[Radiance-general] daylight factor and rtrace cmd

[Thomas Bleicher]

As Chris wrote, -I implies an observer point 1m above the 'point of interest'.
But it also turns around the view vector (your output shows -1.000000e+000).

Basically rtrace introduces a virtual plane of lambertian properties and looks
down onto this plane to calculate the irridance from the reflection (which is
identical).

The offset of 1m is only a problem if you want to use the output to anchor
your results in a model or if your workplane is close to an obstruction that's
lower than 1m above the plane. Then the rtrace rays would hit the back
of the obstruction and not the ideal reflector.

But then, perhaps Greg has anticipated this case and added some magic to
avoid it ...

Thomas


On Thu, Jul 16, 2009 at 5:17 PM, PAUPELIN-HUCHARD
Valere<v.paupelin-huchard at elioth.fr> wrote:
> Hello,
>
> I'm trying to do daylight factor calculation. I am observing a 1
> meter height offset between my workplan point file which is already at 0.85m
> above the floor (*.fld) and the rtrace result (*.irr).
> Someone would tell me why?
>
> the command used is:
> rtrace -ab 7 -ad 2048 -oodv -I
> rcp.oct<numeric/plan_de_travail.fld>numeric/090715_BU_Rennes_07_vitrage_irradiance.irr
>
> four first lines sample of the files:
>
> plan_de_travail.fld:
> x          y         z         o
> 0.50     -0.25     1.84     0 0 1
> 0.50     0.00      1.84     0 0 1
> 0.50     0.25      1.84     0 0 1
> 0.50     0.50      1.84     0 0 1
>
> 090715_BU_Rennes_07_vitrage_irradiance.irr
> x                        y                        z
> o
> r                         g                         b
> 5.000000e-001    -2.500000e-001     2.840000e+000
> 0.000000e+000 0.000000e+000 -1.000000e+000     1.406147e-001
> 1.406147e-001     1.406147e-001
> 5.000000e-001     0.000000e+000    2.840000e+000
> 0.000000e+000 0.000000e+000 -1.000000e+000     1.581891e-001
> 1.581891e-001     1.581891e-001
> 5.000000e-001     2.500000e-001     2.840000e+000
> 0.000000e+000 0.000000e+000 -1.000000e+000     1.765201e-001
> 1.765201e-001     1.765201e-001
> 5.000000e-001     5.000000e-001     2.840000e+000
> 0.000000e+000 0.000000e+000 -1.000000e+000     1.890535e-001
> 1.890535e-001     1.890535e-001
>
> I am afraid my daylight factor result are not valid at the height of 1.84m
> but at 2.84m, am I wrong?
>
> Thanks,
> Valere.
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