gltf-model

NOTE: This version of the documentation tracks unstable development happening on A-Frame’s master branch. If you wish to try it out, grab the unstable build. Otherwise, head to the documentation for the current 0.8.0 version

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, 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 COLLADA models.

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

Type Description
selector Selector to an <a-asset-item>
string url()-enclosed path to a glTF file

Events

Event Name Description
model-loaded glTF model has been loaded into the scene.
model-error glTF model could not be loaded.

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>

Geometry compression with Draco

Geometry in a glTF model may be compressed using the Draco library. For models containing primarily geometry, with simple untextured materials or vertex colors, compression can often reduce file size by 90–95%. When the model contains other large data — like textures or animation, which Draco does not affect — file size savings will be less significant.

The tradeoff with any form of compression will be decoding time. Compressed models take less time to download and use less bandwidth, but cannot be rendered until they’re decompressed. To avoid dropping frames in VR, delay the beginning of the experience until models are downloaded and decompressed.

To apply Draco compression to an existing glTF model, use glTF-Pipeline. You’ll also need to host the Draco decoder library with your scene and configure scene properties as explained below.

Scene properties

When using glTF models compressed with Draco, you must host the Draco decoder library with your scene and configure the path to the decoder:

<a-scene gltf-model="dracoDecoderPath: path/to/decoder/;">
<a-entity gltf-model="url(pony.glb)"></a-entity>
</a-scene>
Property Description Default Value
dracoDecoderPath Path to the Draco decoder libraries. ‘’

The decoder folder must contain three files:

  • draco_decoder.js — Emscripten-compiled decoder, compatible with any modern browser.
  • draco_decoder.wasm — WebAssembly decoder, compatible with newer browsers and devices.
  • draco_wasm_wrapper.js — JavaScript wrapper for the WASM decoder.

All 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.

More Resources

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

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