perlinnoise.cpp

#include "perlinnoise.h"

#include "fakecpp11.h"

#include <math.h>
#include <stdlib.h>

namespace {

const int permutation[] = { 151,160,137,91,90,15,
							131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
							190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
							88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
							77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
							102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
							135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
							5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
							223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
							129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
							251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
							49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
							138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
							};
}

PerlinNoise::PerlinNoise()
{
	p.resize(256);
	for(int i = 0; i < 255; ++i) p[i] = permutation[i];
	p.insert(p.end(), p.begin(), p.end());
}

// Generate a new permutation vector based on the value of seed
PerlinNoise::PerlinNoise(unsigned int seed) {
	p.resize(256);

	// Fill p with values from 0 to 255
	std::iota(p.begin(), p.end(), 0);

	// Initialize a random engine with seed
	//std::default_random_engine engine(seed);
	srandom(seed);

	// Suffle  using the above random engine
	//std::shuffle(p.begin(), p.end(), engine);
	for (int i=0, length=p.size(); i<length; ++i) {
		int r = i + (random() % (length-i)); // Random remaining position.
		std::swap(p[i], p[r]);
	}

	// Duplicate the permutation vector
	p.insert(p.end(), p.begin(), p.end());
}

double PerlinNoise::noise(double x, double y, double z) {
	int X = (int)floor(x) & 255,                  // FIND UNIT CUBE THAT
		Y = (int)floor(y) & 255,                  // CONTAINS POINT.
		Z = (int)floor(z) & 255;
	x -= floor(x);                                // FIND RELATIVE X,Y,Z
	y -= floor(y);                                // OF POINT IN CUBE.
	z -= floor(z);
	double u = fade(x),                                // COMPUTE FADE CURVES
		   v = fade(y),                                // FOR EACH OF X,Y,Z.
		   w = fade(z);
	int A = p[X  ]+Y, AA = p[A]+Z, AB = p[A+1]+Z,      // HASH COORDINATES OF
		B = p[X+1]+Y, BA = p[B]+Z, BB = p[B+1]+Z;      // THE 8 CUBE CORNERS,

	return lerp(w, lerp(v, lerp(u, grad(p[AA  ], x  , y  , z   ),  // AND ADD
								 grad(p[BA  ], x-1, y  , z   )), // BLENDED
						 lerp(u, grad(p[AB  ], x  , y-1, z   ),  // RESULTS
								 grad(p[BB  ], x-1, y-1, z   ))),// FROM  8
				 lerp(v, lerp(u, grad(p[AA+1], x  , y  , z-1 ),  // CORNERS
								 grad(p[BA+1], x-1, y  , z-1 )), // OF CUBE
						 lerp(u, grad(p[AB+1], x  , y-1, z-1 ),
								 grad(p[BB+1], x-1, y-1, z-1 ))));
}

double PerlinNoise::fade(double t) {
	return t * t * t * (t * (t * 6 - 15) + 10);
}

double PerlinNoise::lerp(double t, double a, double b) {
	return a + t * (b - a);
}

double PerlinNoise::grad(int hash, double x, double y, double z) {
	int h = hash & 15;                          // CONVERT LO 4 BITS OF HASH CODE
	double u = h<8 ? x : y,                     // INTO 12 GRADIENT DIRECTIONS.
			 v = h<4 ? y : h==12||h==14 ? x : z;
	return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
}