[Radiance-general] Assistance required with Rendering error / random numbers

[Peter Apian-Bennewitz]

Carsten Bauer wrote:

>Hi DAI-crew,
>
>the artifacts stem most likely from a special random generator  used for all 
>kinds of ray jittering applied in the process of penumbra generation. I don't 
>really know why this is done, because pictures often look rather strange with 
>these patterns. 
>
Basically the idea the is to generate equally distributed random numbers.
A "few" (hundred or thousand) true random numbers (generated with -DMC) 
are a bit "clustered", so, to cover the interval in question ( typically 
[0..1] ) more evenly even with a few  points, an "afterburner" routine 
tries to equalize the distribution of these numbers. The price for this 
is the stupid pattern. Augustinus Topor at FhG-ISE looked into this last 
year too but we found no better idea yet.
-DMC avoids the pattern but the increase in necessary picture size 
before downsampling is substantial (easily a factor of 4). Otherwise the 
random clusters show up in the final image.
A somewhat dis-satisfying situation at present.

-Peter

-- 
 pab-opto, Freiburg, Germany, www.pab-opto.de