[Radiance-general] Again transmissivity for color filter / glass

[Christian Fusenig]

Hi Greg,

thank you again and YES it is confusing!

>Actually, the Y value of transmittance can change for different light  
>sources.
>
Forget my other question, at first i want to make sure that i model a 
simple filter in the right way.
And that is why i want to stick to the values LEE gives for a 3200K lamp.
These are: X= 58.8 , Y=62.4 , Z=37.2
with xyz_srgb.cal i get: R= 76.088002   G=61.6146944   B= 29.8622268, ( 
i want to calculate this with the D65 white point)
As the filter won't have a bigger transmission than 1, i divide through 
100.
Now i get values of: R= .761   G= .616   B= .299;
If i apply these to glass polygon i get a yellow/orange filter with my 
tungsten 3200 K source in the scene.
Then is subtract 1 from RGB =  .239 , .384,  .701;
 These values should now represent my blue filter, and it looks quite good!

void glass LeeGlass
	0
	0
	3  .239  .384  .701

Am i right up to now?

These values would then be my normal transmittance. In order to model a disc of 'real'colored glass (e.g. n=1.52) i would apply these values to 'trans.cal' how you suggested an get the transmissivity.
rcalc -f trans.cal -e '$1=tn($1)'
.239
0.260699013
.384
0.418782103
.701
0.763929466

Am i right here too?

Now i want to triple the effect of the filter, that means have 3  blue filters in a row. My Y=.624 would then be 
Y³ = .243, can i simply multiply my normal transmittance of RGB with this factor to get the triple effect?

I know these are pretty simple questions, but as i plan to use the 'trans' material later i want to make sure to be on the right way!

Christian