feat: NetworkTransform synchronization mode is configured on NetworkConfig

The project wide setting reached NetworkConfig through an IProcessSceneWithReport, which cannot reach
a scene placed NetworkManager in play mode. NetworkManager.OnEnable moves itself into the
DontDestroyOnLoad scene, and it does so before the callback runs, so the scene the callback is handed
no longer contains the object it is looking for. It applied to zero NetworkManagers every time and
nothing reported that, because the setting it read was correct and only the write was missing. A
build was unaffected, since there the callback runs at build time against the authored scene. Its
sibling SetInScenePlaced survives the same callback only because NetworkObject sets InScenePlaced at
runtime as a fallback, which is why this is the first place the callback's limit was visible.

TransformSyncMode is now public on NetworkConfig and authored per NetworkManager under "Transform
Synchronization" in the inspector. It is serialized by the same mechanism as every other NetworkConfig
value, so scenes, prefabs and builds all carry it with no build pipeline involvement. That also
removes the prefab processor, which ran on import and therefore baked whatever the setting happened to
be the last time a prefab was imported.

Being public also lets a project offer the mode as a pre session choice instead of an editor round
trip. NetworkManager captures the value into ActiveTransformSyncMode when it starts and everything on
the send and receive paths reads that, so a write during a session cannot leave already spawned
instances registered under one mode while new ones use the other, and cannot move the connection
configuration hash out from under a client that is still joining.

NetworkTransform's inspector no longer hides UseUnreliableDeltas under the batched mode. The mode
belongs to the NetworkManager that will run the instance, which a prefab cannot know, and the runtime
already ignores the value while batching.

NetworkTransformSyncModeConfigurationTests covers the delivery that nothing covered before: every
other fixture reaches the mode through the same assignment the integration test harness makes, so a
delivery path that never ran left them all green.

Author: NoelStephensUnity

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -10,6 +10,8 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Added
 
+- Added `NetworkConfig.TransformSyncMode`, which determines whether `NetworkTransform` instances detect and synchronize their state individually or as a single batched message per tick. It is set per `NetworkManager` under "Transform Synchronization" in the inspector or from script before a session starts, and the value the session starts with applies for the duration of that session. Every peer in a session has to use the same mode, which the connection configuration hash enforces. (#4123)
+
 ### Changed
 
 - Changed `NetworkTransform.UseHalfFloatPrecision` to synchronize position with a resolution of approximately 1mm regardless of how far an object has travelled. Previously the resolution could degrade to approximately 3cm. This does not increase bandwidth, but projects using `NetworkTransform.UseUnreliableDeltas` will send full precision position updates more often. (#4129)

com.unity.netcode.gameobjects/Editor/Configuration/NetcodeForGameObjectsProjectSettings.cs

@@ -37,16 +37,6 @@ private void OnEnable()
         [SerializeField]
         public bool GenerateDefaultNetworkPrefabs = true;
 
-        /// <summary>
-        /// The project wide <see cref="TransformSyncModes"/> that is applied to <see cref="NetworkConfig.TransformSyncMode"/>.
-        /// </summary>
-        /// <remarks>
-        /// The two modes are not wire compatible with one another, so this is authored once for the project as
-        /// opposed to per <see cref="NetworkManager"/>.
-        /// </remarks>
-        [SerializeField]
-        public TransformSyncModes TransformSyncMode = TransformSyncModes.PerInstance;
-
         internal void SaveSettings()
         {
             Save(true);

com.unity.netcode.gameobjects/Editor/Configuration/NetcodeSettingsProvider.cs

@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using System.IO;
-using Unity.Netcode.Components;
 using UnityEditor;
 using UnityEngine;
 using Directory = UnityEngine.Windows.Directory;
@@ -133,7 +132,6 @@ private static void OnGuiHandler(string obj)
             var settings = NetcodeForGameObjectsProjectSettings.instance;
             var generateDefaultPrefabs = settings.GenerateDefaultNetworkPrefabs;
             var networkPrefabsPath = settings.TempNetworkPrefabsPath;
-            var transformSyncMode = settings.TransformSyncMode;
 
             EditorGUI.BeginChangeCheck();
 
