[Radiance-general] Daylight factor

[Thomas Bleicher]

Victor.

There are a couple of things you should change. If you can't change the
options ECOTECT uses you can run the simulation manually as Marija
has shown above and then read the results back into ECOTECT.

More details within:

On Sun, Dec 13, 2009 at 4:28 AM, Victor Li <victorpermanent at gmail.com> wrote:
> Thank you very much!
>
> Actually i uesed ECOTET exported to DESKTOP RADIANCE to calculate.
> The only differernce between Daylight factor and Illuminance calculation is
> the -B 0.558659 definition in 11_SKY.RAD
>
> In Daylight factor calculation the sky is defined as following:
>
> !gensky 12 21 12.00 -c -a 31.400 -o -121.400 -m -120.000 -B 0.558659 | xform
> -rz -27.000

I can't see a difference between the two gensky commands below but the
"-B 0.558659" will create a sky with 100 Lux diffuse vertical illuminance. This
is very low if you want to calculate Lux values. The only reason to do this
is that you don't have to convert from a 10000 Lux baseline to 100 Lux (or %)
if you want to calculate daylight factors.

Since both setups and scene files (skies) are the same you would
expect the same values for both calculations. However, your settings
for the rtrace command are not very accurate so the absolute results
are going to be different. You haven't told us yet how big the difference
is, btw.

[copied from an older mail]:
>> The rtrace setting is "rtrace -I -h -dp 2048 -ar 32 -ms 0.063 -ds .2 -dt
>> .05 -dc .75 -dr 3 -sj 1 -st .01 -ab 8 -aa .1 -ad 512 -as 256 -av 0.01 0.01
>> 0.01 -lr 12 -lw .0005  -af 11.amb 11.oct < 11.pts > 11.dat"  And the two

For more accuracy I would use something like:
"-ar 128 -ab 6 -aa 0.01 -ad 2048 -as 256"

Mind you, I don't know anything about your scene so these may not
be the right settings at all.

The remaining settings are less important in a daylight calculation
without sun. I would also remove the "-av 0.01 0.01 0.01" because
that would introduce a large amount of artificial ambient light that
is too high for you 100Lux outdoor illuminance.

[...]

> skyfunc glow ground_glow
> 0
> 0
> 4
>      1 .8 .5 0
>
> ground_glow source ground
> 0
> 0
> 4
>      0 0 -1 180

This creates a "ground" hemisphere that is nearly as bright as
the sky (about 80%). You should reduce the values in the
ground_glow definition to a quarter of their current setting
(unless you have ground covered in snow):

skyfunc glow ground_glow
0
0
4
     0.25 0.2 0.125 0

[...]


> In Illuminance calculation, the definition is :
>
> !gensky 12 21 12.00 -c -a 31.400 -o -121.400 -m -120.000 -B 0.558659 | xform
> -rz -27.000
>
> The rest is all the same.
>
> For converting the output, the ECOTECT can convert it automatically.

ECOTECT can read "single" value and "[r,g,b]" value output, but the
values have to be in the right scale. If you want your DF values
to mean anything you have to know the outside illuminance of the
sky and scale all the values if it is anything else than 100 lux.

Hth,
Thomas