src/common/multisamp.c

/* Copyright (c) 1997 Silicon Graphics, Inc. */

#ifndef lint
static char SCCSid[] = "$SunId$ SGI";
#endif

#include "random.h"

/*
 * Binary space partitioning curve for multidimensional sampling.
 *
 *      Written by Christophe Schlick
 */

multisamp(t, n, r)      /* convert 1-dimensional sample to N dimensions */
double  t[];                    /* returned N-dimensional vector */
register int    n;              /* number of dimensions */
double  r;                      /* 1-dimensional sample [0,1) */
{
        int     j;
        register int    i, k;
        int     ti[8];
        double  s;

        i = n;
        while (i-- > 0)
                ti[i] = 0;
        j = 8;
        while (j--) {
                k = s = r*(1<<n);
                r = s - k;
                i = n;
                while (i-- > 0)
                        ti[i] += ti[i] + ((k>>i) & 1);
        }
        i = n;
        while (i-- > 0)
                t[i] = 1./256. * (ti[i] + frandom());
}
Revision:	2.2
Committed:	Mon Dec 1 09:54:59 1997 UTC (26 years, 5 months ago) by gregl
Content type:	text/plain
Branch:	MAIN
Changes since 2.1:	+5 -3 lines
Log Message:	added define to eliminate initurand() reference for -DMC
#	Content
1	/* Copyright (c) 1997 Silicon Graphics, Inc. */
2
3	#ifndef lint
4	static char SCCSid[] = "$SunId$ SGI";
5	#endif
6
7	#include "random.h"
8
9	/*
10	* Binary space partitioning curve for multidimensional sampling.
11	*
12	* Written by Christophe Schlick
13	*/
14
15	multisamp(t, n, r) /* convert 1-dimensional sample to N dimensions */
16	double t[]; /* returned N-dimensional vector */
17	register int n; /* number of dimensions */
18	double r; /* 1-dimensional sample [0,1) */
19	{
20	int j;
21	register int i, k;
22	int ti[8];
23	double s;
24
25	i = n;
26	while (i-- > 0)
27	ti[i] = 0;
28	j = 8;
29	while (j--) {
30	k = s = r*(1<<n);
31	r = s - k;
32	i = n;
33	while (i-- > 0)
34	ti[i] += ti[i] + ((k>>i) & 1);
35	}
36	i = n;
37	while (i-- > 0)
38	t[i] = 1./256. * (ti[i] + frandom());
39	}