[Radiance-general] Problem with Trans material

[Greg Ward]

Hi Andrea,

It is important to use the latest CVS head when generating Klems distributions with genBSDF.  David Geisler-Moroder and Christian Knoflach discovered a bug in the corrections for Klems solid angles built into wrapBSDF, which is called by genBSDF.  These errors are on the order of what you are seeing, so if you are using a distribution built before November of 2016, this could well be your problem.

Best,
-Greg

> From: Andy McNeil <mcneil.andrew at gmail.com>
> Date: May 18, 2017 7:52:15 AM PDT
> 
> Hi Andrea,
> I just ran your BSDF command and got a BSDF with 35.6% direct-hemispherical transmission for all incident angles. 
> How are you calculating the transmission from the BSDF file? Can you send me your BSDF file in a separate email?
> Andy
> 
> On Thu, May 18, 2017 at 7:03 AM, Andrea Zani <andrea89.zani at gmail.com> wrote:
> Hi everyone,
> 
> I am trying to generate a BSDF of a complex translucent facade component. 
> One of the materials in the model is a fabric and I'm trying to simulate its optical behavior using a Trans material, however I have some problems.
> Creating a BSDF of the trans material (you can see the material definition below), I have obtained a particular angular transmission behavior as showed in the pictures below. There is a particular increment between 0° and 30° of the incidence angle, instead i was expected something similar to the dashed lines in the graphs. Is it normal to have this angular transmission trend? If not, how can I fix this problem?  
> 
> 
> 
> Trans material
> void	trans	Fabric					
> 0							
> 0							
> 7	0.8	0.8	0.8	0.01	 0   0.45	0
> 
> BSDF:
> genBSDF -n 4 -c 4000 -dim 0.299 0.338 0.373 0.429 -0.018 0 -r -ab 10 trans_test_tr3.rad
> For the test the material geometry is a rectangle.
>  
> 
> Thanks in advance.
> Best
> 
> -- 
> Andrea Zani
> Meng  |  Phd Student & Researcher
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