In article <opsarz4stqefp2ch@news.povray.org>,
 "Phil Cook" <phi### [at] nospamdeckingdealscouk> wrote:

> Might be bad phrasing on my part I'm not arguing with you I'm am genuinely  
> trying to understand this, the ambient light_source has no point source  
> how does Povray calculate the angle of the light ray from the surface in  
> order to sample along it?

It doesn't. Ambient light does not come from any direction, that's why 
it makes things flat colored instead of shaded.


> lets put it another way. I shine a parallel  
> light into a scattering media box that has a hole cut in it, the result is  
> a 'light beam' through the media, I now substitute the parallel  
> light_source for an ambient 1 plane will this still produce the 'light  
> beam' with radiosity enabled. Hmm just tried it,seems to be a no.

No, it won't. Radiosity does not affect media, doing so would be either 
extremely slow or memory consuming. However, media can optionally affect 
radiosity. This is slow, but workable.


> Ah here we are, what are they seen with?

They block light. Scattering media without direct light is essentially 
absorbing media.


> All I can assume is that with  
> radiosity a ray is being produced as a reflection from the surface from  
> the ambient light_source to any surrounding surfaces and that the media  
> affects this or uses this to sample along. I saw this when I altered a  
> scattering media in front of an ambient 1 object and saw the apparent  
> brightness drop, however the media was not illuminated around the object.  
> In the code previously the media was red scattering with an white ambient,  
> if the radiosity was being affected by the media why did the object  
> continue to appear white when it should have been red?

This assumption is wrong. It can't work this way...at least, not in a 
reasonable period of time. What you describe would be how a forward 
raytracer would do it. Global photon mapping could do the job, but the 
memory requirements would be huge.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: <chr### [at] tagpovrayorg>
http://tag.povray.org/

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