This is supposed to be a basic question.

I am running the example in the “Radiance_tutorial” to learn how to get illuminance reading using **rtrace**. The dimensions of the room are 4m*5m*3m. Then, I placed two bulbs at a height of 2.6m, and the total lumens of each bulb is 1,500 lumens.

In the tutorial, these two bulbs will give approx. 500lux illuminance at a height of 0.85m, but my simulation just gives me approx. 100 lux?

This is the commands I used to calculate the Illuminance values.

"cat data/line.pts | rtrace -I -ab 3 -h -oov scene.oct | rcalc -e ’$1=179*(.265*$4+.670*$5+.065*$6)’ "

I don’t know what is missing in my calculation.

Thanks in advance

Fan