Re-implemented chunk sending (#304)

Re-implement chunk sending, send chunks inside a radius instead of below a count

This sends chunks in concentric squares around players. When the radius is hit, it will pad out the radius until a full circle of chunks is loaded around the player.
TODO: implement radius-per-tick, send chunks in concentric circles, use radius for player spawning.

To set your server chunk radius, change `view-distance` in server.properties. Values are intended to be the same as MCPE render distance values. With matching client and server render distances the chunks should reach the horizon.

NOTE: You may notice significantly increased memory usage per player when increasing these values to something respectable. This is normal and expected.
A player with render distance 14 for example will cause loading of 600+ chunks. A player cannot however exceed the render distance limit set in server.properties - the server will simply not send any more chunks.

Render distance of 8 chunks is approximately 200 chunks. This is roughly equivalent to the original default max-chunks of 192 in pocketmine.yml, but sent in a circle instead of a square.

Wait for client to request a chunk radius before ordering chunks

Use 8 for default maximum radius (roughly matches old setting of 192)

Calculate spawn chunk count from chunk-sending.spawn-radius

src/pocketmine/MemoryManager.php

@@ -47,7 +47,7 @@ class MemoryManager{
 	private $garbageCollectionTrigger;
 	private $garbageCollectionAsync;
 
-	private $chunkLimit;
+	private $chunkRadiusOverride;
 	private $chunkCollect;
 	private $chunkTrigger;
 
@@ -104,7 +104,7 @@ class MemoryManager{
 		$this->garbageCollectionTrigger = (bool) $this->server->getProperty("memory.garbage-collection.low-memory-trigger", true);
 		$this->garbageCollectionAsync = (bool) $this->server->getProperty("memory.garbage-collection.collect-async-worker", true);
 
-		$this->chunkLimit = (int) $this->server->getProperty("memory.max-chunks.trigger-limit", 96);
+		$this->chunkRadiusOverride = (int) $this->server->getProperty("memory.max-chunks.chunk-radius", 4);
 		$this->chunkCollect = (bool) $this->server->getProperty("memory.max-chunks.trigger-chunk-collect", true);
 		$this->chunkTrigger = (bool) $this->server->getProperty("memory.max-chunks.low-memory-trigger", true);
 
@@ -122,8 +122,15 @@ class MemoryManager{
 		return !($this->lowMemory and $this->chunkTrigger);
 	}
 
-	public function getViewDistance($distance){
-		return $this->lowMemory ? min($this->chunkLimit, $distance) : $distance;
+	/**
+	 * Returns the allowed chunk radius based on the current memory usage.
+	 *
+	 * @param int $distance
+	 *
+	 * @return int
+	 */
+	public function getViewDistance(int $distance) : int{
+		return $this->lowMemory ? min($this->chunkRadiusOverride, $distance) : $distance;
 	}
 
 	public function trigger($memory, $limit, $global = false, $triggerCount = 0){

src/pocketmine/Player.php

@@ -216,7 +216,7 @@ class Player extends Human implements CommandSender, InventoryHolder, ChunkLoade
 	/** @var Vector3 */
 	protected $newPosition;
 
-	protected $viewDistance;
+	protected $viewDistance = -1;
 	protected $chunksPerTick;
 	protected $spawnThreshold;
 	/** @var null|WeakPosition */
@@ -421,6 +421,17 @@ class Player extends Human implements CommandSender, InventoryHolder, ChunkLoade
 		$this->inAirTicks = 0;
 	}
 
