I am a geologist and software engineer trying to use POV-Ray to visualise
volumetric data encoded in binary df3 files.  I have a C++ program which
generates multiple df3 files - one df3 volume for each object in my
simulation - and also generates the .pov scene files for each of these and
a top level file to combine these into a single scene and set up a camera.
My own work is inspired by Paul Bourke's work at:

http://astronomy.swin.edu.au/~pbourke/povray/df3/

When rendering a scene containing only a single df3 media volume everything
works fine, but when I try to combine multiple df3 media volumes into a
single scene I run into problems.  The media volumes nearest to the camera
seem to obscure those behind. This even happens when large parts of the
volume are empty (i.e. have zero values) Note that several volumes may
overlap in space.

Each of my volumes is created in its own scene file containing code like the
following:

box {
0 , 1
  texture {
    pigment {
      rgbft 1
    }
  }
  interior {
    media {
      intervals 300
      samples 1, 20
      emission <0.005, 0.005, 0.005>
      absorption <0,0,0>
      scattering { 1,<0,0,0> }
      confidence 0.9999
      variance 1/900
      method 3
      density {
        density_file df3 "St_Bees_1.df3" interpolate 0
        density_map {
          [0 rgb 0 ]
          [1 rgb <1,0.0509804,0> ]
        }
      }
    }
  }
  hollow
  no_shadow
  scale <2400,1800,1900>
  translate <-53.0267,-1586.02,-750.003>
}

Each of these files is then #included into a top-level file which sets up
the camera.  Am I using the wrong parameters on my media to allow for
transparency? The effect I'm looking for is one of transparent glowing fog
with a density proportional to the value in my df3 files.  This works great
except when combining multiple volumes!

Any suggestions welcome.

Many thanks for your help,

Rob

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