Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Matrix Mode
GV_POLY_MODE
Parameter: Use Deformed Points
GV_POLY_USE_DEFORMED
Parameter: Polygon Index
GV_POLY_INPUT_POLY
Parameter: Polygon Count
GV_POLY_OUTPUT_POLY
Parameter: Index Point 1
GV_POLY_OUTPUT_POINT1
Parameter: Index Point 2
GV_POLY_OUTPUT_POINT2
Parameter: Index Point 3
GV_POLY_OUTPUT_POINT3
Parameter: Index Point 4
GV_POLY_OUTPUT_POINT4
Parameter: Polygon Normal
GV_POLY_OUTPUT_NORMAL
Parameter: Polygon Center
GV_POLY_OUTPUT_CENTER