gltf-model

glTF (GL Transmission Format) is an open project by Khronos providing a common, extensible format for 3D assets that is both efficient and highly interoperable with modern web technologies.

The gltf-model component loads a 3D model using a glTF (.gltf or .glb) file.

Note that glTF is a fairly new specification and adoption is still growing. Work on the three.js glTF loader and converters are still active.

NOTE: A-Frame supports glTF 2.0. For models using older versions of the glTF format, use gltf-model-legacy from donmccurdy/aframe-extras.

Why use glTF?

In comparison to the older OBJ format, which supports only vertices, normals, texture coordinates, and basic materials, glTF provides a more powerful set of features. In addition to all of the above, glTF offers:

• Hierarchical objects
• Scene information (light sources, cameras)
• Skeletal structure and animation
• More robust materials and shaders

For simple models with no animation, OBJ is nevertheless a common and reliable choice.

In comparison to COLLADA or FBX, the supported features are very similar. However, because glTF focuses on providing a “transmission format” rather than an editor format, it is more interoperable with web technologies. By analogy, the .PSD (Adobe Photoshop) format is helpful for editing 2D images, but images are converted to .JPG for use on the web. In the same way, glTF is a simpler way of transmitting 3D assets while rendering the same result.

In short, expect glTF models to work with A-Frame more reliably than other formats.

Example

Load a glTF model by pointing to an asset that specifies the src for a glTF file.

<a-scene>
  <a-assets>
    <a-asset-item id="tree" src="/path/to/tree.gltf"></a-asset-item>
  </a-assets>

  <a-entity gltf-model="#tree"></a-entity>
</a-scene>

Values

Events

Loading Inline

Alternatively, load a glTF model by specifying the path directly within url(). However, the scene won’t wait for the resource to load before rendering.

<a-entity gltf-model="url(/path/to/tree.gltf)"></a-entity>

Using animations

If you want to use the animations from your glTF model, you can use the animation-mixer component from aframe-extras. By default all animations are played in a loop.

<a-entity gltf-model="#monster" animation-mixer></a-entity>

Using compression

glTF file size may be reduced using Draco or Meshopt compression. Neither of these affect textures, which should be compressed or resized by other methods. Furthermore, compression does not particularly affect framerate — if the model has too many triangles or draw calls, compression will not change that, and the model should be simplified using tools like Blender or gltfpack, instead.

• Draco: Compression for geometry, often reducing geometry size by 90-95%. Requires some extra time to decompress on the device, but this occurs off the main thread in a Web Worker.
• Meshopt: Compression for geometry, morph targets, and animation. If combined with additional lossless compression (like gzip) Meshopt may have similar compression ratios to Draco, with much faster decompression. Note: Some web servers do not support gzip with .glb or .gltf files (see: GitHub Pages).

To optimize an existing glTF model, use tools such as:

• Blender for Draco compression
• glTF-Pipeline for Draco compression
• glTF-Transform for Draco or Meshopt compression
• gltfpack for Meshopt compression

You’ll also need to load a decoder library by configuring scene properties as explained below.

Scene properties

When using glTF models compressed with Draco, KTX2 or Meshopt, you must configure the path to the necessary decoders:

<a-scene gltf-model="dracoDecoderPath: path/to/decoder/;
    basisTranscoderPath: path/to/transcoder/;
    meshoptDecoderPath: path/to/meshopt_decoder.js;">
  <a-entity gltf-model="url(pony.glb)"></a-entity>
</a-scene>

dracoDecoderPath path must be a folder containing three files:

• draco_decoder.js — Emscripten-compiled decoder, compatible with old browsers like IE11.
• draco_decoder.wasm — WebAssembly decoder, compatible with modern browsers.
• draco_wasm_wrapper.js — JavaScript wrapper for the WASM decoder.

These files are available from the three.js repository, under examples/js/libs/draco/gltf. The gltf-model component will automatically choose whether to use a WASM or JavaScript decoder, so both should be included.

basisTranscoderPath path must be a folder containing two files:

basis_transcoder.js — JavaScript wrapper for the WebAssembly transcoder.
basis_transcoder.wasm — WebAssembly transcoder.

These files are available from the three.js repository in /examples/jsm/libs/basis. You can use a CDN like this: basisTranscoderPath:https://cdn.jsdelivr.net/npm/[email protected]/examples/jsm/libs/basis/;

meshoptDecoderPath path should be the complete file path (including filename) for a Meshopt decoder, typically named meshopt_decoder.js. Meshopt requires WebAssembly support. A CDN-hosted, versioned decoder is available at https://unpkg.com/[email protected]/meshopt_decoder.js, or you may download copies from the meshoptimizer GitHub repository.

More Resources

Over 100,000 glTF models are free for download on Sketchfab, and various exporters and converters converters are available:

• Blender 2.80+
• OBJ → glTF
• FBX → glTF
• COLLADA → glTF
• glTF Workflow for A Saturday Night

See the official glTF specification for available features, community resources, and ways to contribute.