In my opinion, the 'artifacts' in this scene do not look at all unnatural,
giving the wall and ceiling a dirty worn look, which actually looks quite
good to me. Obviously only a problem if the wall should look pristine.

As for the wallpaper..I've seen worse.

Andy Cocker

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Gilles Tran wrote:

>It uses some of the recently gained radiosity knowledge posted in this
>group (Arnold settings and outdoors lighting particularly). There's only
>one light source, coming from the window. Everything else is indirect
>lighting. Balancing the light was difficult. I ended up raising the
>brightness to 2 and lowering the Kari Kivisalo light intensity.
>Assumed_gamma is 1. It took 4 hours to render on a PIII 733 at 800*600
>aa 0.3.
>

In Simons Garden I used a somewhat simmilar setup with the following 
settings:
global_settings {
   ini_option "+qr"
   ini_option "+sp16"
   ini_option "+ep4"
   assumed_gamma 1.0
   radiosity {
      count 150
      nearest_count 15
      error_bound 1
      recursion_limit 5
      low_error_factor 0.5
      gray_threshold 0.0
      minimum_reuse 0.015
      brightness 1.0
      max_sample 1
      adc_bailout 0.01/1
   }
}
All artifacts on the window-wall are a result of the compression and not 
in the original tga. I used scattering media in the window, it has a big 
influence on the lightning result of the room.


Newsgroups: povray.binaries.images
Subject: Simons Garden (~75kB)
Message-ID: <8E9DCA589seed7@204.213.191.228>
Date: 15 Dec 1999 13:02:37 -0500

Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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Gilles Tran wrote:
> I ended up raising the
> brightness to 2 and lowering the Kari Kivisalo light intensity.

I have a theory on why these changes were necessary to produce more
pleasing image than the "scientific settings".

We are used to looking at photographs on paper which have contrast
ratios ranging from 4 to 100 depending on viewing conditions and the
quality of the paper and print process.

Contrast ratio is the ratio of luminance between the brightest white and
the darkest black of a particular device or a particular environment.

Human vision can operate in an environment with a several hundred times
larger contrast ratios. Considerable research has gone into capturing
this huge dynamic range on paper with limited range so that the image
still appears natural or acceptable to the viewer.

Some kind of compression is clearly needed to "zip" a dynamic range
of a scene on paper. The most logical place to start is to limit and
compress the high intensities. Look at this graph from Kodak:
http://hammer.prohosting.com/~kkivisal/trans1_rgb.gif

Density 0 is the maximum value and density 2 is 100 times dimmer than
the maximum value. The high intensities are considerably compressed
(notice the log exposure).

--------------------------------------------------------------------------
Computer monitors can display images with contrast ratios 5-170 which
is quite similar to photographs on paper. My theory is that to get natural
looking images we should emulate the compression scheme used in photographs
as a post processing step and use the "scientific settings" on a scene. 
--------------------------------------------------------------------------

Gilles' tweak is essentially a compression scheme and this is why the
scene looks better.

Once I get 48bit pov output to Matlab I will test my theory. If someone
knows this isn't going to work please tell now :)


______________________________________________________________________
Kari Kivisalo                                  http://www.kivisalo.net

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Even your "ugly" scenes are amazing!

Jim


"Gilles Tran" <tra### [at] inapginrafr> wrote in message
news:39BE8414.E6634119@inapg.inra.fr...
> Disclaimer : this scene has no artistical merit whatsoever. It's ugly,
> but it's just a test for a radiosity setup that could be acceptable for
> a "real" interior scene.
> It uses some of the recently gained radiosity knowledge posted in this
> group (Arnold settings and outdoors lighting particularly). There's only
> one light source, coming from the window. Everything else is indirect
> lighting. Balancing the light was difficult. I ended up raising the
> brightness to 2 and lowering the Kari Kivisalo light intensity.
> Assumed_gamma is 1. It took 4 hours to render on a PIII 733 at 800*600
> aa 0.3.
>
> Some of the radiosity effects are really OK. Vicky's face is nicely lit,
> and there's even a backlit effect on her right arm. The shadow of the
> chair on the left seems good too. On the bad side, there are quite a
> number of radiosity artifacts visible on the right wall and on Vicky's
> face and right foot (note : raising the recursion level to 2 had
> appalling effects on Vicky so I left it to 1). Also, I had to add
> reflection to the chairs to make them look better, which lets me think
> that one last thing to improve in Megapov radiosity is it's ability to
> react like a regular light with some of  the texture properties
> (highlights). I didn't try to "cheat" with light groups or area lights
> to fix that, though I'll do it probably on a real pic.
>
> Credits : Victoria is the hi-detail Poser girl from Zygote (dress by
> Catherine Todd). The chairs and the library are available on my website
> (when it works). The wallpaper is just terrible.
> The whole scene (but big Vicky who weights around 15 Mb) is posted on
> p.b.s-f.
>
> G.
>
>
>


----------------------------------------------------------------------------
----

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Good... dang good. Did you see my pathetic little render of Nick?

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I think Daren Wilson wrote a patch that handled that kind of exposure
curve. It was called unlimited light, and at the time I didn't really
see any purpose for it, but when the interest in radiosity started
peaking around here it really started to sound like a good idea. 
Unfortunately his site doesn't appear to exist anymore.  Anyone still
have the original source?  It was part of the dispersion patch.

-Mike

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On Tue, 12 Sep 2000 19:36:07 -0500, MikeH <Ama### [at] aolcom> wrote:

>I think Daren Wilson wrote a patch that handled that kind of exposure
>curve. It was called unlimited light, and at the time I didn't really
>see any purpose for it, but when the interest in radiosity started
>peaking around here it really started to sound like a good idea. 
>Unfortunately his site doesn't appear to exist anymore.  Anyone still
>have the original source?  It was part of the dispersion patch.
>
>-Mike

Actually his technique didn't emulate the response of film at all. It
*was* a type of compression, but not a very good replication of film
response. Of course, he never claimed that was his goal.

Personally, I've always wanted POV to behave more like real-world
cameras and film. It makes merging images created by the two systems
much easier, and most people would think the realism of POV was
greater, if it looked "just like film."

Later,
Glen

( Remove the "7" from 7no### [at] ezwvcom to email me. )

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MikeH wrote in message <39BECBF7.613A207D@aol.com>...
>I think Daren Wilson wrote a patch that handled that kind of exposure
>curve. It was called unlimited light, and at the time I didn't really
>see any purpose for it, but when the interest in radiosity started
>peaking around here it really started to sound like a good idea.
>Unfortunately his site doesn't appear to exist anymore.  Anyone still
>have the original source?  It was part of the dispersion patch.


I've made an "infinite light" modification to POV-Ray for my
wavelenght-dependant media patch.  Should I post the source code for the
"infinite light" stuff?

Mark

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Hey, anytime you can do something like this with Pov you have done something
'those other guys' could never do. ;)

Nice setup here.

I had no idea there were such things as 'Vicki girls' out there.

Grim

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Kari Kivisalo wrote:
> 
> I have a theory on why these changes were necessary to produce more
> pleasing image than the "scientific settings".
> 
[...]

Sounds reasonable (although i *try* to judge realism from comparing to reality
and not to photos). What we should not forget is, that the "scientific settings"
are only a simplified mathematical model for reality, that maybe produces good
results in many cases but that is far from being perfect.  

Christoph

--
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/

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