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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: sphsamp.cal,v 1.3 2005/02/15 23:45:14 greg Exp $ }
{
Jittered sampling of a sphere
2/15/2005 G. Ward
Constant:
N - total number of samples on sphere
Input:
i - sample number [0,N-1]
Output:
theta - polar angle (0-PI)
phi_un - azimuthal angle (unnormalized)
phi - azimuthal angle (0-2*PI)
Dx - X-component of direction vector
Dy - Y-component of direction vector
Dz - Z-component of direction vector
}
S : .7; { jitter amount (0-1) }
k : 2*sqrt(PI/N); { k^2 is solid angle of each sample }
mod(n,d) : n - floor(n/d)*d;
alpha0 = asin(2/N*(i+.5) - 1);
theta = alpha0 + PI/2 + k*S*(rand(.35*i+10.3) - .5);
phi_un = sqrt(PI*N)*alpha0 + k*S*(rand(-.83*i-17.9) - .5);
phi = mod(phi_un, 2*PI);
sint = sin(theta);
Dx = cos(phi)*sint;
Dy = sin(phi)*sint;
Dz = cos(theta);
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