Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Voxel Range Threshold
ID_VOLUMETOMESH_THRESHOLD
Parameter: Use Absolute Value (ISO)
ID_VOLUMETOMESH_USE_ISO
Parameter: Surface Threshold
ID_VOLUMETOMESH_ISO
Parameter: Adaptive
ID_VOLUMETOMESH_ADAPTIVE_VALUE
Parameter: Create Curvature Map
ID_VOLUMETOMESH_CREATE_CURVATURE_MAP
Parameter: Curvature Direction
ID_VOLUMETOMESH_CURVATURE_DIRECTION