Gaussian.php

<?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 array_sum;
use function exp;
use function sqrt;
 
final class Gaussian{
    public array $kernel = [];
 
    public readonly float $weightSum;
 
    public array $kernel1D = [];
 
    public readonly float $weightSum1D;
 
    public function __construct(public int $smoothSize){
        $bellSize = 1 / $this->smoothSize;
        $bellHeight = 2 * $this->smoothSize;
 
        for($sx = -$this->smoothSize; $sx <= $this->smoothSize; ++$sx){
            $bx = $bellSize * $sx;
 
            $this->kernel1D[$sx + $this->smoothSize] = sqrt($bellHeight) * exp(-($bx * $bx) / 2);
 
            $this->kernel[$sx + $this->smoothSize] = [];
            for($sz = -$this->smoothSize; $sz <= $this->smoothSize; ++$sz){
                $bz = $bellSize * $sz;
                $this->kernel[$sx + $this->smoothSize][$sz + $this->smoothSize] = $bellHeight * exp(-($bx * $bx + $bz * $bz) / 2);
            }
        }
 
        $this->weightSum1D = array_sum($this->kernel1D);
        $this->weightSum = $this->weightSum1D ** 2;
    }
}