$translucent

From Valve Developer Community

The $translucent VMT command specifies that Source should use the alpha channel of $basetexture to mask the material on a pixel-by-pixel basis. It is available with UnlitGeneric, VertexLitGeneric, LightmappedGeneric and many more shaders.

Warning.png Warning: $translucent can sometimes cause rendering artefacts; consider $alphatest when this happens.
Image:note.png Note: $translucent cannot be used in conjunction with $envmap, and probably other parameters like it. If you have trouble, try stripping everything non-essential from your VMT.
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VMT syntax example

LightmappedGeneric
{
    $basetexture "decals/mydecal"
    $decal 1
    $decalscale 0.10
    $translucent 1
}
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Related parameters

$additive 1
Renders the texture additively - its colors add to, instead of replacing, what is displayed behind.
$alpha <float>
Scales overall material opacity by the given value. Every pixel with an alpha value less than 178 will be completely transparent in game - but values close to that will confuse the shader at distances (see $alphatest).
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