"Christoph Hormann" <chr### [at] gmxde> wrote in message 
news:dcn984$3f2$1@chho.imagico.de...
> The transmission of light is nothing that makes sense to simulate in 
> POV-Ray since it has no effect on the image POV-Ray renders (light itself 
> isn't visible).  Therefore using emitting media for the glow and placing a 
> spotlight at the end is the way to go.

I don't think I can debate you on that, especially since I'm not sure what 
you meant by "no effect on the image", but never say never. Not sure what 
all Anthony knows about fiber optics but I know only enough to describe it 
to people with no knowledge of it in the first place. ;)

As I might have said elsewhere already, I was once able to get a simulated 
fiber optic cable made in POV and at least partially succeeded (maybe). It 
was done by using photons and reflection on the inside of an S-shaped 
sphere_sweep. I think it is total internal reflection effect, I believe, 
that is the operative factor IRL. Meaning, the boundary of the tube with the 
air is supposed to cause the light to stay within the tube walls because of 
a specific limiting angle whereby light only reflects instead of breaks 
through.

My test scene wasn't very good for anything as I recall, and I was counting 
on faking it with reflection, not refraction. I'm not good enough with 
photons to be sure if it really works or not anyway. I guess there would be 
trouble due to how the photons are designed to map out into the scene, not 
very sure of anything about it though. Probably was never designed to bounce 
around inside of curving tubes.

Sure hope you can manage to do something with your idea, Anthony. I just 
found the test scene I had done and rendered it as-is. Only got a bunch of 
red spots everywhere, mostly at the ground beyond the opposite end of the 
tube. Probably wouldn't help to see the scene yourself, it's basically just 
a narrow spotlight close to one end of that sphere_sweep (hollowed out with 
a smaller twin), which then has refraction and reflection including 
interior_texture.

I just looked for info about TIR and fiber optics and there's mention of 
critical angles for the light entering the tube and the bends in the tube. 
Gets beyond me but this one web page allows for calculating the critical 
incidence angle for different ior, if you're interested.

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/totint.html

Bob

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