In article <web.3fb90bc3df2bb6e4541c87100@news.povray.org>,
 "Tom York" <tom### [at] compsocmanacuk> wrote:

> I have no idea what the best solution would be. Is it such a bad idea to
> obey the user-specified reflection_min/max even in the case of TIR?

Well, there's a reason it's called *total* internal reflection...

-- 
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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Christopher James Huff wrote:
>In article <web.3fb90bc3df2bb6e4541c87100[at]news.povray.org>,
> "Tom York" <tom### [at] compsocmanacuk> wrote:
>
>> I have no idea what the best solution would be. Is it such a bad idea to
>> obey the user-specified reflection_min/max even in the case of TIR?
>
>Well, there's a reason it's called *total* internal reflection...
>
>Christopher James Huff <cja### [at] earthlinknet>
>http://home.earthlink.net/~cjameshuff/
>POV-Ray TAG: chr### [at] tagpovrayorg
>http://tag.povray.org/
>

Then surely the extinction keyword should never be allowed to take a value
other than unity, and the conserve_energy feature should always be on, and
reflection_min should always be forced to take a value less than
reflection_max ...

I understand that 100% reflection would be the physically correct value, and
I'm sure that there is a good argument for making it independent of
reflection_max, but I'm just not sure that physical correctness is that
argument - it could be taken to apply a lot more widely than it does.

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I altered lighting.cpp so that the sign of the sqrt is checked before use.
If it is negative, F is set to 1 (leading to Reflection_Max). Otherwise the
behaviour is unchanged. I ran the scene provided by sascha with the same
width and height and got this:

http://www.compsoc.man.ac.uk/~tomy/pov/tir.jpg

(~3K JPEG).

This was on a linux PC, gcc 2.95.3. The edges (where TIR is undoubtably
occurring) seem a bit cleaner to me.

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