Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Random Seed
HP_SURFACEPOS_SEED
Parameter: Object
HP_SURFACEPOS_OBJECT
Parameter: Type
HP_SURFACEPOS_TYPE
Parameter: Selection
HP_SURFACEPOS_SELECTION
Parameter: Animation Time
HP_SURFACEPOS_ATIME
Parameter: Position
HP_SURFACEPOS_OUT_POSITION
Parameter: Alignment
HP_SURFACEPOS_OUT_ALIGNMENT