Fix: scene start up failure

[mikhail-dcl]

Fixes #2684

Got rid of empty scenes

There was an issue

NullReferenceException: Object reference not set to an instance of an object.
  at ECS.SceneLifeCycle.Systems.UpdateCurrentSceneSystem.Update (System.Single t) [0x00000] in <00000000000000000000000000000000>:0 
  at ECS.Abstract.BaseUnityLoopSystem.Update (System.Single& t) [0x00000] in <00000000000000000000000000000000>:0 

which indicates ISceneStateProvider is not set for the scene facade.

Instead of finding and fixing a potential source of the issue I got rid of the concept of empty scene entirely as it's been completely redundant since we introduced Terrain:

• There will be no entity representing an empty scene that will lead faster querying over SceneEntityDefinitionComponent
• Scene readiness will be resolved immediately just like for LODs, and roads.

Centralized handling of TeleportIntent

Now the single system TeleportCharacterSystem is responsible for the whole flow of handling TeleportIntents:

• Happy path (before it was only this)
• Cancellation (including Timeout), all local timeouts were removed
• Failure with exceptions
• Synchronizing with the existing queue
• Recovery from failed teleport intents

Strict binding of loading progress with loading screen

There was no direct binding of the state of AsyncLoadProcessReport with the view.

Empowered LoadingScreen to handle all possible outcomes of the process (which is driven externally) and reflect them on the report itself, including:

• TimeOut
• Hard Cancellation
• Failure of the internal process
• Happy path

Now, UI fully relies on the state of AsyncLoadProcessReport and does not do any checks of timeouts, errors, etc locally.

Exception-free flow is fixed up

There was a mix of exceptions and Results in Teleport and Start-up flows. The guidelines are formalized and the code was refactored to follow this principle.

Before it was hard to follow the flow that can freely violate the contracts.

Related issues

The loading process can be interrupted at any time, leaving the game in an unpredictable state. This PR does not cover this case as it's much wider. It will be addressed in the separate issue #2821

How to QA:

• Try to break the loading process by:
• teleporting between realms, empty parcels, and real scenes
• adjusting the debug loading timeout (by default is 2 minutes) to low values to simulate cancellation in the middle of the loading process. I expect you will find more bugs for which you will be able to create tickets (and later we will address them as part of No Recovery from critical failures during start-up, teleport & at runtime #2821
• no matter what the loading screen should always correspond to the loading process: whether it's failed, canceled or succeeded, and never be stuck
• Even if teleport has failed the user should be properly teleported back, and all the surroundings loaded properly (inc. without moving)

[github-actions]

Windows and Mac build successfull in Unity Cloud! You can find a link to the downloadable artifact below.

Name	Link
Commit	183b93b
Logs	https://github.com/decentraland/unity-explorer/actions/runs/12013546602
Download Windows	https://github.com/decentraland/unity-explorer/suites/31305118183/artifacts/2233974862
Download Windows S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/fix/scene-statr-up-fail/Decentraland_windows64.zip
Download Mac	https://github.com/decentraland/unity-explorer/suites/31305118183/artifacts/2234040381
Download Mac S3	https://explorer-artifacts.decentraland.org/@dcl/unity-explorer/branch/fix/scene-statr-up-fail/Decentraland_macos.zip
Built on	2024-11-25T16:20:01Z

[dalkia]

Question about the original requirement of the scene fail

On Init.js, delete line 60. This will make the Rapture scene (-89,-64) fail to load.

Start the client normally, and go to that position. You will see the ScriptEngineException: ReferenceError: __VERSION__ is not defined error straight away. This scene wont load.

But, I still have to wait for the loading screen timeout.

Is it possible to stop set the result of the teleport as Faulted, so we don't have to wait for the timeout?

[mikhail-dcl]

@dalkia I addressed your comment so it will fail immedeately by propagating the exception

[dalkia]

@mikhail-dcl

It works, but I get the following result

1. I start in editor in 0,0
2. I try to teleport to -89,-64 with goto
3. It fails immediatly
4. I get thrown into an unloaded version of GP, and the -89,-64 scene is still loaded in the hierarchy

If I recall correctly, the rollback teleport is for another PR. But shouldn't the failed scene be unloaded?

[DafGreco]

Fix verified on both platforms! Windows and macOS ✅