> Alain wrote:
> 
>> It could be a max_trace_level isue. Try adding 2 to it and use the 
>> glass pane.
> 
> I had max_trace_level set to 20 with no special value for photons,
> as far as I understand photons should then also use 20. I tried 22
> both in global and photon block but it didn't make any difference.
> 
> I attached two test renders, the version without pane shows a
> bright line to the right of the rainbow. Also, it gives wildly
> different photon statistics (count is set to 20.000, with the
> water using 7 dispersion_samples).
> 
> // With window pane
> 
> Number of photons shot:           39761
> Surface photons stored:          197605
> 
> // Without window pane
> 
> Number of photons shot:           31731
> Surface photons stored:           64749
> 
> 
> I noticed the bright line goes away if I change the light source
> from "parallel" to a normal point light. The statistics remain
> similar however.
> 
> 
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> 
> 
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> 
The window pane have a frame that cast a shadow near the base of the 
glass. The caustics in that area are still there without, but are less 
visible on a brighter surface. Try removing the glass itself, but leave 
it's frame.
Even with your settings, the window can still affect the photons coming 
from another object. At least, that's what the documentation seems to imply.
With the window pane, the rainbow is brighter and cover a whider arc.

Without the pane, the bright line that you mention is very hard to see 
here, even with the brightness pushed to the max. I also need to sellect 
the two images and unsellect the window to be able to see it. Tested on 
two different monitors.



Alain

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