[Radiance-general] better results on genBSDF

Fri Feb 22 09:19:31 PST 2013

Great! Glad it all works out.

On Thu, Feb 21, 2013 at 10:48 AM, Germán Molina Larrain <gmolina1 at uc.cl>wrote:

> Andy,
>
> your suggestion worked perfectly.
>
> THANKS
>
>
> 2013/2/20 Germán Molina Larrain <gmolina1 at uc.cl>
>
>> Ok, I will try those changes, and let you know my results.
>>
>> THANKS ANDY!
>>
>>
>> 2013/2/20 Andrew McNeil <amcneil at lbl.gov>
>>
>>> I think all you need to do is change  lines 350 and 351 of genBSDF.pl so
>>> they look like this:
>>>
>>> Kazi = 360*DEGREE * Kcol / Knaz(Krow);
>>> Kpol = DEGREE * (0.5*Kpola(Krow) + 0.5*Kpola(Krow-1));
>>>
>>> (this only changes it for Klems BSDF generation)
>>>
>>> Andy
>>>
>>>
>>> On Wed, Feb 20, 2013 at 5:44 AM, Germán Molina Larrain <gmolina1 at uc.cl>wrote:
>>>
>>>> actually, now that you mention it, I think that the errors I thought
>>>> were caused by the borders can be explained by what you say.
>>>>
>>>>
>>>> 2013/2/19 Germán Molina Larrain <gmolina1 at uc.cl>
>>>>
>>>>> Andy, indeed I did not do that; probably that is what causes the
>>>>> problem...
>>>>>
>>>>> Could you explain me how to do that?
>>>>>
>>>>> THANKS
>>>>>
>>>>>
>>>>> 2013/2/19 Andrew McNeil <amcneil at lbl.gov>
>>>>>
>>>>>> German,
>>>>>> Did you consider that genBSDF integrates over the incident Klems
>>>>>> patch while radiosity method used in window 6 just uses the center of the
>>>>>> patch for incident energy?
>>>>>> It is easy to modify genBSDF to use the ceter of the Klems patch by
>>>>>> removing a couple of the random variables in incident ray generation.
>>>>>>
>>>>>> Andy
>>>>>>
>>>>>>
>>>>>> On Sat, Feb 16, 2013 at 12:49 PM, Greg Ward <gregoryjward at gmail.com>wrote:
>>>>>>
>>>>>>> The 3-phase method is restricted to matrix (Klems) BSDFs for the
>>>>>>> time being.  A more sophisticated method is in the works, but won't be
>>>>>>> ready for several months.
>>>>>>>
>>>>>>> Cheers,
>>>>>>> -Greg
>>>>>>>
>>>>>>> *From: *Germán Molina Larrain <gmolina1 at uc.cl>
>>>>>>>
>>>>>>> *Date: *February 16, 2013 12:27:02 PM PST
>>>>>>>
>>>>>>> *
>>>>>>> *
>>>>>>>
>>>>>>> Thanks Greg and Lars!
>>>>>>>
>>>>>>> I intend to use these BSDFs for annual simulations (three-phase
>>>>>>> method). Is it possible to use the Tensor-tree implementation on that? I
>>>>>>> think I can live with the claimed error anyway...
>>>>>>>
>>>>>>> THANKS AGAIN
>>>>>>>
>>>>>>> Germán
>>>>>>>
>>>>>>> 2013/2/16 Greg Ward <gregoryjward at gmail.com>
>>>>>>>
>>>>>>>> The genBSDF program produces a limited resolution matrix
>>>>>>>> representation using the options you've given.  This is appropriate if you
>>>>>>>> want to use it with WINDOW (although I think some modifications to the
>>>>>>>> output are still required) or if your material is fairly diffusing.  It
>>>>>>>> will not resolve the direct peak to anything finer than 10 degrees, which
>>>>>>>> is the resolution of the full Klems matrix basis.  Some spreading of the
>>>>>>>> direct is unavoidable.
>>>>>>>>
>>>>>>>> You can improve upon this using the tensor tree formulation by
>>>>>>>> setting the -t3 or -t4 option.  If your system produces an isotropic
