Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Texture
PRIM_RELIEF_TEXTURE
Parameter: Size
PRIM_RELIEF_LEN
Parameter: Width Segments
PRIM_RELIEF_SUBW
Parameter: Depth Segments
PRIM_RELIEF_SUBH
Parameter: Bottom Level
PRIM_RELIEF_BLEVEL
Parameter: Top Level
PRIM_RELIEF_TLEVEL
Parameter: Spherical
PRIM_RELIEF_SPHERICAL
Parameter: Switch to Updated Relief
PRIM_RELIEF_SWITCH_TO_UPDATED