Terraforming regions in PocketMine-MP worlds using Scripter plugin

test.php

<?php

declare(strict_types=1);

use cosmicpe\CosmicPE;
use pocketmine\block\Block;
use pocketmine\block\BlockTypeIds;
use pocketmine\block\Liquid;
use pocketmine\block\VanillaBlocks;
use pocketmine\event\EventPriority;
use pocketmine\event\HandlerListManager;
use pocketmine\event\player\PlayerItemUseEvent;
use pocketmine\item\ItemTypeIds;
use pocketmine\math\Facing;
use pocketmine\player\Player;
use pocketmine\Server;
use pocketmine\world\World;

$server = Server::getInstance();
$player = $server->getPlayerExact("NeedleGalaxy");

/** @var CosmicPE $plugin */
$plugin = $server->getPluginManager()->getPlugin("Scripter");

$execute = function(Player $player) : void{
	$test_for_top_block = static fn(Block $block) => $block->blocksDirectSkyLight();

	$origin = $player->getTargetBlock(100);
	if($origin === null){
		return;
	}
	if(!$test_for_top_block($origin)){
		$origin = $origin->getSide(Facing::DOWN);
		if(!$test_for_top_block($origin)){
			return;
		}
	}

	$radius = mt_rand(16, 24);
	$position = $origin->getPosition();
	$diff = [];
	$blocks = [];
	for($i = -$radius; $i <= $radius; $i++){
		for($j = -$radius; $j <= $radius; $j++){
			$column_height = $position->y;
			for($y = $column_height; $y > 0; $y--){
				if($test_for_top_block($position->world->getBlockAt($position->x + $i, $y, $position->z + $j))){
					$column_height = $y;
					break;
				}
			}
			$diff[] = $position->y - $column_height;
			$blocks[World::blockHash($position->x + $i, 0, $position->z + $j)] = $position->world->getBlockAt($position->x + $i, $y, $position->z + $j);
		}
	}

	// Define a kernel for smoothing. This one is a simple 3x3 averaging kernel.
	// Adjust the weights as you like.
	$kernel = [
		[0.05, 0.1, 0.05],
		[0.1, 0.4, 0.1],
		[0.05, 0.1, 0.05]
	];

	$kernelSize = 3;
	$halfKernel = intdiv($kernelSize, 2);

	// Create a 2D array for $diff for easier access.
	$diff2D = [];
	for($i = 0; $i < 2 * $radius + 1; $i++){
		for($j = 0; $j < 2 * $radius + 1; $j++){
			$diff2D[$i][$j] = array_shift($diff);
		}
	}

	$adjustTerrainHeight = function($x, $targetY, $z, $originalDiff) use ($blocks ,$position){
		$block = $blocks[World::blockHash($x, 0, $z)];
		if($block instanceof Liquid){
			return;
		}

		$currentY = $position->y - $originalDiff;
		$world = $position->world;

		if($currentY > $targetY){
			// Remove blocks to reach targetY
			for($y = $currentY; $y > $targetY; $y--){
				$world->setBlockAt($x, $y, $z, VanillaBlocks::AIR()); // 0 is usually Air in Minecraft.
				if($world->getBlockAt($x, $y - 1, $z)->getTypeId() === BlockTypeIds::DIRT){
					$world->setBlockAt($x, $y - 1, $z, VanillaBlocks::GRASS(), false);
				}
			}
		}else if($currentY < $targetY){
			// Add blocks to reach targetY, for simplicity let's use Dirt blocks
			for($y = $currentY + 1; $y <= $targetY; $y++){
				if($block->getTypeId() === BlockTypeIds::DIRT){
					$block = VanillaBlocks::GRASS();
				}
				$world->setBlockAt($x, $y, $z, $block, false);
				if($world->getBlockAt($x, $y - 1, $z)->getTypeId() === BlockTypeIds::GRASS){
					$world->setBlockAt($x, $y - 1, $z, VanillaBlocks::DIRT(), false);
				}
			}
		}
	};

	// Smooth using the kernel
	for($i = 0; $i < 2 * $radius + 1; $i++){
		for($j = 0; $j < 2 * $radius + 1; $j++){
			$sum = 0;
			$weightSum = 0;

			for($ki = -$halfKernel; $ki <= $halfKernel; $ki++){
				for($kj = -$halfKernel; $kj <= $halfKernel; $kj++){
					if(isset($diff2D[$i + $ki][$j + $kj])){
						$sum += $kernel[$ki + $halfKernel][$kj + $halfKernel] * $diff2D[$i + $ki][$j + $kj];
						$weightSum += $kernel[$ki + $halfKernel][$kj + $halfKernel];
					}
				}
			}

			$smoothedValue = $sum / $weightSum;

			// Adjust the block heights in the region based on the smoothed value.
			$adjustedHeight = $position->y - $smoothedValue;
			$adjustTerrainHeight($position->x + $i - $radius, $adjustedHeight, $position->z + $j - $radius, $diff2D[$i][$j]);
		}
	}
};

$listener = $plugin->getServer()->getPluginManager()->registerEvent(PlayerItemUseEvent::class, function(PlayerItemUseEvent $event) use(&$listener, $player, $execute) : void{
	if($event->getPlayer() === $player){
		if($event->getItem()->getTypeId() !== ItemTypeIds::STICK){
			HandlerListManager::global()->getListFor(PlayerItemUseEvent::class)->unregister($listener);
			return;
		}
		$execute($player);
	}
}, EventPriority::NORMAL, $plugin);

This is a script that can be executed using Scripter.

1. Rename NeedleGalaxy to your gamertag
2. Run /script test.php
3. Hold a stick in your hand
4. Right-click the stick on the topmost block in the region you'd like to terraform
5. The region should now be terraformed. Right click again if you'd like to terraform it further.
6. To exit, give yourself any item other than a stick and right-click it.