[Radiance-general] evalglare with regular lens

[J. Alstan Jakubiec]

Dear Ery,

You can use evalglare with a regular hdr image as far as I understand it.  
Jan can correct me if I'm wrong :). As Thomas notes, it is best to have  
the full hemisphere image, but if you don't have such an image, you can  
still get pretty good results with a couple of steps:

1. Make sure your hdr is calibrated to photometric units of cd/m2. Doyle  
and Reinhart also have a pretty reasonable tutorial on doing this using  
Photosphere:  
http://www.gsd.harvard.edu/research/gsdsquare/Publications/HDR_II_Photosphere.pdf
2. You'll want to make sure that in the header to your HDR, it has a  
Radiance view type that is pretty close to the opening angle of the camera  
lens you are using. An example will be something like, "VIEW= -vtv -vh 60  
-vv 40" which are some parameters I just pulled from a random  
rpict-generated image on my computer. In the ideal case, your view type  
would be the angular fisheye, "-vta -vh 180 -vv 180". I think that this is  
automatically taken care of to some degree by Photosphere, but its worth  
checking before using your images for analysis.
3. It is also useful to have an illuminance reading from the time the  
photo was taken. The DGP calculations rely on total vertical eye  
illuminance and contrast. Usually, the illumimance at the eye is  
calculated directly from the fisheye image, but when you don't have a view  
encompassing a hemisphere, you can provide the illuminance separately by  
calling evalglare as, "evalglare -i VerticalEyeIllumianance file.hdr."

Best,
Alstan

On Mon, 06 Feb 2012 21:26:49 -0500, Thomas Bleicher  
<tbleicher at googlemail.com> wrote:

> Ery
>
> You can use the pinterp program to convert from one projection to  
> another.
> See the man page for an example or dig in the archives where this has  
> been
> discussed before. However, note that the glare equations are based on a
> full hemispherical image. You will have to fill in the missing perimeter  
> of
> your converted fisheye image with values of the right brightness or your
> glare evaluation will be off.
>
> Regards,
> Thomas
>
> On Mon, Feb 6, 2012 at 9:15 PM, Ery Djunaedy  
> <ery.mailinglist at gmail.com>wrote:
>
>> Folks,
>>
>> I have a bunch of HDR images generated from photographs taken with  
>> regular
>> -- non-fisheye -- lens. Is there a way that we can use these images for
>> glare analysis in evalglare? The evalglare description says that it only
>> accepts fisheye images. There is a tutorial from Harvard GSD (Doyle and
>> Reihart) that shows a non-fisheye photo in evalglare:
>> http://www.gsd.harvard.edu/**research/gsdsquare/**Publications/HDR_III_**
>> Evalglare.pdf<http://www.gsd.harvard.edu/research/gsdsquare/Publications/HDR_III_Evalglare.pdf>
>>
>> I am wondering whether this can be done at all.
>>
>> Thanks,
>>
>> Ery
>>
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