ClientNetworkTransform in local space wrongly synchronized before first move

[kevincastejon]

Description

When a player joins and has its player object spawned and parented into a parent NetworkObject, has its "InLocalSpace" field checked, and has not made any move yet, then it's local position is synchronized wrongly serverside. It acts as if the server do not know about that client position being local, as it counter balance the move of the parent object to keep the player at {0.0.0} world (were it should be at {0.0.0} locally into the parent). As soon as the player makes a move, the position is synchronized correctly.

This bug is present from 1.8.1 to 1.12.2, it's not present on 1.7.1- nor on 2.0.0+ versions.

Reproduce Steps

1. Open this minimalistic reproduction project : https://github.com/kevincastejon/NetcodeIssue-ClientNetworkTransformAndLocalSpace.git
2. Start a server, then a client instance.
3. See how the player transform is not synchronized correctly server side.

Actual Outcome

The player transform values seems to be treated as global server side.

Expected Outcome

The player transform values should be treated as local server side.

Workarounds

• Checking the half float precision field makes the bug disappear.
• Setting the position or scale threshold to 0 makes the bug disappear.

Environment

• OS: Windows11
• Unity Version: 2022.3.15f1
• Netcode Version: from 1.8.1 to 1.12.2

Additional Context

The reproduction project contains the ClientNetworkTransform sample script, a ConnectionManager component with serialized bool field to determine starting a server or a client, and PlayerSpawner component that spawns the clients players and parent it into the associated gameobject, it also move this object on a loop.

[NoelStephensUnity]

@kevincastejon

Hmmm... so it is a mixed server authoritative and client authoritative type of issue. I think I see what could be the cause.

What you can do to resolve this issue (for now if you are going to use 12.2.0 vs v2.2.0) is this:

    public class ClientNetworkTransform : NetworkTransform
    {
        /// <summary>
        /// Used to determine who can write to this transform. Owner client only.
        /// This imposes state to the server. This is putting trust on your clients. Make sure no security-sensitive features use this transform.
        /// </summary>
        protected override bool OnIsServerAuthoritative()
        {
            return false;
        }

        public override void OnNetworkSpawn()
        {
            // After the NetworkTransform has initialized 
            base.OnNetworkSpawn();
           // on the clien-authority side
            if (CanCommitToTransform)
            {
                // send a teleport state update
                SetState(teleportDisabled: false);
            }
        }
    }
}

Where upon the client being fully synchronized and the player object spawned on the client-owner side, Teleport the parented player to its current, client-side, position relative to the in-scene placed NetworkObject that is constantly moving and using a server-authoritative motion model.

I will mark the bug for import, but the above should help work around your issue.

[kevincastejon]

Thank you very much sir

[EmandM]

This should be fixed by #3361

[LeonardA-L]

Hello!
I am a colleague of Kevin's. I ran tests today, and can confirm this fixes our issues.
On top of the issue mentioned, we had a similar problem when roaming between multiple wifi access points (this is a VR application). This is also fixed, however I cannot wrap my head around why it works.
Here's what happens:

• We use M. Stephens' ClientNetworkTransform with the line from #3361. From what I understand, this simply "refreshes" the state of the client transform on the server once.
• Upon joining the game, the client runs the OnNetworkSpawn and the SetState line
• When we reboot the wifi AP:
  • The client freezes until the network is found again
  • Then runs the OnNetworkSpawn and the SetState line
  • No bug. Which is understandable.
• When roaming between APs:
  • The client does not run OnNetworkSpawn upon reconnection
  • Still no bug, which I don't understand because it should need this "refresh" from what I understand, shouldn't it?

Furthermore, the documentation explicitely states "This isn't resistant to network jitter", but we haven't observed the bug since adding this line.
If you could please shed some light on how this SetState works, I would rest easier when we ship this to clients 🙏