/usr/share/radiance/glazing.cal is in radiance-materials 4R1+20120125-1.1.
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The following calculation uses the BRTDfunc type to reproduce the
calculation used by LBL's Window 4 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.
5/20/93 Greg Ward
Arguments used for this material should look like:
mod BRTDfunc my_glazing
10 rrho grho brho
rtau gtau btau
0 0 0
glazing.cal
0
18 0 0 0
0 0 0
0 0 0
FRRHO FGRHO FBRHO
BRRHO BGRHO BBRHO
RTAU GTAU BTAU
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;
{ get normal transmittance }
Tred = arg(16)*CrP;
Tgrn = arg(17)*CgP;
Tblu = arg(18)*CbP;
{ reflectance coefficients }
Rclear = .999 + RdotP*(-.563 + RdotP*(2.043 + RdotP*(-2.532 + RdotP*1.054)));
Rbronze = .997 + RdotP*(-1.868 + RdotP*(6.513 + RdotP*(-7.862 + RdotP*3.225)));
{ transmittance coefficients }
Tclear = -.0015 + RdotP*(3.355 + RdotP*(-3.840 + RdotP*(1.460 + RdotP*.0288)));
Tbronze = -.002 + RdotP*(2.813 + RdotP*(-2.341 + RdotP*(-.05725 + RdotP*.599)));
Tcutoff : .645; { transmittance cutoff constant }
{ returned spectral reflectance }
rrho = Rred*if(Tred-Tcutoff, Rclear, Rbronze);
grho = Rgrn*if(Tgrn-Tcutoff, Rclear, Rbronze);
brho = Rblu*if(Tblu-Tcutoff, Rclear, Rbronze);
{ returned spectral transmittance }
rtau = Tred*if(Tred-Tcutoff, Tclear, Tbronze);
gtau = Tgrn*if(Tgrn-Tcutoff, Tclear, Tbronze);
btau = Tblu*if(Tblu-Tcutoff, Tclear, Tbronze);
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