c4d_objects/description/oprimitiveaxis.hParameters are accessed with cinema::C4DAtom::GetParameter() and cinema::C4DAtom::SetParameter(). See Parameters.
Parameter: Orientation
PRIM_AXISPRIM_AXIS_XPPRIM_AXIS_XNPRIM_AXIS_YPPRIM_AXIS_YNPRIM_AXIS_ZPPRIM_AXIS_ZN