[Radiance-general] Glare analysis of BSDF representation of light redirecting glass

[Humann Chris]

Hi Greg,
Thank you for the response.  Do you think the BSDF estimate used would  
give a fair approximation of glare were it to be an issue?

Cheers!
Chris
Christian Humann ~ Associate
LOISOS + UBBELOHDE
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On Jan 14, 2013, at 11:41 AM, Greg Ward wrote:

> Hi Chris,
>
> Changing the -c setting in genBSDF may result in a more accurate  
> BSDF estimate, but it will not increase the resolution of the  
> recorded distribution, which is defined by the 145x145 Klems basis.   
> Near normal incidence, the resolution is about 5 degrees, but  
> increases to 15 or 20 degrees towards grazing angles.
>
> To obtain a higher-resolution BSDF, you will need to switch to the  
> tensor tree representation, which means using the -t4 option,  
> probably '-t4 5' or '-t4 6' in your case.  The '-t4 5' setting will  
> yield a BSDF with 1024 incoming and 1024 outgoing directions, which  
> corresponds roughly to 2-degree resolution near normal incidence.   
> The higher setting of '-t4 6' gives you about twice the resolution,  
> or 1-degree accuracy.  However, it does take about 4 times as long  
> to calculate, and any tensor tree BSDF will take much longer to  
> compute with genBSDF than the Klems basis.  Final rendering times  
> should be similar, however.
>
> Hope this helps!
> -Greg
>
>> From: Humann Chris <chris at coolshadow.com>
>> Date: January 14, 2013 11:26:16 AM PST
>>
>> Dear group,
>>
>> I have a BSDF description of a light redirecting glass generated  
>> with the following command:
>> genBSDF -n 8 -c 20000 -r -ab 6 -ad 1 +f +b -g- millimeter -dim  
>> 12.49 12.51 12.47449 12.52551 -3.158 0
>>
>> We are using this file to understand the effective light  
>> distribution of a particular product as well as calculating DGP.    
>> We are wondering if the number of samples (20000) used per each of  
>> the 145 klems directions would be sufficient to give an accurate  
>> representation of glare when looking at the scene description from  
>> inside the space?  I've looked for published studies of comparative  
>> glare analysis using DGP and BSDF files but have come up short.
>>
>> Thanks as always,
>> Chris
>
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