[Radiance-general] Photon map + rcontrib Advisory

[Schregle Roland HSLU T&A]

Dear colleagues,

it has come to our attention that the contribution photon mapping module  
in the current RADIANCE 5.0 release exhibits systematic underestimation.  
This affects photon maps generated with mkpmap using the -apC option, and
evaluated with rcontrib using the -ab 1 option (the default). In  
particular, we have observed deviations exceeding 50% in some cases with  
GLOW sources.

We are issuing this advisory to inform current and prospective users of  
the RADIANCE photon map about this issue. As a workaround, we suggest  
using the -ab -1 option with rcontrib, which evaluates contributed photons  
directly at the sensor points. This will increase performance but results  
in substantially higher noise, possibly requiring a larger photon map for  
acceptable quality.

We will issue a bugfix and commit it to the RADIANCE CVS and HEAD release  
in January. Sorry for any inconvenience this may cause in the interim.

Happy holidays and best wishes for the new year,

--Roland


-- 
Dr. Roland Schregle
Senior Research Associate

Lucerne University of Applied Sciences and Arts
School of Engineering and Architecture
CC Envelopes and Solar Energy (EASE)
www.hslu.ch/ccease

T direct: +41 41 349 36 26 (New)
roland.schregle at hslu.ch

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Ebenaustrasse 20, CH-6048 Horw (Office)
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