LoadAllAssetsAsync from AssetBundle is not really async

We are making a WebGL app that has to use AssetBundles to load props into a scene. The problem is that once the bundle is downloaded the app freezes for around 2.5 MINUTES until the prefabs are loaded into a list... We have tried all the load methods. One by one, all at once, normal and async and we get the same thing every time. It takes a LONG time to load the prefabs. Our current code is:

Code (CSharp):

1. public IEnumerator LoadPrefabsAsync()
2.      {
3.          print("start loading prefabs");
4.          AssetBundleRequest request = assetBundle.LoadAllAssetsAsync<GameObject>();
5.          yield return request;
6.          prefabs = request.allAssets as GameObject[];
7.          while (!request.isDone)
8.              yield return null;
9.          //List<GameObject> objs = new List<GameObject>();
10.          //foreach (var i in assetNames)
11.          //    {
12.          //    AssetBundleRequest request = assetBundle.LoadAssetAsync(i);
13.          //    objs.Add(request.asset as GameObject);
14.          //    yield return null;
15.          //    }
16.          //prefabs = objs.ToArray();
17.          //Debug.Log(prefabs.Length + " prefabs from " + assetBundle.name + " loaded.");
18.          prefabsLoaded = true;
19.          yield return null;
20.      }

Has anyone found any kind of workaround or fix or this?

 

Hi FairGamesProductions,

I'm having the same issue as you with AssetBundle.LoadAllAssetsAsync and LoadAssetAsync. Did you find out anything else?

I've made a reproduction project (find Bitbucket repo here) where I try to load an asset bundle with audio clips (~300MB compressed / ~2 GB uncompressed). Reproduction steps are:

1. Open either CallbackTest or CoroutineTest. The first one listens to the completed events of the async requests of AssetBundle.LoadAllAssetsAsync and LoadAssetAsync and the second one uses a coroutine to monitor the progress of the async requests.
2. Press play and notice that the animated cube stops moving during most of the duration of AssetBundle.LoadAllAssetsAsync.

 

Hi Ryanc_unity,

I'm having the same issue, but not using WebGL? Admittedly, it's not a matter of minutes, but i can't have things moving smoothly on the screen.

 

It's a known issue that Unity's asynchronous systems often cause the game to freeze or stutter, unfortunately.

The public issue tracker contains various of these reports, such as:
https://issuetracker.unity3d.com/issues/async-load-is-not-async
https://unity3d.com/search?refinement=issues&gq=async freeze

Here is a talk from Playdead, how they achieved "stutter free gameplay". Unfortunately, as far as I remember, you'd require Unity source code to fix/workaround those issues. It's worth watching though, lots of good points made in that talk!

Spoiler: Unite 2016 - Tools, Tricks and Technologies for Reaching Stutter Free 60 FPS in INSIDE

 

Hi Peter77!

Thanks for the links! That Playdead talk sounds great. I will definitely check it out.

I did check the issue tracker, but all the related issues I found were from rather old versions of Unity (the one you linked to was on 5.5). I'm working on Unity 2018.1, so I wasn't sure how relevant those issues where at this point.

My understanding was that only the last phase of the loading, the "activation phase" should freeze the main thread (after the AsyncRequest.progress reaches 0.9).

 

Hi Ryanc_unity,

Thanks for getting back to me. All my tests are on a standalone project. An I'm seeing the stuttering both when AsyncRequest.progress is between 0 and 0.9, and in the final activation phase after that. I only expected stuttering on the last phase between 0.9 and 1.

I will have a look at the profiler and see.

 

I made a test project that is available on bitbucket (using git LFS for the ~300MB asset bundle), here is the snippet:

Code (CSharp):

