[Radiance-general] gensky_-B option

Thu Nov 26 09:38:43 PST 2015

Dear Urtza,

the 160 instead of 180 degree should not be a big problem, of course you 
underestimate the illuminance a bit, but you can provide the external 
measured illuminance value.

In case you have a problem in matching the calculated illuminance of the 
captured image (evalglare -V) with the measured illuminance, caused by 
pixel overflow, there exist since long time an undocumented option in 
evalglare to adjust the overflow pixels to match the measured 
illuminance. I could help you with that - in that case send me one 
example image and the related measured illuminance value directly (not 
via discussion group).

Jan

Am 11/26/15 um 4:59 PM schrieb urtza.uriarte at upc.edu:
>
> Dear Jan,
>
> Thank you very much for your answer and suggestions.
>
> I had illuminance value also at camera level, because I had spots of 
> high luminance. I have an fish-eye lens, the specifications said that 
> it gets 180º but it catches 160º. I hope that it can work. Ok, first I 
> will check if calculated illuminance is the same as measured.
>
> I understand that perhaps DGP is not the best option to describe glare 
> in a restaurant, excuse me. However, we have problems with highly 
> glazed façade that provides very high luminance values to achieve good 
> concentration on the taste and calm quality atmosphere, as well as, 
> privacy. We have done surveys and usually people tolerate more visual 
> discomfort in this activity, due to the habit probably, but when you 
> show atmospheres with less out luminance values, they prefer. I am not 
> sure if I am ok, but, the perception results are quite similar to the 
> DGP results. Anyway, thank you again and I will listen to you and 
> check all variations to demonstrate this problem.
>
> Yours sincerely,
> Urtza.
>
>
> Jan Wienold <jan.wienold at epfl.ch <mailto:jan.wienold at epfl.ch>> escribió:
>
>> Dear Urtza,
>>
>> it is not 100% clear to me what you have measured besides your image. 
>> Do you have an illuminance value also at camera level? This is very 
>> much needed to check the validity of the image, especially when you 
>> have spots of high luminances (e.g. the sun or reflections of it) in 
>> the field of view. Do you have an fish-eye lens?
>> So the first step is to check compare the calculated illuminance from 
>> you fish-eye image with this value to check if you have problems with 
>> pixel overflow/saturation. This would explain big differences between 
>> image calculated illuminance and measured. If you don't have a 
>> fish-eye lens you cannot make this simple check. Then you need to 
>> measure with a spot luminance meter the highest luminance in the 
>> field of view and compare it with the value in the image.
>>
>> If you have measurements of the Direct and Diffuse Irradiation, then 
>> it is better to use gendaylit, where you can provide both values.
>>
>> For your simulated data, there must be an mistake in your workflow. 
>> If you calculate the illuminance by "rtrace -I"  you should get the 
>> same value for the illuminance than calculated from the image (you 
>> can calculate the illuminance with evalglare -V . If you use the -I 
>> option in evalglare, it is just replacing the internal calculated 
>> illuminance value by the external one, all other algorithms are the 
>> same. So if you get different values, then you have a problem either 
>> with your image or with the illumiance calculation. So check first 
>> the difference in the illuminance. In case you are simulating a 
>> trans-material (e.g. for a fabric), pixel sampling, limit weight ect. 
>> might play a big role and could cause huge differences between image 
>> and rtrace calculations. But there could be many other reasons, 
>> depending on you scene you are simulating. Then parameter settings 
>> play a big role.
>>
>> And another important comment is, that I don't believe that the DGP 
>> is a metrics to describe glare in a restaurant. The needs are very 
>> much different between an office and a restaurant. In a restaurant 
>> you are dealing mainly with disability glare, I'm not sure if 
>> discomfort glare is perceived so much for this kind of usage. Of 
>> course with the DGP you can compare different variants and judge 
>> which variant has more often glare than other ones. But I would say 
>> you cannot make a distinct glare evaluation in a restaurant using DGP.
>>
>> Jan
>>
>>
>>
>> Am 11/26/15 um 9:30 AM schrieb urtza.uriarte at upc.edu:
>>>
> Dear experts,
>
> I am testing glare at restaurants of Barcelona for my thesis. I am 
> using Evalglare v 1.11 with real illuminance (-I Ev) data for 
> photographs converted to hdr by WebHDR and for visualizations got by 
> Radiance. Furthermore, I am testing glare by DIVA. I have tested with 
> both, Evalglare and DIVA’s Evalglare with Clear Sky without 
> Illuminance data and with illuminance data.
>
> # gensky 7 22 11 +s -a 41 -o -2 -m -15
>
> # gensky 7 22 11 +s -a 41 -o -2 -m -15 -B 458.100
>
> I have taken photograph’s Daylight Glare Probability index with real 
> illuminance data as reference. Therefore, without Ev data, DGP’s with 
> Clear Sky without illuminance data is more similar than Sky with 
> illuminance data (-B):
>
> dgp photographs= 71%
> dgp DIVA Sky without illuminance data= 63%
> dgp DIVA Sky with illuminance data (-B)= 100%
> dgp (just Radiance-Evalglare) Clear Sky without illuminance data= 62%
> dgp (just Radiance-Evalglare) Clear Sky with illuminance data (-B)= 100%
>
> My illuminance data has both, direct and diffuse irradiance. Could 
> someone confirm if –B parameter is only for diffuse radiance? I think, 
> that is explained in the program specifications.
> Thank you in advance.
>
> Kind regards,
> Urtza.
>
>
>
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>
> -- 
> Dr.-Ing.  Jan Wienold
> Ecole Polytechnique Fédérale de Lausanne (EPFL)
> EPFL ENAC IA LIPID
>
> http://people.epfl.ch/jan.wienold
> LE 1 111 (Office)
> Phone    +41 21 69 30849
>
>
>
>
>
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-- 
Dr.-Ing.  Jan Wienold
Ecole Polytechnique Fédérale de Lausanne (EPFL)
EPFL ENAC IA LIPID

http://people.epfl.ch/jan.wienold
LE 1 111 (Office)
Phone    +41 21 69 30849

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