.GLTF

Introduction

glTF is an open standard from the Khronos Group for delivering 3D scenes and models, often described as the JPEG of 3D. Version 2.0 was released in 2017. It carries meshes, physically based materials, textures, cameras, skeletons and animation, in a layout that maps closely onto how graphics cards draw, so it loads quickly in browsers and game engines.

There are two forms. A .gltf file is JSON that points to separate binary buffers and images. A .glb file packs the JSON and the binary data into a single file.

Software

• Blender (Windows, macOS, Linux)
• three.js (web browsers)
• Babylon.js (web browsers)
• Godot (Windows, macOS, Linux)
• Unreal Engine (Windows, macOS, Linux)
• Khronos glTF Sample Viewer (web browsers)

Structure

The JSON describes the scene as arrays that refer to each other by index. scenes list root nodes; a node has a transform and may hold a mesh, a camera or a skin. A mesh’s primitives read their vertex data through accessors, which describe a typed view into a bufferView, which is a slice of a buffer of raw bytes. materials, textures, images and animations complete the scene, and asset gives the version.

A GLB file is a 12-byte header followed by chunks. All values are little-endian.