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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.

ExtensionPreprocessedDescription
[KHR_draco_mesh_compression][KHR_draco_mesh_compression]YDecompresses draco-compressed geometries
[EXT_meshopt_compression][EXT_meshopt_compression])YDecompresses meshopt-compressed geometries
[KHR_texture_basisu][KHR_texture_basisu])Y
[KHR_texture_webp][KHR_texture_webp])Y
[KHR_lights_punctual][KHR_lights_punctual])Y*Deprecated
[KHR_materials_unlit][KHR_materials_unlit])Y*Deprecated

Official Extensions​

KHR_draco_mesh_compression​

Supports compression of mesh attributes (geometry).

The GLTFLoader by default fully decompresses draco compressed geometries, removing the draco extension and the compressed data from the parsed glTF data structure.

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

KHR_texture_basisu​

This extension adds the ability to specify textures using KTX v2 images with Basis Universal supercompression.

The GLTFLoader by default fully decompresses compressed textures, removing the basisu extension and the compressed data from the parsed glTF data structure.

KHR_texture_basisu

Custom Extensions​

EXT_meshopt_compression​

This extension provides a support for the meshopt binary geometry data compression format that is tailored to the common types of data seen in glTF buffers. The GLTFLoader by default fully decompresses meshopt compressed geometries, removing the meshopt extension and the compressed data from the parsed glTF data structure.

EXT_meshopt_compression

KHR_draco_mesh_compression: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_draco_mesh_compression KHR_lights_punctual: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
KHR_materials_unlit: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_unlit
KHR_texture_basisu: https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_texture_basisu
EXT_meshopt_compression: https://github.com/KhronosGroup/glTF/blob/main/extensions/2.0/Vendor/EXT_meshopt_compression)