/usr/share/radiance/glaze1.cal is in radiance-materials 4R1+20120125-1.1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | { RCSid: $Id: glaze1.cal,v 2.3 2008/02/18 23:44:39 greg Exp $ }
{
glaze1.cal - single-pane fritted and low-E glazings
Uses BRTDfunc type to get correct behavior.
Oct. 2002 Greg Ward
Material parameters for fritted glazing are:
arg(10) - orientation (1 == glass front)
arg(11) - fractional coverage
Parameters for low-E glazing are:
arg(10) - orientation (1 == glass front)
arg(11) - glass-side reflectance (red)
arg(12) - glass-side reflectance (green)
arg(13) - glass-side reflectance (blue)
arg(14) - coating-side reflectance (red)
arg(15) - coating-side reflectance (green)
arg(16) - coating-side reflectance (blue)
arg(17) - transmittance (red)
arg(18) - transmittance (green)
arg(19) - transmittance (blue)
}
{ Fresnel approximation }
fresne = exp(-5.85*abs(Rdot)) - exp(-5.85);
fresne_refl(r) = r + fresne*(1 - r);
fresne_trans(t) = t*(1 - fresne);
{ glass reflectance and transmittance }
glass_refl = fresne_refl(0.076);
glass_trans = fresne_trans(0.883);
clear_side = arg(10) * Rdot; { ray coming from plain side? }
frac_glass = 1 - arg(11); { glass coverage }
{ frit specular components }
sr_frit_r = if(clear_side, glass_refl, frac_glass*glass_refl);
sr_frit_g = if(clear_side, glass_refl, frac_glass*glass_refl);
sr_frit_b = if(clear_side, glass_refl, frac_glass*glass_refl);
st_frit_r = frac_glass*glass_trans;
st_frit_g = frac_glass*glass_trans;
st_frit_b = frac_glass*glass_trans;
{ low-E specular components }
sr_clear_r = fresne_refl(if(clear_side, arg(11), arg(14)));
sr_clear_g = fresne_refl(if(clear_side, arg(12), arg(15)));
sr_clear_b = fresne_refl(if(clear_side, arg(13), arg(16)));
st_clear_r = fresne_trans(arg(17));
st_clear_g = fresne_trans(arg(18));
st_clear_b = fresne_trans(arg(19));
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