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ouboca A Valve Material is a file type with the file extention .vmt, used to define a material for use with the Source engine. It contains a high-level script that refers to textures (Valve Texture Files (.vtf)) and shaders, defining how the surface of the material appears and behaves in the game.

Creating a Valve Material (.vmt) file

There are many shaders that can be used to render a texture. To begin with, we'll use a simple shader: LightmappedGeneric. This shader is used for world surfaces that should receive lightmaps.

The simplest definition of this shader is:

"LightmappedGeneric"
{
    "$basetexture" "test/MyTexture"
}

This will render the "test/MyTexture" texture file (.vtf) opaquely and with lightmaps applied to it. This is most generally used for textures applied to brush surfaces (like walls).

One of the easiest methods of creating new .vmt files is to open an existing .vmt that has similar properties to the material you are creating. Edit the contents of the file and save it with a different name to create a new material.

More about material files

Let’s start by looking at an example of a material file:

"LightmappedGeneric"
{             
    // String values are quoted 
    "$basetexture" "shadertest/LightmappedTexture"
    "$envmap" "shadertest/LightmappedTexture_envmap"

    // Vector values are quoted 
    "$color" "[1 0 0]"
    // Float and integer values are *not* quoted 

    "$alpha" 0.5 
    "$nocull" 1
}

The first line of the material file is the name of the shader to be used. The material variables for the shader are defined inside the curly braces. Note that you should not have '=' between the material variable name and its value. Also note that comment lines use '//'. Any text after the '//' on the same line will be ignored when the material is loaded.

If the shader needs to fallback to a simpler shader because it's running on a lower-end system, you can optionally specify an additional block to override material variable values specified in the original block.

Here's an example:

"LightmappedGeneric"
{               
    "$basetexture" "shadertest/LightmappedTexture"
	
    "$envmap" "shadertest/LightmappedTexture_envmap"

    // If the shader falls back to shader "LightmappedGeneric_DX7",
    // then the environment map defined in this block will be used instead of the
    // one defined above. Since $basetexture isn't defined in this block,
    // the original one will be used.
    "LightmappedGeneric_DX7"
    {
        "$envmap" "shadertest/OverrideEnvMap"
    }
	
    // If the shader falls back to shader "LightmappedGeneric_DX6",
    // then the base texture defined in this block will be used instead of the
    // one defined above. Since $envmap isn't defined in this block, the original
    // one will be used.
    "LightmappedGeneric_DX6"
    {
        "$basetexture" "shadertest/OverrideTexture"
    }
}

For information on shader fallbacks, see Material choices and rendering performance in Controlling Geometry Visibility and Compile Times and Half-Life 2 Shader Fallbacks.

One other thing you'll see in Valve Material files is the occasional variable starting with a '%'.

For example:

"UnlitGeneric"
{
    $envmap" "shadertest/shadertest_envmap"
    %tooltexture" "shadertest/shadertest_envmap"
}

This simply means that the variable is used by tools only and won't be loaded by the engine. The only variables that need '%' are '%tooltexture", "%keywords", "%detailtype", and all of the compile variables like "%compileWater" or "%compileHint".

See also

• Material
• Creating a Material
• Shader Types and Parameters