POV-Ray : Newsgroups : povray.newusers : Photon mapping: strange light distribution? Server Time
29 Jul 2024 18:20:14 EDT (-0400)
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From: Artur Rataj
Subject: Photon mapping: strange light distribution?
Date: 26 Jul 2005 06:35:00
Message: <web.42e60f6d72a4b0e9d8b2350@news.povray.org>
Hello!

I have modeled a rectangular frame from a sphere_sweep, and put a light
inside the right part of the top cylinder. But in the rendered image the
left part of the cylinder is more lit than the right part. There is only
a small light spot at the light source. I do not know if it really would
look like that or is it some artefact?

Here is the resulting image: http://www.iitis.gliwice.pl/~arataj/a.tga

Here is the POV file:

#include "colors.inc"
#include "shapes.inc"
#include "textures.inc"

global_settings {
  assumed_gamma 2.2
  max_trace_level 7

  photons {
     count 150000
     max_trace_level 7
     adc_bailout 0.1
     media 150
     radius ,1.5
   }

}

camera {
   orthographic
   location <0.2, 2.5, -0.15>
   up  <0, 0.75, 0>
   right <1, 0, 0>
   look_at <0.2, 0.0, -0.15>
}

   sphere_sweep {
     linear_spline
     5,
     <-1, 0.5,  0.5>, 0.2
     < 1, 0.5,  0.5>, 0.2
     < 1, 0.5, -0.5>, 0.2
     <-1, 0.5, -0.5>, 0.2
     <-1, 0.5,  0.5>, 0.2
     scale <0.2, 1.0, 0.2>
     translate <0, 0.3, 0>

      translate <0.0, 0.5, -0.0>
      pigment { color <0.95, 0.95, 0.95> filter 0.95 }
      hollow on

      interior{
         ior 1.45
         media {
           scattering {
              1, rgb <0.1, 0.2, 0.3>
           }
         }
      }
      finish {
         ambient 0.2
         diffuse 0.02
         reflection 0.4
         specular 1.0
         roughness 0.0001
      }
      photons {
         target
         refraction on
         reflection on
         collect on
       }
   }

light_source {
     < 0.5, 0.5,  0.5>
     colour red 0.5 green 0.5 blue 0.5
     scale <0.2, 1.0, 0.2>
     translate <0, 0.3, 0>
     translate <0.0, 0.5, -0.0>
}

Cheers,
Artur


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From: Artur Rataj
Subject: Re: Photon mapping: strange light distribution?
Date: 26 Jul 2005 06:50:00
Message: <web.42e615186f6c7df0e9d8b2350@news.povray.org>
I thought the image is in the TGA format, but it appeared it is a PNG, so
here is another link with the right extension:

http://www.iitis.gliwice.pl/~arataj/a.png


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From: PM 2Ring
Subject: Re: Photon mapping: strange light distribution?
Date: 26 Jul 2005 22:00:00
Message: <web.42e6e9ff6f6c7df0ad93754b0@news.povray.org>
"Artur Rataj" <nomail@nomail> wrote:
> Hello!
>
> I have modeled a rectangular frame from a sphere_sweep, and put a light
> inside the right part of the top cylinder. But in the rendered image the
> left part of the cylinder is more lit than the right part. There is only
> a small light spot at the light source. I do not know if it really would
> look like that or is it some artefact?

Light sources in POV are invisible, unless you use the looks_like attribute.


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From: Artur Rataj
Subject: Re: Photon mapping: strange light distribution?
Date: 27 Jul 2005 04:25:00
Message: <web.42e744506f6c7df0e9d8b2350@news.povray.org>
"PM 2Ring" <nomail@nomail> wrote:

> Light sources in POV are invisible, unless you use the looks_like attribute.

I know, but the lights were in scattering media. I modeled some symmetric
things that POVRAY rendered very asymmetric usign photon maps. Especially,
making the material very reflective can make the photon map rendering in
POVRAY 3.6 very strange and with unstable results.


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From: PM 2Ring
Subject: Re: Photon mapping: strange light distribution?
Date: 27 Jul 2005 05:10:01
Message: <web.42e74e4a6f6c7df0ef8bd73c0@news.povray.org>
"Artur Rataj" <nomail@nomail> wrote:
> "PM 2Ring" <nomail@nomail> wrote:
>
> > Light sources in POV are invisible, unless you use the looks_like attribute.
>
> I know, but the lights were in scattering media.

Good point. I haven't done very much with media on this slow old machine, so
I'll have to leave this question for the experts.

> I modeled some symmetric
> things that POVRAY rendered very asymmetric usign photon maps. Especially,
> making the material very reflective can make the photon map rendering in
> POVRAY 3.6 very strange and with unstable results.

Unstable is one way to describe it... frustrating is another. I tried to do
diamonds in fog & gave up in confusion. :(


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