@@ -194,26 +192,6 @@ private static void OnGuiHandler(string obj)
                     networkPrefabsPath,
                     GUILayout.Width(s_MaxLabelWidth + 270));
                 GUILayout.EndVertical();
-
-                GUILayout.BeginVertical("Box");
-                GUILayout.Label("NetworkTransform Synchronization", EditorStyles.boldLabel);
-                transformSyncMode = (TransformSyncModes)EditorGUILayout.EnumPopup(
-                    new GUIContent(
-                        "Synchronization Mode",
-                        "Determines how NetworkTransform instances detect and synchronize their state. " +
-                        "Batched mode detects changes for all instances within a job and sends them as a single message per tick. " +
-                        "This is a global setting for all NetworkTransforms since the two modes are not compatible on a per instance basis."),
-                    transformSyncMode,
-                    GUILayout.Width(s_MaxLabelWidth + 120));
-
-                if (transformSyncMode == TransformSyncModes.Batched)
-                {
-                    EditorGUILayout.HelpBox(
-                        $"{nameof(NetworkTransform.UseUnreliableDeltas)} does not apply in this mode and will no longer be visible when viewing " +
-                        "NetworkTransform in the inspector view. Delivery is determined per state update as opposed to per component.",
-                        MessageType.Info);
-                }
-                GUILayout.EndVertical();
             }
             EditorGUILayout.EndFoldoutHeaderGroup();
             GUILayout.EndVertical();
@@ -224,7 +202,6 @@ private static void OnGuiHandler(string obj)
                 NetcodeForGameObjectsEditorSettings.SetNetcodeInstallMultiplayerToolTips(multiplayerToolsTipStatus ? 0 : 1);
                 settings.GenerateDefaultNetworkPrefabs = generateDefaultPrefabs;
                 settings.TempNetworkPrefabsPath = networkPrefabsPath;
-                settings.TransformSyncMode = transformSyncMode;
                 settings.SaveSettings();
             }
         }

com.unity.netcode.gameobjects/Editor/Configuration/TransformSyncModeProcessor.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using Unity.Netcode.Components;
 using Unity.Netcode.GameObjects.Editor.Configuration;
 using Unity.Netcode.Logging;
 using UnityEditor;
@@ -51,6 +52,7 @@ public class NetworkManagerEditor : NetcodeEditorBase<NetworkManager>
         private SerializedProperty m_SpawnTimeOutProperty;
         private SerializedProperty m_RpcHashSizeProperty;
         private SerializedProperty m_LoadSceneTimeOutProperty;
+        private SerializedProperty m_TransformSyncModeProperty;
         private SerializedProperty m_PrefabsList;
 
         private SerializedProperty m_NetworkProfileMetrics;
@@ -138,6 +140,7 @@ private void Initialize()
             m_NetworkMessageMetrics = m_NetworkConfigProperty.FindPropertyRelative("NetworkMessageMetrics");
 #endif
             m_RpcHashSizeProperty = m_NetworkConfigProperty.FindPropertyRelative("RpcHashSize");
+            m_TransformSyncModeProperty = m_NetworkConfigProperty.FindPropertyRelative(nameof(NetworkConfig.TransformSyncMode));
             m_PrefabsList = m_NetworkConfigProperty
                 .FindPropertyRelative(nameof(NetworkConfig.Prefabs))
                 .FindPropertyRelative(nameof(NetworkPrefabs.NetworkPrefabsLists));
@@ -183,6 +186,7 @@ private void CheckNullProperties()
 #endif
 
             m_RpcHashSizeProperty = m_NetworkConfigProperty.FindPropertyRelative("RpcHashSize");
+            m_TransformSyncModeProperty = m_NetworkConfigProperty.FindPropertyRelative(nameof(NetworkConfig.TransformSyncMode));
             m_PrefabsList = m_NetworkConfigProperty
                 .FindPropertyRelative(nameof(NetworkConfig.Prefabs))
                 .FindPropertyRelative(nameof(NetworkPrefabs.NetworkPrefabsLists));
@@ -319,6 +323,17 @@ private void DisplayNetworkManagerProperties()
                     EditorGUILayout.PropertyField(m_PrefabsList);
                 }
 
