POV-Ray : Newsgroups : povray.beta-test : weird white stain with beta povray v3.8.0 (not with povray v3.7.0) : Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0) Server Time
28 Sep 2022 13:03:35 EDT (-0400)
  Re: weird white stain with beta povray v3.8.0 (not with povray v3.7.0)  
From: Thomas de Groot
Date: 20 Jan 2022 11:09:40
Message: <61e98944$1@news.povray.org>
Op 20-1-2022 om 14:20 schreef Kenneth:
> I decided to go through all of the scene's include files-- turning off all of
> the light sources, correcting any out-of-gamut srgb colors to 1.0 max, and
> eliminating every object except the pentagram and the ground.
> 
> And I was still seeing the bright radiosity patches :-(
> 
> So I made my own VERY simplified scene-- posted below-- using just the bare
> necessities of Warren's code plus a few simplifications... and finally
> discovered what I think are the root causes of those bright patches. There are
> THREE reasons, as far as I can tell:
> 
> 1) The sky-sphere object is the primary cause. Comment-out that sphere, and the
> problem patches disappear.
> 
> 2) Radiosity's 'media ON' switch is also a primary problem; turn that OFF and
> the patches disappear.
> 
> 3) The media-pentagram is, I think, halfway embedded in the ground; that seems
> to definitely be adding to the problem, for some reason. Move it even slightly
> upward (like William P. mentioned), and the number of bright patches greatly
> decreases. Not completely, though, as 1) and 2) still produce some patches at
> random.
> 
> I don't know what is going on with rad's 'media on' switch; but the sky-sphere
> problem does not make any sense to me, as its colors are only 0.3 maximum...
> certainly not 'super bright'.
> 
> Maybe others here have some additional clues?
> 
[snip]

I have been very silent on this topic until now. A bit short on time.

I also came across your point (2) so thought it might (at least) be a 
radiosity/media problem. Then I thought that maybe the very thin value 
of the pentagram cylinders might play a role, so I made the cylinder 
radii much thicker while also setting intervals and samples to more 
default values and playing with sample values, but while renders where 
different, the (small) patches remained. I think that (3) might be an 
important issue here, but point (1) is really baffling.

Good work, Kenneth!

-- 
Thomas


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