I am by no means an expert, but here are some suggestions.
The reason you get a dark image is quite obvious: the media is very
thick. Decreasing extinction will make the image lighter, but it will
not make the media more transparent. A highly directional scattering
model would help, but only when viewed at certain angles, i.e. nearly
parallel or anti-parallel. Another way would be to increase the
intensity of the light source - I see no reason why this shouldn't make
the light cone brighter.
The way density/colour_map and scattering/emission/absorption values
work together is pretty simple; if I'm not mistaken they are simply
multiplied together.

Margus


Nieminen Juha wrote:
> 
>   I'm really confused with this media thing. If someone could enlighten me.
> 
>   Suppose this simple scene:
> 
> //-----------------
> global_settings { ambient_light 2 }
> camera { location -z*25+y*7 look_at 0 angle 35 }
> light_source
> { (-x*10+y*5)*4, 2
>   spotlight point_at 0 radius 5 falloff 6
> }
> plane { y,-2 pigment { checker rgb 1, rgb .5 } }
> plane { -z,-2 pigment { checker rgb 1, rgb .5 } }
> cylinder { -y*2, y*2, 1 pigment { rgb z } finish { specular .5 } }
> //-----------------
> 
>   Now I want some media there so that I can see the light beam and the
> cylinder casting the shadow on the dust. I add this:
> 
> media
> { intervals 20
>   scattering { 3, rgb .01 }
>   confidence .9999
> }
> 
>   I get some slightly visible media.
>   Now I want to make the media stronger so that I could see a strong bright
> white beam of light and a clear shadow of the cylinder on the air.
>   I just can't find a way to do it. If I make the color of the scattering
> brighter, eg:
> 
>   scattering { 3, rgb .05 }
> 
> I just get an extremely dark (???) image instead of getting a brighter one.
>   If I specify density, that doesn't help either. With a higher density
> (eg. density { rgb 4 }) I get a dark image and with a lower density (eg.
> density { rgb .1 }) I get an almost invisible media. Modifying the density
> seems to work exactly like modifying the color of the scattering.
>   Changing the type of scattering (from the type 3 I used here) doesn't help
> either. I'm running out of parameters to modify...
> 
>   How can I get a bright white beam of light? I just can't figure it out.
> With the atmosphere in povray3.0 it was easy.
> 
> --
> main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
> ):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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