And lo on Thu, 01 Jul 2004 16:12:44 +0100, Phil Cook  
<phi### [at] nospamdeckingdealscouk> did spake, saying:

> And lo on Thu, 01 Jul 2004 09:56:17 -0500, Mike Raiford  
> <mra### [at] hotmailcom> did spake, saying:
>
>> Mike Raiford wrote:
>>
>>> Phil Cook wrote:
>>>>  AFAIK ambient, like emission,
>>>> doesn't  produce light in this way even using radiosity.
>>
>> Erm.. Ambient does produce light, but the light does no react with the  
>> media. Media affects radiosity, radiosity does not affect media.
>>
>
> *in this way* :)
>
> 3.7.5: "POV-Ray uses the ambient keyword to determine how much light  
> coming from the ambient light source is reflected by a surface" and
>
> 6.7.3.1 "Computing real ambient light would take far too much time, so  
> we simulate ambient light by adding a small amount of white light to  
> each texture whether or not a light is actually shining on that texture."
>
> So if you think about it what is the location of the ambient light  
> source and how do you trace a ray along it it through the media to  
> sample along?
>
> Gods I've been fiddling with media to long :P

And it's driving me nuts :)

In theory I suppose you could back-track for ambient light from the camera  
to the surface and use that as a ray to sample along I don't know if  
that's how ambient light interacts with media in povray

//simple code
global_settings{
radiosity{media on}}

//switch these round for comparision
//light_source{z*12 rgb 1}
cylinder{0,z*5 1 pigment{rgb 1} finish{ambient 1} translate z*10}

cylinder{0,z*7 8 pigment{rgbt 1} translate z*8 hollow  
interior{media{scattering{3, rgb 0.1}}}}
//end code

note that if you lower the scattering rgb the ambient cylinder appears  
brighter and vice versa, which indicates something is being altered by the  
media, but you don't get the spread light effect as with the light-source.

Anyone know?

--
Phil Cook

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

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