Fixed a server-side off-by-one error in the player input IDs

I'm guessing this one comes from the player's position not being updated immediately after the input is processed, so that's where most of the remaining error came from.
Also added some rounding to the horizontal velocity when approaching 0, and changed something that depended on the head limb to use the collider instead, which should hopefully further reduce the chance of syncing errors.

Subsurface/Source/Characters/Animation/HumanoidAnimController.cs

@@ -489,6 +489,10 @@ namespace Barotrauma
             {
                 movement = Vector2.Normalize(movement);
             }
+            if (Math.Abs(movement.X)<0.005f)
+            {
+                movement.X = 0.0f;
+            }
         }
 
         private void ClimbOverObstacles()

Subsurface/Source/Characters/Animation/Ragdoll.cs

@@ -571,6 +571,7 @@ namespace Barotrauma
             }
 
             Collider.DebugDraw(spriteBatch, frozen ? Color.Red : (inWater ? Color.SkyBlue : Color.Gray));
+            spriteBatch.DrawString(GUI.Font, Collider.LinearVelocity.X.ToString(), new Vector2(Collider.DrawPosition.X, -Collider.DrawPosition.Y), Color.Orange);
 
             foreach (RevoluteJoint joint in limbJoints)
             {

Subsurface/Source/Characters/Character.cs

@@ -839,13 +839,13 @@ namespace Barotrauma
                 AnimController.Anim != AnimController.Animation.UsingConstruction &&
                 AnimController.Anim != AnimController.Animation.CPR)
             {
-                Limb head = AnimController.GetLimb(LimbType.Head);
+                //Limb head = AnimController.GetLimb(LimbType.Head);
 
-                if (cursorPosition.X < head.Position.X - 10.0f)
+                if (cursorPosition.X < AnimController.Collider.Position.X - 10.0f)
                 {
                     AnimController.TargetDir = Direction.Left;
                 }
-                else if (cursorPosition.X > head.Position.X + 10.0f)
+                else if (cursorPosition.X > AnimController.Collider.Position.X + 10.0f)
                 {
                     AnimController.TargetDir = Direction.Right;
                 }
@@ -1249,7 +1249,7 @@ namespace Barotrauma
         {
             foreach (Character c in CharacterList)
             {
-                if (!c.Enabled) continue;
+                if (!c.Enabled || c.AnimController.Frozen) continue;
                 
                 c.AnimController.UpdateAnim(deltaTime);
             }
@@ -1610,25 +1610,37 @@ namespace Barotrauma
                 if (aiTarget != null) aiTarget.Draw(spriteBatch);
             }
             
-            if (memPos != null && memPos.Count > 0)
+            if (memPos != null && memPos.Count > 0 && controlled == this)
             {
                 PosInfo serverPos = memPos.Last();
                 Vector2 remoteVec = ConvertUnits.ToDisplayUnits(serverPos.Position);
-                if (Submarine!=null)
+                if (Submarine != null)
                 {
                     remoteVec += Submarine.DrawPosition;
                 }
                 remoteVec.Y = -remoteVec.Y;
 
                 PosInfo localPos = memLocalPos.Find(m => m.ID == serverPos.ID);
+                int mpind = memLocalPos.FindIndex(lp => lp.ID == localPos.ID);
+                PosInfo? localPos1 = mpind > 0 ? memLocalPos[mpind - 1] : (PosInfo?)null;
+                PosInfo? localPos2 = mpind < memLocalPos.Count-1 ? memLocalPos[mpind + 1] : (PosInfo?)null;
+
                 Vector2 localVec = ConvertUnits.ToDisplayUnits(localPos.Position);
+                Vector2 localVec1 = localPos1 != null ? ConvertUnits.ToDisplayUnits(((PosInfo)localPos1).Position) : Vector2.Zero;
+                Vector2 localVec2 = localPos2 != null ? ConvertUnits.ToDisplayUnits(((PosInfo)localPos2).Position) : Vector2.Zero;
                 if (Submarine != null)
                 {
                     localVec += Submarine.DrawPosition;
+                    localVec1 += Submarine.DrawPosition;
+                    localVec2 += Submarine.DrawPosition;
                 }
                 localVec.Y = -localVec.Y;
+                localVec1.Y = -localVec1.Y;
+                localVec2.Y = -localVec2.Y;
 
-                GUI.DrawLine(spriteBatch, remoteVec, localVec, Color.Yellow,0,10);
+                GUI.DrawLine(spriteBatch, remoteVec, localVec, Color.Yellow, 0, 10);
+                if (localPos1 != null) GUI.DrawLine(spriteBatch, remoteVec, localVec1, Color.Lime, 0, 6);
+                if (localPos2 != null) GUI.DrawLine(spriteBatch, remoteVec, localVec2, Color.Red, 0, 3);
             }
 
             Vector2 mouseDrawPos = CursorWorldPosition;
@@ -2037,7 +2049,7 @@ namespace Barotrauma
                     //length of the message
                     msg.Write((byte)(4+4+4));
                     msg.Write(true);
-                    msg.Write((UInt32)(LastNetworkUpdateID - memInput.Count));
+                    msg.Write((UInt32)(LastNetworkUpdateID - memInput.Count - 1));
                 }
                 else
                 {

Subsurface/Source/Physics/PhysicsBody.cs

@@ -146,6 +146,11 @@ namespace Barotrauma
             get { return body.Position; }
         }
 
+        public Vector2 Position
+        {
+            get { return ConvertUnits.ToDisplayUnits(body.Position); }
+        }
+
         public Vector2 PrevPosition
         {
             get { return prevPosition; }