[page:Loader] →

# [name]

A loader for geometry compressed with the Draco library.
[link:https://google.github.io/draco/ Draco] is an open source library for compressing and decompressing 3D meshes and point clouds. Compressed geometry can be significantly smaller, at the cost of additional decoding time on the client device.

Standalone Draco files have a .drc extension, and contain vertex positions, normals, colors, and other attributes. Draco files do not contain materials, textures, animation, or node hierarchies – to use these features, embed Draco geometry inside of a glTF file. A normal glTF file can be converted to a Draco-compressed glTF file using [link:https://github.com/AnalyticalGraphicsInc/gltf-pipeline glTF-Pipeline]. When using Draco with glTF, an instance of DRACOLoader will be used internally by [page:GLTFLoader].

## 代码示例

`// Instantiate a loader const loader = new DRACOLoader(); // Specify path to a folder containing WASM/JS decoding libraries. loader.setDecoderPath( '/examples/js/libs/draco/' ); // Optional: Pre-fetch Draco WASM/JS module. loader.preload(); // Load a Draco geometry loader.load( // resource URL 'model.drc', // called when the resource is loaded function ( geometry ) { const material = new THREE.MeshStandardMaterial( { color: 0x606060 } ); const mesh = new THREE.Mesh( geometry, material ); scene.add( mesh ); }, // called as loading progresses function ( xhr ) { console.log( ( xhr.loaded / xhr.total * 100 ) + '% loaded' ); }, // called when loading has errors function ( error ) { console.log( 'An error happened' ); } );`

## 例子

[example:webgl_loader_draco]

## Browser compatibility

DRACOLoader relies on ES6 [link:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise Promises], which are not supported in IE11. To use the loader in IE11, you must [link:https://github.com/stefanpenner/es6-promise include a polyfill] providing a Promise replacement. DRACOLoader will automatically use either the JS or the WASM decoding library, based on browser capabilities.

## Constructor

### [name]( [param:LoadingManager manager] )

[page:LoadingManager manager] — The [page:LoadingManager loadingManager] for the loader to use. Default is [page:LoadingManager THREE.DefaultLoadingManager].

Creates a new [name].

## Properties

See the base [page:Loader] class for common properties.

## Methods

See the base [page:Loader] class for common methods.

### [method:undefined load]( [param:String url], [param:Function onLoad], [param:Function onProgress], [param:Function onError] )

[page:String url] — A string containing the path/URL of the .drc file.
[page:Function onLoad] — A function to be called after the loading is successfully completed.
[page:Function onProgress] — (optional) A function to be called while the loading is in progress. The argument will be the XMLHttpRequest instance, that contains .[page:Integer total] and .[page:Integer loaded] bytes.
[page:Function onError] — (optional) A function to be called if an error occurs during loading. The function receives error as an argument.

Begin loading from url and call the onLoad function with the decompressed geometry.

### [method:this setDecoderPath]( [param:String value] )

[page:String value] — Path to folder containing the JS and WASM decoder libraries.

### [method:this setDecoderConfig]( [param:Object config] )

[page:String config.type] - (Optional) "js" or "wasm".

Provides configuration for the decoder libraries. Configuration cannot be changed after decoding begins.

### [method:this setWorkerLimit]( [param:Number workerLimit] )

[page:Number workerLimit] - Maximum number of workers to be allocated. Default is 4.

Sets the maximum number of [link:https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers Web Workers] to be used during decoding. A lower limit may be preferable if workers are also for other tasks in the application.

### [method:this preload]()

Requests the decoder libraries, if not already loaded.

### [method:this dispose]()

Disposes of the decoder resources and deallocates memory. The decoder [link:https://github.com/google/draco/issues/349 cannot be reloaded afterward].

## Source

[link:https://github.com/mrdoob/three.js/blob/master/examples/jsm/loaders/DRACOLoader.js examples/jsm/loaders/DRACOLoader.js]