{ RCSid $Id: window.cal,v 2.1 2006/05/19 03:50:13 greg Exp $ }
{
	The following calculation uses the BRTDfunc type to reproduce the
	calculation used by LBL's Optics 5 program for the transmittance
	and reflectance of coated glazings.  This calculation is based
	on fits for the angular dependence for clear and bronze-coated
	glazing, and is not terribly accurate.  The variables ??_clear
	below should be replaced by ??_bronze in the case of the bronze
	glazing model.  Used with optics2rad script.

	5/18/2006	Greg Ward

	Arguments used for this material should look like:

	mod BRTDfunc my_glazing
	10	rR_clear	rG_clear	rB_clear
		RTAU*tR_clear	GTAU*tG_clear	BTAU*tB_clear
		0	0	0
		window.cal
	0
	15	0	0	0
		0	0	0
		0	0	0
		FRRHO	FGRHO	FBRHO
		BRRHO	BGRHO	BBRHO

	where:
		FRRHO	FGRHO	FBRHO	is front normal spectral reflectance
		BRRHO	BGRHO	BBRHO	is back normal spectral reflectance
		RTAU	GTAU	BTAU	is normal spectral transmittance
}
				{ get normal reflectance }
rbase = if(Rdot,10,13);			{ different front and back }
Rred = arg(rbase)*CrP;
Rgrn = arg(rbase+1)*CgP;
Rblu = arg(rbase+2)*CbP;
				{ transmittance coefficients }
Tclear = clip(-.0015 + RdotP*(3.355 + RdotP*(-3.840 +
			RdotP*(1.460 + RdotP*.0288))));

Tbronze = clip(-.002 + RdotP*(2.813 + RdotP*(-2.341 +
			RdotP*(-.05725 + RdotP*.599))));

				{ reflectance coefficients }
Rclear = clip(.999 + RdotP*(-.563 + RdotP*(2.043 +
			RdotP*(-2.532 + RdotP*1.054))) - Tclear);

Rbronze = clip(.997 + RdotP*(-1.868 + RdotP*(6.513 +
			RdotP*(-7.862 + RdotP*3.225))) - Tbronze);

				{ returned spectral transmittance }
tR_clear = CrP*Tclear;
tG_clear = CgP*Tclear;
tB_clear = CbP*Tclear;

tR_bronze = CrP*Tbronze;
tG_bronze = CgP*Tbronze;
tB_bronze = CbP*Tbronze;
				{ returned spectral reflectance }
rR_clear = Rred*(1 - Rclear) + Rclear;
rG_clear = Rgrn*(1 - Rclear) + Rclear;
rB_clear = Rblu*(1 - Rclear) + Rclear;

rR_bronze = Rred*(1 - Rbronze) + Rbronze;
rG_bronze = Rgrn*(1 - Rbronze) + Rbronze;
rB_bronze = Rblu*(1 - Rbronze) + Rbronze;