.MD2

Introduction

MD2 is the model format of Quake II, released by id Software in 1997. Like the Quake MDL before it, it animates a model by storing every vertex position for every frame, and the engine blends between frames. Skins became separate image files, and the vertices are packed into single bytes per coordinate to keep files small.

The Quake II source code was released under the GPL in 2001. MD2 was popular with modders and in later engines and tutorials, and was followed by MD3 in Quake III Arena.

Structure

An MD2 file is binary and little-endian. The 68-byte header starts with IDP2 and version 8, then gives the skin size, the size of one frame, the counts of skins, vertices, texture coordinates, triangles, OpenGL commands and frames, and the offset of each list.

Skins are 64-character paths to image files. Texture coordinates are pairs of 16-bit integers in pixels. Each triangle names three vertices and three texture coordinates. Each frame has a scale and a translation, a 16-character name such as run1, and then every vertex as three bytes, which the scale and translation turn back into positions, plus one byte choosing a normal from a fixed table of 162 directions. The OpenGL commands list triangle strips and fans for fast drawing.

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