[Radiance-general] rtrace values too low compared to 3-phase method

[Marouane.Boudhaim at ise.fraunhofer.de]

Hello,
 
I’m trying to calculate vertical illuminance with 3-phase method and 
validate it against rtrace results.  My results are very different. 
3-phase method has illuminance values two order of magnitudes higher. I 
can only see the the direct solar illuminance on the floor. I suspect that 
my rtrace command fails to find the sky, because of the complexity of the 
geometry of my fenestration system. I was wondering if anyone here has 
already had such a problem in the past with rtrace giving too low 
illuminance values.
 
My CFS geometry consists of uniformly spaced boxes of 5 cm (picture in the 
end). The gap between the boxes allow 4%  normal transmittance (tested 
with 20% too and it’s still dark, 30% start giving some light).
Here are the parameters used to calculate the vertical illuminance (and 
which I suspect may be wrong)
 
1st way : 3PM : View matrix of the picture (on which I use evalglare to 
get the vertical illuminance) :  -n 35 -ab 10 -ad 65536 -lw 1.52e-5 -c 9
 
2nd way : Vertical illuminance with rtrace :  rtrace -h -I -n 40 -ab 10 
-ad 8192 -ar 1024 -as 4096 -aa 0.1
 
3rd way : Rtrace picture (I use evalglare on it) :  rtrace -n 40 -ab 5 -ad 
512 -ar 128 -as 256 -aa 0.15 -dc 1
 
Needless to say I made the parameters vary many times before contacting 
the mailing list, but there are so much parameters and simulation times 
increase a lot (I mainly increased ab and ar). I have already tried the 
parameters on the old and new 3pm/5pm tutorials to be sure my 3-pm results 
are not wrong. Has anyone else had similar experience with rtrace and know 
how to solve it ?
 
Sincerely,
Marouane.



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