[running Windows 10. Most of my notes are a recap of what has already been
said.]

According to the documentation, POV-ray's disc object is actually a transparent
plane with a colored circle on it(?). So there are a lot of overlapping
transparent planes in Paul's scene!

Using his original scene code as-is:
In v3.7.0:
The parsing of the include file takes a very long time, then the render fails
about 1/3rd of the way down during the first animation frame. That render area
seems to coincide with a very dense collection of discs in the far distance.

Interestingly, by removing the finish {'transmits'} from the discs, the entire
scene renders OK.

In v3.8 beta 1:
The render crashes (hangs) during the parsing of the first frame. However, by
adding 'emission 0' to the disc's finish{...} as William P. suggested-- to
eliminate all of the many text warnings that are generated concerning a
'too-high ambient value'-- the scene renders OK. Nice call, William!

Also, v3.8 parses the scene at least 10X faster than 3.7.

-----------
In several of the posted renders here, I noticed what look like
coincident-surface problems on some of the discs. I set up a simple 2-disc scene
to see if I could recreate that, where the disc-planes exactly overlap.  I don't
see such a problem-- but if I reverse the 'normal' of one of the discs,
coincident surface artifacts do show up. It is probably due to numerical
precision under-the-hood.

-----------
#version 3.8;
global_settings{assumed_gamma 1.0 max_trace_level 5}

camera {
  perspective
  location  <.1, .1, -1.5>
  look_at   <0, .3,  0>
  right     x*image_width/image_height  // aspect
   angle 50
}

background{rgb .1}

// left
disc {
    <-.25,.5,.7>, <0,0,1>, .5
texture{
pigment{rgb <.5,1,1>}  // LIGHT BLUE-GREEN
finish{ambient 1 emission 0 diffuse 0}
       }
interior_texture{
pigment{rgb .5*<1,.2,.2>}  // DARK RED
finish{ambient 1 emission 0 diffuse 0}
                }
    }

// right:
// Change the z-normal to -1 to see the coincident-surface effect.
disc {
    <.25,.5,.7>, <0,0,1>, .5
texture{
pigment{rgb <.2,1,.2>}  // GREEN
finish{ambient 1 emission 0 diffuse 0}
       }
interior_texture{
pigment{rgb <0,.5,1>}  // SKY BLUE
finish{ambient 1 emission 0 diffuse 0}
                }
    }

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