Does POV-Ray properly render internal reflactions?  I can't seem to get it 
to.  I'm trying to set up a light pipe that should be near TIR (total 
internal reflaction).  What I've tried so far is to wrap the pipe with a 
mirror, but that isn't quite the correct to do this.

Ideally, the surface smoothness would affect the internal reflections so I 
could correctly model what happens on a scuffed or scratched surface.

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LEDpipe nous apporta ses lumieres en ce 26/01/2006 16:33:
> Does POV-Ray properly render internal reflactions?  I can't seem to get it 
> to.  I'm trying to set up a light pipe that should be near TIR (total 
> internal reflaction).  What I've tried so far is to wrap the pipe with a 
> mirror, but that isn't quite the correct to do this.
> 
> Ideally, the surface smoothness would affect the internal reflections so I 
> could correctly model what happens on a scuffed or scratched surface.
> 
> 
It does do total internal reflection realisticaly, but... for the light from a
light_source to do 
it, it must emit photons.
You need to add a protons block in the #global_settings{}
You also need to add a photons block to your object. That one will look like:
photons{target refraction on}
You can also add "reflection on" but probably don't need it.
In your case, you probably also need to increase the max_trace_level, possibly to it's
maximum value 
of 255.

Read section 3.6.3  Photons in the documentations.

-- 
Alain
-------------------------------------------------
Just because someone doesn't love you the way you
want them to, doesn't mean they don't love you with
all they have.

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Thanks.  I had been using photons.  I think my pipe just needs more work ...


> It does do total internal reflection realisticaly, but... for the light 
> from a light_source to do it, it must emit photons.
> You need to add a protons block in the #global_settings{}
> You also need to add a photons block to your object. That one will look 
> like:
> photons{target refraction on}
> You can also add "reflection on" but probably don't need it.
> In your case, you probably also need to increase the max_trace_level, 
> possibly to it's maximum value of 255.
>
> Read section 3.6.3  Photons in the documentations.
>
> -- 
> Alain

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I've been trying to model a light-pipe also, and I've gotten internal
reflection to work, but only if I turn conserve_energy off. If it's
enabled, I get no visible internal reflection at all. My photons are all
emitted in a very narrow beam (spotlight of 0.04 degrees divergence), which
requires an extremely small photon-spacing on the glass pipe target, but it
doesn't seem to make any difference how small the spacing is unless
conserve_energy is off (i.e. you get no visible effect from photons, even
with no other lighting in the scene).

My light pipe and light source are configured such that I should be getting
total internal reflection. So perhaps conservation of energy isn't
important in this case, assuming that 100% of the incoming light gets
reflected (internally). But I wanted to look at step-index light pipes, so
ideally there would be partial reflection at the interface between two
slightly different indices of refraction. I think this will probably
require that conserve_energy is enabled for realistic behavior to be seen.

Dave

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