A terrain material file is a file used to define terrain splat and tile materials. It is a Lua file with the .terrainmaterial extension located in the DATA:art\scenarios\textures\splats or DATA:art\scenarios\textures\tiles folders. Terrain material files have the following format (the alp texture is only required for splats):

material =
    alp = "<alpha texture name>",
    dif = "<diffuse texture name>",
    nrm = "<normal map texture name>",
    spc = "<specular texture name>",