Unity 5.3, unclear API of SceneManager.LoadSceneAsync() and SceneManager.SetActiveScene()

Question

I try to understand the "multiscene" feature of unity 5.3. My goal is to have 2 loaded scenes and only one of them will be active.

I have the Following Script to load the second scene async in background and do not set as active scene after finishing loading.

         IEnumerator LoadGameScene()
         {
             Debug.Log ( "START Load Async" );
             var result = SceneManager.LoadSceneAsync ( "Game", LoadSceneMode.Additive );
             result.allowSceneActivation = false;
 
             while (!result.isDone) 
             {
                 Debug.Log ( "progress: " + result.progress );
                 yield return new WaitForEndOfFrame ();
             }
             Debug.Log ( "YEAH Loaded Async" );
             // still scene one should be active, tryed it as workaround, did not help
             SceneManager.SetActiveScene (SceneManager.GetSceneByName ("Main"));
         }

what happens here is that progress is allways 0.9 and isDone is never getting true. if i change result.allowSceneActivation to true, it works but both scene are active.

i dont get it.

maybe someone can help or could explain how i achieve my goal ;)

Answer 1

Answer by Fattie · Feb 23, 2016 at 01:40 PM

It's just another screw-up by Unity

Note my comment ... http://answers.unity3d.com/answers/1073667/view.html

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koopatroopas · Feb 23, 2016 at 03:23 PM 0

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Seems that i am not the only one who do not understand the API :) maybe it is just a bug. but unfortunately i did not find any issue to that topic. I think i will report it.

Answer 2

Answer by Andy Lee · May 25, 2016 at 02:57 AM

Seems both of you have been confused by "allowSceneActivation". I agree that Unity's documentation can be done better. But to be fair, "allowSceneActivation" was introduced in Unity 4, way before multi-scene was a thing. It has nothing to do with such feature. It is used for loading a scene asynchronously without having it immediately opened when loading is completed.

E.g. load the main scene asynchronously while splash animation is played. Typically you don't want the splash animation being cut when loading is completed. Therefore, "allowSceneActivation" is useful in this case. Set it to false before animation ends, and to true after that.

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Answer 3

Answer by Decabus · Jan 23, 2017 at 04:33 PM

Alright, this is actually covered by the API. Basically, you can't uncheck for allowing scene activation before loading, and then check for isDone to load - because allowSceneActivation actually counts towards whether it's done or not. So it you don't allow it, it'll never be done. Alternatively, you could check if progress is at 0.9, THEN allow it, THEN load.

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Unity 5.3, unclear API of SceneManager.LoadSceneAsync() and SceneManager.SetActiveScene()

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