[Radiance-general] experiences with the photon map

[Lars O. Grobe]

Hi list!

While I am trying this on Radzilla now (as there is no photon-mapping
available in Radiance-3.9 at the time of this writing), I am pretty sure
that the effects I get are not related to Radzilla but on the way I use
the pmap-System.

I am trying to model a simple, highly specular horizontal light duct,
with a rectangular cross-section (yes I know that in THIS case I could
use the mirror material and Radiance, but I will go for non-planar
surfaces later).

Now either I get very splotchy luminance images in the inside, or,
increasing the `bandwith` to rather high values, have a blurry result
with - and this is the problem - light leaving the geometry even though
it is closed (the duct has a 45 degree mirror at its end that should
actually close it, but the sides extend besides the mirror and appear
illuminated even behind it).

I am working with an initial photon count for both global and caustic
photons of 2.000.000 and a bandwith value of 2000 at the moment.

Is it possible to get such systems rendered in a way that I have both a
smooth luminance and no light escaping the geometry?

Is there any source for a starting point in what way rtcontrib could be
used for modeling such systems? I know the qt-movie from the workshop,
but I did not get it - and it seams that I know noone except Greg who
got it so far ;-)

Thank You & CU, Lars.