fix

This is the back port of PR-3387 that resolves some issues with in-scene placed NetworkObjects in parent-child hierarchy and the synchronization of late joining clients when the hierarchy has changed from that of its default hierarchy defined within the scene.

Author: NoelStephensUnity

com.unity.netcode.gameobjects/Runtime/Core/NetworkObject.cs

@@ -185,15 +185,18 @@ private bool IsEditingPrefab()
         /// </remarks>
         private void CheckForInScenePlaced()
         {
-            if (PrefabUtility.IsPartOfAnyPrefab(this) && !IsEditingPrefab() && gameObject.scene.IsValid() && gameObject.scene.isLoaded && gameObject.scene.buildIndex >= 0)
+            if (gameObject.scene.IsValid() && gameObject.scene.isLoaded && gameObject.scene.buildIndex >= 0)
             {
-                var prefab = PrefabUtility.GetCorrespondingObjectFromSource(gameObject);
-                var assetPath = AssetDatabase.GetAssetPath(prefab);
-                var sourceAsset = AssetDatabase.LoadAssetAtPath<NetworkObject>(assetPath);
-                if (sourceAsset != null && sourceAsset.GlobalObjectIdHash != 0 && InScenePlacedSourceGlobalObjectIdHash != sourceAsset.GlobalObjectIdHash)
+                if (PrefabUtility.IsPartOfAnyPrefab(this))
                 {
-                    InScenePlacedSourceGlobalObjectIdHash = sourceAsset.GlobalObjectIdHash;
-                    EditorUtility.SetDirty(this);
+                    var prefab = PrefabUtility.GetCorrespondingObjectFromSource(gameObject);
+                    var assetPath = AssetDatabase.GetAssetPath(prefab);
+                    var sourceAsset = AssetDatabase.LoadAssetAtPath<NetworkObject>(assetPath);
+                    if (sourceAsset != null && sourceAsset.GlobalObjectIdHash != 0 && InScenePlacedSourceGlobalObjectIdHash != sourceAsset.GlobalObjectIdHash)
+                    {
+                        InScenePlacedSourceGlobalObjectIdHash = sourceAsset.GlobalObjectIdHash;
+                        EditorUtility.SetDirty(this);
+                    }
                 }
                 IsSceneObject = true;
             }
@@ -1241,7 +1244,7 @@ private void OnTransformParentChanged()
         // we call CheckOrphanChildren() method and quickly iterate over OrphanChildren set and see if we can reparent/adopt one.
         internal static HashSet<NetworkObject> OrphanChildren = new HashSet<NetworkObject>();
 
-        internal bool ApplyNetworkParenting(bool removeParent = false, bool ignoreNotSpawned = false, bool orphanedChildPass = false)
+        internal bool ApplyNetworkParenting(bool removeParent = false, bool ignoreNotSpawned = false, bool orphanedChildPass = false, bool enableNotification = true)
         {
             if (!AutoObjectParentSync)
             {
@@ -1314,7 +1317,10 @@ internal bool ApplyNetworkParenting(bool removeParent = false, bool ignoreNotSpa
                 // to WorldPositionStays which can cause scaling issues if the parent's
                 // scale is not the default (Vetctor3.one) value.
                 transform.SetParent(null, m_CachedWorldPositionStays);
-                InvokeBehaviourOnNetworkObjectParentChanged(null);
+                if (enableNotification)
+                {
+                    InvokeBehaviourOnNetworkObjectParentChanged(null);
+                }
                 return true;
             }
 
@@ -1340,7 +1346,10 @@ internal bool ApplyNetworkParenting(bool removeParent = false, bool ignoreNotSpa
 
             m_CachedParent = parentObject.transform;
             transform.SetParent(parentObject.transform, m_CachedWorldPositionStays);
-            InvokeBehaviourOnNetworkObjectParentChanged(parentObject);
+            if (enableNotification)
+            {
+                InvokeBehaviourOnNetworkObjectParentChanged(parentObject);
+            }
             return true;
         }
 
@@ -1819,6 +1828,8 @@ internal SceneObject GetMessageSceneObject(ulong targetClientId)
         {
             var obj = new SceneObject
             {
+                HasParent = transform.parent != null,
+                WorldPositionStays = m_CachedWorldPositionStays,
                 NetworkObjectId = NetworkObjectId,
                 OwnerClientId = OwnerClientId,
                 IsPlayerObject = IsPlayerObject,
@@ -1829,31 +1840,16 @@ internal SceneObject GetMessageSceneObject(ulong targetClientId)
                 TargetClientId = targetClientId
             };
 
