In article <slr### [at] fwicom>, ron### [at] povrayorg 
wrote:

> Yes.  A bug in your thinking.  The idea of a parallel area light doesn't
> make any sense.  

An actual parallel area light would give the same results as a point 
area light, but with slower rendering. Instead of being truely parallel 
in the area light case, the rays should be adjusted so soft shadows 
still work. This isn't physically realistic, but the realistic method is 
useless.
It isn't a bug in my thinking, just a compromise to make a feature more 
useful.


> When MCB wrote the parallel-light code, he put in a special case for 
> parallel area lights that does *something* that produces soft 
> shadows, but it doesn't have any physical basis and his arguments at 
> the time were (to me) less than convincing.

Ah, then it already does what I think it should. Why weren't you 
convinced?


> If you want parallel lights, use parallel lights.  If you want soft 
> shadows, use area lights.  If you want parallel lights with soft 
> shadows, you should really stop smoking that stuff because it's bad 
> for you,

I'm not smoking anything...and what is wrong with wanting "parallel" 
lights with soft shadows instead of parallel light that simply renders 
slower? The alternative, a large area light positioned far away, could 
cause precision problems. Parallel area lights can come close to 
simulating that case, though they would never occur in the real world.
Besides, people will expect having area lights to blur the shadows.


> and the brain damage might get in the way of implementing 
> physically-based diffraction effects.

That *would* be fun...maybe photon mapping could be twisted and hacked 
to simulate it.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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