$alphatest

$alphatest is a material shader parameter avaliable 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. This effect is similar to $translucent, except that it can not be semi-opaque, is much faster to render, and the engine can sort it properly when layered.

VMT syntax example

$alphatest <bool>

LightmappedGeneric
{
	$basetexture		"glass\window001a"

	$alphatest		1

	$alphatestreference	.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. The rest show alphatest with $alphatestreference ranging from 0.1 to 0.9

Notice how the right circle hardly changes.

See also

• $alpha
• $distancealpha
• $vertexalpha