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root/radiance/ray/src/gen/skybright.cal
Revision: 2.2
Committed: Fri Mar 20 12:23:37 1992 UTC (32 years ago) by greg
Branch: MAIN
Changes since 2.1: +2 -1 lines
Log Message:
added +c option for uniform cloudy sky

File Contents

# Content
1 { SCCSid "$SunId$ LBL" }
2
3 {
4 Sky brightness function for sunny and cloudy skies.
5
6 6/6/86
7
8 Additional arguments required for calculation of skybright:
9
10 A1 - boolean, positive for cloudy sky
11 (A1>=2 for cloudy uniform sky)
12 A2 - zenith brightness
13 A3 - ground plane brightness
14 A4 - normalization factor based on sun direction
15 A5,A6,A7 - sun direction
16 }
17
18 skybright = wmean((Dz+1.01)^10, if(A1, cloudysky, sunnysky),
19 (Dz+1.01)^-10, A3);
20
21 wmean(a, x, b, y) = (a*x + b*y) / (a + b);
22
23 cloudysky = A2 * if(A1-1, 1, (1 + 2*Dz)/3);
24
25 sunnysky = A2 * (.91 + 10*exp(-3*gamma) + .45*cosgamma*cosgamma)
26 * if( Dz - .01, 1.0 - exp(-.32/Dz), 1.0) / A4;
27
28 gamma = Acos(cosgamma);
29
30 cosgamma = Dx*A5 + Dy*A6 + Dz*A7;