> 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:

Which POV-Ray version and platform are you using? I could not reproduce your
results, I got quite the same effect I was getting with constant density:
overbright media with "aa_level 8 samples 3" even if I introduce a slope in
the color_map (then the media is different, of course, but still not
similar when the samples and aa_level are varied).

-- 
light_source{9+9*x,1}camera{orthographic look_at(1-y)/4angle 30location
9/4-z*4}light_source{-9*z,1}union{box{.9-z.1+x clipped_by{plane{2+y-4*x
0}}}box{z-y-.1.1+z}box{-.1.1+x}box{.1z-.1}pigment{rgb<.8.2,1>}}//Jellby

Post a reply to this message

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

Slime wrote:
| I was under the impression that the adaptive sampling only took
into account
| the values of the media density, and not the lighting.
|
	Nope, adaptive sampling takes into account the total contribution of
the samples to the resulting color. For emission media, this is only
the density, for absorption it depends on whatever's behind the
media, and for scattering you add the light source(s).

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

iD8DBQFB3DwrqIYJdJhyixIRAjpyAJ4s+yIsb7IQDzQT9u9TogE48TaBsQCdHBV7
2XU+XpIdy//srMOljpobRNg=
=ICRU
-----END PGP SIGNATURE-----

Post a reply to this message

In article <41db3ff6@news.povray.org>, "Slime" <fak### [at] emailaddress> 
wrote:

> > You are essentially correct, except that the adaptive sampling
> > *should* take care of that.
> 
> I was under the impression that the adaptive sampling only took into account
> the values of the media density, and not the lighting.

If it does so, it should probably be considered a bug...I can't see how 
it would discard any samples that don't actually need to be taken.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

Post a reply to this message

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

Jellby wrote:
| Which POV-Ray version and platform are you using? I could not
reproduce your
| results, I got quite the same effect I was getting with constant
density:
| overbright media with "aa_level 8 samples 3" even if I introduce a
slope in
| the color_map (then the media is different, of course, but still not
| similar when the samples and aa_level are varied).
|
	I was using MegaPov 0.7 on linux. A quick try with version 3.6.1
shows the same results as you. I think MP0.7 has the correct behavior
here...

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

iD8DBQFB3EayqIYJdJhyixIRAgc+AKCNfpPRAuN5CIiwOvqLAWOYCtUKUgCgiPvL
9RDWgfaY0weIFB20JealIlU=
=Mtl/
-----END PGP SIGNATURE-----

Post a reply to this message

Mike Raiford <mra### [at] hotmailcom> wrote:
> Someone care to explain the following from the manual:
>
> "It's usually best to only use one interval with method 3. Too many
> intervals can lead to artefacts, and POV will create more intervals if
> it needs them."
>
> It seems with one interval, I don't get good results. If I up the
> intervals to 5 or 10, it seems to work better, but is slower in general.
>
> Anyone have any clue about the relationship and why the manual asks to
> use only 1 interval?
>
>
> --
> ~Mike

Btw, I think it would be a great idea to put the valuable info learned here
into the new POV-Ray Wiki at http://www.wikipov.org/

(see this thread:
http://news.povray.org/povray.general/thread/%3C41dd4071%40news.povray.org%3E/?mtop=13
)

George

Post a reply to this message