MDX

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MDX files are binary 3d model files engineered and used by Blizzard Entertainment. Several variations of MDX exist. The document focuses on the format used in Warcraft III and its expansion, The Frozen Throne. The format also has a human-readable textual representation whose file format ends in MDL. Several converters exist to convert between the two formats.

Converters

This is a list of known converters to convert to and from the MDX formats.

Regarding the 3D model format:

Editors

This is a list of known editors for manipulating the MDX files.

Code syntax

All code samples below will be given in a C/C++ like pseudo-code. To simplify syntax and readability some have been split into substructures. The following notations are used to describe this.

  • X - A structure X that must be present and in the given order
  • {X} - A structure X that may or may not be present. They may also be in a different order.

A few special fields exist which has specific meanings.

  • ChunkSize - The size of the chunk (see General structure below)
  • InclusiveSize - The size of the structure including the size of this variable
  • ExclusiveSize - The size of the structure NOT including the size of this variable

Other notations.

  • #X - A flag value. Multiple flags can be combined in a single variable.

Datatypes

In the code below various datatypes are used. This is a table describing these datatypes.

  • UINT8 - An 8-bit unsigned integer, little endian
  • UINT16 - A 16-bit unsigned integer, little endian
  • UINT32 - A 32-bit unsigned integer, little endian
  • FLOAT - A 32-bit floating point number, IEEE single precision
  • FLOAT[N] - A sequence of N 32-bit floating point numbers forming a vector
  • STRING[N] - A sequence of N 8-bit characters forming a string

General structure

All models have a tree hierarchy of components or chunks. Many components lie directly under the root while others are subcomponents. The contents vary from type to type though most of them have the same kind of header as shown below.

struct Chunk
{
  UINT32 Tag;
  UINT32 ChunkSize;
  
  ...
};

Each chunk begins with two 32-bit unsigned integers. The first is a tag describing the type. It is constructed as a sequence of four 8-bit characters giving them a descriptive ID if viewed in a hex editor (or Notepad). The second integer tells the size of the chunk. This size does not include the tag and size itself; it includes only the following contents. The ChunkSize is useful for determining the number of subcomponents. It is useful for skipping whole chunks in the writing of a non-complete MDX loader, in which case the tag and size are read and then that many bytes are skipped to start reading the next chunk.

Some structures have IDs to refer to other objects. These are 0-based indexes, referring to the object in the order in which they appear in the file. The special value 0xFFFFFFFF (or -1 in signed format) represents "No ID", or in some cases "Many IDs". In the latter case, the reference has to be made in some other way, usually from the other object.

References