func AlphaFunc(xfunc uint32, ref float32) {
	syscall.Syscall(gpAlphaFunc, 2, uintptr(xfunc), uintptr(math.Float32bits(ref)), 0)
}
func AlphaFunc(xfunc uint32, ref float32) {
	syscall.Syscall(gpAlphaFunc, 2, uintptr(xfunc), uintptr(math.Float32bits(ref)), 0)
}
func AlphaFunc ( xfunc uint32 , ref float32 ) { syscall . Syscall ( gpAlphaFunc , 2 , uintptr ( xfunc ) , uintptr ( math . Float32bits ( ref ) ) , 0 ) }
// specify the alpha test function
specify the alpha test function