[Radiance-general] gensky_-B option

[Jan Wienold]

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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