Fix projectile yaw & position synchronization issues

src/main/java/io/github/togar2/pvp/projectile/CustomEntityProjectile.java

@@ -24,6 +24,7 @@
 import org.jetbrains.annotations.Nullable;
 
 import java.util.Random;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -194,6 +195,18 @@ protected boolean canHit(Entity entity) {
 		return entity instanceof LivingEntity;
 	}
 
+	@Override
+	protected void synchronizePosition() {
+		// For some reason, sending a synchronization when stuck means the position of the arrow will change slightly
+		// on the client even though the position on the server has not changed at all. Why? No clue.
+		// This check does solve the issue though.
+		if (isStuck()) return;
+
+		super.synchronizePosition();
+	}
+
+	private float prevYaw, prevPitch;
+
 	@Override
 	protected void movementTick() {
 		// Mostly copied from Minestom
@@ -206,6 +219,8 @@ protected void movementTick() {
 					instance.getWorldBorder(), instance, hasPhysics, previousPhysicsResult, true);
 			this.previousPhysicsResult = physicsResult;
 
+			Pos newPosition = physicsResult.newPosition();
+
 			if (!noClip) {
 				// We won't check collisions with self for first ticks of projectile's life, because it spawns in the
 				// shooter and will immediately be triggered by him.
@@ -219,6 +234,8 @@ protected void movementTick() {
 				if (entityResult.hasCollision() && entityResult.collisionShapes()[0] instanceof Entity collided) {
 					AtomicBoolean entityCollisionSucceeded = new AtomicBoolean();
 
+					Vec prevVelocity = velocity;
+
 					var event = new ProjectileCollideWithEntityEvent(this, Pos.fromPoint(entityResult.newPosition()), collided);
 					EventDispatcher.callCancellable(event, () -> entityCollisionSucceeded.set(onHit(collided)));
 
@@ -227,14 +244,16 @@ protected void movementTick() {
 						scheduler().scheduleNextProcess(this::remove);
 						// Prevent hitting blocks
 						return;
+					} else {
+						// If velocity has been changed because of bounce, prevent projectile from moving further
+						if (velocity != prevVelocity) newPosition = position;
 					}
 				}
 			}
 
 			Chunk finalChunk = ChunkUtils.retrieve(instance, currentChunk, physicsResult.newPosition());
 			if (!ChunkUtils.isLoaded(finalChunk)) return;
 
-			Pos newPosition = physicsResult.newPosition();
 			if (physicsResult.hasCollision() && !isStuck()) {
 				double signumX = physicsResult.collisionX() ? Math.signum(velocity.x()) : 0;
 				double signumY = physicsResult.collisionY() ? Math.signum(velocity.y()) : 0;
@@ -244,16 +263,16 @@ protected void movementTick() {
 				Point collidedPosition = collisionDirection.add(physicsResult.newPosition()).apply(Vec.Operator.FLOOR);
 				Block block = instance.getBlock(collidedPosition);
 
-				AtomicBoolean collisionSucceeded = new AtomicBoolean();
+				AtomicBoolean shouldRemove = new AtomicBoolean();
 
 				var event = new ProjectileCollideWithBlockEvent(this, physicsResult.newPosition().withCoord(collidedPosition), block);
 				EventDispatcher.callCancellable(event, () -> {
 					setNoGravity(true);
 					this.collisionDirection = collisionDirection;
-					collisionSucceeded.set(onStuck());
+					shouldRemove.set(onStuck());
 				});
 
-				if (collisionSucceeded.get()) {
+				if (shouldRemove.get()) {
 					// Don't remove now because rest of Entity#tick might throw errors
 					scheduler().scheduleNextProcess(this::remove);
 				}
@@ -267,16 +286,47 @@ protected void movementTick() {
 			).sub(0, hasNoGravity() ? 0 : getAerodynamics().gravity() * ServerFlag.SERVER_TICKS_PER_SECOND, 0);
 			onGround = physicsResult.isOnGround();
 
-			refreshPosition(newPosition, true, false);
+			float yaw = position.yaw();
+			float pitch = position.pitch();
 
 			if (!noClip) {
-				float yaw = (float) Math.toDegrees(Math.atan2(diff.x(), diff.z()));
-				float pitch = (float) Math.toDegrees(Math.atan2(diff.y(), Math.sqrt(diff.x() * diff.x() + diff.z() * diff.z())));
-				refreshPosition(position.withView(yaw, pitch), false, false);
+				yaw = (float) Math.toDegrees(Math.atan2(diff.x(), diff.z()));
+				pitch = (float) Math.toDegrees(
+						Math.atan2(diff.y(), Math.sqrt(diff.x() * diff.x() + diff.z() * diff.z())));
+
+				// Vanilla really likes to use variables from the render code
+				// on the server side in a way that does not make sense at all
+				yaw = lerp(prevYaw, yaw);
+				pitch = lerp(prevPitch, pitch);
 			}
+
+			this.prevYaw = yaw;
+			this.prevPitch = pitch;
+
+			refreshPosition(newPosition.withView(yaw, pitch), noClip, isStuck());
 		}
 	}
 
