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From: Mike Kost
Subject: Generating Good Skies
Date: 1 Feb 2006 18:49:33
Message: <43e1490d@news.povray.org>
Hey All,

I've been spending a fair amount of time thinking about how to generate
realistic looking sky spheres. Most of my efforts have been focused on
translating real-world pictures into appropriate looking sky spheres in a
time-efficient way. Here are my latest results.

Mike
--
http://povray.tashcorp.net


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Attachments:
Download '1.jpg' (26 KB) Download '2.jpg' (25 KB) Download '3.jpg' (23 KB) Download '4.jpg' (27 KB)

Preview of image '1.jpg'
1.jpg

Preview of image '2.jpg'
2.jpg

Preview of image '3.jpg'
3.jpg

Preview of image '4.jpg'
4.jpg


 

From: Skip Talbot
Subject: Re: Generating Good Skies
Date: 1 Feb 2006 19:25:03
Message: <43e1515f@news.povray.org>
You've got the colors down... now you just need another gradient running 
in the opposite axis to wash them out.  I always fake the sun with a 
spherical texture too:

http://www.drugrecognition.com/skip/3d/highres/st400-2.jpg

Skip


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From: Thomas de Groot
Subject: Re: Generating Good Skies
Date: 2 Feb 2006 03:13:16
Message: <43e1bf1c@news.povray.org>
"Skip Talbot" <Ski### [at] aolcom> schreef in bericht
news:43e1515f@news.povray.org...
> You've got the colors down... now you just need another gradient running
> in the opposite axis to wash them out.  I always fake the sun with a
> spherical texture too:
>
Hey! That other gradient is a good idea! Never thought of that!

> http://www.drugrecognition.com/skip/3d/highres/st400-2.jpg
>

Beautiful image.

Thomas


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From: Sebastian H 
Subject: Re: Generating Good Skies
Date: 2 Feb 2006 06:09:41
Message: <43e1e875$1@news.povray.org>
Mike Kost wrote:
> http://povray.tashcorp.net

Your sky sphere tutorial is really helpful.
I'll try it out on the weekend. Good work.

Sebastian


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From: Mike Kost
Subject: Re: Generating Good Skies
Date: 2 Feb 2006 11:11:02
Message: <43e22f16@news.povray.org>
Skip Talbot wrote:
> You've got the colors down... now you just need another gradient running
> in the opposite axis to wash them out.  I always fake the sun with a
> spherical texture too:
> 
> http://www.drugrecognition.com/skip/3d/highres/st400-2.jpg
> 
> Skip

Skip,

Great idea to get the dimming effect. I took a quick swing at it and I like
the results...

Here's my sky_sphere:

  sky_sphere {
      pigment {
          function { max(min(y,1),0) }
          color_map { cm_realsky_01 }
      }
      scale (1/2)
      pigment {
          function { abs(max(min(x,1),-1)) }
          color_map {
              [ 0.0 rgbt <0.1, 0.1, 0.1, 1.0> ]
              [ 0.2 rgbt <0.1, 0.1, 0.1, 1.0> ]
              [ 0.6 rgbt <0.1, 0.1, 0.1, 0.9> ]
              [ 1.0 rgbt <0.1, 0.1, 0.1, 0.6> ]
          }
      }  
  }


Mike
--
http://povray.tashcorp.net


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Attachments:
Download 'final2.jpg' (25 KB)

Preview of image 'final2.jpg'
final2.jpg


 

From: Mike Kost
Subject: Re: Generating Good Skies
Date: 2 Feb 2006 15:47:17
Message: <43e26fd4@news.povray.org>
Sebastian H. wrote:

> Mike Kost wrote:
>> http://povray.tashcorp.net
> 
> Your sky sphere tutorial is really helpful.
> I'll try it out on the weekend. Good work.
> 
> Sebastian

Thanks - I'm glad it's helpful. 

I've started using a series of Python scripts to automate the whole process,
so what I'm doing now has advanced beyond my tutorial. Something new to
write-up when it settles down, I guess.

