src/px/brandom.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 *  brandom.c - blue noise function.
 *
 *      11/8/87
 */

#include  "random.h"


double
brandom(l)                      /* blue noise function */
int  l;                         /* length between 1 and 8 */
{
        static float  his[8] = {.5,.5,.5,.5,.5,.5,.5,.5};
        static double  avg = .5;
        static int  x = 0;
        double  y = frandom();
        
        if (avg < .5)
                y = 1 - 2*y*avg;
        else
                y = 2*y*(1 - avg);
                                        /* update */
        avg += (y - his[x])/l;
        his[x] = y;
        if (++x >= l) x = 0;
        
        return(y);
}
Revision:	1.2
Committed:	Sat Feb 22 02:07:27 2003 UTC (22 years, 9 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad3R6P1, rad3R6, rad3R5
Changes since 1.1:	+1 -4 lines
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
#	Content
1	#ifndef lint
2	static const char RCSid[] = "$Id$";
3	#endif
4	/*
5	* brandom.c - blue noise function.
6	*
7	* 11/8/87
8	*/
9
10	#include "random.h"
11
12
13	double
14	brandom(l) /* blue noise function */
15	int l; /* length between 1 and 8 */
16	{
17	static float his[8] = {.5,.5,.5,.5,.5,.5,.5,.5};
18	static double avg = .5;
19	static int x = 0;
20	double y = frandom();
21
22	if (avg < .5)
23	y = 1 - 2yavg;
24	else
25	y = 2y(1 - avg);
26	/* update */
27	avg += (y - his[x])/l;
28	his[x] = y;
29	if (++x >= l) x = 0;
30
31	return(y);
32	}