+                EditorGUILayout.Space();
+                EditorGUILayout.LabelField("Transform Synchronization", EditorStyles.boldLabel);
+                EditorGUILayout.PropertyField(m_TransformSyncModeProperty, new GUIContent("Mode"));
+                if (m_NetworkManager.NetworkConfig.TransformSyncMode == TransformSyncModes.Batched)
+                {
+                    EditorGUILayout.HelpBox(
+                        $"{nameof(NetworkTransform.UseUnreliableDeltas)} does not apply in this mode. Delivery is determined per state " +
+                        "update as opposed to per component. Every peer in a session has to use the same mode.",
+                        MessageType.Info);
+                }
+
                 EditorGUILayout.Space();
                 EditorGUILayout.LabelField("Scene Management Settings", EditorStyles.boldLabel);
                 EditorGUILayout.PropertyField(m_EnableSceneManagementProperty);

com.unity.netcode.gameobjects/Editor/Configuration/TransformSyncModeProcessor.cs.meta

@@ -1,6 +1,5 @@
 using System.Runtime.CompilerServices;
 using Unity.Netcode.Components;
-using Unity.Netcode.GameObjects.Editor.Configuration;
 using UnityEditor;
 using UnityEngine;
 using UnityEngine.Scripting.APIUpdating;
@@ -220,41 +219,37 @@ private void DisplayNetworkTransformProperties()
             EditorGUILayout.LabelField("Delivery", EditorStyles.boldLabel);
             EditorGUILayout.PropertyField(m_TickSyncChildren);
 
-            // UseUnreliableDeltas only applies to per instance synchronization mode. Under the batched mode
-            // delivery is determined per state update as opposed to per component, so the property (and
-            // everything it constrains) is hidden. See Project Settings -> Multiplayer -> Netcode for GameObjects.
-            var perInstanceSync = NetcodeForGameObjectsProjectSettings.instance.TransformSyncMode == TransformSyncModes.PerInstance;
-            if (perInstanceSync)
+            // UseUnreliableDeltas only applies to per instance synchronization mode, but the mode is authored on
+            // the NetworkManager that will run this instance, which a prefab cannot know. So it is always drawn
+            // and the runtime ignores it under the batched mode, where delivery is determined per state update
+            // as opposed to per component.
+            // If both are set from a previous configuration, then SwitchTransformSpaceWhenParented takes
+            // precedence.
+            if (networkTransform.UseUnreliableDeltas && networkTransform.SwitchTransformSpaceWhenParented)
             {
-                // If both are set from a previous configuration, then SwitchTransformSpaceWhenParented takes
-                // precedence.
-                if (networkTransform.UseUnreliableDeltas && networkTransform.SwitchTransformSpaceWhenParented)
-                {
-                    networkTransform.UseUnreliableDeltas = false;
-                }
-                SetGUIActive(!networkTransform.SwitchTransformSpaceWhenParented);
-                if (networkTransform.SwitchTransformSpaceWhenParented)
-                {
-                    EditorGUILayout.BeginHorizontal();
-                    EditorGUILayout.PropertyField(m_UseUnreliableDeltas);
-                    EditorGUILayout.LabelField($"Cannot use with {nameof(NetworkTransform.SwitchTransformSpaceWhenParented)}.");
-                    EditorGUILayout.EndHorizontal();
-                }
-                else
-                {
-                    EditorGUILayout.PropertyField(m_UseUnreliableDeltas);
-                }
-
-                SetGUIActive(true);
+                networkTransform.UseUnreliableDeltas = false;
+            }
+            SetGUIActive(!networkTransform.SwitchTransformSpaceWhenParented);
+            if (networkTransform.SwitchTransformSpaceWhenParented)
+            {
+                EditorGUILayout.BeginHorizontal();
+                EditorGUILayout.PropertyField(m_UseUnreliableDeltas);
+                EditorGUILayout.LabelField($"Cannot use with {nameof(NetworkTransform.SwitchTransformSpaceWhenParented)}.");
+                EditorGUILayout.EndHorizontal();
+            }
+            else
+            {
+                EditorGUILayout.PropertyField(m_UseUnreliableDeltas);
             }
 
+            SetGUIActive(true);
+
             EditorGUILayout.Space();
             EditorGUILayout.LabelField("Configurations", EditorStyles.boldLabel);
 
