glTF Extensions

glTF extensions can be present in glTF files, and will be present in the parsed JSON. glTF extensions can supported by applications by inspecting the extensions fields inside glTF objects, and it is up to each application to handle or ignore them.

loaders.gl aims to provide support for glTF extensions that can be handled completely or partially during loading, and article describes glTF extensions that are fully or partially processed by the @loaders.gl/gltf classes.

Note that many glTF extensions affect aspects that are firmly outside of the scope of loaders.gl (e.g. rendering), and no attempt is made to process those extensions in loaders.gl.

Official Extensions

KHR_draco_mesh_compression

Supports compression of mesh attributes (geometry).

Specification: KHR_draco_mesh_compression.

Parsing Support:

• By adding the decompress: true options to the GLTFParser any decompressed by the GLTFParser.
• The expanded attributes are placed in the mesh object (effectively making it look as if it had never been compressed).
• The extension objects are removed from the glTF file.

Encoding Support:

• Meshes can be compressed as they are added to the GLTFBuilder.

KHR_lights_punctual

Supports specification of point light sources and addition of such sources to the scenegraph node.

Specification: KHR_lights_punctual

Parsing Support:

• Any nodes with a KHR_lights_punctual extension will get a light field with value containing a light definition object with properties defining the light (this object will be resolved by index from the global KHR_lights_punctual extension object's lights array) .
• The KHR_lights_punctual extensions will be removed from all nodes.
• Finally, the global KHR_lights_punctual extension (including its light list)) will be removed.

Encoding Support:

• N/A

KHR_materials_unlit

Specifies that a material should not be affected by light. Useful for pre-lit materials (e.g. photogrammetry).

KHR_materials_unlit

Custom Extensions

UBER_draco_point_cloud_compression

Specification: Similar to KHR_draco_mesh_compression, but supports point clouds (draw mode 0). Also does not support any fallback or non-compressed accessors/attributes.

Parsing support:

• The primitive's accessors field will be populated after decompression.
• After decompression, the extension will be removed (as if the point cloud was never compressed).

Encoding support:

• Point clouds can be compressed as they are added to the GLTFBuilder and decompressed by the GLTFParser.