Mike


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From: Skip Talbot
Subject: Re: Generating Good Skies
Date: 2 Feb 2006 20:41:09
Message: <43e2b4b5@news.povray.org>
Looks great, Mike.  What are you using for the water?

Skip


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From: Mike Kost
Subject: Re: Generating Good Skies
Date: 2 Feb 2006 22:06:53
Message: <43e2c8cc@news.povray.org>
Skip Talbot wrote:
> Looks great, Mike.  What are you using for the water?
> 
> Skip

It's a bump mapped plane based on a functions from Chrisoph Horrman's
Realistic Water with POV-Ray tutorial
(http://www.imagico.de/pov/water/index.html). The water sdl is below (a
full scene file can be found off of here
http://povray.tashcorp.net/tutorials/qd_realskysphere/)

plane {
    y, 0.0
    material {
        texture {
            pigment { color rgbt <0.8, 0.9, 1, 0.9> }
            finish {
                ambient 0.0
                diffuse 0.0
                reflection {
                    0.2, 1.0
                    fresnel on
                }
                specular 0.4
                roughness 0.003
            }
            normal {
                function {
                    f_ridged_mf(x/9, y, z/5, 0.1, 3.0, 7, 0.7, 0.7, 2)
                } 0.6
                turbulence 2.5
                scale 0.13
            }
        }
        interior { ior 1.3 }
    }
}

All the best,

Mike
--
http://povray.tashcorp.net


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From: Paolo Gibellini
Subject: Re: Generating Good Skies
Date: 3 Feb 2006 04:13:52
Message: <43e31ed0$1@news.povray.org>
Nice tutorial!
;-)
Paolo

> "Mike Kost" wrote:

> It's a bump mapped plane based on a functions from Chrisoph Horrman's
> Realistic Water with POV-Ray tutorial
> (http://www.imagico.de/pov/water/index.html). The water sdl is below (a
> full scene file can be found off of here
> http://povray.tashcorp.net/tutorials/qd_realskysphere/)
>


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From: Abe
Subject: Re: Generating Good Skies
Date: 3 Feb 2006 15:30:00
Message: <web.43e3bada85aa7b8ffc69adc50@news.povray.org>
Mike Kost <con### [at] povraytashcorpnet> wrote:
> Sebastian H. wrote:
>
> > Mike Kost wrote:
> >> http://povray.tashcorp.net
> >
> > Your sky sphere tutorial is really helpful.
> > I'll try it out on the weekend. Good work.
> >
> > Sebastian
>
> Thanks - I'm glad it's helpful.
>
> I've started using a series of Python scripts to automate the whole process,
> so what I'm doing now has advanced beyond my tutorial. Something new to
> write-up when it settles down, I guess.
>
> Mike

How about letting POV do the work? I was able to do a reasonable facsimile
of the sampling process in POV sdl.

#declare Pigment_img=pigment{image_map{png "skygrad.png" interpolate 0}}

#declare Ximg_dim=48;
#declare Yimg_dim=270;

#declare Cmap_dim=30; //number of color map entries
#declare Xsamp=5;  //averageing horizontally across the image
#declare Sample_bias=2; //bias the number of samples towards the bottom (>1)
or top (<1) of the image


#macro GetColor(SampleP, GradientFunc)
 #local SamplePX=SampleP.x;
 #local SamplePY=SampleP.y;
 GradientFunc(SamplePX, SamplePY, 0)
#end

#declare SkyColorMap=
color_map{
  #declare i=0;
  #while (i<Cmap_dim)
   [pow(i/(Cmap_dim), Sample_bias)
     #declare j=0;

     #declare Color_vector=(
     #while (j<Xsamp) //loop to average over several horizontal samples
       #declare XSamplePoint=(.5+int(Ximg_dim*j/Xsamp))/Ximg_dim;
       #declare YSamplePoint=pow((.5+int(Yimg_dim*i/Cmap_dim))/Yimg_dim,
Sample_bias);

       +GetColor(<XSamplePoint, YSamplePoint>,
function{pigment{Pigment_img}})

       #declare j=j+1;
     #end
     )/Xsamp;

     color rgb Color_vector
     ]
   #declare i=i+1;
  #end
}

Abe


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