+	private static float lerp(float first, float second) {
+		return first + (second - first) * 0.2f;
+	}
+
+	@Override
+	public void setView(float yaw, float pitch) {
+		this.prevYaw = yaw;
+		this.prevPitch = pitch;
+
+		super.setView(yaw, pitch);
+	}
+
+	@Override
+	public @NotNull CompletableFuture<Void> teleport(@NotNull Pos position) {
+		this.prevYaw = position.yaw();
+		this.prevPitch = position.pitch();
+
+		return super.teleport(position);
+	}
+
 	protected int getUpdateInterval() {
 		return 20;
 	}

src/main/java/io/github/togar2/pvp/projectile/ProjectileListener.java

@@ -323,13 +323,11 @@ public static EventNode<PlayerInstanceEvent> events(ProjectileConfig config) {
 
 			// Arrow shooting
 			Pos position = player.getPosition().add(0D, player.getEyeHeight() - 0.1, 0D);
-			arrow.setInstance(Objects.requireNonNull(player.getInstance()), position);
-
 			arrow.shootFromRotation(position.pitch(), position.yaw(), 0 , power * 3, 1.0);
-
 			Vec playerVel = player.getVelocity();
 			arrow.setVelocity(arrow.getVelocity().add(playerVel.x(),
 					player.isOnGround() ? 0.0D : playerVel.y(), playerVel.z()));
+			arrow.setInstance(Objects.requireNonNull(player.getInstance()), position);
 
 			ThreadLocalRandom random = ThreadLocalRandom.current();
 			ViewUtil.viewersAndSelf(player).playSound(Sound.sound(

src/test/java/io/github/togar2/pvp/test/PvpTest.java

@@ -15,14 +15,13 @@
 import net.minestom.server.entity.damage.EntityDamage;
 import net.minestom.server.event.EventDispatcher;
 import net.minestom.server.event.GlobalEventHandler;
-import net.minestom.server.event.player.AsyncPlayerConfigurationEvent;
-import net.minestom.server.event.player.PlayerSpawnEvent;
-import net.minestom.server.event.player.PlayerTickEvent;
-import net.minestom.server.event.player.PlayerUseItemOnBlockEvent;
+import net.minestom.server.event.player.*;
 import net.minestom.server.extras.lan.OpenToLAN;
 import net.minestom.server.instance.Instance;
 import net.minestom.server.instance.block.Block;
 import net.minestom.server.item.Material;
+import net.minestom.server.network.packet.server.common.KeepAlivePacket;
+import net.minestom.server.network.packet.server.play.*;
 import net.minestom.server.utils.NamespaceID;
 import net.minestom.server.utils.time.TimeUnit;
 import net.minestom.server.world.DimensionType;
@@ -95,6 +94,21 @@ public static void main(String[] args) {
 			//event.getPlayer().addEffect(new Potion(PotionEffect.REGENERATION, (byte) 10, CustomPotionEffect.PERMANENT));
 		});
 
+		MinecraftServer.getGlobalEventHandler().addListener(PlayerPacketOutEvent.class, event -> {
+			if (event.getPacket() instanceof ActionBarPacket) return;
+			if (event.getPacket() instanceof UpdateHealthPacket) return;
+			if (event.getPacket() instanceof TimeUpdatePacket) return;
+			if (event.getPacket() instanceof PlayerInfoUpdatePacket) return;
+			if (event.getPacket() instanceof ChunkDataPacket) return;
+			if (event.getPacket() instanceof KeepAlivePacket) return;
+			if (event.getPacket() instanceof SetSlotPacket) return;
+			if (event.getPacket() instanceof WindowItemsPacket) return;
+			if (event.getPacket() instanceof EntitySoundEffectPacket) return;
+			if (event.getPacket() instanceof CollectItemPacket) return;
+			if (event.getPacket() instanceof DestroyEntitiesPacket) return;
+			System.out.println(event.getPacket());
+		});
+
 		MinecraftServer.getCommandManager().register(new Command("shoot") {{
 			setDefaultExecutor((sender, args) -> {
 				if (sender instanceof Player player) {