c4d_objects/description/ofieldforce.hParameters are accessed with cinema::C4DAtom::GetParameter() and cinema::C4DAtom::SetParameter(). See Parameters.
Parameter: Velocity Type
ID_FIELDFORCE_MODEID_FIELDFORCE_MODE_ADDID_FIELDFORCE_MODE_ABSOLUTEID_FIELDFORCE_MODE_DIRECTIONParameter: Strength
ID_FIELDFORCE_STRENGTHParameter: Consider Mass
ID_FIELDFORCE_CONSIDER_MASSParameter: Field
ID_FIELDFORCE_FIELDLISTParameter: Display Box
ID_FIELDFORCE_DISPLAYParameter: Box Size
ID_FIELDFORCE_BOX_SIZEParameter: Line Density
ID_FIELDFORCE_DENSITYParameter: Display Vector Length
ID_FIELDFORCE_DISPLAY_LENGTHParameter: Length As
ID_FIELDFORCE_VECTOR_MODEID_FIELDFORCE_VECTOR_MODE_LINESID_FIELDFORCE_VECTOR_MODE_COLORParameter: Scale Displayed Length
ID_FIELDFORCE_SCALE_LENGTH_DISPLAY