cal/cal/sphsamp.cal

{
        Uniform sampling of sphere

        Define:
                N       - total number of samples
                i       - sample number

        Output:
                theta   - polar angle (degrees)
                phi     - azimuthal angle (degrees)
                Dx      - X-component of direction vector
                Dy      - Y-component of direction vector
                Dz      - Z-component of direction vector
}

DEGREE : PI/180;
bound(a,x,b) : if(a-x, a, if(x-b, b, x));
Acos(x) : acos(bound(-1,x,1));
Sqrt(x) : if(x, sqrt(x), 0);

nalt = floor(sqrt(2/PI*N) + .5);
nazi = floor(PI/2*nalt + .5);

cond = nalt*nazi-.9999 - i;

ialt = floor(i/nazi);
iazi = i - ialt*nazi;

ralt = (ialt + rand(i*.328+.112))/nalt;
razi = (iazi + rand(i*-.731+.318))/nazi;

rtheta = Acos(Dz);
rphi = 2*PI*razi;
Dxy = Sqrt(1 - Dz*Dz);
theta = rtheta/DEGREE;
phi = rphi/DEGREE;
Dx = Dxy*cos(rphi);
Dy = Dxy*sin(rphi);
Dz = 1 - 2*ralt;
Revision:	1.1
Committed:	Sat Feb 22 02:07:21 2003 UTC (21 years, 2 months ago) by greg
Branch:	MAIN
CVS Tags:	rad3R5, rad3R6, rad3R6P1
Log Message:	Changes and check-in for 3.5 release Includes new source files and modifications not recorded for many years See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release
#	User	Rev	Content
1	greg	1.1	{
2			Uniform sampling of sphere
3
4			Define:
5			N - total number of samples
6			i - sample number
7
8			Output:
9			theta - polar angle (degrees)
10			phi - azimuthal angle (degrees)
11			Dx - X-component of direction vector
12			Dy - Y-component of direction vector
13			Dz - Z-component of direction vector
14			}
15
16			DEGREE : PI/180;
17			bound(a,x,b) : if(a-x, a, if(x-b, b, x));
18			Acos(x) : acos(bound(-1,x,1));
19			Sqrt(x) : if(x, sqrt(x), 0);
20
21			nalt = floor(sqrt(2/PI*N) + .5);
22			nazi = floor(PI/2*nalt + .5);
23
24			cond = nalt*nazi-.9999 - i;
25
26			ialt = floor(i/nazi);
27			iazi = i - ialt*nazi;
28
29			ralt = (ialt + rand(i*.328+.112))/nalt;
30			razi = (iazi + rand(i*-.731+.318))/nazi;
31
32			rtheta = Acos(Dz);
33			rphi = 2PIrazi;
34			Dxy = Sqrt(1 - Dz*Dz);
35			theta = rtheta/DEGREE;
36			phi = rphi/DEGREE;
37			Dx = Dxy*cos(rphi);
38			Dy = Dxy*sin(rphi);
39			Dz = 1 - 2*ralt;