[Radiance-general] How to calculate the ( rtn gtn btn ) values of the material type glass ?

[Greg Ward]

Good question.  Apply the formula you cite at each of three wavelengths:

	Red:	700 nm
	Green:	546 nm
	Blue:	436 nm

-Greg

> From: marina aviles <marina.aviles at gmail.com>
> Date: March 11, 2009 4:12:27 AM PDT
>
> Hello all,
>
> i don´t know haw can you get the values rtn, gtn and btn of the  
> material description "glass":
>
> void   glass  id
> 0
> 0
> 3   rtn  gtn  btn
>
> from some glass samples.
>
> I have measured their transmittance values with a Spectrometer  
> ( Varian - Cary 5000) in the field 350 - 780 nm wavelenght and have  
> calculate the Transmittace.
> Should I then calculate the transmissivity from the transmittance  
> by computing
> tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/ 
> Tn ?
>
>
> and, in this case, how can I get the values rtn, gtn and btn?
>
> Thanks a lot,
>
> Marina