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 (21 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad3R6P1, rad3R5, rad3R6
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
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	1.2	static const char RCSid[] = "$Id$";
3	greg	1.1	#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			}