1.  
2. public class AsyncBundleCoroutineLoader : MonoBehaviour {
3.     public string bundlePath;
4.     public Text text;
5.     AssetBundle assetBundle;
6.  
7.     void Start () {
8.         StartCoroutine(Load());
9.     }
10.  
11.     IEnumerator Load()
12.     {
13.         AssetBundleCreateRequest assetBundleCreateRequest = AssetBundle.LoadFromFileAsync(bundlePath);
14.         while(!assetBundleCreateRequest.isDone)
15.         {
16.             text.text = "LoadFromFileAsync progress: " + (assetBundleCreateRequest.progress * 100.0f) + "%";
17.             yield return null;
18.         }
19.         Debug.Log("AssetBundle.LoadFromFileAsync completed");
20.         assetBundle = assetBundleCreateRequest.assetBundle;
21.         AssetBundleRequest assetBundleRequest = assetBundle.LoadAllAssetsAsync();
22.         while (!assetBundleRequest.isDone)
23.         {
24.             text.text = "LoadAllAssetsAsync progress: " + (assetBundleRequest.progress * 100.0f) + "%";
25.             yield return null;
26.         }
27.         text.text = "Loading completed";
28.         Debug.Log("AssetBundle.LoadAllAssetsAsync completed");
29.     }
30.  
31.     private void OnDestroy()
32.     {
33.         assetBundle.Unload(true);
34.     }
35. }

 

Hi we may be having a similar issue here. We just upgraded to Unity 2018.1.3f1 and noticed a large increase in our Time ms to get assets from downloaded asset bundles. This is an example of the code that is now failing us in Unity 2018:



Previously we ran Unity 5.5.2p2 with no issues and smooth asset bundle loading. The profiler looks like this during the LoadAssetsAsync call:


Now with Unity 2018.1.3f1 (and several other versions we tried in 2018 and in the 2017 range), we see a loading freeze / pop, where Unity hangs almost as if it is synchronously loading the bundle assets:



Notice how the AssetBundle.asset line in the profiler in 5.5.2p2 has a 0ms time and no additional nested calls, however in Unity 2018 we're seeing a much larger > 700ms time and several additional nested calls starting with "AssetBundle.asset/allAssets [Forced assets loading]." Any idea what that means or work arounds we can try?

This is a deal breaker for us to upgrade and is holding up our team. Thanks!

*This was demonstrated on Windows PC for a PC Standalone build.

 

If it works in an earlier Unity versions, but stops working in Unity 2018, you most likely found a bug.

If this is important to you, you should submit a bug-report, following the advice given in this document: https://unity3d.com/unity/qa/bug-reporting

Unity Technologies does not use the forum to track bugs. If you do not submit a bug-report, they're most likely not going to fix it.

If you submit a bug-report, make sure to post the Case number in this forum thread, for UT staff to pick up.

 

Ok bug report submit, haven't received a Case number yet..

 

(Case 1047238) LoadAssetAsync behaves like sychronous call instead, creates large runtime hang / freeze

 

Confirmed that the loading performs smoothly all the way through 5.6.6f2 but begins failing as soon as we switch to Unity 2017+

 

Ha! Issue is now working ok on our end, we found a missing yield at a later point in the same function:

This code was missing a yield:

Code (CSharp):

1. abr = ab.LoadAssetAsync<Texture2D>("AssetName");
2.         if (abr.asset == null)
3.         {
4.             Debug.LogException(new System.Exception("abr.asset is null"));
5.             yield break;
6.         }

Our loading issue is smooth again in Unity 2018.1.3f1 with this:

Code (CSharp):

1. abr = ab.LoadAssetAsync<Texture2D>("AssetName");
2.         yield return abr;
3.  
4.         if (abr.asset == null)
5.         {
6.             Debug.LogException(new System.Exception("abr.asset is null"));
7.             yield break;
8.         }

The only thing we can't explain is why the first set of code works smoothly in 5.5.2p2 given that this was actually an error on our end?

 

That's strange indeed, because according to the documentation:

https://docs.unity3d.com/ScriptReference/AssetBundleRequest-asset.html

 

Hi all,

I have just found the same type of issue after migrating from 2017.3.1 to 2018.2.5, except my issue is with AsynLoad of a scene.

Here is an extract of the code I use:

Code (CSharp):

1.  
2. AsyncOperation sceneLoadOperation = UnityEngine.SceneManagement.SceneManager.LoadSceneAsync(locationDefinition.SceneFilePath, UnityEngine.SceneManagement.LoadSceneMode.Additive);
3.  
4. while (!sceneLoadOperation.isDone)
5. {
6.     if (this.LocationLoadUpdated != null)
7.     {
8.         this.LocationLoadUpdated.Invoke(sceneLoadOperation.progress);
9.     }
10.  
11.     yield return null;
12. }
13.  

