How To

Load Files with Assests Manager


How To Load Files with Assests Manager

In order to help developers load multiple assets, Babylon.js (starting with version 1.14) introduced the AssetsManager class.

This class can be used to import meshes into a scene or load text and binary files.

Using AssetsManager

Initializing and creating tasks

To use it, you just have to instantiate it with a current scene:

var assetsManager = new BABYLON.AssetsManager(scene);

Then you can add tasks to the manager:

var meshTask = assetsManager.addMeshTask("skull task", "", "scenes/", "skull.babylon");

Each task provides an onSuccess and an onError callback:

meshTask.onSuccess = function (task) {
    task.loadedMeshes[0].position = BABYLON.Vector3.Zero();
}
meshTask.onError = function (task, message, exception) {
    console.log(message, exception);
}

You can do the same thing but with text and binary files:

var textTask = assetsManager.addTextFileTask("text task", "msg.txt");
textTask.onSuccess = function(task) {
    console.log(task.text);
}

var binaryTask = assetsManager.addBinaryFileTask("binary task", "grass.jpg");
binaryTask.onSuccess = function (task) {
    // Do something with task.data
}

Images are also supported through imageTask:

var imageTask = assetsManager.addImageTask("image task", "img.jpg");
imageTask.onSuccess = function(task) {
    console.log(task.image.width);
}

Textures can also be loaded, through textureTask:

var textureTask = assetsManager.addTextureTask("image task", "img.jpg");
textureTask.onSuccess = function(task) {
    material.diffuseTexture = task.texture;
}

Task state and error handling

Each task has a state object that represents the current execution state of the task. The state is represented by an enum, BABYLON.AssetTaskState and has 4 states:

  • INIT - before the task started executing
  • RUNNING - when the task started executing but hasn't finished yet.
  • DONE - when the task successfully finished execution
  • ERROR - when the task failed.

If a task has the error state (BABYLON.AssetTaskState.ERROR) a new object will be added to the task: task.errorObject . The error object have 2 variables defined, both optional:

  • message - a string explaining the error shortly (such as "request returned 404")
  • exception - in case an exception was thrown during execution, the exception object will contain the stack trace information

This way the error is accessible also when using the assets manager observers:

assetsManager.onTaskErrorObservable.add(function(task) {
    console.log('task failed', task.errorObject.message, task.errorObject.exception);
});

Manager callbacks and observables

The manager itself provides four callbacks:

  • onFinish
  • onProgress
  • onTaskSuccess
  • onTaskError
assetsManager.onProgress = function(remainingCount, totalCount, lastFinishedTask) {
    engine.loadingUIText = 'We are loading the scene. ' + remainingCount + ' out of ' + totalCount + ' items still need to be loaded.';
};

assetsManager.onFinish = function(tasks) {
    engine.runRenderLoop(function() {
        scene.render();
    });
};

The manager also allows you to use observers in order to handle onFinish, onProgress, onTaskSuccess and onTaskError:

  • onTaskSuccessObservable - registered observers will be executed when a single task finished successfully.
  • onTaskErrorObservable - registered observers will be executed when a single task failed.
  • onProgressObservable - registered observers will be executed when a single task finished successfully or failed.
  • onTasksDoneObservable - registered observers will be execute when all tasks' executions are done (success or failed!)
assetsManager.onTaskSuccessObservable.add(function(task) {
    console.log('task successful', task)
});
assetsManager.onTasksDoneObservable.add(function(tasks) {
    var errors = tasks.filter(function(task) {return task.taskState === BABYLON.AssetTaskState.ERROR});
    var successes = tasks.filter(function(task) {return task.taskState !== BABYLON.AssetTaskState.ERROR});
});

Executing the tasks

To launch all the tasks, you have to call:

assetsManager.load();
  • You can see a live demo here
  • Playground demo here -

Available tasks

There are 7 types of tasks that can be executed using the assets manager.

Each task is extending the AbstractAssetTask class (and implementing IAssetTask interface) with the following properties:

onSuccess: (task: IAssetTask) => void;
onError: (task: IAssetTask, message?: string, exception?: any) => void;

isCompleted: boolean = false;
name: string;
taskState: AssetTaskState;
errorObject: { message?: string; exception?: any; };

Note that the properties required to initialize a task are always corresponding to the object type it creates. Foe example, the constructor signature of the CubeTextureAssetTask takes the same variables as the class BABYLON.CubeTexture . The order of the variables might vary.

MeshAssetTask

The mesh asset task is used to load a model externally (a .babylon, .obj, .gltf and so on).

Constructor signature:

constructor(name: string, meshesNames: any, rootUrl: string, sceneFilename: string)

Extra properties:

public loadedMeshes: Array<AbstractMesh>;
public loadedParticleSystems: Array<ParticleSystem>;
public loadedSkeletons: Array<Skeleton>;

TextFileAssetTask

Is used to async-load a (text) file.

Constructor signature:

constructor(name: string, url: string)

Extra properties:

public url: string;
public text: string;

BinaryFileAssetTask

This task is used to load a binary file. The main difference between this and the TextFileAssetTask is that the data will be stored in an ArrayBuffer

Constructor signature:

constructor(name: string, url: string)

Extra properties:

public url: string;
public data: ArrayBuffer;

ImageAssetTask

This function will load an image (.png, .jpg, .gif). It will create an HTMLImageElement object

Constructor signature:

constructor(name: string, url: string)

Extra properties:

public url: string;
public image: HTMLImageElement;

TextureAssetTask

This will create a new BABYLON.Texture from a provided single url.

Constructor signature:

constructor(name: string, url: string, noMipmap?: boolean, invertY?: boolean, samplingMode: number = BABYLON.Texture.TRILINEAR_SAMPLINGMODE)

Extra properties:

public texture: Texture;

CubeTextureAssetTask

The same as the TextureAssetTask but for a cube texture

Constructor signature:

constructor(name: string, url: string, extensions?: string[], noMipmap?: boolean, files?: string[])

Extra properties:

public texture: CubeTexture;

HDRCubeTextureAssetTask

Same as the CubeTextureAssetTask, but for HDR cube textures

constructor(name: string, url: string, size?: number, noMipmap = false, generateHarmonics = true, useInGammaSpace = false, usePMREMGenerator = false)

Extra properties:

public texture: HDRCubeTexture;

Using a loading screen

By default, the AssetsManager will display a loading screen while loading assets:

If you want to disable the loading screen, you have to set useDefaultLoadingScreen to false:

assetsManager.useDefaultLoadingScreen = false;

The loading screen will also be displayed while loading a scene using SceneLoader if ShowLoadingScreen is set to true (by default).

BABYLON.SceneLoader.ShowLoadingScreen = false;

In the same way, you can also display or hide the loading screen manually using these functions:

engine.displayLoadingUI();
engine.hideLoadingUI();

Loading text is controlled using loadingUIText :

engine.loadingUIText = "text";

Background color is controlled using loadingUIBackgroundColor :

engine.loadingUIBackgroundColor = "red";