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greg |
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{ RCSid: $Id$ } |
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{ |
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glaze1.cal - single-pane fritted and low-E glazings |
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Uses BRTDfunc type to get correct behavior. |
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Oct. 2002 Greg Ward |
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Material parameters for fritted glazing are: |
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arg(10) - orientation (1 == glass front) |
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arg(11) - fractional coverage |
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Parameters for low-E glazing are: |
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arg(10) - orientation (1 == glass front) |
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arg(11) - glass-side reflectance (red) |
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arg(12) - glass-side reflectance (green) |
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arg(13) - glass-side reflectance (blue) |
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arg(14) - coating-side reflectance (red) |
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arg(15) - coating-side reflectance (green) |
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arg(16) - coating-side reflectance (blue) |
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arg(17) - transmittance (red) |
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arg(18) - transmittance (green) |
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arg(19) - transmittance (blue) |
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} |
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{ Fresnel approximation } |
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fresne = exp(-6*abs(Rdot)) - exp(-6); |
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fresne_refl(r) = r + fresne*(1 - r); |
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fresne_trans(t) = t*(1 - fresne); |
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{ glass reflectance and transmittance } |
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glass_refl = fresne_refl(0.076); |
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glass_trans = fresne_trans(0.883); |
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clear_side = arg(10) * Rdot; { ray coming from plain side? } |
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frac_glass = 1 - arg(11); { glass coverage } |
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{ frit specular components } |
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sr_frit_r = if(clear_side, glass_refl, frac_glass*glass_refl); |
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sr_frit_g = if(clear_side, glass_refl, frac_glass*glass_refl); |
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sr_frit_b = if(clear_side, glass_refl, frac_glass*glass_refl); |
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st_frit_r = frac_glass*glass_trans; |
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st_frit_g = frac_glass*glass_trans; |
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st_frit_b = frac_glass*glass_trans; |
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{ low-E specular components } |
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sr_lowE_r = fresne_refl(if(clear_side, arg(11), arg(14))); |
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sr_lowE_g = fresne_refl(if(clear_side, arg(12), arg(15))); |
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sr_lowE_b = fresne_refl(if(clear_side, arg(13), arg(16))); |
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st_lowE_r = fresne_trans(arg(17)); |
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st_lowE_g = fresne_trans(arg(18)); |
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st_lowE_b = fresne_trans(arg(19)); |
