Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Object
OSHAPE_OBJECT
Parameter: Bounding Radius
OSHAPE_RADIUS
Parameter: Render Instance
OSHAPE_RENDERINSTANCE
Parameter: On
IN_OSHAPE_ON
Parameter: Animation Time
IN_OSHAPE_ATIME