What is a X file?

A file with .x extension refers to DirectX 3D Graphics legacy file format that was introduced with Microsoft DirectX 2.0. It was used for 3D graphics rendering in games and specifies the structures for meshes, textures, animations, and user-defined objects. It has been deprecated since 2014 as the Autodesk FBX file format serves better as a more modern format. X is template-driven and is free of any usage knowledge.

You can open DirectX X files using Microsoft DirectX and common text editors.

X File Format

The X file reference contains reference information for the API elements that are used to work with DirectX .x files. The format provides low-level data primitives that are used by other applications to define higher-level primitives through data templates. DirectX 6.0 introduced interfaces and methods that enable reading from and writing to .x files. DirectX 3.0 introduced a binary version of this file format.

The X file format reference defined by DirectX 9 contains reference information for .x files in Binary as well as Text Encodings.

Binary Encoding

The binary format defines the DirectX X format as a tokenized representation of the text format. These tokens can be standalone to give grammatical structure or can be record-bearing tokens supplying the necessary data.

Header

The binary header can be read and write using the following definitions.

#define XOFFILE_FORMAT_MAGIC \
  ((long)'x' + ((long)'o' << 8) + ((long)'f' << 16) + ((long)' ' << 24))

#define XOFFILE_FORMAT_VERSION \
  ((long)'0' + ((long)'3' << 8) + ((long)'0' << 16) + ((long)'2' << 24))

#define XOFFILE_FORMAT_BINARY \
  ((long)'b' + ((long)'i' << 8) + ((long)'n' << 16) + ((long)' ' << 24))

#define XOFFILE_FORMAT_TEXT   \
  ((long)'t' + ((long)'x' << 8) + ((long)'t' << 16) + ((long)' ' << 24))

#define XOFFILE_FORMAT_COMPRESSED \
  ((long)'c' + ((long)'m' << 8) + ((long)'p' << 16) + ((long)' ' << 24))

#define XOFFILE_FORMAT_FLOAT_BITS_32 \
  ((long)'0' + ((long)'0' << 8) + ((long)'3' << 16) + ((long)'2' << 24))

#define XOFFILE_FORMAT_FLOAT_BITS_64 \
  ((long)'0' + ((long)'0' << 8) + ((long)'6' << 16) + ((long)'4' << 24))

Text Encoding

DirectX .x files don’t depend on the way how the file is used and is not specific to any application. This template-driven approach allows the .x file format to be used by any client application.

Header

The variable-length header is compulsory and must be at the beginning of the data stream. The header contains the following data.

References

• X Files Legacy
• DirectX 9 File Format Reference