> Vincent Le Chevalier  wrote in message <471d1c2f$1@news.povray.org>:
>> 								Or 
>> diminishing that of the sky_sphere.
> 
> I do not know how to do that. Is it possible?

It is not possible with a sky_sphere because you cannot specify a 
finish. However, you can do that with a really big hollow sphere 
centered on the origin.

With this method, you can specify an ambient value, but you must set 
diffuse to 0, otherwise the sky sphere will be illuminated by the sun, 
and it becomes impossible to adjust their brightness separately.

And then you can play with the diffuse component of the objects (that 
can be done in the #default block).

The next problem is that POV-Ray has no exposure control, so in fact it 
will not necessarily look right when you diminish the ambient value of 
the sky sphere. It will get you a very dark sky...

In my experience it is better to first adjust the ambient of the 
sky_sphere to obtain the right color in the places where you see the 
sky. Then, set the sunlight and the diffuse component to get the 
lighting you like. Playing with these three things it's possible to 
obtain many results...

I'm not quite sure it's the right way to do it though ;-)

Here is an example:

#if(1)
global_settings {
     radiosity {}
}
#default {finish{ambient 0}}
#end
// Use this to control the brightness of the shadows
#default {finish{diffuse 0.35}}

plane {
   y, 0
   pigment { rgb <0.804, 0.569, 0.494> }
   normal { bumps 0.5 }
}

union{
     sphere{y,1}

     cylinder {
         0,3*y,0.5
         translate <2,0,-2>
     }
     pigment{rgb 1}
     scale 30
}

camera {
   location <220, 50, 0> look_at <0, 0, 0>
}

sphere {
     0,1
     texture {
         pigment {
             gradient y
             color_map {
             [ 0.0 rgb <0.9, 0.9, 1> ]
             [ 0.5 rgb <0.3, 0.3, 1> ]
             }
         }
         finish {
             // Use this to adjust the brightness of the sky
             ambient 1
             diffuse 0 }
     }

   scale 200000
   hollow
}

light_source {
     <100000, 100000, -100000>
     rgb <1,1,0.9>*6 // And this to adjust the sunlight
}


-- 
Vincent

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