/*
 * Copyright (c) 2005-2023 Radiance Kirill Grouchnikov. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 *  o Redistributions of source code must retain the above copyright notice, 
 *    this list of conditions and the following disclaimer. 
 *     
 *  o Redistributions in binary form must reproduce the above copyright notice, 
 *    this list of conditions and the following disclaimer in the documentation 
 *    and/or other materials provided with the distribution. 
 *     
 *  o Neither the name of the copyright holder nor the names of
 *    its contributors may be used to endorse or promote products derived 
 *    from this software without specific prior written permission. 
 *     
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, 
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; 
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
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 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */
package org.pushingpixels.radiance.theming.internal.utils;

/**
 * A class for producing Perlin-inspired noise. The code written by Ken Perlin.
 * 
 * @author Ken Perlin http://mrl.nyu.edu/~perlin/
 */
public class PerlinNoiseGenerator {
	/**
	 * Returns noise for the specified coordinates.
	 * 
	 * @param x
	 *            X coordinate.
	 * @param y
	 *            Y coordinate.
	 * @param z
	 *            Z coordinate.
	 * @return Noise for the specified coordinates.
	 */
	static public double noise(double x, double y, double z) {
		int X = (int) Math.floor(x) & 255, // FIND UNIT CUBE THAT
		Y = (int) Math.floor(y) & 255, // CONTAINS POINT.
		Z = (int) Math.floor(z) & 255;
		x -= Math.floor(x); // FIND RELATIVE X,Y,Z
		y -= Math.floor(y); // OF POINT IN CUBE.
		z -= Math.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))));
	}

	/**
	 * Fades the specified value.
	 * 
	 * @param t
	 *            Value to fade.
	 * @return faded value.
	 */
	static double fade(double t) {
		return t * t * t * (t * (t * 6 - 15) + 10);
	}

	/**
	 * Interpolates the specified value.
	 * 
	 * @param t
	 *            Value.
	 * @param a
	 *            Starting interpolation value.
	 * @param b
	 *            Ending interpolation value.
	 * @return Interpolated value.
	 */
	static double lerp(double t, double a, double b) {
		return a + t * (b - a);
	}

	/**
	 * @param hash
	 * @param x
	 * @param y
	 * @param z
	 * @return
	 */
	static double 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);
	}

	/**
	 * Permutations.
	 */
	static final int[] p = new int[512];

	/**
	 * Permutations.
	 */
	static final 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 };
	static {
		for (int i = 0; i < 256; i++)
			p[256 + i] = p[i] = permutation[i];
	}
}
