And lo on 1 Jul 2004 13:16:31 -0400, Warp <war### [at] tagpovrayorg> did spake,  
saying:

> Phil Cook <phi### [at] nospamdeckingdealscouk> wrote:
>> I thought media would only function with a light_source producing a ray  
>> to
>> sample along as stated in 6.8, AFAIK ambient, like emission, doesn't
>> produce light in this way even using radiosity.
>
>   You thought wrong.

As usual

>   Media does not need light sources to show up. Radiosity doesn't check
> light sources, only the brightness of things. (Whether or not radiosity
> takes media into account at all is another issue I haven't studied.
> However, that's unrelated to light sources anyways.)

So what does it use to sample along if their are no light_source's? Does  
radiosity mean that ambient objects produce traceable light rays that  
media can use, really interested as I've never had media show up without a  
light_source regardless of radiosity or not and it would be useful to know.

//code
#declare Radiosity=on;
#declare Emission=off;

global_settings
{
#if (Radiosity)
radiosity{
media on
}
#end
}

camera{
location <10,15,10.5>
look_at <10,10,11>
}

box{0,<20,20,12> pigment{rgb 1} finish{ambient 0

#if (Radiosity)
diffuse 1
#end

} hollow
interior{media{scattering{3 rgb 0.001}
density{spotted
color_map{
[0 red 0]
[0.1 red 5]}
warp{turbulence 10}
}
}}
}

light_source{10 rgb 1}
#if (Radiosity)
#if (Emission)
sphere{10,1 pigment{rgbt 1} finish{diffuse 1} hollow
interior{media{emission rgb 1}}
}
#else
sphere{10,1 pigment{rgb 1} finish{ambient 1}}
#end
#else

#if (Emission)
sphere{10,1 pigment{rgbt 1} finish{diffuse 1} hollow
interior{media{emission rgb 1}}
}
#else
light_source{10 rgb 0.5}
#end
#end

sphere{<7,10,10>,1 pigment{rgb 1} finish{diffuse 1}}
//end code

Altering the Radiosity and Emission variables the only time I get a hint  
of red from the media is when the light_source is present.

Neither the wall nor second sphere displays any redness without the  
light_source present, neither does the emission.

I would be really really curious as to getting ambient and media working  
in this way.

--
Phil Cook

-- 
All thoughts and comments are my own unless otherwise stated and I am  
happy to be proven wrong.

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