In a related test-scene employing a hexagonal prism:

camera {
  location <2,1,-2>
  look_at <0,0,0>
}

light_source { <0,20,0> color rgb 1 }

plane {
  y, -1
  pigment { checker color rgb 0 color rgb 1 }
}

prism {
  linear_sweep
  -0.5,0.5,7
  <-1,-0.5>,<-1,0.5>,<0,1>,<1,0.5>,<1,-0.5>,<0,-1>,<-1,-0.5>
  pigment { color rgbt <1,0,0,0.9> }
  interior {
    ior 1.5
    dispersion 1.1
    dispersion_samples 25
  }
}

There are again marked differences between the output of pov 3.6 and pov
3.7beta11c-ss2:
1. In 3.7 'dispersion' has an effect on all facets of the prism, which is
probably a good thing; 3.6 shows no dipersion-effect when looking straight
through the prism.
2. However, the top of the prism in 3.7 produces a highly complex and pretty
awful looking pattern wheras 3.6 produces gives slight colour attenuation at
the top facet which seems much more consistent with 'the real thing'.

Jeroen.

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