During Internet outages, I have been trying to organize my old scenes 
that never got properly integrated into my current directory structure 
when I bought a new computer in 2006.  For most of these scenes the 
images were lost, so I'm rerendering them.

One scene was to trace the path of light through two prisms using media 
photons.  Obviously these scenes were written prior to v3.7, so I first 
tried rendering it with v3.6.  That turned out horrendously slow (how 
did we ever survive back then?), so I tried with v3.7 for the SMP speed 
advantage, but the media photons did not show.  After some 
investigation, it turned out that removing a looks_like in a totally 
unrelated light source restored the photons!

Image beam0-pared-by37-1.jpg was rendered by v3.7.0 with all the 
original elements of the original scene file.  The media photons are 
missing.  V3.7.1.rc1 yields the same result.

Image beam0-pared-by37-2.jpg was rendered by v3.7.0 with the looks_like 
removed, and the media photons are traced.  (As it turned out, SMP saved 
a lot less time than one might think, as 2/3 of the elapsed time was 
taken by just one render block, and a second block used almost all the 
rest!)

Image beam0-pared-by36-1.jpg was rendered by v3.6.1 with all the 
original elements of the original scene file, and the media photons are 
traced.

I will post the scene file and the statistics logs in p.b.s-f.

POV-Ray versions:
   3.6.1 (g++ 3.4.1 @ i686-pc-linux-gnu)
   This is an official version prepared by the POV-Ray Team.

   3.7.0.unofficial [no source code alterations]
   Compilation settings:
     Build architecture:  x86_64-unknown-linux-gnu
     Built/Optimized for: x86_64-unknown-linux-gnu (using -march=native)
     Compiler vendor:     gnu
     Compiler version:    g++ 4.8
     Compiler flags:      -pipe -Wno-multichar -Wno-write-strings 
-fno-enforce-eh-specs -s -O3 -ffast-math -march=native -pthread

OS: openSUSE 13.2 (GNU/Linux)

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