Am 12.07.2012 00:13, schrieb Crippso:

> One thing I have noticed that is strange in a scene I have created is
> absorption. If I shoot photons towards a box with ior = 3.2 that has a thinner
> box inside it with same ior but with exponential absorption (alpha) and
> thickness (t_box2) I get unexpected results. I use 'difference' to cut two
> 45degree angles through the two boxes, with the angled sides facing each other
> (resulting shape like a truncated pyramid). If I shoot photons so that they hit
> an angled side at a position in the midpoint of the absorbing box the photons
> are reflected towards the other 45degree face where they are again reflected and
> are sent back towards the light source (offset slightly but parallel).
>
>  From my results of this it looks like the reflected rays are not absorbed by the
> absorbing layer (the path length through the absorber for these photons should
> be long because the reflection is in the long dimension of this absorber, rather
> than through its smaller thickness).

Examining your problem, I did indeed find a bug in the handling of the 
interior fade feature (wrong interior being applied under certain 
circumstances), which I suspect to be relevant in your case. (I also 
found a flaw regarding total internal reflections, but so far I did not 
manage to come up with a situation where it would manifest as a bug, so 
that one can probably be ruled out.)

The interior fade bug is also present in POV-Ray 3.6.2, so I don't think 
it will be fixed in POV-Ray 3.7.0 release proper.

One possible workaround might be to use media instead.

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