fix: Nested NetworkTransform synchronization fails when parent has non-Vector3.one scale [MTT-6304] (#2538)

* fix

This fixes an issue with interpolation causing nonauthoritative NetworkTransform instances to not properly reflect the final axis values when parenting changes.

* test

Updating the parenting test to validate the fix for parenting a nested NetworkTransform and assuring that values are the same.

* fix

Handle the condition that no new states have been pushed for a late joining client.
(i.e. it just synchronized a nested NetworkTransform and that is it)

* test

Did an overhaul on the parented NetworkTransformTest (formerly NetworkTransformParentedLocalSpaceTest), renamed it to ParentedNetworkTransformTest, and now it tests both world and local space values depending upon how the NetworkObject is parented.

* style

removing commented out code.

* update

Adding entry to changelog

* fix

Migrating SetStateInternal into the Initialization method so it handles change of ownership.

Author: NoelStephensUnity

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -15,6 +15,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - Fixed issue where some temporary debug console logging was left in a merged PR. (#2562)
 - Fixed the "Generate Default Network Prefabs List" setting not loading correctly and always reverting to being checked. (#2545)
 - Fixed missing value on `NetworkListEvent` for `EventType.RemoveAt` events.  (#2542,#2543)
+- Fixed issue where parenting a NetworkTransform under a transform with a scale other than Vector3.one would result in incorrect values on non-authoritative instances. (#2538)
 - Fixed issue where a server would include scene migrated and then despawned NetworkObjects to a client that was being synchronized. (#2532)
 - Fixed the inspector throwing exceptions when attempting to render `NetworkVariable`s of enum types. (#2529)
 - Making a `NetworkVariable` with an `INetworkSerializable` type that doesn't meet the `new()` constraint will now create a compile-time error instead of an editor crash (#2528)

com.unity.netcode.gameobjects/Components/NetworkTransform.cs

@@ -2392,16 +2392,6 @@ public override void OnNetworkSpawn()
             m_CachedNetworkManager = NetworkManager;
 
             Initialize();
-            // This assures the initial spawning of the object synchronizes all connected clients
-            // with the current transform values. This should not be placed within Initialize since
-            // that can be invoked when ownership changes.
-            if (CanCommitToTransform)
-            {
-                var currentPosition = GetSpaceRelativePosition();
-                var currentRotation = GetSpaceRelativeRotation();
-                // Teleport to current position
-                SetStateInternal(currentPosition, currentRotation, transform.localScale, true);
-            }
         }
 
         /// <inheritdoc/>
@@ -2472,6 +2462,7 @@ protected void Initialize()
             CanCommitToTransform = IsServerAuthoritative() ? IsServer : IsOwner;
             var replicatedState = ReplicatedNetworkState;
             var currentPosition = GetSpaceRelativePosition();
+            var currentRotation = GetSpaceRelativeRotation();
 
             if (CanCommitToTransform)
             {
@@ -2483,6 +2474,9 @@ protected void Initialize()
                 // Authority only updates once per network tick
                 NetworkManager.NetworkTickSystem.Tick -= NetworkTickSystem_Tick;
                 NetworkManager.NetworkTickSystem.Tick += NetworkTickSystem_Tick;
+
+                // Teleport to current position
+                SetStateInternal(currentPosition, currentRotation, transform.localScale, true);
             }
             else
             {
@@ -2494,15 +2488,42 @@ protected void Initialize()
                 NetworkManager.NetworkTickSystem.Tick -= NetworkTickSystem_Tick;
 
                 ResetInterpolatedStateToCurrentAuthoritativeState();
-                m_CurrentPosition = GetSpaceRelativePosition();
+                m_CurrentPosition = currentPosition;
                 m_CurrentScale = transform.localScale;
-                m_CurrentRotation = GetSpaceRelativeRotation();
+                m_CurrentRotation = currentRotation;
 
             }
 
             OnInitialize(ref replicatedState);
         }
 
+        /// <inheritdoc/>
+        /// <remarks>
+        /// When a parent changes, non-authoritative instances should:
+        /// - Apply the resultant position, rotation, and scale from the parenting action.
+        /// - Clear interpolators (even if not enabled on this frame)
+        /// - Reset the interpolators to the position, rotation, and scale resultant values.
+        /// This prevents interpolation visual anomalies and issues during initial synchronization
+        /// </remarks>
+        public override void OnNetworkObjectParentChanged(NetworkObject parentNetworkObject)
+        {
+            // Only if we are not authority
+            if (!CanCommitToTransform)
+            {
+                m_CurrentPosition = GetSpaceRelativePosition();
+                m_CurrentRotation = GetSpaceRelativeRotation();
+                m_CurrentScale = GetScale();
+                m_ScaleInterpolator.Clear();
+                m_PositionInterpolator.Clear();
+                m_RotationInterpolator.Clear();
+                var tempTime = new NetworkTime(NetworkManager.NetworkConfig.TickRate, NetworkManager.ServerTime.Tick).Time;
+                UpdatePositionInterpolator(m_CurrentPosition, tempTime, true);
+                m_ScaleInterpolator.ResetTo(m_CurrentScale, tempTime);
+                m_RotationInterpolator.ResetTo(m_CurrentRotation, tempTime);
+            }
+            base.OnNetworkObjectParentChanged(parentNetworkObject);
+        }
+
         /// <summary>
         /// Directly sets a state on the authoritative transform.
         /// Owner clients can directly set the state on a server authoritative transform
@@ -2656,6 +2677,12 @@ protected virtual void Update()
                 }
             }
 
+            // If we have not received any additional state updates since the very
+            // initial synchronization, then exit early.
+            if (m_LocalAuthoritativeNetworkState.IsSynchronizing)
+            {
+                return;
+            }
             // Apply the current authoritative state
             ApplyAuthoritativeState();
         }