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Diffstat (limited to 'src/noise.cpp')
| -rw-r--r-- | src/noise.cpp | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/src/noise.cpp b/src/noise.cpp new file mode 100644 index 000000000..dda0e5614 --- /dev/null +++ b/src/noise.cpp @@ -0,0 +1,92 @@ +/* +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; +} + |