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/*
Minetest-c55
Copyright (C) 2010-2011 celeron55, Perttu Ahola <celeron55@gmail.com>
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 the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <math.h>
#include "noise.h"
#define NOISE_MAGIC_X 1619
#define NOISE_MAGIC_Y 31337
#define NOISE_MAGIC_SEED 1013
double cos_lookup[16] = {
1.0,0.9238,0.7071,0.3826,0,-0.3826,-0.7071,-0.9238,
1.0,-0.9238,-0.7071,-0.3826,0,0.3826,0.7071,0.9238
};
double dotProduct(double vx, double vy, double wx, double wy){
return vx*wx+vy*wy;
}
double easeCurve(double t){
return 6*pow(t,5)-15*pow(t,4)+10*pow(t,3);
}
double linearInterpolation(double x0, double x1, double t){
return x0+(x1-x0)*t;
}
double biLinearInterpolation(double x0y0, double x1y0, double x0y1, double x1y1, double x, double y){
double tx = easeCurve(x);
double ty = easeCurve(y);
double u = linearInterpolation(x0y0,x1y0,tx);
double v = linearInterpolation(x0y1,x1y1,tx);
return linearInterpolation(u,v,ty);
}
double noise2d(int x, int y, int seed)
{
int n = (NOISE_MAGIC_X * x + NOISE_MAGIC_Y * y
+ NOISE_MAGIC_SEED * seed) & 0x7fffffff;
n = (n>>13)^n;
n = (n * (n*n*60493+19990303) + 1376312589) & 0x7fffffff;
return 1.0 - (double)n/1073741824;
}
double noise2d_gradient(double x, double y, int seed)
{
int x0 = (x > 0.0 ? (int)x : (int)x - 1);
int y0 = (y > 0.0 ? (int)y : (int)y - 1);
double xl = x-x0;
double yl = y-y0;
int n00 = (int)((noise2d(x0, y0, seed)+1)*8);
int n10 = (int)((noise2d(x0+1, y0, seed)+1)*8);
int n01 = (int)((noise2d(x0, y0+1, seed)+1)*8);
int n11 = (int)((noise2d(x0+1, y0+1, seed)+1)*8);
double s = dotProduct(cos_lookup[n00], cos_lookup[(n00-4)%16], xl, yl);
double u = dotProduct(-cos_lookup[n10], cos_lookup[(n10-4)%16], 1.-xl, yl);
double v = dotProduct(cos_lookup[n01], -cos_lookup[(n01-4)%16], xl, 1.-yl);
double w = dotProduct(-cos_lookup[n11], -cos_lookup[(n11-4)%16], 1.-xl, 1.-yl);
return biLinearInterpolation(s,u,v,w,xl,yl);
}
double noise2d_perlin(double x, double y, int seed,
int octaves, double persistence)
{
double a = 0;
double f = 1.0;
double g = 1.0;
for(int i=0; i<octaves; i++)
{
a += g * noise2d_gradient(x*f, y*f, seed+i);
f *= 2.0;
g *= persistence;
}
return a;
}
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