Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Type
ID_CA_SURFACE_DEFORMER_OBJECT_TYPEParameter: Plane
ID_CA_SURFACE_DEFORMER_OBJECT_MAP_PLANEParameter: U
ID_CA_SURFACE_DEFORMER_OBJECT_MAP_UParameter: V
ID_CA_SURFACE_DEFORMER_OBJECT_MAP_VParameter: Scale
ID_CA_SURFACE_DEFORMER_OBJECT_MAP_SCALEParameter: Initialize
ID_CA_SURFACE_DEFORMER_OBJECT_INITIALParameter: Restore
ID_CA_SURFACE_DEFORMER_OBJECT_RESTOREParameter: Strength
ID_CA_SURFACE_DEFORMER_OBJECT_STRENGTHParameter: Offset
ID_CA_SURFACE_DEFORMER_OBJECT_OFFSETParameter: Proportional
ID_CA_SURFACE_DEFORMER_OBJECT_AREAParameter: Surface
ID_CA_SURFACE_DEFORMER_OBJECT_CAGE