In article <3875f3e3@news.povray.org>, "Gail Shaw" 
<gsh### [at] monotixcoza> wrote:

> Do you have an example handy? I tried that yesterday and my entire 
> container
> was filled with media, instead if the spiral that the function describes.

Here is a simple function that I came up with, it should be a good start 
for the density function.
The media itself needs a lot of work, though.

box {<-4, 0,-4>, < 4, 10, 4>
   pigment {color White filter 1}
   hollow
   interior {
      media {
         scattering {1, color White*10 extinction 0.15}
         intervals 1 samples 20, 20
         variance 1/128 confidence 0.99
         method 3
         density {
            function {
               max(0,min(1,
                  (y*0.25+noise3d(x,y,z))-
                  (
                     sqr(x+noise3d(x,y,z))+
                     sqr(z+noise3d(x,y,z))
                  )
               ))
            }
            color_map {
               [0 color Black]
               [1 color White]
            }
         }
      }
   }
}

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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