What is an MTL file?

MTL file, short for Material Template Library, is companion file format used in 3D computer graphics and modeling. It is often associated with Wavefront OBJ file format, which is common format for storing 3D models and their associated materials and textures.

MTL File Format

The MTL file format is associated with 3D computer graphics and is often used in conjunction with the OBJ (Wavefront .obj) file format. OBJ files define 3D geometry, and MTL files define material properties for the associated OBJ files.

Here is a simple example of an MTL file:

newmtl MaterialName
Ka 0.6 0.6 0.6    # Ambient color
Kd 0.8 0.8 0.8    # Diffuse color
Ks 1.0 1.0 1.0    # Specular color
Ns 100            # Shininess
d  1.0            # Dissolve (transparency)
map_Kd texture.jpg  # Diffuse texture map

In this example:

  • Ka represents ambient color.
  • Kd represents diffuse color.
  • Ks represents specular color.
  • Ns represents shininess.
  • d represents dissolve (transparency).
  • map_Kd specifies the diffuse texture map.

These material properties can be applied to different parts of the 3D model defined in the corresponding OBJ file.

MTL file is optional and OBJ files can be used without associated MTL files. However, using MTL files allows for more detailed and realistic rendering of 3D models by specifying surface properties and textures.

Material Template Library

Here is important information about MTL files:

  1. Material Definitions: The “.mtl” file contains definitions for materials that are applied to 3D objects in corresponding OBJ file. Each material definition specifies various properties, such as color, shininess, transparency and texture maps.

  2. Text-Based Format: “.mtl” files are typically plain text files, which means they can be easily edited with text editor. Each material definition consists of set of statements and these statements define material’s attributes.

  3. Texture Mapping: One of essential functions of an “.mtl” file is to define how textures (image files) are mapped onto 3D model’s surfaces. It specifies texture file’s path and how it should be wrapped or applied to model.

  4. Example MTL Statements: Here are some example statements you might find in an “.mtl” file:

    • newmtl MaterialName: This defines new material with name “MaterialName.”
    • Ka r g b: Ambient color of material, specified in RGB values.
    • Kd r g b: Diffuse color of material, specified in RGB values.
    • Ks r g b: Specular color of material, specified in RGB values.
    • Ns value: Shininess or specular exponent of material.
    • map_Kd texturefile.jpg: Specifies diffuse texture map for material.

  5. Multiple Materials: An OBJ file can reference multiple materials and each material is defined within “.mtl” file. This allows for complex 3D models with different materials applied to different parts.

  6. Compatibility: “.mtl” files are widely supported by 3D modeling software and rendering engines, making it possible to transfer 3D models and their materials between different software applications.

How to open an MTL file?

MTL file are text based files, so they can be opened with any text editor including

  • Notepad (Windows)
  • Notepad++ (Windows)
  • Visual Studio Code
  • Sublime Text
  • Atom
  • TextEdit (macOS)

Programs that open or reference MTL files include

  • Adobe Photoshop 2023
  • Autodesk Maya 2023
  • MeshLab
  • Cheetah3D

References

See Also