From 49b4f0c79d70c156becf41060a07a0934434b007 Mon Sep 17 00:00:00 2001
From: jglrxavpok <jglrxavpok@gmail.com>
Date: Fri, 31 Jul 2020 18:55:08 +0200
Subject: [PATCH] Fixed non-smooth pathfinding by setting the velocity of the
 creature, therefore allowing the client to predict the position and smooth
 the path

---
 .../themode/demo/commands/SimpleCommand.java  |  2 +-
 .../net/minestom/server/entity/Entity.java    |  9 +++++++-
 .../server/entity/EntityCreature.java         | 23 +++++++++++++------
 3 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/src/main/java/fr/themode/demo/commands/SimpleCommand.java b/src/main/java/fr/themode/demo/commands/SimpleCommand.java
index 9f3b0d65b..4ba29dd75 100644
--- a/src/main/java/fr/themode/demo/commands/SimpleCommand.java
+++ b/src/main/java/fr/themode/demo/commands/SimpleCommand.java
@@ -53,7 +53,7 @@ public class SimpleCommand implements CommandProcessor {
 
         Instance instance = player.getInstance();
 
-        ChickenCreature chickenCreature = new ChickenCreature(new Position(-10, 40, -10));
+        ChickenCreature chickenCreature = new ChickenCreature(new Position(-10, 43, -10));
         chickenCreature.setInstance(instance);
 
         chickenCreature.setPathTo(player.getPosition());
diff --git a/src/main/java/net/minestom/server/entity/Entity.java b/src/main/java/net/minestom/server/entity/Entity.java
index 192ee0736..8d9a06d1c 100644
--- a/src/main/java/net/minestom/server/entity/Entity.java
+++ b/src/main/java/net/minestom/server/entity/Entity.java
@@ -428,7 +428,7 @@ public abstract class Entity implements Viewable, EventHandler, DataContainer {
                 sendSynchronization();
 
                 if (shouldSendVelocityUpdate(time)) {
-                    sendPacketToViewersAndSelf(getVelocityPacket());
+                    sendVelocityPacket();
                     lastVelocityUpdateTime = time;
                 }
             }
@@ -482,6 +482,13 @@ public abstract class Entity implements Viewable, EventHandler, DataContainer {
         }
     }
 
+    /**
+     * Equivalent to <code>sendPacketsToViewers(getVelocityPacket());</code>
+     */
+    public void sendVelocityPacket() {
+        sendPacketsToViewers(getVelocityPacket());
+    }
+
     /**
      * Get the number of ticks this entity has been active for
      *
diff --git a/src/main/java/net/minestom/server/entity/EntityCreature.java b/src/main/java/net/minestom/server/entity/EntityCreature.java
index 7176f0020..0001cd3cc 100644
--- a/src/main/java/net/minestom/server/entity/EntityCreature.java
+++ b/src/main/java/net/minestom/server/entity/EntityCreature.java
@@ -2,6 +2,7 @@ package net.minestom.server.entity;
 
 import com.extollit.gaming.ai.path.HydrazinePathFinder;
 import com.extollit.gaming.ai.path.model.PathObject;
+import net.minestom.server.MinecraftServer;
 import net.minestom.server.attribute.Attribute;
 import net.minestom.server.collision.CollisionUtils;
 import net.minestom.server.entity.pathfinding.PFPathingEntity;
@@ -50,8 +51,6 @@ public abstract class EntityCreature extends LivingEntity {
 
     @Override
     public void update(long time) {
-        super.update(time);
-
         // Path finding
         path = pathFinder.update();
         if (path != null) {
@@ -61,12 +60,11 @@ public abstract class EntityCreature extends LivingEntity {
             } else {
                 final float speed = getAttributeValue(Attribute.MOVEMENT_SPEED);
                 Position targetPosition = pathingEntity.getTargetPosition();
-                //targetPosition = new Position(-5.5f, 40f, -5.5f);
-                //System.out.println("target: " + targetPosition + " : " + (System.currentTimeMillis() - time));
-                //System.out.println("current: " + getPosition());
                 moveTowards(targetPosition, speed);
             }
         }
+
+        super.update(time);
     }
 
     @Override
@@ -306,12 +304,23 @@ public abstract class EntityCreature extends LivingEntity {
         final float currentZ = position.getZ();
         final float targetX = direction.getX();
         final float targetZ = direction.getZ();
+        final float dz = targetZ - currentZ;
+        final float dx = targetX - currentX;
 
-        final float radians = (float) Math.atan2(targetZ - currentZ, targetX - currentX);
+        // the purpose of these few lines is to slow down entities when they reach their destination
+        float distSquared = dx * dx + dz * dz;
+        if(speed > distSquared) {
+            speed = distSquared;
+        }
+
+        final float radians = (float) Math.atan2(dz, dx);
         final float speedX = (float) (Math.cos(radians) * speed);
         final float speedZ = (float) (Math.sin(radians) * speed);
 
-        move(speedX, 0, speedZ, true);
+        // TODO: is a hard set an issue if there are other external forces at play?
+        final float tps = MinecraftServer.TICK_PER_SECOND;
+        velocity.setX(speedX * tps);
+        velocity.setZ(speedZ * tps);
     }
 
     private ItemStack getEquipmentItem(ItemStack itemStack, ArmorEquipEvent.ArmorSlot armorSlot) {