+	public function getViewDistance() : int{
+		return $this->viewDistance;
+	}
+
+	public function setViewDistance(int $distance){
+		$this->viewDistance = $this->server->getAllowedViewDistance($distance);
+		$pk = new ChunkRadiusUpdatedPacket();
+		$pk->radius = $this->viewDistance;
+		$this->dataPacket($pk);
+	}
+
 	/**
 	 * @return bool
 	 */
@@ -556,11 +567,10 @@ class Player extends Human implements CommandSender, InventoryHolder, ChunkLoade
 		$this->clientID = $clientID;
 		$this->loaderId = Level::generateChunkLoaderId($this);
 		$this->chunksPerTick = (int) $this->server->getProperty("chunk-sending.per-tick", 4);
-		$this->spawnThreshold = (int) $this->server->getProperty("chunk-sending.spawn-threshold", 56);
+		$this->spawnThreshold = (int) (($this->server->getProperty("chunk-sending.spawn-radius", 4) ** 2) * M_PI);
 		$this->spawnPosition = null;
 		$this->gamemode = $this->server->getGamemode();
 		$this->setLevel($this->server->getDefaultLevel());
-		$this->viewDistance = $this->server->getViewDistance();
 		$this->newPosition = new Vector3(0, 0, 0);
 		$this->boundingBox = new AxisAlignedBB(0, 0, 0, 0, 0, 0);
 
@@ -859,7 +869,7 @@ class Player extends Human implements CommandSender, InventoryHolder, ChunkLoade
 	}
 
 	protected function orderChunks(){
-		if($this->connected === false){
+		if($this->connected === false or $this->viewDistance === -1){
 			return false;
 		}
 
@@ -867,59 +877,77 @@ class Player extends Human implements CommandSender, InventoryHolder, ChunkLoade
 
 		$this->nextChunkOrderRun = 200;
 
-		$viewDistance = $this->server->getMemoryManager()->getViewDistance($this->viewDistance);
+		$radius = $this->server->getAllowedViewDistance($this->viewDistance);
+		$radiusSquared = $radius ** 2;
 
 		$newOrder = [];
-		$lastChunk = $this->usedChunks;
+		$unloadChunks = $this->usedChunks;
 
 		$centerX = $this->x >> 4;
 		$centerZ = $this->z >> 4;
 
-		$layer = 1;
-		$leg = 0;
-		$x = 0;
-		$z = 0;
+		for($x = 0; $x < $radius; ++$x){
+			for($z = 0; $z <= $x; ++$z){
+				if(($x ** 2 + $z ** 2) > $radiusSquared){
+					break; //skip to next band
+				}
 
-		for($i = 0; $i < $viewDistance; ++$i){
+				//If the chunk is in the radius, others at the same offsets in different quadrants are also guaranteed to be.
 
-			$chunkX = $x + $centerX;
-			$chunkZ = $z + $centerZ;
+				/* Top right quadrant */
+				if(!isset($this->usedChunks[$index = Level::chunkHash($centerX + $x, $centerZ + $z)]) or $this->usedChunks[$index] === false){
+					$newOrder[$index] = true;
+				}
+				unset($unloadChunks[$index]);
 
-			if(!isset($this->usedChunks[$index = Level::chunkHash($chunkX, $chunkZ)]) or $this->usedChunks[$index] === false){
-				$newOrder[$index] = true;
-			}
-			unset($lastChunk[$index]);
+				/* Top left quadrant */
+				if(!isset($this->usedChunks[$index = Level::chunkHash($centerX - $x - 1, $centerZ + $z)]) or $this->usedChunks[$index] === false){
+					$newOrder[$index] = true;
+				}
+				unset($unloadChunks[$index]);
 
