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MDL (GoldSrc)

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English (en)

MDL (sometimes referred to as Half-Life MDL or HLMDL) is a model format used by GoldSrc GoldSrc to store dynamically lit models which can be animated using skeletal animation, along with their associated textures. It is a heavily modified version of the Quake MDL format.



HLMDL has the following limits per input SMD:

  • 1 mesh
    • 2048 vertices (and vertex normals) per mesh
    • 4080 triangles per mesh
  • 1 animation sequence
    • 512 keyframes per sequence
  • 128 bones

Additionally, the following limits apply to the whole MDL:

  • 4 bone attachments
  • 8 bone controllers
  • 32 meshes across all submodels
  • 256 animation sequences.

Textures must:

  • Be 8-bit uncompressed BMP files.
  • Have a resolution which is a multiple of 8 (multiples of 16 are preferred).
  • Have a resolution which does not exceed 512x512 (soft limit; raised to 1024x1024 in Sven Co-op Sven Co-op and other engines like FTE FTE).
  • Have a file name which is not longer than 64 characters (including the .bmp extension).

Icon-Important.pngImportant:Older versions of StudioMDL, including the version found in the Half-Life SDK Half-Life SDK on Steam, do not support tiling UVs, clamping them to the edge of the texture. This is not a limitation of the HLMDL file format; the Sven Co-op StudioMDL can create MDLs compatible with vanilla GoldSrc GoldSrc which have tiled UVs.
Icon-Bug.pngBug:The latest version of the Sven Co-op StudioMDL (from December 2020), as found in the Sven Co-op SDK, has some bugs with bounding boxes; use the version linked above instead (from November 2018).
Tip.pngTip:To create a model or submodel with more than 4080 tris, split the model into multiple SMD meshes, with a separate $body or $bodygroup entry for each mesh in the QC file.
Warning.pngWarning:Avoid going over 9000 tris!
While the HLMDL format can handle over 100K tris, the old OpenGL renderer struggles with such "high-poly" models, even on high-end GPUs.[1]
Note.pngNote:Third party games that upgrade the renderer (ex: Paranoia, Cry of Fear or Counter-Strike Nexon: Studio) can handle higher polygon MDLs better. This does not include Sven Co-op Sven Co-op, which uses a mostly vanilla renderer.
This is obviously not a problem for games on engines much newer than GoldSrc GoldSrc that use the HLMDL format, such as Codename: Loop Codename: Loop (Unity) or FreeCS FreeCS (FTE).
Confirm.pngConfirm: Is this soft limit 9000 total, or 9000 being displayed simultaneously?
Confirm.pngConfirm: Can replacement renderers without engine access, such as Trinity Engine, improve performance for higher-poly MDLs?
Confirm.pngConfirm: Max textures, max skins, and other limits?


Model flags

Particle effects cannot be combined, but all others can.[Clarify]

Bit Flag name Particle effect? Description
1 EF_ROCKET Yes Quake Quake I rocket trail particles and dynamic light
2 EF_GRENADE Yes Quake Quake I grenade trail smoke particles
4 EF_GIB Yes Quake Quake I gib blood trail particles
8 EF_ROTATE No Rotate this model around its origin, like the weapon pickups in Quake Quake I; requires supported game code.
16 EF_TRACER Yes Quake Quake I skrag spit particles
32 EF_ZOMGIB Yes Quake Quake I zombie blood; like EF_GIB, but darker
64 EF_TRACER2 Yes Quake Quake I death knight slashing particles
128 EF_TRACER3 Yes Like EF_GRENADE, but only has one trail
256 EF_NOSHADELIGHT No Reduces intensity of shadows on the model, without making the model flat
Confirm.pngConfirm: Half Lambert?
512 EF_HITBOXCOLLISIONS No Use hitbox for collision instead of bounding box
1024 EF_FORCESKYLIGHT No Always use skybox lighting, regardless of model location

Texture flags

Bit Flag name Description
1 STUDIO_NF_FLATSHADE Shade the model a single tint, without any shadowing, resulting in the model looking "flat" like a cartoon character.
2 STUDIO_NF_CHROME Use matcap environment mapping to render the texture as a sphere map.
Icon-Bug.pngBug:Limited to 64x64 in vanilla GoldSrc GoldSrc; this is fixed in Sven Co-op Sven Co-op. Chrome resolutions higher than 256x256 tend to have diminishing returns.
Note.pngNote:Automatically set for any textures that contain the string chrome somewhere in their name.
Icon-Important.pngImportant:Setting the chrome flag via StudioMDL will also add the flatshade flag, as well as move all UV coordinates to the top-left corner (chrome doesn't use UV mapping).
4 STUDIO_NF_FULLBRIGHT Display texture at maximum brightness, ignoring lighting.
Icon-Bug.pngBug:Doesn't work in vanilla GoldSrc GoldSrc; fixed in Sven Co-op Sven Co-op and custom renderers.
8 STUDIO_NF_MIPMAPS Generates mipmaps for the texture, greatly reducing texture aliasing at a distance.
No effect in Sven Co-op Sven Co-op, which always generates mipmaps for models, regardless of this flag.
Icon-Bug.pngBug:This flag was actually originally intended to disable mipmaps for a texture, but this behavior was accidentally inverted.
Confirm.pngConfirm: Allegedy fixed in 25th Anniversary Update.
Tip.pngTip:Recommended for most textures except alphatested ones. Due to the way textures are stored, enabling mipmaps of alphatested texture will result in the texture transparency becoming more exaggerated at a distance, with fine details like thin foliage and wire fences disappearing, and shadowing occurring around the edges occurring due to transparent texels not being dilated.
32 STUDIO_NF_ADDITIVE Use additive translucency. Still affected by entity lighting; use the Additive rendermode on an entity to ignore lighting.
Icon-Bug.pngBug:Sometimes breaks normals of non-additive faces on the same mesh.
PlacementTip.pngWorkaround: Split the additive portions onto a different mesh, by listing it as a separate SMD with a separate $body line (usually after the main mesh).
Tip.pngTip:This affects the order in which faces are loaded into the z-buffer, which can be used for manual alpha sorting. In practice, this means defining an additive chrome overlay (to simulate specular highlights) as a separate mesh after the main mesh will prevent Wikipedia icon z-fighting, even if the mesh is coplanar.
64 STUDIO_NF_MASKED Use binary alphatest transparency, wherein the last palette entry of the texture is transparent.

In other engines

Half-Life MDLs are supported by FTE FTE and the Unity Unity game Codename: Loop Codename: Loop.

External links


  1. From the GoldSrc Model Export Tutorial by The303:
    In order to compile models with more than 4080 triangles, you must break up your SMD's into parts and give them their own $body lines for compiling. Also, FOR THE LOVE OF ALL THAT IS HOLY PLEASE DO NOT GO CRAZY ON YOUR TRIANGLE COUNT; remember this is goldsrc, not source engine. Going any higher than 9000 tris is excessive and direct ports from source/other games are inefficent, wasteful, and cause performance issues for the old renderer.
    — The303