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root/radiance/ray/src/cal/cal/trans.cal
Revision: 1.2
Committed: Wed Oct 8 17:10:53 2003 UTC (20 years, 6 months ago) by greg
Branch: MAIN
CVS Tags: rad5R4, rad5R2, rad4R2P2, rad5R0, rad5R1, rad3R7P2, rad3R7P1, rad4R2, rad4R1, rad4R0, rad3R6, rad3R6P1, rad3R8, rad3R9, rad4R2P1, rad5R3, HEAD
Changes since 1.1: +23 -3 lines
Log Message:
Added formula for normal reflectance

File Contents

# User Rev Content
1 greg 1.2 { RCSid $Id$ }
2     {
3     These formulas give exact results from the infinite
4     series solution for an uncoated pane of glass.
5    
6     Inputs:
7     Tn = normal transmittance
8     n = index of refraction
9    
10     Outputs:
11     rn = single-layer normal reflectivity
12     tn = transmissivity
13     Rn = normal reflectance
14     }
15     Tn = 0.88; { normal transmittance }
16     n = 1.52; { index of refraction }
17    
18 greg 1.1 sq(x) : x*x;
19 greg 1.2
20     rn = sq((1-n)/(1+n));
21    
22     tn = (sqrt(sq(sq(1-rn))+4*sq(rn*Tn))-sq(1-rn)) / (2*sq(rn)*Tn);
23    
24     Rn = rn + rn*sq((1-rn)*tn)/(1-sq(tn*rn));