quakeforge/qw/source/fractalnoise.c

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