-Hail

  There are a couple of issues concerning photon mapping. You can find
source code and images in the binary section.
  First issue is related to the distance between light source and target
object, when the light source moves away the photons begin to act
erratically. Each pov unit added to that distance will give completely
different results. Sometimes about half the area where the photons should
hit is a bit fuzzy and the rest is normal and other times it is fuzzy all
the way and sometimes it is correct. The resulting fuzziness is always the
same at identical settings.
  The second issue has to do with the way photons are shot from area lights.
If the area_light feature is not used then the photons are shot from the
corner of the area light (first light?) and this causes caustics to fall in
obviously wrong places.

P2-450, 64Mb Ram, W2k, Pov 3.5 b-6

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