29 Jan
2005
29 Jan
'05
6 a.m.
On Sat, 29 Jan 2005 04:16:05 -0600, Jan Depner
<eviltwin69(a)cableone.net> wrote:
Here's a short and simple implementation of generating a fractal line
with the midpoint displacement method. (Taken from tap_doubler.c, from
tap-plugins-0.7.0)
/* generate fractal pattern using Midpoint Displacement Method
* v: buffer of floats to output fractal pattern to
* N: length of v, MUST be integer power of 2 (ie 128, 256, ...)
* H: Hurst constant, between 0 and 0.9999 (fractal dimension)
*/
void
fractal(LADSPA_Data * v, int N, float H) {
int l = N;
int k;
float r = 1.0f;
int c;
v[0] = 0;
while (l > 1) {
k = N / l;
for (c = 0; c < k; c++) {
v[c*l + l/2] = (v[c*l] + v[((c+1) * l) % N]) / 2.0f +
2.0f * r * (rand() - (float)RAND_MAX/2.0f) /
(float)RAND_MAX;
v[c*l + l/2] = LIMIT(v[c*l + l/2], -1.0f, 1.0f);
}
l /= 2;
r /= powf(2, H);
}
}
Tom
Is there any
way I could try to understand what good it does without
having to decompose Tom's plugin ?
Just got back from a gig and it's 0330 so this might ramble a bit -
almost everything in nature is fractal. There are a couple of good
books on chaos theory that cover this. Fractals can be generated using
FFTs but they're very compute intensive. You can google for midpoint
displacement and find some good info on it. Almost all of the digital
terrains that you see in games are generated using midpoint
displacement. It gives you a very natural looking surface and just uses
a pseudo random number generator to approximate a fractal surface (or
line in this case). It's actually a pretty simple algorithm. I was
lucky enough to take the fractal seminars at the 1986 Siggraph.
Unfortunately stupid me lost the books. Doh!