io_dwg/description/CBconic.hParameters are accessed with cinema::C4DAtom::GetParameter() and cinema::C4DAtom::SetParameter(). See Parameters.
Parameter: Conic Type
CONICCURVE_TYPECONICCURVE_DEPRECIATEDCONICCURVE_ELLIPSECONICCURVE_HYPERBOLACONICCURVE_PARABOLAParameter: Coefficients A,B,C
CONICCURVE_ABCParameter: Coefficients D,E,F
CONICCURVE_DEFParameter: Start Point
CONICCURVE_P1Parameter: End Point
CONICCURVE_P2