If you have a plug-in which you don’t want exposed to the 3ds Max user interface you can return “FALSE” (or 0) from the “IsPublic()” exported DLL function. This has the sometimes undesirable side-effect that MAXScript can’t create the object.

To explicitly expose the hidden class to MAXScript you can use the MAXClass macro. For example adding the following line to a modifier plug-in project named DeleteSplineModifier would expose it to MAXScript even if it IsPublic() returns FALSE:

 MAXClass delete_spline (
  _T("DeleteSplineModifier"),
    Class_ID(SDELETE_CLASS_ID, 0),
    OSM_CLASS_ID,
    &modifier,
    md_auto_parms,
  end
);