-            NetworkObject parentNetworkObject = null;
-
-            if (!AlwaysReplicateAsRoot && transform.parent != null)
+            // Handle Parenting
+            if (!AlwaysReplicateAsRoot && obj.HasParent)
             {
-                parentNetworkObject = transform.parent.GetComponent<NetworkObject>();
-                // In-scene placed NetworkObjects parented under GameObjects with no NetworkObject
-                // should set the has parent flag and preserve the world position stays value
-                if (parentNetworkObject == null && obj.IsSceneObject)
-                {
-                    obj.HasParent = true;
-                    obj.WorldPositionStays = m_CachedWorldPositionStays;
-                }
-            }
+                var parentNetworkObject = transform.parent.GetComponent<NetworkObject>();
 
-            if (parentNetworkObject != null)
-            {
-                obj.HasParent = true;
-                obj.ParentObjectId = parentNetworkObject.NetworkObjectId;
-                obj.WorldPositionStays = m_CachedWorldPositionStays;
-                var latestParent = GetNetworkParenting();
-                var isLatestParentSet = latestParent != null && latestParent.HasValue;
-                obj.IsLatestParentSet = isLatestParentSet;
-                if (isLatestParentSet)
+                if (parentNetworkObject)
                 {
-                    obj.LatestParent = latestParent.Value;
+                    obj.ParentObjectId = parentNetworkObject.NetworkObjectId;
+                    obj.LatestParent = GetNetworkParenting();
+                    obj.IsLatestParentSet = obj.LatestParent != null && obj.LatestParent.HasValue;
                 }
             }
 
@@ -1866,12 +1862,6 @@ internal SceneObject GetMessageSceneObject(ulong targetClientId)
                 var syncRotationPositionLocalSpaceRelative = obj.HasParent && !m_CachedWorldPositionStays;
                 var syncScaleLocalSpaceRelative = obj.HasParent && !m_CachedWorldPositionStays;
 
-                // Always synchronize in-scene placed object's scale using local space
-                if (obj.IsSceneObject)
-                {
-                    syncScaleLocalSpaceRelative = obj.HasParent;
-                }
-
                 // If auto object synchronization is turned off
                 if (!AutoObjectParentSync)
                 {
@@ -1949,6 +1939,15 @@ internal static NetworkObject AddSceneObject(in SceneObject sceneObject, FastBuf
             var bufferSerializer = new BufferSerializer<BufferSerializerReader>(new BufferSerializerReader(reader));
             networkObject.SynchronizeNetworkBehaviours(ref bufferSerializer, networkManager.LocalClientId);
 
+            // If we are an in-scene placed NetworkObject and we originally had a parent but when synchronized we are
+            // being told we do not have a parent, then we want to clear the latest parent so it is not automatically
+            // "re-parented" to the original parent. This can happen if not unloading the scene and the parenting of
+            // the in-scene placed Networkobject changes several times over different sessions.
+            if (sceneObject.IsSceneObject && !sceneObject.HasParent && networkObject.m_LatestParent.HasValue)
+            {
+                networkObject.m_LatestParent = null;
+            }
+
             // Spawn the NetworkObject
             networkManager.SpawnManager.SpawnNetworkObjectLocally(networkObject, sceneObject, sceneObject.DestroyWithScene);
 

com.unity.netcode.gameobjects/Runtime/SceneManagement/SceneEventData.cs

@@ -322,7 +322,14 @@ internal void AddSpawnedNetworkObjects()
                     m_NetworkObjectsSync.Add(sobj);
                 }
             }
+            SortObjectsToSync();
+        }
 
+        /// <summary>
+        /// Used to order the object serialization for both synchronization and scene loading
+        /// </summary>
+        private void SortObjectsToSync()
+        {
             // Sort by INetworkPrefabInstanceHandler implementation before the
             // NetworkObjects spawned by the implementation
             m_NetworkObjectsSync.Sort(SortNetworkObjects);
@@ -568,20 +575,31 @@ internal void SerializeScenePlacedObjects(FastBufferWriter writer)
             // Write our count place holder (must not be packed!)
             writer.WriteValueSafe((ushort)0);
 
+            // Clear our objects to sync and build a list of the in-scene placed NetworkObjects instantiated and spawned locally
+            m_NetworkObjectsSync.Clear();
             foreach (var keyValuePairByGlobalObjectIdHash in m_NetworkManager.SceneManager.ScenePlacedObjects)
             {
                 foreach (var keyValuePairBySceneHandle in keyValuePairByGlobalObjectIdHash.Value)
                 {
                     if (keyValuePairBySceneHandle.Value.Observers.Contains(TargetClientId))
                     {
-                        // Serialize the NetworkObject
-                        var sceneObject = keyValuePairBySceneHandle.Value.GetMessageSceneObject(TargetClientId);
-                        sceneObject.Serialize(writer);
-                        numberOfObjects++;
+                        m_NetworkObjectsSync.Add(keyValuePairBySceneHandle.Value);
                     }
                 }
             }
 
