[Radiance-general] HDR Sky Camera @ LBNL's Flexlab

[Rob Guglielmetti]

Hi German, and everyone else. Certainly one could use these HDR images to
generate sky vectors and apply them to daylight coefficients for a given
model(s). Greg Ward has created a cool tool called mksource to facilitate
this process in Radiance, identifying small, intense pixels in the image;
creating and placing Radiance light sources in their stead, and zeroing the
pixels to avoid double counting.

Considerations:
- Capturing the true (full) dynamic range of an exterior scene with direct
sun is difficult.
- Using locally-captured HDR images for daylight availability analysis is
statistically dubious. Granted, so is using TMY data, for different
reasons. This is why I changed the title of this list to "considerations",
from "problems". =)





On Fri, Jun 27, 2014 at 3:38 PM, CHI-German Molina <gmolina at hdlao.com>
wrote:

> Wow, I have been thinking on doing this for a while... although I have no
> idea where to start from.
>
> Is it possible to calculate the Daylight Coefficients of the building; and
> use the HDR image to generate sky vectors and calculate different options
> for optimizing daylighting?
>
> I am picturing a computer that, every 5 minutes, calculate the sky vector,
> computes the interior lighting conditions, and simulates the different
> lighting options performing a whole-building lighting control with no photo
> sensors. Even more, maybe a whole neighborhood could use the same camera.
> Nonsense?
>
> Thanks for sharing!
>
>
> 2014-06-27 0:59 GMT-04:00 Joe Smith <the.oat.cracker at gmail.com>:
>
>> Hi, Andy, thanks for sharing LBNL's sky mapping experiment!
>>
>> Can you kindly advice on resources that elaborate on how to use HDR sky
>> image for daylight simulation? Does it involve specifying the HDR image,
>> rather than a "skyfunc", as the material identifier for the sky geometry?
>> How is the pixel value of a given point on the HDR image converted to
>> luminance value of the corresponding position on the sky?
>>
>> Thanks!
>> - Joe
>>
>> Andrew McNeil <amcneil at lbl.gov>于2014年6月27日星期五写道：
>>
>> Hi Everyone,
>>>
>>> LBNL has installed an HDR sky camera at our new FLEXLAB site:
>>> http://flexskycam.lbl.gov. I've uploaded sample data, including hdr
>>> images and csv datafiles, recorded by the camera for three days over the
>>> past week( clear, partly cloudy and overcast). We're happy to share more
>>> data with other researchers and daylight practitioners (but we don't have
>>> much to offer yet).
>>>
>>> The images can be mapped to a Radiance sky for simulation under real sky
>>> conditions. I have not used the sky HDR images yet, myself, so if anybody
>>> uses them successfully please report back and share what you've done!
>>>
>>> Questions about the camera hardware and capabilities should be directed
>>> to Chris Humann at Terrestrial Light.
>>>
>>> Best,
>>> Andy
>>>
>>
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>>
>
>
> --
> *Germán Molina L.*
> Ingeniero Trainee
> Hunter Douglas Chile S.A.
> Celular +569 89224445
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