forked from Mirrorlandia_minetest/minetest
93 lines
2.8 KiB
C++
93 lines
2.8 KiB
C++
/*
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Minetest-c55
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Copyright (C) 2010-2011 celeron55, Perttu Ahola <celeron55@gmail.com>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(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. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <math.h>
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#include "noise.h"
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#define NOISE_MAGIC_X 1619
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#define NOISE_MAGIC_Y 31337
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#define NOISE_MAGIC_SEED 1013
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double cos_lookup[16] = {
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1.0,0.9238,0.7071,0.3826,0,-0.3826,-0.7071,-0.9238,
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1.0,-0.9238,-0.7071,-0.3826,0,0.3826,0.7071,0.9238
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};
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double dotProduct(double vx, double vy, double wx, double wy){
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return vx*wx+vy*wy;
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}
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double easeCurve(double t){
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return 6*pow(t,5)-15*pow(t,4)+10*pow(t,3);
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}
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double linearInterpolation(double x0, double x1, double t){
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return x0+(x1-x0)*t;
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}
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double biLinearInterpolation(double x0y0, double x1y0, double x0y1, double x1y1, double x, double y){
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double tx = easeCurve(x);
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double ty = easeCurve(y);
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double u = linearInterpolation(x0y0,x1y0,tx);
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double v = linearInterpolation(x0y1,x1y1,tx);
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return linearInterpolation(u,v,ty);
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}
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double noise2d(int x, int y, int seed)
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{
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int n = (NOISE_MAGIC_X * x + NOISE_MAGIC_Y * y
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+ NOISE_MAGIC_SEED * seed) & 0x7fffffff;
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n = (n>>13)^n;
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n = (n * (n*n*60493+19990303) + 1376312589) & 0x7fffffff;
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return 1.0 - (double)n/1073741824;
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}
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double noise2d_gradient(double x, double y, int seed)
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{
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int x0 = (x > 0.0 ? (int)x : (int)x - 1);
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int y0 = (y > 0.0 ? (int)y : (int)y - 1);
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double xl = x-x0;
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double yl = y-y0;
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int n00 = (int)((noise2d(x0, y0, seed)+1)*8);
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int n10 = (int)((noise2d(x0+1, y0, seed)+1)*8);
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int n01 = (int)((noise2d(x0, y0+1, seed)+1)*8);
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int n11 = (int)((noise2d(x0+1, y0+1, seed)+1)*8);
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double s = dotProduct(cos_lookup[n00], cos_lookup[(n00-4)%16], xl, yl);
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double u = dotProduct(-cos_lookup[n10], cos_lookup[(n10-4)%16], 1.-xl, yl);
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double v = dotProduct(cos_lookup[n01], -cos_lookup[(n01-4)%16], xl, 1.-yl);
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double w = dotProduct(-cos_lookup[n11], -cos_lookup[(n11-4)%16], 1.-xl, 1.-yl);
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return biLinearInterpolation(s,u,v,w,xl,yl);
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}
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double noise2d_perlin(double x, double y, int seed,
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int octaves, double persistence)
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{
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double a = 0;
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double f = 1.0;
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double g = 1.0;
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for(int i=0; i<octaves; i++)
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{
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a += g * noise2d_gradient(x*f, y*f, seed+i);
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f *= 2.0;
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g *= persistence;
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}
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return a;
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}
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