clipka schrieb:
> scott schrieb:
> 
>> That's what I don't understand, Fresnel should determine the 
>> reflection % based on the IOR and the angle, nothing else, I don't get 
>> what the other two parameters do in this cae, or what I should set 
>> them to.  I just use reflection{1 fresnel on} for now - I hope that is 
>> physically correct.
> 
> To get physically correct results (well, as close as you get with 
> POV-Ray's "fresnel" feature), it should be:
> 
>     reflection { 0, 1 fresnel on }
> 
> though for convenience the syntax
> 
>     reflection { MAX fresnel on }
> 
> is interpreted as:
> 
>     reflection { 0, MAX fresnel on }
> 
> so the syntax you use does work as well.

I have closely examined the code by now, to find out the following:

- The code does indeed implement the exact Fresnel equations for the 
special case that the incident light is unpolarized, though I have not 
the slightest clue how; the implemented function doesn't look anywhere 
close to anything I've been able to find on the 'net so far. But the 
values are flawless.

- when specifying "reflection{MIN,MAX fresnel on}", this will reduce the 
maximum reflectivity to MAX, while at the same time increasing the 
minimum reflectivity. However, MIN in this case is /not/ to be taken 
literally as the minimum effective reflectivity; instead, it specifies a 
kind of "zero reference" for reflectivity calculations; i.e. if the 
minimum reflectivity according to the Fresnel equations would be 
FRESNEL_MIN, the resulting effective minimum would be MIN + 
FRESNEL_MIN*(MAX-MIN).

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