-Issue
>
>Ah, thank you, now I understand. It does make sense after all... ;-)
>
>> To make things even better, you could try rewriting the whole thing to
>> use patterns instead of pigments. The code will probably be simpler and
>> the processing more efficient without those unwanted .blue and .green
>> channels.
>
>Care to give a small starter with how to use patterns with functions? What I
>do now is simply use a pattern and use a colormap ranging from rgb 0 to rgb
>1, but not just {[0 rgb 0][1 rgb 1]}, so I'm not sure if that is possible
>with just patterns.

Patterns naturally produce a value in the range 0 to 1. The colour map
specifies what colours correspond to those values.
So by using {[0 rbg <0,0,0>][1 rgb <1,1,1>]} and then using only the red
channel (.x) you actually just get back the value that the pattern
returned in the fist place.

So if you had something like

#declare F1=function {
  pigment {
   granite turbulence 1 
   colour_map {[0 rgb 0][1 rgb 1]}
  }
}
#declare F2 = function {F1(x,y,z).x}


You can, instead, write just

#declare F2=function {
  pattern {
    granite turbulence 1
  }
}

-- 
Mike Williams
Gentleman of Leisure

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