{ RCSid: $Id: glaze2.cal,v 2.2 2003/06/30 18:12:24 greg Exp $ }
{
	glaze2.cal - double-pane fritted and low-E glazings

		Uses BRTDfunc type to get correct behavior.
		Oct. 2002 Greg Ward

	We only provide support functions for the nasty expressions
	spat out for dual-glazings by glaze.csh.
}
				{ Fresnel approximation }
fresne = exp(-5.85*abs(Rdot)) - exp(-5.85);
fr(r) = r + fresne*(1 - r);
ft(t) = t*(1 - fresne);
				{ glass reflectance and transmittance }
rclr = fr(0.076);
tclr = ft(0.883);
				{ combined double-pane reflectance }
cr(rf,t,rb) : rf + t*t*rb;
