/usr/share/radiance/perezlum.cal is in radiance-materials 4R0+20110410-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | { RCSid $Id: perezlum.cal,v 1.1 2009/06/06 20:20:04 greg Exp $ }
{
All-weather Angular Sky Luminance Distribution .
Additional arguments required for calculation of skybright:
A1 - diffus normalization
A2 - ground brightness
A3,A4,A5,A6,A7 - coefficients for the Perez model
A8,A9,A10 - sun direction
}
skybright = wmean((Dz+1.01)^10, intersky, (Dz+1.01)^-10, A2 );
wmean(a, x, b, y) = (a*x+b*y)/(a+b);
intersky = if( (Dz-0.01),
A1 * (1 + A3*Exp(A4/Dz) ) * ( 1 + A5*Exp(A6*gamma) + A7*cos(gamma)*cos(gamma) ),
A1 * (1 + A3*Exp(A4/0.01) ) * ( 1 + A5*Exp(A6*gamma) + A7*cos(gamma)*cos(gamma) ) );
cosgamma = Dx*A8 + Dy*A9 + Dz*A10;
gamma = Acos(cosgamma); { angle from sun to this point in sky }
zt = Acos(A10); { angle from zenith to sun }
eta = Acos(Dz); { angle from zenith to this point in sky }
|