In my last image I came across a bug in the dispersion code that other
people also seems to have found.
I posted a small part of the image showing the bug in a message titled
"Dispersion bug?" in p.b.i. I got an answer pointing me to the thread "Lucy
in the sky with diamonds". Reading it I found out that the bug is present in
the official win32 build and disappears if you recompile with MSVC. I could
not find any more information about the bug so I have started to make an
investigation.

I made a little test scene to see when the bug shows up.
The source is posted in p.b.s-f and the results on my computer is posted in
p.b.i.

The error that happens is that the red channel is missing from the image at
some places resulting in areas that are blue-cyan-green. The red is not only
missing from the refracted part but also from reflections and specular
highlights.
I think that the problem shows up when total internal reflection occurs
because the error in the image is near the edge of the sphere.
It seems it is only when you use despersion in combination with both fresnel
reflection and the conserve_enegry keyword that the bug is there.

I would like that other people try my test scene and post the result here so
we can get a list of what versions have the bug.

My system:
PovRay 3.5 win32 official build, Windows XP SP1, Athlon XP 2400+ => Buggy

--
Daniel Nilsson

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