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https://git.code.sf.net/p/quake/quakeforge
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84 lines
2.2 KiB
C
84 lines
2.2 KiB
C
/*
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fractalnoise.c
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LordHavocs fractal noise generator.
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Copyright (C) 2000 Forest `LordHavoc` Hale.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to:
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Free Software Foundation, Inc.
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59 Temple Place - Suite 330
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Boston, MA 02111-1307, USA
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$Id$
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*/
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#include <stdlib.h>
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void
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fractalnoise (unsigned char *noise, int size)
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{
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int x, y, g, g2, amplitude, min, max, size1 = size - 1;
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int *noisebuf;
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#define n(x,y) noisebuf[((y)&size1)*size+((x)&size1)]
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noisebuf = calloc (size * size, sizeof (int));
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amplitude = 32767;
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g2 = size;
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n (0, 0) = 0;
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for (; (g = g2 >> 1) >= 1; g2 >>= 1) {
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// subdivide, diamond-square algorythm (really this has little to do
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// with squares)
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// diamond
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for (y = 0; y < size; y += g2)
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for (x = 0; x < size; x += g2)
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n (x + g, y + g) =
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(n (x, y) + n (x + g2, y) + n (x, y + g2) +
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n (x + g2, y + g2)) >> 2;
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// square
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for (y = 0; y < size; y += g2)
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for (x = 0; x < size; x += g2) {
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n (x + g, y) =
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(n (x, y) + n (x + g2, y) + n (x + g, y - g) +
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n (x + g, y + g)) >> 2;
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n (x, y + g) =
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(n (x, y) + n (x, y + g2) + n (x - g, y + g) +
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n (x + g, y + g)) >> 2;
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}
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// brownian motion theory
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amplitude >>= 1;
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for (y = 0; y < size; y += g)
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for (x = 0; x < size; x += g)
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n (x, y) += (rand () & amplitude);
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}
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// find range of noise values
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min = max = 0;
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for (y = 0; y < size; y++)
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for (x = 0; x < size; x++) {
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if (n (x, y) < min)
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min = n (x, y);
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if (n (x, y) > max)
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max = n (x, y);
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}
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max -= min;
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// normalize noise and copy to output
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for (y = 0; y < size; y++)
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for (x = 0; x < size; x++)
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*noise++ = (n (x, y) - min) * 255 / max;
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free (noisebuf);
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#undef n
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}
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