Warp <war### [at] tagpovrayorg> wrote:
> clipka <nomail@nomail> wrote:
> > The "big normals" approach instead uses very large-scale bump maps - e.g. larger
> > than the whole picture. Multiple sampling is achieved by rendering the shot
> > multiple times, while the variations in pertubation are generated by
> > translating the bump map by a (large) random offset. Averaging is done in a
> > post-processing step.
>
>   I think you should read this:
>
> http://tag.povray.org/povQandT/languageQandT.html#blurredreflection

Did already a while ago.

The averaged textures approach didn't stick though. Maybe because it's *fatal*
if you have a lot of reflecting surfaces: The rays POV needs to trace will
explode exponentially with each reflection.

In contrast, if you do the averaging via multiple renders + post-processing, the
number of rays is only increased by a constant factor; at each reflection, the
number of rays multiplies only by the same amount as if the scene used sharp
reflections.

If you let adaptive Anti-aliasing do the job, you still can go with a relatively
low number of rays per pixel in areas that don't have blurred reflective
surfaces. Let alone that you'll usually use Anti-aliasing (or focal blur) for a
final shot anyway.

After the first blurred reflection, there's actually not much benefit in
multiplying the number of rays even more.

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