genBSDF runtime

radiance-openstudio
1

Hello:

I would like to generate a number of BSDF .xml files dynamically in command
line or code. I prefer to use genBSDF because it is more flexible than
Window 6, which cannot run in command line (right?). However, the
computation time of genBSDF seems rather long compared to Window 6. I
believe the major reason is the algorithm is different.

The test file is given below. The default parameter setting "-ab 5" is not
high. Besides increasing -n option in genBSDF, is there any way to reduce
the runtime with an similar accuracy level as Window 6? or is there any
other tool that can simulate BSDF in command line?

The test file is:
####### file: glazingBase.rad ######
glazingRef_0.5 polygon glazing_1
0
0
12
2 0.0 3
0.0 0.0 3
0.0 0.0 0.0
2 0.0 0.0

########### file: basf.rad ###########
void glass glazingRef_0.5
0
0
3
0.545168692741 0.545168692741 0.545168692741

void plastic blindRef_0.2
0
0
5
0.2 0.2 0.2 0 0

! genblinds blindRef_0.2 blinds_0.2 0.02 2 3 200 0 | xform -rz -90 -rx 90
-t 0 0 -0.02
!xform -rx 90 glazingBase.rad
################ end ########

In Ubuntu, use "genBSDF bsdf.rad > test.xml"

Thank you!

Jia

2

Hi Jia,

as far as I know, Window is using a rather simple radiosity method, which makes the calculation of the BSDF quick. The method is not really suitable to maintain sharp transmissive or reflective peaks, but that is not a concern for most energy simulation. For daylighting however, you usually need the high angular resolution that the path-tracing algorithm of genBSDF provides.

Writing a tool that traces through a model and derives the BSDF from the transmission / reflection at varied incident directions is not that hard, however, that would certainly not be more efficient and useful then what genBSDF does. And - the big advantage of genBSDF is its variable resolution BSDF, which allows you to maintain much more detail in the distribution. If you wanted to write your own "genBSDF", implementing the data reduction would probably be the most difficult step.

By the way, seams not to be much Openstudio-specific but more a Radiance topic.

Cheers, Lars.

ยทยทยท

I would like to generate a number of BSDF .xml files dynamically in command line or code. I prefer to use genBSDF because it is more flexible than Window 6, which cannot run in command line (right?). However, the computation time of genBSDF seems rather long compared to Window 6. I believe the major reason is the algorithm is different.
The test file is given below. The default parameter setting "-ab 5" is not high. Besides increasing -n option in genBSDF, is there any way to reduce the runtime with an similar accuracy level as Window 6? or is there any other tool that can simulate BSDF in command line?