[Radiance-general] I can't get even similar irradiance values from a lamp.

[Greg Ward]

How did you measure the UV reflectance of the surfaces of your box?   
Most paints drop off dramatically from the visible spectrum to UV.   
White paints may re-emit UV as visible so they appear "whiter" under  
daylight illumination.  You really need to know the behavior of your  
paint with respect to ultraviolet wavelengths to do this correctly.

-Greg

> From: Minki Sung <minki.sung at gmail.com>
> Date: March 14, 2009 10:52:03 PM PDT
>
> Dear Radiance users,
>
> I'm writing here for third time and I always sorry for just asking.  
> I'm modeling a small box has a several bared cylindrical  
> fluorescent lamps (actually UV lamps) inside and want to know the  
> irradiance level on the surfaces of the box. The cylindrical lamps  
> has 32mm in diameter and 540mm in length and The radiance of 44W/sr/ 
> m2 calculated with the UV output of the lamps (7.5W) was applied to  
> the lamps. Before calculating the small box model I checked  
> irradiance values with an experiment measuring UV intensity at the  
> distance of 1 m and compared that with the same simple RADIANCE  
> calculation and the result was reasonable. However, the calculation  
> results are higher than those of experiments by 2~4 times with the  
> small box model. The small box is not simple but not so  
> complicated. I have modeled the lamp both as a cylinder and 72  
> polygons  but there were not so much changes. Only one channel was  
> used to calculate irradiances of UV from modeling to issuing  
> results and only diffused reflections were assumed. Geometric  
> errors or abnormal radiance distributions of lamps could be assumed  
> to cause the discrepancy, but 2~5 times are too large
> Here is my rtrace options.
>
> cat pts_sensor.pts | rtrace -I -oov -ar 128 -ad 512 -as 256 -ab 2 - 
> ds 0.02 uv.oct > uv.dat
>
> It would be appreciated if anyone give me advice.
>
>
> Sung