Asset Loading

In Galacean, asset loading is generally divided into three situations based on its usage:

• The asset is imported into the editor and used in a scene
• The asset is imported into the editor but not used in a scene
• The asset is not imported into the editor

If the project loader is used to load the project, only the resources used in the main scene will be loaded, and other resources in the editor will not be loaded.

await engine.resourceManager.load({
  type: AssetType.Project,
  url: "xxx.json",
});

Correspondingly, if the scene loader is used to load a scene, the scene loader will only load the resources used in that scene, and other resources will not be loaded by default.

const scene = await engine.resourceManager.load({
  type: AssetType.Scene,
  url: "xxx.json",
});
engine.sceneManager.activeScene = scene;

As for those assets that are not used in the scene, you can use resourceManager.load mounted on the Engine instance to load the resources.

// 若只传入 URL ，引擎会依据后缀推断加载的资产类型，如 `.png` 对应纹理， `.gltf` 则对应模型
const gltf1 = await this.engine.resourceManager.load<GLTFResource>(
  "test1.gltf"
);
// 也可以通过 `LoadItem` 定义加载的资产类型，重试次数，重试间隔等信息
const gltf2 = await this.engine.resourceManager.load<GLTFResource>({
  type: AssetType.GLTF,
  url: "test2.gltf",
  retryCount: 5,
  timeout: 500,
  retryInterval: 500,
});
// 也支持传入数组批量加载，返回按顺序排列的加载好的资源队列。
const [texture2D, glTFResource] = await this.engine.resourceManager.load([
  "a.png",
  "b.gltf",
]);

The following will specifically introduce how to load resources at runtime:

• Resource path
• Loading progress
• Cancel loading
• Get loaded assets

Resource Path

The URL path of the resource supports relative paths, absolute paths, and virtual paths:

• Relative paths are relative to the runtime root path. If the path is incorrect, you can adjust it based on the loading error information in the developer tools.
• Absolute paths specify the complete file location, such as https://xxxx.png, and also include blob and base64.
• Virtual paths are the paths in the asset files of the editor, generally Assets/sprite.png.

// 加载相对路径下的资源
this.engine.resourceManager.load("a.png");
 
// 加载绝对路径下的资源
this.engine.resourceManager.load("https://a.png");
 
// 加载 base64
this.engine.resourceManager.load<GLTFResource>({
  url: "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8/5+hHgAHggJ/PchI7wAAAABJRU5ErkJggg==",
  type: AssetType.Texture2D,
});
 
// 加载编辑器虚拟路径下的资源
this.engine.resourceManager.load<GLTFResource>("Assets/texture.png");

In the editor, you can quickly copy the relative path of the asset through Asset Panel -> Right-click asset -> Copy relative path.

baseUrl

ResourceManger currently also supports setting baseUrl:

engine.resourceManager.baseUrl = "https://cdn.galacean.com";

If baseUrl is set, the relative path loaded will be combined with baseUrl:

engine.resourceManager.load("img/2d.png");

The actual loading path from the above two lines of code will be https://cdn.galacean.com/img/2d.png.

Loading Progress

Calling the loading queue can get an AssetPromise object, and you can use onProgress to get the loading progress.

this.engine.resourceManager
  .load(["a.png", "b.gltf"])
  .onProgress((progress: number) => {
    console.log(`当前加载进度为 ${progress}`);
  });

Cancel Loading

The ResourceManager object has a cancelNotLoaded method, which can be used to cancel resources that have not been loaded yet. Passing in a URL will cancel the resource loading for that specific URL.

// 取消所有未加载完的资源。
this.engine.resourceManager.cancelNotLoaded();
// 取消特定的 url 资源加载。
this.engine.resourceManager.cancelNotLoaded("test.gltf");

Note: Currently, canceling the loading of unfinished resources will throw an exception.

Get Loaded Assets

Currently, loaded assets are cached in the ResourceManager. If you need to get loaded assets, you can use the more reliable load asynchronous method. Even if the asset is not in the cache, this interface will reload the corresponding resource.

const asset = await this.engine.resourceManager.load(assetItem);

If you know for sure that this resource is now in the cache, you can also call the getFromCache synchronous method:

// Get the asset corresponding to the passed URL
const asset = this.engine.resourceManager.getFromCache(url);

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