TC schrieb:

> Now: under 3.7 I get a grey background, under 3.6 everything is fine. What 
> am I doing wrong? Have there been changes to the behaviour of photons? Or is 
> something broken in 3.7?

Apparently there is a /lot/ of stuff wrong in 3.7 regarding this scene.

So far I found the following issues:

* Cylindrical light sources and photons don't appear to mix well in 
POV-Ray 3.7.

* POV-Ray 3.7's current dispersion implementation is bogus in the 
multiple respects:

- At the first interface taking account dispersion, POV-Ray 3.7 does 
split up the RGB ray into multiple "spectral" ones, but fails to apply 
dispersion at this initial interface.

- When transmitting from one object that has dispersion directly into 
another one that doesn't, POV-Ray 3.7 fails to take into account the 
dispersion effects that should occur at this interface.

- At all other subsequent interfaces, POV-Ray erroneously applies the 
same correctional factor to the IOR that should have been applied at the 
very first dispersion interface.


I'll file a bug report to bugs.povray.org, and try to clean up that mess.

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