>>>>>>>> distribution (i.e., you can rotate the system about its center with no
>>>>>>>> change to the output), you can try "genBSDF -t3 6" or so.  In the more
>>>>>>>> general case, you can use "genBSDF -t4 6", which will resolve the direct
>>>>>>>> component to within a few degrees.  You can increase to "-t4 7" to get
>>>>>>>> twice the resolution, but you'll have to increase the -c parameter as well,
>>>>>>>> and I can't predict when the calculation will finish.
>>>>>>>>
>>>>>>>> The real solution is to incorporate and employ the actual system
>>>>>>>> geometry using the proxy method described near slide 7 in my 2011 workshop
>>>>>>>> presentation:
>>>>>>>>
>>>>>>>>
>>>>>>>> http://www.radiance-online.org/community/workshops/2011-berkeley-ca/presentations/day2/GW5_BSDFFirstClass.pdf
>>>>>>>>
>>>>>>>> Cheers,
>>>>>>>> -Greg
>>>>>>>>
>>>>>>>> *From: *Germán Molina Larrain <gmolina1 at uc.cl>
>>>>>>>>
>>>>>>>> *Date: *February 16, 2013 11:49:09 AM PST
>>>>>>>>
>>>>>>>> *
>>>>>>>> *
>>>>>>>>
>>>>>>>> Hi Lars,
>>>>>>>>
>>>>>>>> considering that the specular transmission is that light that does
>>>>>>>> not touch any surface, the analytical solution would be the exact one (am I
>>>>>>>> right?). Also, HERE<http://windows.lbl.gov/materials/optics/Bidirectional%20Properties%20of%20Slat%20Shading.pdf>,
>>>>>>>> those results were compared agains TracePro, and the results of the forward
>>>>>>>> ray-tracing gave, basically, the same results as the model I am using.
>>>>>>>>
>>>>>>>> THANKS
>>>>>>>>
>>>>>>>> German
>>>>>>>>
>>>>>>>> 2013/2/16 Lars O. Grobe <grobe at gmx.net>
>>>>>>>>
>>>>>>>>> Hi German!
>>>>>>>>>
>>>>>>>>> > I am using genBSDF to get the BTDF of a shading system,
>>>>>>>>> comparing it to
>>>>>>>>> > an analytical model using the radiosity method. No surprise, the
>>>>>>>>> > calculations seem to be really good, nevertheless, there are some
>>>>>>>>> > important differences on directly transmitted (specular)
>>>>>>>>> calculations. I
>>>>>>>>>
>>>>>>>>> Why do you think that "an analytical model using the radiosity
>>>>>>>>> method"
>>>>>>>>> results in "better" results than raytracing does for specular
>>>>>>>>> transmission?
>>>>>>>>>
>>>>>>>>> Cheers, Lars.
>>>>>>>>>
>>>>>>>>>
>>>>>>>> ---------------------------
>>>>>>>>
>>>>>>>> *From: *Germán Molina Larrain <gmolina1 at uc.cl>
>>>>>>>>
>>>>>>>> *Date: *February 16, 2013 7:06:26 AM PST
>>>>>>>>
>>>>>>>> *
>>>>>>>> *
>>>>>>>>
>>>>>>>> Dear list,
>>>>>>>>
>>>>>>>> I am using genBSDF to get the BTDF of a shading system, comparing
>>>>>>>> it to an analytical model using the radiosity method. No surprise, the
>>>>>>>> calculations seem to be really good, nevertheless, there are some important
>>>>>>>> differences on directly transmitted (specular) calculations. I am using the
>>>>>>>> following parameters:
>>>>>>>>
>>>>>>>> genBSDF -n 4 -c 4000 -r '-ab 4 -ad 512 -as 0 -aa 0 -ds 0.01 -dj 0'
>>>>>>>> material.mat geometry.rad > ../TMX/file.xml
>>>>>>>>
>>>>>>>> I tried modifying the -c option, but it did not show any
>>>>>>>> improvements, so I stayed on 4000. Any suggestions from gurus?
>>>>>>>>
>>>>>>>> THANKS
>>>>>>>>
>>>>>>>> German
>>>>>>>>
>>>>>>>>
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