Invalid Destroy Error in DA When Changing Scenes

[KadaXuanwu]

Description

In Distributed Authority (DA) topology, when I spawn objects using NetworkObject.Spawn(destroyWithScene: true), then change scene as SessionOwner using NetworkManager.SceneManager.LoadScene("Lobby", LoadSceneMode.Single), the network objects owned by the clients are correctly destroyed, but the SessionOwner receives an error:
Destroy a spawned NetworkObject on a non-owner client is not valid during a distributed authority session.

Additionally, unchecking Scene Migration Synchronization on the NetworkObject was required, even though in my opinion it should be irrelevant when destroyWithScene: true is set.

Reproduce Steps

1. Set up a multiplayer game using Netcode for GameObjects (NGO) with Distributed Authority topology.
2. In a game scene, let clients spawn their own network objects with destroyWithScene: true.
3. Have the session owner call NetworkManager.SceneManager.LoadScene("Lobby", LoadSceneMode.Single).
4. Observe the session owner's console output.

Actual Outcome

• Network objects are destroyed as expected.
• The session owner receives an error

Expected Outcome

• Network objects should be destroyed without errors since destroyWithScene: true was explicitly set.
• in my opinion, Scene Migration Synchronization should not require manual disabling in this context.

Screenshots

NetworkObject on an object owned by a client:

Environment

• OS: Windows 11
• Unity Version: 6000.0.28f1
• Multiplayer Services: 1.0.2
• Netcode Commit: https://docs.unity3d.com/Packages/[email protected]/changelog/CHANGELOG.html

Additional Context

As far as I know, the player object has to be destroyed by each client manually, where as other spawned network objects should be destroyed automatically on scene change if destroyWithScene: true. Please correct me if I'm wrong.

[NoelStephensUnity]

@KadaXuanwu
You make some very good points and I finally have some time later this week to setup a replication project to run through some of the issues you are describing.

Regarding the Scene Migration Synchronization, we are doing a quality pass and I am looking at the possibility of expanding the Netcode for GameObjects Project Settings to include some additional global default settings for things like NetworkObject and such where you would be able to define what default values you want when creating new component instances.

[KadaXuanwu]

Thanks!

Yes, I could see this feature save some time if you have to manually add a lot of NetworkObjects.

[NoelStephensUnity]

Following up on this issue.

Additionally, unchecking Scene Migration Synchronization on the NetworkObject was required, even though in my opinion it should be irrelevant when destroyWithScene: true is set.

While scene migration synchronization seems like it would be associated with the NetworkObject.DestroyWithScene property, there are distinct differences:

• Scene Migration Synchronization:
  • When enabled, any migration of a NetworkObject from one scene to another is synchronized between all instances.
• Destroy With Scene:
  • When enabled, if the scene that a NetworkObject resides in is unloaded then the NetworkObject will be destroyed.
    • If the NetworkObject is migrated out of the scene prior to unloading it, then it will not be destroyed since it no longer resides in the scene being unloaded.

So, you can have both properties enabled or disabled and they should not impact each other.

As an example:

• NetworkObject-A resides in the currently active scene "FirstScene".
  • NetworkObject-A has both SceneMigrationSynchonization and DestroyWithScene enabled
    • For this example, we will just assume the session owner owns/is the authority of NetworkObject-A.
• The session owner additively loads another scene ("SecondScene").
• Upon the "SecondScene" being loaded and all connected clients reporting having loaded the scene, the session owner migrates NetworkObject-A to the SecondScene.
  • All clients would receive a scene migration notification and would migrate NetworkObject-A into their locally loaded "SecondScene".
• A few minutes later, the session owner unloads the "SecondScene".
  • During the unloading of the "SecondScene", NetworkObject-A is despawned and destroyed.

Regarding the error message, looking into this issue as it should just despawn without an error message using the replication steps you outlined originally.