$alphatest

$alphatest is a material shader parameter available in all Source games. It specifies a mask to use to determine binary opacity. White represents fully opaque, while black represents fully transparent. Any values in-between are rounded to either 0 or 1, unless $allowalphatocoverage is also used. This effect is similar to $translucent, except that it can not be semi-opaque (without  banding), is much faster to render, and the engine can always sort it properly when layered (instead of only on non-detail worldspawn).

Syntax

$alphatest <bool>

VMT example

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LightmappedGeneric { $basetexture "glass\window001a" $alphatest 1 $alphatestreference 0.5 $allowalphatocoverage 1 }

Additional parameters

$alphatestreference

$allowalphatocoverage

Comparison

$translucent	$alphatest
Original image, rendered with $translucent	Animated preview of the same image, but with $alphatest. The first image shows the effect of $allowalphatocoverage 1 (at 4x MSAA). The rest show $alphatest with $alphatestreference ranging from 0.1 to 0.9. Click image if not animating.

Notice how the right circle, which has a sharp alpha channel, hardly changes.

See also

• $alpha
• $distancealpha
• $vertexalpha