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Orchid XP v2 wrote:
>
> As I understand it, "gather radius" effectively controls how "big" each
> individual photon is. I would have expected that to require shooting
> *fewer* photons, and hence be *faster*...
>
> OTOH, I haven't actually tried it.
I'm never ever looked at the code so far, but as I understood the docs and the
discussions in this forum, the radius and the gather values doesn't influence
the number of photons to be shot at each induvidual object, this is done by the
count/spacing value together with the target multiplier.
Radius and gather kick in when allready all photons are shot. They influence
which of the stored photons should be taken into account for each induvidual
point in your render.
To few photons will result in a coarse photon map which won't reveal much
details. On the other hand lots of photons will give a finer photon map, but
unless you adjust the gather values not all off them will be "collected" while
searching through the photon map (the max value limits the number of photons to
be collected and therefore to be taken into account). AFAIUI the gather min
value decides if the the search radius has to be expanded adaptively to collect
at least a minimal number of photons, and can cause problems when not enough
photons are present.
to put it other words, I imagine the code looks roughly like this:
-sort all photons stored in the photon map by means of the distance to the
point rendered
-take those photons which distance is less then the search radius
-if the number of this photons is less then gather min value expand the
search radius until the minimal number of photons to be collected is reached
-if the number of photons found is larger then gather max value take those
photons nearest to the point rendered
-average the collected photons weighted by there distance
please correct me if this is nonsense; the more I understand the concept and how
it's implemented the better (I think) I can make use of it and know which value
have to be changed to get what I want.
... dave
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