Tested with the basic scene template with +AM1 and +AM2
- The method 2 scene is noticeably brighter (in both TGA and PNG versions)
- I suspected a gamma problem but I can't correct one image to match the 
other using only gamma correction. For instance, the blue in the AM2 scene 
is slightly greener.

Of course, this could be caused by the 20% extra sampling, I don't know.

G.

-- 
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters

Post a reply to this message

Gilles Tran wrote:
> Tested with the basic scene template with +AM1 and +AM2
> - The method 2 scene is noticeably brighter (in both TGA and PNG versions)
> - I suspected a gamma problem but I can't correct one image to match the 
> other using only gamma correction. For instance, the blue in the AM2 scene 
> is slightly greener.
> 
> Of course, this could be caused by the 20% extra sampling, I don't know.

No, it was indeed a bug.  This will be fixed  in the next beta.

As far s the 20% is concerned, to explain that a bit better, what currently 
happens is, if you look at the algorithm description in the manual at 
<http://www.povray.org/documentation/view/3.6.1/223/> you will notice that a 
cross of five sample is taken for subdivision in method 2.  Now what happen 
is that if in all four quadrants a cross is sampled, four samples overlap in 
the same position.  And the current code does not take care of not sampling 
those four points again.  Fortunately, most of the time not all four 
quadrants need to be sampled, so 20% more samples only is the worst case (if 
all four quadrants need to be supersampled 16 samples should be taken, but a 
total of 20 are taken).

	Thorsten

Post a reply to this message