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+//-----------------------------------------------------------------------------
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+// Copyright (c) 2013 GarageGames, LLC
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+//
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+// Permission is hereby granted, free of charge, to any person obtaining a copy
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+// of this software and associated documentation files (the "Software"), to
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+// deal in the Software without restriction, including without limitation the
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+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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+// sell copies of the Software, and to permit persons to whom the Software is
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+// furnished to do so, subject to the following conditions:
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+//
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+// The above copyright notice and this permission notice shall be included in
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+// all copies or substantial portions of the Software.
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+//
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+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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+// IN THE SOFTWARE.
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+//-----------------------------------------------------------------------------
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+
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+#include "Perlin.h"
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+#include <cmath>
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+#include <random>
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+#include <algorithm>
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+#include <numeric>
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+
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+// THIS IS A DIRECT TRANSLATION TO C++11 FROM THE REFERENCE
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+// JAVA IMPLEMENTATION OF THE IMPROVED PERLIN FUNCTION (see http://mrl.nyu.edu/~perlin/noise/)
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+// THE ORIGINAL JAVA IMPLEMENTATION IS COPYRIGHT 2002 KEN PERLIN
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+
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+// THERE IS AN EXTRA METHOD THAT GENERATES A NEW PERMUTATION VECTOR (THIS IS NOT PRESENT IN THE ORIGINAL IMPLEMENTATION)
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+
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+// Initialize with the reference values for the permutation vector
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+PerlinNoise::PerlinNoise() {
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+
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+ // Initialize the permutation vector with the reference values
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+ p = {
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+ 151,160,137,91,90,15,131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,
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+ 8,99,37,240,21,10,23,190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,
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+ 35,11,32,57,177,33,88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,
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+ 134,139,48,27,166,77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,
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+ 55,46,245,40,244,102,143,54, 65,25,63,161,1,216,80,73,209,76,132,187,208, 89,
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+ 18,169,200,196,135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,
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+ 250,124,123,5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,
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+ 189,28,42,223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167,
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+ 43,172,9,129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,
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+ 97,228,251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,
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+ 107,49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
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+ 138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180 };
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+ // Duplicate the permutation vector
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+ p.insert(p.end(), p.begin(), p.end());
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+}
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+
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+// Generate a new permutation vector based on the value of seed
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+PerlinNoise::PerlinNoise(U32 seed) {
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+ p.resize(256);
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+
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+ // Fill p with values from 0 to 255
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+ std::iota(p.begin(), p.end(), 0);
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+
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+ // Initialize a random engine with seed
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+ std::default_random_engine engine(seed);
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+
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+ // Suffle using the above random engine
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+ std::shuffle(p.begin(), p.end(), engine);
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+
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+ // Duplicate the permutation vector
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+ p.insert(p.end(), p.begin(), p.end());
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+}
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+
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+F64 PerlinNoise::noise(F64 x, F64 y, F64 z) {
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+ // Find the unit cube that contains the point
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+ S32 X = (S32)floor(x) & 255;
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+ S32 Y = (S32)floor(y) & 255;
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+ S32 Z = (S32)floor(z) & 255;
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+
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+ // Find relative x, y,z of point in cube
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+ x -= floor(x);
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+ y -= floor(y);
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+ z -= floor(z);
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+
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+ // Compute fade curves for each of x, y, z
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+ F64 u = fade(x);
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+ F64 v = fade(y);
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+ F64 w = fade(z);
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+
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+ // Hash coordinates of the 8 cube corners
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+ S32 A = p[X] + Y;
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+ S32 AA = p[A] + Z;
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+ S32 AB = p[A + 1] + Z;
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+ S32 B = p[X + 1] + Y;
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+ S32 BA = p[B] + Z;
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+ S32 BB = p[B + 1] + Z;
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+
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+ // Add blended results from 8 corners of cube
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+ F64 res = lerp(w, lerp(v, lerp(u, grad(p[AA], x, y, z), grad(p[BA], x - 1, y, z)), lerp(u, grad(p[AB], x, y - 1, z), grad(p[BB], x - 1, y - 1, z))), lerp(v, lerp(u, grad(p[AA + 1], x, y, z - 1), grad(p[BA + 1], x - 1, y, z - 1)), lerp(u, grad(p[AB + 1], x, y - 1, z - 1), grad(p[BB + 1], x - 1, y - 1, z - 1))));
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+ return (res + 1.0) / 2.0;
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+}
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+
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+F64 PerlinNoise::fade(F64 t) {
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+ return t * t * t * (t * (t * 6 - 15) + 10);
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+}
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+
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+F64 PerlinNoise::lerp(F64 t, F64 a, F64 b) {
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+ return a + t * (b - a);
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+}
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+
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+F64 PerlinNoise::grad(S32 hash, F64 x, F64 y, F64 z) {
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+ S32 h = hash & 15;
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+ // Convert lower 4 bits of hash into 12 gradient directions
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+ F64 u = h < 8 ? x : y,
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+ v = h < 4 ? y : h == 12 || h == 14 ? x : z;
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+ return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
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+}
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