Alphatexture: Difference between revisions
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{{toc-right}}{{this is a|shader parameter|internal=1<!--is there a better way to do this?-->|name=%alphatexture|game=Garry's Mod}} | {{toc-right}}{{this is a|shader parameter|internal=1<!--is there a better way to do this?-->|name=%alphatexture|game=Garry's Mod|game1=Mapbase}} | ||
Used on [[static prop]]s when the prop is flagged for [[texture shadows]] and compiling [[VRAD]] with {{code|-textureshadows}}. The alpha channel of the specified VTF will be used instead of {{ent|$basetexture}}, even if {{ent|$alphatest}} and {{ent|$translucent}} are absent. | Used on [[static prop]]s when the prop is flagged for [[texture shadows]] and compiling [[VRAD]] with {{code|-textureshadows}}. The alpha channel of the specified VTF will be used instead of {{ent|$basetexture}}, even if {{ent|$alphatest}} and {{ent|$translucent}} are absent. | ||
Latest revision as of 09:54, 29 July 2025
%alphatexture is an internal material shader parameter available in 
Garry's Mod and 
Mapbase.
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: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.
Code:See this GitHub PR for how to add this to a custom VRAD.The source code for
Mapbase 8.0 includes this implementation.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:
- Making the shadows for a given prop less dark, which can be useful if it uses
$halflambert(or$phongwithout$phongdisablehalflambert). - When
$detailblendmode 4is used, as the shadows would then make more sense to be cast from $detail - When
$additiveis used, as no alpha channel will be present and neither $translucent nor $alphatest are used - When a shader such as
Refractis used, as no alpha channel will be present and neither $translucent nor $alphatest are used, and $basetexture won't be used as the diffuse - If a shader such as
Wireframeis used, as $basetexture will not be present - When
$alphais used, as VRAD doesn't account for it - For creating a sharp high-resolution texture shadow without bloating the map's filesize, as the shadow-casting texture does not need to be shipped with the map.
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: 
), 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.