<?php

/*
 *
 *  ____            _        _   __  __ _                  __  __ ____
 * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
 * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
 * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
 * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * @author PocketMine Team
 * @link http://www.pocketmine.net/
 *
 *
*/

declare(strict_types=1);

namespace pocketmine\world\generator;

use function exp;

final class Gaussian{

	/** @var int */
	public $smoothSize;
	/** @var float[][] */
	public $kernel = [];

	public function __construct(int $smoothSize){
		$this->smoothSize = $smoothSize;

		$bellSize = 1 / $this->smoothSize;
		$bellHeight = 2 * $this->smoothSize;

		for($sx = -$this->smoothSize; $sx <= $this->smoothSize; ++$sx){
			$this->kernel[$sx + $this->smoothSize] = [];

			for($sz = -$this->smoothSize; $sz <= $this->smoothSize; ++$sz){
				$bx = $bellSize * $sx;
				$bz = $bellSize * $sz;
				$this->kernel[$sx + $this->smoothSize][$sz + $this->smoothSize] = $bellHeight * exp(-($bx * $bx + $bz * $bz) / 2);
			}
		}
	}
}