In article <opr5ofawzup4ukzs@news.povray.org>,
 Phil Cook <phi### [at] nospamdeckingdealscouk> wrote:

> Well I've gone through optics.pov which shows reflected beams etc., 
> unfortunately without explaining how it works, and pulled together the 
> following scene with comments.

Hmm. I'll try to make some more informative comments for the 3.6 version.


> If anyone can offer an explaination why 
> both refraction and reflection need to be on in the light_source;

Because you use both refraction and reflection. Sort of. It seems that 
photons will only be generated if the target is the first object the ray 
from the light source hits. In this scene, the first object hit is the 
media container, which then blocks the mirror from getting any photons. 
I recently ran into this with a candle scene, where the offending shape 
was the flame container. You can sometimes partially work around it by 
making the media container shadowless, but that won't work for this 
situation. It's almost certainly a bug.


> why the 
> light_source must be outside the media container in order to get a 
> reflected beam;

No idea. I'll have to investigate that further.


> and why a cylinder light_source produces sharp edges in 
> the original beam with refraction on, I'd be most interested.

You might be seeing the difference between the original light source 
beam, rendered by usual raytracing, and the beam of media-deposited 
photons.

-- 
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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