             // SwitchTransformSpaceWhenParented is only constrained by UseUnreliableDeltas while the latter applies.
-            var blockedByUnreliableDeltas = perInstanceSync && networkTransform.UseUnreliableDeltas;
-            SetGUIActive(!blockedByUnreliableDeltas);
-            if (blockedByUnreliableDeltas)
+            SetGUIActive(!networkTransform.UseUnreliableDeltas);
+            if (networkTransform.UseUnreliableDeltas)
             {
                 EditorGUILayout.BeginHorizontal();
                 EditorGUILayout.PropertyField(m_SwitchTransformSpaceWhenParented);
@@ -269,10 +264,7 @@ private void DisplayNetworkTransformProperties()
             if (m_SwitchTransformSpaceWhenParented.boolValue)
             {
                 m_TickSyncChildren.boolValue = true;
-                if (perInstanceSync)
-                {
-                    networkTransform.UseUnreliableDeltas = false;
-                }
+                networkTransform.UseUnreliableDeltas = false;
             }
             else
             {

com.unity.netcode.gameobjects/Editor/NetworkManagerEditor.cs

@@ -1971,7 +1971,7 @@ protected override void OnSynchronize<T>(ref BufferSerializer<T> serializer)
             // This is the best place to define the handle since it is the first thing that reaches
             // every receiver and is only ever invoked once for the entire duration of the objects spawn
             // life cycle.
-            if (NetworkManager.NetworkConfig.TransformSyncMode == TransformSyncModes.Batched)
+            if (NetworkManager.NetworkConfig.ActiveTransformSyncMode == TransformSyncModes.Batched)
             {
                 if (serializer.IsWriter && TransformHandle == TransformHandleAllocator.InvalidHandle)
                 {
@@ -2403,7 +2403,7 @@ private TransformDeltaConfig GetTransformDeltaConfig()
                 // unreliable deltas to compensate for. Forcing this off also retires the axial frame
                 // synchronization: that exists solely to re-send a full set of axes once a second in case an
                 // unreliable delta was lost, which cannot happen here.
-                UseUnreliableDeltas = UseUnreliableDeltas && m_CachedNetworkManager.NetworkConfig.TransformSyncMode != TransformSyncModes.Batched,
+                UseUnreliableDeltas = UseUnreliableDeltas && m_CachedNetworkManager.NetworkConfig.ActiveTransformSyncMode != TransformSyncModes.Batched,
                 SwitchTransformSpaceWhenParented = SwitchTransformSpaceWhenParented,
 #if COM_UNITY_MODULES_PHYSICS || COM_UNITY_MODULES_PHYSICS2D
                 UseRigidbodyForMotion = m_UseRigidbodyForMotion,
@@ -3883,7 +3883,7 @@ private void ReleaseTransformHandle()
         /// </summary>
         private void RegisterForBatchedInterpolation()
         {
-            if (m_CachedNetworkManager == null || m_CachedNetworkManager.NetworkConfig.TransformSyncMode != TransformSyncModes.Batched)
+            if (m_CachedNetworkManager == null || m_CachedNetworkManager.NetworkConfig.ActiveTransformSyncMode != TransformSyncModes.Batched)
             {
                 return;
             }
@@ -3916,7 +3916,7 @@ private void DeregisterFromBatchedInterpolation()
 
         private void RegisterForBatchedStateTracking()
         {
-            if (m_CachedNetworkManager == null || m_CachedNetworkManager.NetworkConfig.TransformSyncMode != TransformSyncModes.Batched)
+            if (m_CachedNetworkManager == null || m_CachedNetworkManager.NetworkConfig.ActiveTransformSyncMode != TransformSyncModes.Batched)
             {
                 return;
             }
@@ -5163,7 +5163,7 @@ internal void TickUpdate()
                 }
 
                 // 
-                if (m_NetworkManager.NetworkConfig.TransformSyncMode == TransformSyncModes.Batched)
+                if (m_NetworkManager.NetworkConfig.ActiveTransformSyncMode == TransformSyncModes.Batched)
                 {
                     // Batched: every registered instance is checked in parallel and anything that comes back
                     // dirty will add its state update to the outbound batch.