-			switch($leg){
-				case 0:
-					++$x;
-					if($x === $layer){
-						++$leg;
+				/* Bottom right quadrant */
+				if(!isset($this->usedChunks[$index = Level::chunkHash($centerX + $x, $centerZ - $z - 1)]) or $this->usedChunks[$index] === false){
+					$newOrder[$index] = true;
+				}
+				unset($unloadChunks[$index]);
+
+
+				/* Bottom left quadrant */
+				if(!isset($this->usedChunks[$index = Level::chunkHash($centerX - $x - 1, $centerZ - $z - 1)]) or $this->usedChunks[$index] === false){
+					$newOrder[$index] = true;
+				}
+				unset($unloadChunks[$index]);
+
+				if($x !== $z){
+					/* Top right quadrant mirror */
+					if(!isset($this->usedChunks[$index = Level::chunkHash($centerX + $z, $centerZ + $x)]) or $this->usedChunks[$index] === false){
+						$newOrder[$index] = true;
 					}
-					break;
-				case 1:
-					++$z;
-					if($z === $layer){
-						++$leg;
+					unset($unloadChunks[$index]);
+
+					/* Top left quadrant mirror */
+					if(!isset($this->usedChunks[$index = Level::chunkHash($centerX - $z - 1, $centerZ + $x)]) or $this->usedChunks[$index] === false){
+						$newOrder[$index] = true;
 					}
-					break;
-				case 2:
-					--$x;
-					if(-$x === $layer){
-						++$leg;
+					unset($unloadChunks[$index]);
+
+					/* Bottom right quadrant mirror */
+					if(!isset($this->usedChunks[$index = Level::chunkHash($centerX + $z, $centerZ - $x - 1)]) or $this->usedChunks[$index] === false){
+						$newOrder[$index] = true;
 					}
-					break;
-				case 3:
-					--$z;
-					if(-$z === $layer){
-						$leg = 0;
-						++$layer;
+					unset($unloadChunks[$index]);
+
+					/* Bottom left quadrant mirror */
+					if(!isset($this->usedChunks[$index = Level::chunkHash($centerX - $z - 1, $centerZ - $x - 1)]) or $this->usedChunks[$index] === false){
+						$newOrder[$index] = true;
 					}
-					break;
+					unset($unloadChunks[$index]);
+				}
 			}
 		}
 
-		foreach($lastChunk as $index => $bool){
+		foreach($unloadChunks as $index => $bool){
 			Level::getXZ($index, $X, $Z);
 			$this->unloadChunk($X, $Z);
 		}
@@ -2932,12 +2960,7 @@ class Player extends Human implements CommandSender, InventoryHolder, ChunkLoade
 				}
 				break;
 			case ProtocolInfo::REQUEST_CHUNK_RADIUS_PACKET:
-				if($this->spawned){
-					$this->viewDistance = $packet->radius ** 2;
-				}
-				$pk = new ChunkRadiusUpdatedPacket();
-				$pk->radius = $packet->radius;
-				$this->dataPacket($pk);
+				$this->setViewDistance($packet->radius);
 				break;
 			case ProtocolInfo::SET_PLAYER_GAME_TYPE_PACKET:
 				if($packet->gamemode !== ($this->gamemode & 0x01)){

src/pocketmine/Server.php

@@ -333,8 +333,19 @@ class Server{
 	/**
 	 * @return int
 	 */
-	public function getViewDistance(){
-		return max(56, $this->getProperty("chunk-sending.max-chunks", 256));
+	public function getViewDistance() : int{
+		return max(2, $this->getConfigInt("view-distance", 8));
+	}
+
+	/**
+	 * Returns a view distance up to the currently-allowed limit.
+	 *
+	 * @param int $distance
+	 *
+	 * @return int
+	 */
+	public function getAllowedViewDistance(int $distance) : int{
+		return max(2, min($distance, $this->memoryManager->getViewDistance($this->getViewDistance())));
 	}
 
 	/**
@@ -1384,6 +1395,7 @@ class Server{
 				"enable-rcon" => false,
 				"rcon.password" => substr(base64_encode(random_bytes(20)), 3, 10),
 				"auto-save" => true,
+				"view-distance" => 8
 			]);
 
 			$this->forceLanguage = $this->getProperty("settings.force-language", false);

src/pocketmine/resources/pocketmine.yml

@@ -58,8 +58,8 @@ memory:
   low-memory-trigger: true
 
  max-chunks:
-  #Limit of chunks to load per player, overrides chunk-sending.max-chunks
-  trigger-limit: 96
+  #Maximum render distance per player when low memory is triggered
+  chunk-radius: 4
 
   #Do chunk garbage collection on trigger
   trigger-chunk-collect: true
@@ -117,12 +117,11 @@ level-settings:
  always-tick-players: false
 
 chunk-sending:
+ #To change server normal render distance, change view-distance in server.properties.
  #Amount of chunks sent to players per tick
  per-tick: 4
- #Amount of chunks sent around each player
- max-chunks: 192
- #Amount of chunks that need to be sent before spawning the player
- spawn-threshold: 56
+ #Radius of chunks that need to be sent before spawning the player
+ spawn-radius: 4
  #Save a serialized copy of the chunk in memory for faster sending
  #Useful in mostly-static worlds where lots of players join at the same time
  cache-chunks: false