hl2_ep2_content/materials/shadertest/cubemap.vmt

"unlitgeneric"
{
	// Original shader: cubemap
	"$envmap" "shadertest/shadertest_env"

	"Proxies"
	{
		"Sine"
		{
			"resultVar" "$ALPHA"
			"sineperiod" 2.00
			"sinemin" 0
			"sinemax" 1
		}
	}
}