Hi,

I have a question concerning the definition of "glass" material. I am

trying to determine the transmittance of a window pane using spectrum

measurements.

I have derived the following values for rgb (0.78, 0.85, 0.80).

-Are those values determining transmittance or transmissivity?

-Can the transmittance be derived using the formula Tn = 0.265r + 0.67g +

0.065b ?

_Nicolas

Hi,

I have a question concerning the definition of "glass" material. I am trying

to determine the transmittance of a window pane using spectrum measurements.

I have derived the following values for rgb (0.78, 0.85, 0.80).

-Are those values determining transmittance or transmissivity?

Radiance expects transmissivity

-Can the transmittance be derived using the formula Tn = 0.265r + 0.67g + 0.065b ?

No. The formula is

Tn = (sqrt(0.8402529435+0.0072522239*t*t) - 0.9166530661) / 0.0036261119 / t

where t = transmittance and Tn = Transmissivity

Sorry for the format. I have copied it from a python script. Best thing I could

do in plain text.

I have a PDF document where this is further detailed. I just can't find it or

it's source on the web.

Regards,

Thomas

## ยทยทยท

On 20 Nov 2007, at 10:36, Nicolas Roy wrote: