[Radiance-general] calculating transmissivity

[Rob Guglielmetti]

mastersb@conwag.com wrote:
> Project Code : .
> 
> I am having trouble calculating the correct transmissity values to use
> within Radiance.
> 
> The transmittance values i need to calculate from are 0.46 and 0.70. Can
> someone please tell me what the corresponding transmissivity values will
> be?
> I am trying to use a formula from the Rayfront website, but I am getting
> some strange results...

There is a .cal file in the UNIX distribution (in /src/cal/cal) of 
Radiance that you can use with the calc utility to easily compute these 
values.  You type "calc /path/to/trans.cal" at the comand line, and feed 
it your transmission values (tn), and it spits out a transmissivity value:

% calc trans.cal (or full pathname if not in a PATH location)
tn(.88)
$1=0.958415435
tn(.57)
$2=0.621392084

Just keep on feedin' it values and recording the output, and hit 
control+D to quit when you're done.

----

      Rob Guglielmetti

e. rpg@rumblestrip.org
w. www.rumblestrip.org