%alphatexture

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%alphatexture is an internal material shader parameter available in Garry's Mod Garry's Mod.

Used on static props when the prop is flagged for texture shadows and compiling VRAD with -textureshadows. The alpha channel of the specified VTF will be used instead of $basetexture, even if $alphatest and $translucent are absent.

Tip.pngTip:As this parameter is only used by VRAD, the VTF mentioned does not need to be shipped with the map if it is unused elsewhere.
Cpp.pngCode:See this GitHub PR for how to add this to a custom VRAD.

Syntax

"VertexLitGeneric"
{
    $basetexture "models/props_custom/myprop_base"
    %alphatexture "models/props_custom/myprop_alpha"
}

Potential usecases

%alphatexture is most useful for materials that are translucent enough for light to pass through, but are opaque to the human eye. Common materials that would exhibit this behavior are:

  • Foliage such as leaves and grass
  • Curtains, awnings, and umbrellas
  • Paper

This parameter can be useful in certain other niche instances:

Workaround for other versions of VRAD

If mapping for a game that does not have an SDK that includes the source code to compile your own version of VRAD (ex: Left 4 Dead 2 Portal 2), it is still possible to simulate the effect of %alphatexture by creating a separate $translucent material to use in VRAD only, and setting the alpha texture to that material's $basetexture. To avoid needing to swap VMTs every time the map is being compiled, the -insert_search_path parameter can be used with VRAD, which should take priority over the search paths declared in gameinfo.txt.