[Radiance-general] Ambient parameters optimization/tweaking

[Vaib]

Thank you Lars, Andrew, Rob..

After including the sky glow and source, the issue of 'no illuminance' is
solved.. That make sense..
I am now trying different ambient options based on Lars suggestion, and the
results are getting closer.. Thank you all again..

Best regards,
Vaib


On 2 April 2014 19:47, Guglielmetti, Robert <Robert.Guglielmetti at nrel.gov>wrote:

> A short add to Andy's post, you will notice Andy is defining the sky and
> ground hemispheres as a single 360-degree source, called "skyball".  This
> works because skyfunc will automatically use the ground ambient value
> (adjusted with the -g option to gensky) when the ray direction vector has a
> negative zed value.
>
> This is, in a word, cool.
>
> Some more words: this means Radiance will automatically derate the "sky"
> luminance when a traced ray hits below the horizon, knowing that it's
> actually hitting the "ground", and not the sky. The default for -g is 0.20,
> for a 20% reflectance ground "plane". Reasonable enough, but be advised you
> should really also have actual geometry to define the local exterior
> environment -- this includes the ground as well as neighboring buildings, so
> that your local ground is shaded by your building and its neighbors.
>
> - Rob
>
> On 4/2/14, 11:24 AM, "Andrew McNeil" <amcneil at lbl.gov<mailto:
> amcneil at lbl.gov>> wrote:
>
> Hi Vaib,
>
> I believe you have a more fundamental error in your model. gendaylit and
> gensky do not create the sky source, you have to manually add a sky
> material and source to your model. If you append the text at the end of
> this email to your sky description I believe you will have non zero
> illuminance for the north facing window. Though you will still need to
> adjust ambient parameters to suit your model as Lars describes.
>
> Best,
> Andy
>
> ### Add the following to the end your sky sky description:
> skyfunc glow skymat
> 0
> 0
> 4 1 1 1 0
>
> skymat source skyball
> 0
> 0
> 4 0 0 1 360
>
>
>
>
> On Wed, Apr 2, 2014 at 6:07 AM, Vaib <vaibhavjain.co at gmail.com<mailto:
> vaibhavjain.co at gmail.com>> wrote:
> Hello Everyone!
>
> For my master thesis project, I have conducted an experiment to measure
> daylighting/lighting illuminance on the last Equinox days in Vienna. The
> room is a small hall (7mx9m), has white walls/ceilings, and only North
> facing windows. I have measured reflectivity of all the surface to come
> closer to the reality.
>
> Now I have to calibrate my simulation model to match its illuminance
> output with the measured illuminance, for both daylight and artificial
> light condition.
>
> For daylight, gendaylit sky model is used (listed below), and all
> artificials lights are off. For this case, I have tried a number of ambient
> parameter combinations (listed below), but since all windows are facing
> North, the simulation model only results in 0 illuminance. When I rotated
> the North offset, to face windows towards South then I get some
> illuminance. From this it seems that windows North orientation is the
> reason behind 0 illuminance. In measurements, these values are approx. 1500
> lux.
>
> My question is: What ambient parameters should be tweaked so that the
> model behaves reasonably (especially for daylight)?
>
> I am following Dr.John Mardaljevic's PhD for ambient parameters
> combination. But I don't have much time to do an extensive parametric
> analysis of these parameters.
>
> Global, and Diffuse irradiance (for gendaylit) are taken from weather
> station in place.
>
> I have tried only rtrace. May be I shall use rsensor now ??
>
> Thank you for your time.
>
> Best regards,
> Vaib
>
> Ambient parameter combinations:
> 1. rtrace -w -as 512 -ar 512 -aa 0.15 -ab 2 -I -h foo.oct | rcalc -e
> '$1=($1*.265+$2*.67+$3*.065)*179'
>
> 2. cat allSens.txt | rtrace -w -ab 7 -ad 2048 -as 32 -I -h foo.oct | rcalc
> -e '$1=($1*.265+$2*.67+$3*.065)*179'
>
> 3. cat allSens.txt | rtrace -w -ab 7 -ad 2048 -ar 2 -aa 0.10 -as 32 -I -h
> foo.oct | rcalc -e '$1=($1*.265+$2*.67+$3*.065)*179'
>
> 4. cat allSens.txt | rtrace -w -ab 7 -ad 2048 -ar 64 -aa 0.15 -as 512 -I
> -h foo.oct | rcalc -e '$1=($1*.265+$2*.67+$3*.065)*179'
>
> Gendaylit model for (12:00 time):
> # xform -rz 30
> # gendaylit 03 22 12:00 -a 48.198724 -o -16.369458 -m -15.00 -W 967.3 187.2
> # Ground ambient level: 33.9
>
> void light solar
> 0
> 0
> 3            7791000            7791000            7791000
>
> solar source sun
> 0
> 0
> 4     0.378842567554    -0.642038575073           0.666532
>  0.533
>
> void brightfunc skyfunc
> 6 skybright perezlum.cal -i 1 -rz 30
> 0
> 10              38.97              29.25          -0.878528
>  -0.366494          12.997644           -3.44062           0.249106
>   0.007068
>
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