func GetClipPlane(plane uint32, equation *float64) {
	syscall.Syscall(gpGetClipPlane, 2, uintptr(plane), uintptr(unsafe.Pointer(equation)), 0)
}
func GetClipPlane(plane uint32, equation *float64) {
	syscall.Syscall(gpGetClipPlane, 2, uintptr(plane), uintptr(unsafe.Pointer(equation)), 0)
}
// return the coefficients of the specified clipping plane