func ClipPlane(plane uint32, equation *float64) {
	syscall.Syscall(gpClipPlane, 2, uintptr(plane), uintptr(unsafe.Pointer(equation)), 0)
}
func ClipPlane(plane uint32, equation *float64) {
	syscall.Syscall(gpClipPlane, 2, uintptr(plane), uintptr(unsafe.Pointer(equation)), 0)
}
// specify a plane against which all geometry is clipped