I have tried adding "yield return sceneLoadOperation;" before the "while" statement, but the result is the same : a huge performance spike in the profiler while loading the level.

Do you have any idea of what I am doing wrong?

Edit: just to clarify, this happens only in the editor (but was fine in 2017.3), but all my runtime content is in the Resources folder, pending my migration to the addressable system. Maybe some changes in the internal data structure of Unity, for the addressables system, is causing this?

Thanks!

 

When I use

Code (CSharp):

1. while (assetBundleRequest.isDone) {yield return null;}

I also get the "AssetBundle.asset/allAssets [Forced assets loading]" spike just like the screenshot someone else posted.
But another bug is:if I use

Code (CSharp):

1. yield return assetBundleRequest;

it cost a lot of monobehaiour missing errors.
unity version is 2018.3.b+

 

i found out the problem(monobehaiour missing),when LoadSceneAsync finish(or even LoadScene), scene.isLoaded is still false。
I use

Code (CSharp):

1. while (!scene.isLoaded || !scene.IsValid())
2.         {
3.             //Debug.LogFormat("scene.isLoaded={0}, scene.IsValid() = {1}", scene.isLoaded, scene.IsValid());
4.             yield return null;
5.         }

after load finish and everything goes fine.

i'll test asset loading spike again

 

It means that there is no difference either you use LoadAsset or LoadAssetAync? Both will freez the game as it runs in main thread? If this is the case then, what you will recommend for smooth asset bundle loading?? I have to load/unload so many asset bundles based on my camera position what you will recommend for best practices?

 

Hi:
I have the same problem trying to load assets async.
I share a Log where you can see that Bundle Request is not done (status == false), but Progress is 0 (402 times).

 

I am also looking for help to smoothly load bundles in webgl. Any help will be appreciated.

 

This should work:

Code (CSharp):

1.    
2.     private void Start()
3.     {
4.         StartCoroutine("myCoolBundle.unity3d");
5.     }
6.  
7.     AssetBundleCreateRequest bundleLoadRequest;
8.  
9.     private IEnumerator LoadBundle(string bundlePath)
10.     {
11.         StartCoroutine(LoadFromFileAsync(bundlePath));
12.  
13.         while (!bundleLoadRequest.isDone)
14.         {
15.             Debug.Log(bundleLoadRequest.progress);
16.             loadingBar.GetComponent<Image>().fillAmount = bundleLoadRequest.progress;
17.             yield return null;
18.         }
19.     }
20.  
21.     private IEnumerator LoadFromFileAsync(string filePath)
22.     {
23.         bundleLoadRequest = AssetBundle.LoadFromFileAsync(Path.Combine(Application.streamingAssetsPath, filePath), 0);
24.         yield return null;
25.     }

 

Hi:
I had a similar problem.
Here is my code and the results.

Unity: 5.6.3 p3
for( 1000 )

Code (CSharp):

1. AssetBundleRequest mRequest = assetbundle.LoadAssetAsync(assetName);
2.          
3.             while (!mRequest.isDone)
4.             {
5.                 yield return null;
6.             }
7.  
8.             if (null != mRequest.asset)
9.             {
10.                 ABLog.Log("not Null");
11.             }
12.             else
13.             {
14.                 ABLog.Log("Null");
15.             }

 

Hi,
still doesn't work

when I execute:
bundleLoadRequest = AssetBundle.LoadFromFileAsync(Path.Combine(Application.streamingAssetsPath, filePath), 0);

1) bundleLoadRequest.done is true immediately (thats weird)
2) when I use "yield return bundleLoadRequest;" it stops updates and waits

is this bug compression method related ? will it be better on different compression method ? I use LZ4

Any help ?

Btw I cant find any bug report of LoadFromFileAsync

Cheers. Petr

 

Hi,

I am still experiencing this issue all the way in 2020. When I run AssetBundle.LoadFromFileAsyn(Path), isDone is true immediately.

I tried making my while condition while (request.progress < 1), but progress stays at 0 forever.

I'm currently using Unity 2018.4.9f1. Has this been fixed in any later versions of 2018.4?

