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MDL File Format Explained

The MDL format is Valve's proprietary model format used by the Source engine, with a related MDL format also used by GoldSrc. It serves as the final compiled format for characters, props, and environmental assets within games like Half-Life 2 and Counter-Strike.

	Icon	Extension	Original Software	Year	Primary Industry	Geometry	UV Maps	Textures	PBR	Animation	Rigging	Open Use
		.MDL	Iray Renderer	2014	Materials Rendering	None	–	✔	✔	–	–	✔
MDL File Format Details What It Stores It defines model structure, animation data, bounding boxes, hitboxes, material references, mesh information, and LOD information, while some vertex or hardware-optimized mesh data may be stored in companion files such as VVD and VTX. Additionally, it stores animation sequences and hitboxes, and references external material VMT files, which in turn reference VTF texture files. Primary Use Cases Storing compiled model data for real-time rendering within the Source engine. Character performance and skeletal animation for gameplay. Defining collision physics and hitboxes for in-game objects. Strengths Highly optimized for real-time performance and skeletal deformation. Supports flex-based facial animation and coordinates with companion physics data when present. Efficiently packages multiple Levels of Detail within the model structure. Limitations Proprietary nature makes it difficult to edit without decompile tools. Largely limited to the Source ecosystem; lacks native interoperability with modern general-purpose engines. Common Software Support Valve Source SDK, HLMV (Half-Life Model Viewer), and Blender (via community-developed plugins).

MDL File Format Details