[Radiance-general] gensky_-B option

[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> 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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