func StencilOp(fail uint32, zfail uint32, zpass uint32) {
	syscall.Syscall(gpStencilOp, 3, uintptr(fail), uintptr(zfail), uintptr(zpass))
}
func StencilOp(fail uint32, zfail uint32, zpass uint32) {
	syscall.Syscall(gpStencilOp, 3, uintptr(fail), uintptr(zfail), uintptr(zpass))
}
// set front and back stencil test actions