2017.3.0b6 freezes when entering playmode

Unity Engine
1

Every time I press “Play”, I see the editor enters play mode and a few frames later, the editor freezes. Windows Task Manager says “Unity.exe is not responding”.

The project did not freeze in 2017.1 nor 2017.2, so this is new to me :slight_smile:

Is anyone else seeing such that freezy behavior? Is UT aware of a problem in that area?

2

What I found so far, it seems to be related to loading additive scenes, where a timing problem has been introduced in either b5 or b6.

The original scene loading code looks like this. which causes the editor to freeze while loading the 3rd additive scene:

for(var n = 0; n < SceneIds.Count; ++n)
{
   var sceneName = SceneIds[n].SceneName;

   // If the scene is already added (during edit mode), do not load it again
   var existingScene = SceneManager.GetSceneByName(sceneName);
   if(existingScene.IsValid() && existingScene.isLoaded)
       continue;

   var asyncOp = SceneManager.LoadSceneAsync(sceneName, LoadSceneMode.Additive);
   while(!asyncOp.isDone)
       yield return null;
}

Adding several yield statements after loading a scene, works around the issue.

for(var n = 0; n < SceneIds.Count; ++n)
{
   var sceneName = SceneIds[n].SceneName;

   // If the scene is already added (during edit mode), do not load it again
   var existingScene = SceneManager.GetSceneByName(sceneName);
   if(existingScene.IsValid() && existingScene.isLoaded)
       continue;

   var asyncOp = SceneManager.LoadSceneAsync(sceneName, LoadSceneMode.Additive);
   while(!asyncOp.isDone)
       yield return null;
   
   yield return null;
   yield return null;
   yield return null;
   yield return null;
   yield return null;
   yield return null;
   yield return null;
   yield return null;
}

Is this, by any chance, a known issue? It’s probably going to be rather difficult to create a simplified project to reproduce the issue.

3

Hi Peter77,
We are looking with the development team to see if they are aware of the issue and why it happens.
Stay tuned!

1 Like
4

Noticing a similar issue here, sometimes it freezes, sometimes it doesn’t. Haven’t tried the multiple yield thing yet!

5

It’s happening to me without additive scene loading, all I have is just two scenes loaded at stat in the editor

6

Do any of you have a project that reproduces this behaviour somewhat consistently? If so, please share it with us.

7

I tried for hours creating a project to reproduce the issue, but at some point or another, the issue stops occurring.

While dissecting the real project to create a reproduce, I noticed the game is actually loading another additive scene asynchronously in parallel as well. This “parallel scene” consists of UI elements only. All the yield null’s probably cause some timing-changes, so that the loading or awakening of the “parallel scene” does not interfere with the other scene load.

I changed my code that scenes never load in parallel and this does seem to fix the freeze, didn’t occur from then on anymore.

I also noticed that audio keeps playing normally if the editor froze, it seems only the main thread hangs actually.

However, I’m not able to provide a stripped project to reproduce the issue. I hope someone else can!

1 Like