[Radiance-general] Lux-values for points in a plane

[Per Haugaard]

Dear user group,

Yet another hurtle in my adventure through Radiance :)

I am trying to determine the LT-value (LightTransmission-value) for a pane with external shading. The first step is to calculate the LT-value correctly without external shading. I failed on that :)

I followed the steps described in the "Basic Radiance Tutorial" by Axel Jakobs. Here is the data i used.

Coordinates in IllumKoordinater.pts

6.216 0.00 1.8 0 -1 0 (window)
6.216 0.05 1.8 0 -1 0 (black wall located 0.05 m behind the window - in fact all walls are black)

The Window (LT=0,72):
void glass window_glass
0
0
3 .78 .78 .78

cat IllumKoordinater.pts | rtrace -I -ab 4 -h -w -oov kontor.oct | rcalc -e '$1=$2;$2=179*(.265*$4+.670*$5+.065*$6)' > lux.dat

Output
-1       4883.69
-0.95  3049.70

Two things worth noticing here. The output coordinates are not listed correctly which gives me the suspicion that lux-values are is not calculated for the correct coordinates. Furthermore the ratio between the output are not according to the entered LT-value for the window (0,62 vs. 0,72)

Does anyone have an idea of what can be wrong here?


Best regards

Per Hauagaard

 

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Per Haugaard,
Griffenfeldsgade 33, 2.tv
2200 København N
Denmark

mobil:  +45 26 39 06 40
E-mail: perhaugaard at yahoo.dk
       
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