As part of a project I am comparing measured data from both Berkeley and
the Isle de la Reunion to simulated illuminances under the Perez sky model
in both Radiance and 3ds Max Design, however Gendaylit seems to be
producing incorrect sky descriptions for the overcast days in the dataset.
I am wondering if I am missing something critical.
Below is the command I am using to produce a sky description, for 10:30am
on a particularly overcast winter day in Berkeley, with the measured direct
radiation being 0.15W/m^2 and the measured diffuse being 155.13 W/m^2:
gendaylit 12 4 10.5 -W 0.15 155.13 -g 0.2 -a 37.88 -o -122.25 -m -120 >
new.sky
This produces a sky that when simulated (using rtrace, with the -I option,
and multiplying by 179) only gives a global horizontal illuminance of
~12lux, rather than the expected ~19,000lux.
Using the -O option with a value of 2 produces a significantly brighter sky
providing ~800 lux, still far from what I am expecting.
Hopefully someone can spot the problem straight away;
Cheers,
Jake Osborne
Hi Jack,
you missed obviously something important - either you missed to generate the sky (then you have just the sun influence) or you made a mistake in using rtrace.
It has nothing to do with gendaylit.
you need a sky description like this:
skyfunc glow sky_glow
0
4 1 1 1 0
sky_glow source sky
0
4 0 0 1 180
skyfunc glow ground_glow
0
4 1 1 1 0
ground_glow source ground
0
4 0 0 -1 180
putting that into an octree:
oconv -f new.sky outside.rad >test.oct
and then call rtrace using the -I and -ab 1 option:
echo 0 0 0 0 0 1 |rtrace -h -I -ab 1 test.oct | rcalc -e '$1=47.4*$1+120*$2+11.6*$3'
Then you get: 17572.5875 lux.
Best,
Jan
···
On 03/21/2012 09:34 AM, Jake Osborne wrote:
As part of a project I am comparing measured data from both Berkeley and the Isle de la Reunion to simulated illuminances under the Perez sky model in both Radiance and 3ds Max Design, however Gendaylit seems to be producing incorrect sky descriptions for the overcast days in the dataset. I am wondering if I am missing something critical.
Below is the command I am using to produce a sky description, for 10:30am on a particularly overcast winter day in Berkeley, with the measured direct radiation being 0.15W/m^2 and the measured diffuse being 155.13 W/m^2:
gendaylit 12 4 10.5 -W 0.15 155.13 -g 0.2 -a 37.88 -o -122.25 -m -120 > new.sky
This produces a sky that when simulated (using rtrace, with the -I option, and multiplying by 179) only gives a global horizontal illuminance of ~12lux, rather than the expected ~19,000lux.
Using the -O option with a value of 2 produces a significantly brighter sky providing ~800 lux, still far from what I am expecting.
Hopefully someone can spot the problem straight away;
Cheers,
Jake Osborne
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Dr.-Ing. Jan Wienold
Head of Team Passive Systems and Daylighting
Fraunhofer-Institut für Solare Energiesysteme
Thermal Systems and Buildings
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Phone: +49(0)761 4588 5133 Fax:+49(0)761 4588 9133
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Fr: 8:30-15:30
Hi, thanks Jan,
That was it. Not sure how I missed it; perhaps thinking too hard and missed
the obvious.
Cheers,
Jake Osborne
It's a FAQ, along with the "no light sources" message.
Randolph
···
On 2012-03-21 11:29:52 +0000, Jake Osborne said:
Hi, thanks Jan,
That was it. Not sure how I missed it; perhaps thinking too hard and missed the obvious.
Cheers,
Jake Osborne
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Randolph M. Fritz