.FBX

Introduction

Binary FBX is the form in which Maya, 3ds Max, Blender and most other programs save FBX files by default. It holds the same tree of nodes as ASCII FBX, but as typed binary records, with large arrays of vertices and indices optionally compressed.

Autodesk does not publish the layout. What is known comes from reading the files, and the description below follows the notes published by the Blender developers.

Structure

A binary FBX file begins with the text Kaydara FBX Binary, two spaces and a zero byte, then two bytes and a 32-bit version number such as 7400. The rest is a tree of nodes. Each node record gives the offset where it ends, its number of properties, the length of its property list and its name, then its properties, then its child nodes. Properties are typed values: integers, floats, strings, raw bytes, or arrays of numbers, which may be zlib compressed. From version 7500 the offset and length fields grew from 32 to 64 bits.

The top-level nodes include FBXHeaderExtension, GlobalSettings, Definitions, Objects, which holds the geometry, models, materials and animation curves, and Connections, which links the objects into the scene.

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