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/* Copyright (c) 1986 Regents of the University of California */ |
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|
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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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/* |
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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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|
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#include "random.h" |
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|
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|
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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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|
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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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|
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return(y); |
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} |
