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root/radiance/ray/src/gen/perezlum.cal
Revision: 1.1
Committed: Sat Jun 6 20:20:04 2009 UTC (14 years, 9 months ago) by greg
Branch: MAIN
CVS Tags: rad4R2P2, rad5R0, rad5R1, rad4R2, rad4R1, rad4R0, rad4R2P1
Log Message:
Added Jean-Jacques Delaunay's gendaylit program to distribution

File Contents

# User Rev Content
1 greg 1.1 { RCSid $Id$ }
2    
3     {
4     All-weather Angular Sky Luminance Distribution .
5    
6     Additional arguments required for calculation of skybright:
7    
8     A1 - diffus normalization
9     A2 - ground brightness
10     A3,A4,A5,A6,A7 - coefficients for the Perez model
11     A8,A9,A10 - sun direction
12     }
13    
14    
15    
16    
17     skybright = wmean((Dz+1.01)^10, intersky, (Dz+1.01)^-10, A2 );
18    
19     wmean(a, x, b, y) = (a*x+b*y)/(a+b);
20    
21     intersky = if( (Dz-0.01),
22     A1 * (1 + A3*Exp(A4/Dz) ) * ( 1 + A5*Exp(A6*gamma) + A7*cos(gamma)*cos(gamma) ),
23     A1 * (1 + A3*Exp(A4/0.01) ) * ( 1 + A5*Exp(A6*gamma) + A7*cos(gamma)*cos(gamma) ) );
24    
25    
26    
27    
28     cosgamma = Dx*A8 + Dy*A9 + Dz*A10;
29    
30     gamma = Acos(cosgamma); { angle from sun to this point in sky }
31    
32     zt = Acos(A10); { angle from zenith to sun }
33    
34     eta = Acos(Dz); { angle from zenith to this point in sky }