+            // Sort the objects to sync based on parenting hierarchy
+            SortObjectsToSync();
+
+            // Serialize the sorted objects to sync.
+            foreach (var objectToSycn in m_NetworkObjectsSync)
+            {
+                // Serialize the NetworkObject
+                var sceneObject = objectToSycn.GetMessageSceneObject(TargetClientId);
+                sceneObject.Serialize(writer);
+                numberOfObjects++;
+            }
+
             // Write the number of despawned in-scene placed NetworkObjects
             writer.WriteValueSafe(m_DespawnedInSceneObjectsSync.Count);
             // Write the scene handle and GlobalObjectIdHash value

com.unity.netcode.gameobjects/Runtime/Spawning/NetworkSpawnManager.cs

@@ -573,7 +573,6 @@ internal NetworkObject CreateLocalNetworkObject(NetworkObject.SceneObject sceneO
             var scale = sceneObject.HasTransform ? sceneObject.Transform.Scale : default;
             var parentNetworkId = sceneObject.HasParent ? sceneObject.ParentObjectId : default;
             var worldPositionStays = (!sceneObject.HasParent) || sceneObject.WorldPositionStays;
-            var isSpawnedByPrefabHandler = false;
 
             // If scene management is disabled or the NetworkObject was dynamically spawned
             if (!NetworkManager.NetworkConfig.EnableSceneManagement || !sceneObject.IsSceneObject)
@@ -605,33 +604,40 @@ internal NetworkObject CreateLocalNetworkObject(NetworkObject.SceneObject sceneO
                 networkObject.DestroyWithScene = sceneObject.DestroyWithScene;
                 networkObject.NetworkSceneHandle = sceneObject.NetworkSceneHandle;
 
-
                 var nonNetworkObjectParent = false;
                 // SPECIAL CASE FOR IN-SCENE PLACED:  (only when the parent has a NetworkObject)
                 // This is a special case scenario where a late joining client has joined and loaded one or
                 // more scenes that contain nested in-scene placed NetworkObject children yet the server's
-                // synchronization information does not indicate the NetworkObject in question has a parent.
-                // Under this scenario, we want to remove the parent before spawning and setting the transform values.
+                // synchronization information does not indicate the NetworkObject in question has a parent = or =
+                // the parent has changed.
+                // For this we will want to remove the parent before spawning and setting the transform values based
+                // on several possible scenarios.
                 if (sceneObject.IsSceneObject && networkObject.transform.parent != null)
                 {
                     var parentNetworkObject = networkObject.transform.parent.GetComponent<NetworkObject>();
-                    // if the in-scene placed NetworkObject has a parent NetworkObject but the synchronization information does not
-                    // include parenting, then we need to force the removal of that parent
-                    if (!sceneObject.HasParent && parentNetworkObject)
-                    {
-                        // remove the parent
-                        networkObject.ApplyNetworkParenting(true, true);
-                    }
-                    else if (sceneObject.HasParent && !parentNetworkObject)
+                    // special case to handle being parented under a GameObject with no NetworkObject
+                    nonNetworkObjectParent = !parentNetworkObject && sceneObject.HasParent;
+
+                    // If the in-scene placed NetworkObject has a parent NetworkObject...
+                    if (parentNetworkObject)
                     {
-                        nonNetworkObjectParent = true;
+                        // Then remove the parent only if:
+                        // - The authority says we don't have a parent (but locally we do).
+                        // - The auhtority says we have a parent but either of the two are true:
+                        // -- It isn't the same parent.
+                        // -- It was parented using world position stays.
+                        if (!sceneObject.HasParent || (sceneObject.IsLatestParentSet
+                            && (sceneObject.LatestParent.Value != parentNetworkObject.NetworkObjectId || sceneObject.WorldPositionStays)))
+                        {
+                            // If parenting without notifications then we are temporarily removing the parent to set the transform
+                            // values before reparenting under the current parent.
+                            networkObject.ApplyNetworkParenting(true, true, enableNotification: !sceneObject.HasParent);
+                        }
                     }
                 }
 
-                // Set the transform unless we were spawned by a prefab handler
-                // Note: prefab handlers are provided the position and rotation
-                // but it is up to the user to set those values
-                if (sceneObject.HasTransform && !isSpawnedByPrefabHandler)
+                // Set the transform only if the sceneObject includes transform information.
+                if (sceneObject.HasTransform)
                 {
                     // If world position stays is true or we have auto object parent synchronization disabled
                     // then we want to apply the position and rotation values world space relative
@@ -674,7 +680,6 @@ internal NetworkObject CreateLocalNetworkObject(NetworkObject.SceneObject sceneO
                     networkObject.SetNetworkParenting(parentId, worldPositionStays);
                 }
 
-
                 // Dynamically spawned NetworkObjects that occur during a LoadSceneMode.Single load scene event are migrated into the DDOL
                 // until the scene is loaded. They are then migrated back into the newly loaded and currently active scene.
                 if (!sceneObject.IsSceneObject && NetworkSceneManager.IsSpawnedObjectsPendingInDontDestroyOnLoad)