.FBX File Format – Syntax

Comments and the first line

A semicolon starts a comment, which runs to the end of the line; inside a quoted string it is an ordinary character. Files written by the FBX SDK start with comment lines naming the version, such as ; FBX 7.4.0 project file, then a copyright line and a line of dashes. Readers tell an ASCII file from a binary one by the binary magic Kaydara FBX Binary, which ASCII files lack; the comment line is not required.

Nodes

A node is its name, a colon, then its values separated by commas. If it has children, an opening brace follows the values and a closing brace ends the children. A node with children and no values is written as the name, a colon and the brace.

Name: value, value, value
Name: value {
	Child: value
}
Name:  {
	Child: value
}

Line breaks, spaces and tabs separate tokens and otherwise mean nothing; the indentation is only for reading. The characters {, }, , and : are punctuation outside strings. Assimp’s reader also accepts spaces before the colon.

Values

Strings have no escape character, so a reader takes the next double quote as the end. The text carries no type codes: unlike the binary form, a reader must decide from the text, or from the node’s name, whether a number is a 32-bit or 64-bit integer, a float or a double. Ids, KeyTime values and other KTime values need 64 bits.

Arrays

In FBX 7 files a large array is written as an asterisk and its element count, then a block holding one node a whose values are the elements:

Vertices: *12 {
	a: 0,0,0,1,0,0,1,1,0,0,1,0
}

The a: values may run over many lines. FBX 6 files have no count: the elements follow the colon directly, separated by commas and wrapped over lines, as in Vertices: 0,0,0,1,0,0,….

Raw data

Where the binary form has raw bytes, such as an embedded texture in a Video node’s Content, ASCII files carry them as base64 text in strings. Long data can be split into several strings separated by commas, each a piece of one base64 stream, so a reader must join them before decoding. Some exporters do not embed textures in ASCII files at all.

Object names

An object’s name is written with its class in front and two colons between, as in "Model::Cube" or "Geometry::Cube". The binary form stores the same string the other way round, separated by the bytes 00 01.

Example

; FBX 7.4.0 project file
; ----------------------------------------------------

FBXHeaderExtension:  {
	FBXHeaderVersion: 1003
	FBXVersion: 7400
}
Objects:  {
	Model: 2000, "Model::Triangle", "Mesh" {
		Version: 232
		Properties70:  {
			P: "Lcl Translation", "Lcl Translation", "", "A",0,1.5,0
		}
	}
	Geometry: 1000, "Geometry::Triangle", "Mesh" {
		Vertices: *9 {
			a: 0,0,0,1,0,0,0,1,0
		}
		PolygonVertexIndex: *3 {
			a: 0,1,-3
		}
	}
}
Connections:  {
	C: "OO",2000,0
	C: "OO",1000,2000
}