In article <3CA3D327.77480C19@scifi-fantasy.com>,
 "Timothy R. Cook" <tim### [at] scifi-fantasycom> wrote:

> But the light (if we're talking about a point light) is a known
> single point!  It's easy to test if it's on the surface!

POV would have to check that point against the bounding box of every 
object in the scene, and then against the surface of any objects it 
might be on. This would slow things down noticeably, just to handle what 
is really a degenerate case.

And then, the correct thing to do would be to always consider the light 
shadowed by the object, otherwise you will get wrong shadows with 
objects like a torus, where other parts of the object should cast 
shadows from a point just above the surface. Of course, this wouldn't be 
very useful...it would just slow things as mentioned above, and replace 
user complaints about lights not lighting properly with complaints about 
lights not lighting at all.

You could also mess around slightly with the depth values, basically 
have POV lie to itself it doesn't "see" intersections that are very 
close to the light source. The point is this just isn't necessary...just 
don't put your lights on a surface! That situation never occurs in 
reality and there is no reason to bother handling it.

-- 
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/

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