MD3

MD3 is a 3D model file format used by id Software's Quake III Arena engine (id Tech 3). It stores character and object models with animation in a compact binary format designed for efficient real-time rendering in first-person shooter games. An MD3 file can contain multiple animation frames, with the model's polygonal topology and texture coordinates defined once and vertex positions changed per frame to create motion.

The format supports skins and tags. Skins specify the texture images and surface appearances, while tags define attachment points for other models such as weapons or shields. Each frame includes bounding information. The topology (triangles and vertex order) remains constant across frames, enabling simple morph-based animation rather than skeletal rigging.

MD3 files were widely used for player and weapon models in Quake III Arena and in many mods. Exporters exist for 3D modeling packages such as Blender and 3ds Max, and many engines can import MD3 models or convert them to other formats. The format is read by engines that implement id Tech 3, and some modern engines maintain MD3 compatibility for legacy assets.

Limitations and legacy: Because MD3 uses per-vertex animation and fixed topology, it offers limited deformations and no built-in animation blending or bones. Transmission of animation between frames is explicit, and skeleton-based animation became standard in later formats (MD5). MD3 remains a historic standard for Quake III and related games.