[Radiance-general] better results on genBSDF

Thu Feb 21 10:48:04 PST 2013

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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