-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Jellby wrote:
| In my experiments, I did not see any significant difference in the
output by
| fiddling with aa. According to your explanation, "samples 10 aa_level 8
| aa_threshold 0.0001" should give similar results to "samples 160
aa_level 4
| aa_threshold 0.0001", and I don't see that with the above example.
Could
| you give a more clear example?
|
	Like Slime said, you'd need to have aa_threshold set to 0 to get the
same results (if pov accepted). You can however get the same effect
by using a ridiculously small value. Moreover I wrote a little too
fast yesterday: the precise formula is (min_samples-1) * 2^aa_level +
1, assuming of course that min_samples is at least 3.

|
|>Note that this only applies to subsurface scattering simulations: eg
|>in cases when you have a very dense nearly uniform media.
|
|
| Yes, my experiments are confined to uniform media. I wonder if this
adaptive
| sampling and antialiasing is only valid for non-uniform media
(opposite to
| your sentence above), maybe uniform media makes adaptive sampling
| unnecessary...
|
| Or maybe I'm making some mistakes.
|
	It looks like povray does some optimizations in the case of a
constant density media. I did a quick check by adding the following
density to your code:

density {
~  spherical
~  color_map {
~    [ 0.0 rgb 1.0 ]
~    [ 1.0 rgb 1.0 ]
~  }
}

	Since the colormap is rgb 1.0 everywhere, this should give the same
results as the original but it doesn't. The result is pretty much
what I described in my previous post (except that samples 129 takes
much longer to render since there are a lot of pure black samples
taken that get culled in the samples 3 case). You may take a look for
example at those pictures done with aa_threshold 1e-200:

aa_level 8
samples 3
http://jeberger.free.fr/tmp/media-3-8.png
aa_level 2
samples 129
http://jeberger.free.fr/tmp/media-129-2.png

	I'd say that this is a bug.

	Note that you can probably get the correct result with a faster
render time if you disable this optimization by adding a pseudo
density like I just did...

		Jerome

PS: If the pictures aren't there, try again a bit later: as of this
posting, the second one hadn't finished rendering...

- --
******************************
*      Jerome M. Berger      *
* mailto:jbe### [at] ifrancecom *
*  http://jeberger.free.fr/  *
******************************
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.4 (GNU/Linux)

iD8DBQFB2xn0qIYJdJhyixIRAq1IAJ0aa4m+mH6jtx8gp/ak293dlMu1fACgnglN
9sSSzvW20+Za6LOJn1rGj34=
=/Pz9
-----END PGP SIGNATURE-----

Post a reply to this message