Thanks

 

This seems to work most consistently for me and reduces the chance of being stuck in a while loop:

Code (CSharp):

1.  
2. yield return new WaitUntil(() =>
3. {
4.         loadingFill.fillAmount = request.progress;
5.         return request.progress >= .99f;
6. });
7.  

 

I'm also battling with this. I thought it was because I'm on 2018.3 - but then I upgraded my project to 2019.4 LTS, but it still happens.

 

https://forum.unity.com/threads/multithreading-and-webgl.817986/

Code (CSharp):

1. Threads are not supported due to the lack of threading supporting in JavaScript. This applies to both Unity’s internal use of threads to speed up performance, and to the use of threads in script code and managed dlls. Essentially, anything in the System.Threading namespace is not supported.

For platforms which supports threading, helpful may be following source code:

Code (CSharp):

1. using System.Collections;
2. using System.Threading.Tasks;
3. using UnityEngine;
4. using System;
5. using System.Runtime.CompilerServices;
6. using System.IO;
7.  
8. public class AssetBundleAsyncAwait : MonoBehaviour
9. {
10.     public async Task<Texture2D> LoadTextureAsync(string filePath, string address)
11.     {
12.         AssetBundleCreateRequest handle = await AssetBundle.LoadFromFileAsync(filePath);
13.         AssetBundleRequest request = await handle.assetBundle.LoadAssetAsync<Texture2D>(address);
14.         Texture2D texture = request.asset as Texture2D;
15.         return texture;
16.     }
17.  
18.     async void Start()
19.     {
20.         Texture2D texture = await LoadTextureAsync(Path.Combine(Application.streamingAssetsPath, "test.bundle"), "Assets/icon.png");  
21.         GameObject plane = GameObject.CreatePrimitive(PrimitiveType.Plane);
22.         plane.GetComponent<Renderer>().material.mainTexture = texture;
23.     }
24. }
25.  
26. // https://docs.unity3d.com/ScriptReference/AssetBundleCreateRequest.html
27. public class AssetBundleCreateRequestAwaiter : INotifyCompletion
28. {
29.     readonly AssetBundleCreateRequest _Request;
30.     Action _Action;
31.  
32.     public AssetBundleCreateRequestAwaiter(AssetBundleCreateRequest request)
33.     {
34.         this._Request = request;
35.         request.completed += OnRequestCompleted;
36.     }
37.  
38.     public bool IsCompleted { get { return _Request.isDone; } }
39.  
40.     public AssetBundleCreateRequest GetResult() { return this._Request; }
41.  
42.     public void OnCompleted(Action action)
43.     {
44.         this._Action = action;
45.     }
46.  
47.     private void OnRequestCompleted(AsyncOperation command)
48.     {
49.         _Action();
50.     }
51. }
52.  
53. public static class AssetBundleCreateRequestAsync
54. {
55.     public static AssetBundleCreateRequestAwaiter GetAwaiter(this AssetBundleCreateRequest request)
56.     {
57.         return new AssetBundleCreateRequestAwaiter(request);
58.     }
59. }
60.  
61. // https://docs.unity3d.com/ScriptReference/AssetBundleRequest.html
62. public class AssetBundleRequestAwaiter : INotifyCompletion
63. {
64.     readonly AssetBundleRequest _Request;
65.     Action _Action;
66.  
67.     public AssetBundleRequestAwaiter(AssetBundleRequest request)
68.     {
69.         this._Request = request;
70.         request.completed += OnRequestCompleted;
71.     }
72.  
73.     public bool IsCompleted { get { return _Request.isDone; } }
74.  
75.     public AssetBundleRequest GetResult() { return this._Request; }
76.  
77.     public void OnCompleted(Action action)
78.     {
79.         this._Action = action;
80.     }
81.  
82.     private void OnRequestCompleted(AsyncOperation command)
83.     {
84.         _Action();
85.     }
86. }
87.  
88. public static class AssetBundleRequestAsync
89. {
90.     public static AssetBundleRequestAwaiter GetAwaiter(this AssetBundleRequest request)
91.     {
92.         return new AssetBundleRequestAwaiter(request);
93.     }
94. }