send time snaps

Assets/Mirror/Core/Messages.cs

@@ -3,6 +3,14 @@
 
 namespace Mirror
 {
+    // need to send time every sendInterval.
+    // batching automatically includes remoteTimestamp.
+    // all we need to do is ensure that an empty message is sent.
+    // and react to it.
+    // => we don't want to insert a snapshot on every batch.
+    // => do it exactly every sendInterval on every TimeSnapshotMessage.
+    public struct TimeSnapshotMessage : NetworkMessage {}
+
     public struct ReadyMessage : NetworkMessage {}
 
     public struct NotReadyMessage : NetworkMessage {}

Assets/Mirror/Core/NetworkClient.cs

@@ -237,6 +237,7 @@ internal static void RegisterSystemHandlers(bool hostMode)
             }
 
             // These handlers are the same for host and remote clients
+            RegisterHandler<TimeSnapshotMessage>(OnTimeSnapshotMessage);
             RegisterHandler<ChangeOwnerMessage>(OnChangeOwner);
             RegisterHandler<RpcMessage>(OnRPCMessage);
         }

Assets/Mirror/Core/NetworkClient_TimeInterpolation.cs

@@ -60,11 +60,22 @@ static void InitTimeInterpolation()
             deliveryTimeEma = new ExponentialMovingAverage(NetworkServer.config.sendRate * config.deliveryTimeEmaDuration);
         }
 
+        // server sends TimeSnapshotMessage every sendInterval.
+        // batching already includes the remoteTimestamp.
+        // we simply insert it on-message here.
+        // => only for reliable channel. unreliable would always arrive earlier.
+        static void OnTimeSnapshotMessage(TimeSnapshotMessage _)
+        {
+            // insert another snapshot for snapshot interpolation.
+            // before calling OnDeserialize so components can use
+            // NetworkTime.time and NetworkTime.timeStamp.
+            OnTimeSnapshot(new TimeSnapshot(connection.remoteTimeStamp, Time.timeAsDouble));
+        }
+
         // see comments at the top of this file
         public static void OnTimeSnapshot(TimeSnapshot snap)
         {
-            // set local timestamp (= when it was received on our end)
-            snap.localTime = Time.timeAsDouble;
+            // Debug.Log($"NetworkClient: OnTimeSnapshot @ {snap.remoteTime:F3}");
 
             // (optional) dynamic adjustment
             if (config.dynamicAdjustment)

Assets/Mirror/Core/NetworkServer.cs

@@ -1704,6 +1704,10 @@ static void Broadcast()
                 //   pull in UpdateVarsMessage for each entity it observes
                 if (connection.isReady)
                 {
+                    // send time for snapshot interpolation every sendInterval.
+                    // BroadcastToConnection() may not send if nothing is new.
+                    connection.Send(new TimeSnapshotMessage());
+
                     // broadcast world state to this connection
                     BroadcastToConnection(connection);
                 }