Transforming in-sub MemPos/MemLocalPos coordinates to outside coordinates if the character is outside and vice versa, server doesn't start sending ingame updates until they receive the first ingame update message from the client (no need to send updates while the client is loading or if they fail to start the round)

Subsurface/Source/Physics/PhysicsBody.cs

@@ -37,6 +37,42 @@ namespace Barotrauma
 
             Timestamp = time;
         }
+
+        public static PosInfo TransformOutToInside(PosInfo posInfo, Submarine submarine)
+        {
+            //transform outside coordinates to in-sub coordinates
+            return new PosInfo(
+                posInfo.Position - ConvertUnits.ToSimUnits(submarine.Position),
+                posInfo.Direction,
+                posInfo.ID,
+                posInfo.Timestamp);            
+        }
+
+        public static PosInfo TransformInToOutside(PosInfo posInfo)
+        {
+            Submarine closestSub = null;
+            foreach (Submarine sub in Submarine.Loaded)
+            {
+                Rectangle subBorders = sub.Borders;
+                subBorders.Location += sub.HiddenSubPosition.ToPoint() - new Point(0, sub.Borders.Height);
+
+                subBorders.Inflate(500.0f, 500.0f);
+
+                if (subBorders.Contains(ConvertUnits.ToDisplayUnits(posInfo.Position)))
+                {
+                    closestSub = sub;
+                    break;
+                }
+            }
+
+            if (closestSub == null) return posInfo;
+
+            return new PosInfo(
+                posInfo.Position + ConvertUnits.ToSimUnits(closestSub.Position),
+                posInfo.Direction,
+                posInfo.ID,
+                posInfo.Timestamp);            
+        }
     }
 
     class PhysicsBody