FBX files are normally saved in a binary format, but they can also be saved in an ASCII format. Here are the first few lines of a small ASCII-format FBX file:
; FBX ...
; Copyright (C) 1997-2008 ...
; All rights reserved.
; ----------------------------------------------------
FBXHeaderExtension: {FBXHeaderVersion: 1003
FBXVersion: 6000
CurrentCameraResolution: {CameraName: "Model::Producer Perspective"
CameraResolutionMode: "Window Size"
CameraResolutionW: 1
CameraResolutionH: 1
}
CreationTimeStamp: {...
}
}
;Object definitions
;------------------------------------------------------------------
Definitions: {Count: 2
ObjectType: "Model" {Count: 2
}
}
...
Both kinds of FBX files use the .fbx filename extension. You can convert FBX files from binary to ASCII using FBX SDK, or you can use a utility program: seeFBX Converter.
One way to get a feel for FBX is to view and a small FBX file in a 3D viewer, study the file in a text editor, and study the program that created the file or that processes it in some way.