Hi Christoph,

Many thanks for reply.

Christoph Hormann <chr### [at] gmxde> wrote:
> I think you analyzed the situation correctly but could you explain why
> you think with this change it is more 'correct' than before?  The fact
> that your sample scene looks better with it is an indication that it
> leads to more plausible results in some circumstances but i actually
> don't see a reason yet that it is in any way accurate.
>
> What the third case does is in fact a strongly simplified simulation of
> a double reflection - something that indeed will occur quite frequently
> on a strongly bumped surface.  A true double (or more times) reflection
> would however require a complete additional surface handling (including
> possible refraction, attenuation etc.).

You're completely right! Doing a physicaly correct reflection on strongly
bumped surface would be very complicated (multi reflections) and I agree
that this could not be the target. So we need to handle this unrealistic
case (incomming ray behind virtual surface) in a manner that it looks as
realistic as possible.
The proposed modification doesn't give a physical correct/accurate
reflection, but one that is more "realistic" and physicaly more probable
than the flat reflection (second case) on a bumpy surface.
I agree that there should be a bit of attenuation tue to multi-reflection
and some other refinements... but this would only give small advantages in
relation to calculation time compared to proposed simple change.
I found this when I looked for blurred reflections that are not directly
support by PovRay and found workarounds by AA or "micro-normals" that
finally given in some cases unrealistic sharp refections tue to this
problem. This change would be the only chance for me to realy realize
strongly blurred reflections in povray.

Is there any chance that this could flow once in povray, megapov or an other
patch?

Thanks and best regards

zuegs

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