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greg |
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/* Copyright (c) 1986 Regents of the University of California */
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#ifndef lint
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static char SCCSid[] = "$SunId$ LBL";
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#endif
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/*
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* brandom.c - blue noise function.
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*
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* 11/8/87
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*/
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#include "random.h"
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double
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brandom(l) /* blue noise function */
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int l; /* length between 1 and 8 */
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{
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static float his[8] = {.5,.5,.5,.5,.5,.5,.5,.5};
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static double avg = .5;
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static int x = 0;
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double y = frandom();
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if (avg < .5)
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y = 1 - 2*y*avg;
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else
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y = 2*y*(1 - avg);
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/* update */
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avg += (y - his[x])/l;
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his[x] = y;
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if (++x >= l) x = 0;
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return(y);
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}
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