[Radiance-general] GenCumulativeSky compiled for Mac?

[Ji Zhang]

Thank you very much, John and Thomas!

I've found John's paper, and will read it later.

As far as I know, GenCumulativeSky also has two ways to create cumulative
sky: the smeared sun approach (+s1 option) and the binned sun approach (+s2
option), which might be similar to John's method #1 and #2 respectively
(see its options below, the -r, -p, and -E option were added by the
DIVA/DAYSIM team, I guess).


###################################
Usage: GenCumulativeSky [-d] [+s1|+s2] [-a latitude] [-o longitude] [-l]
[-m standard meridian] [-h hour shift] [-G|-B|-E] <climate file>
(Note: longitude +ve East of Greenwich)

        -d      Ignore diffuse irradiance
        +s1     Use "smeared sun" approach (default)
        +s2     Use "binned sun" approach
        -l      Output luminance instead of radiance
        -r      Output radiance/179000 (ensures that units in the Radiance
Image Viewer are in kWhm-2)
        -p      Output radiance/1000 (ensures that units in the Radiance
RGB data file  are in kWhm-2)
        -G      File format is col1=global irradiance (W/m2), col2=diffuse
irradiance (W/m2)
        -B      File format is col1=direct horizontal irradiance (W/m2),
col2=diffuse irradiance (W/m2)
        -E      File format is an energyplus weather file (*.epw) The
gprogram uses the global irradiance (W/m2) and diffuse irradiance (W/m2)
data columns.
                In combination with '-E' the considered time interval can
be specified:
                -time <start time of day> <end time of day>
                -date mm_start dd_start mm_end dd_end (if start-date after
end-date then the winter interval is considered)
####################################

- Cheers, Ji



On Mon, Dec 17, 2012 at 1:32 AM, John Mardaljevic <J.Mardaljevic at lboro.ac.uk
> wrote:

>  Hi Ji,
>
>   Is your approach of generating cumulative sky described in your PhD
> thesis?
>
>
>  No, it came a little later -- though the sky model mixing function used
> is the one in the thesis.  Also, the brightdata format used for the
> cumulative sky is very similar to the one used to get the sky luminance
> scans into Radiance for the validation.
>
>  There's a number of ways that a cumulative sky can be fashioned.
>
>  1. Single 'glow' source with associated brightdata file containing the
> cumulative radiance of the diffuse sky and all the suns, i.e. the sun
> radiance is 'smeared' over the brightdata patch.
>
>  2. A 'glow' source as above, but now only for the cumulative diffuse sky
> component.  Additionally, you must add a number of direct 'light' sources
> where each one is set to have the cumulative radiance of all the suns that
> occur in the occupied bins for a gridded distribution in altitude and
> azimuth.  An 8deg bin width for both altitude and azimuth results in about
> 200 'light' sources depending on the latitude.  Now, rather than being
> smeared, the suns are slightly displaced to the bin-mean alt-azi position.
>
>  I use option #2, i.e. 'glow' source for the sky and multiple 'light'
> sources for all the suns.  It's more computationally expensive than #1,
> however the 'light' sources will get illumination deep into a model (i.e.
> through windows etc) without having to rely on cranking-up the resolution
> of the ambient parameters.  Both types have their attractions; I don't know
> which one GenCumulativeSky uses.
>
>  The method used in #2 to aggregate the sun radiance is (mostly)
> described in this paper: J. Mardaljevic and M. Rylatt. Irradiation mapping
> of complex urban environments: an image-based approach. Energy and
> Buildings, 35(1):27–35, 1 2003. Send me an email if you have trouble
> getting hold of it.
>
>  Cheers
> John
>
>    John Mardaljevic
> Professor of Building Daylight Modelling
> School of Civil & Building Engineering
> Loughborough University
> Loughborough
> Leicestershire
> LE11 3TU, UK
>
> Tel: +44 1509 222630 (Direct)
> Tel: +44 1509 228529 (Pam Allen, secretary)
>
> j.mardaljevic at lboro.ac.uk
> http://www.lboro.ac.uk/departments/cv/staff/profile/367.html<http://www.lboro.ac.uk/departments/cv/>
>
>  Personal daylighting website:
> http://climate-based-daylighting.com
>
>
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>
>
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