The following sample demonstrates how to split a brep with another brep using the RhinoSplitBrep SDK function:

  CRhinoCommand::result CCommandTest::RunCommand( const CRhinoCommandContext& context )
  {
    // Pick the brep to split
    CRhinoGetObject go;
    go.SetCommandPrompt( L"Select surface or polysuface to split" );
    go.SetGeometryFilter( CRhinoGetObject::surface_object | CRhinoGetObject::polysrf_object );
    go.GetObjects( 1, 1 );
    if( go.CommandResult() != success )
      return go.CommandResult();


    const CRhinoObjRef& split_ref = go.Object(0);


    const CRhinoObject* split_object = split_ref.Object();
    if( !split_object )
      return failure;


    const ON_Brep* split = split_ref.Brep();
    if( !split )
      return failure;


    // Pick the cutting brep
    go.SetCommandPrompt( L"Select cutting surface or polysuface" );
    go.EnablePreSelect( FALSE );
    go.EnableDeselectAllBeforePostSelect( FALSE );
    go.GetObjects( 1, 1 );
    if( go.CommandResult() != success )
      return go.CommandResult();


    const ON_Brep* cutter = go.Object(0).Brep();
    if( !cutter )
      return failure;


    ON_SimpleArray<ON_Brep*> pieces;
    double tol = context.m_doc.AbsoluteTolerance();


    // Try splitting the brep
    if( !RhinoBrepSplit(*split, *cutter, tol, pieces) )
      RhinoApp().Print( L"Unable to split brep.\n" );


    int i, count = pieces.Count();
    if( count == 0 || count == 1 )
    {
      if( count == 1 )
        delete pieces[0];
      return nothing;
    }


    CRhinoObjectAttributes attrib = split_object->Attributes();
    attrib.m_uuid = ON_nil_uuid; 


    const CRhinoObjectVisualAnalysisMode* vam_list = split_object->m_analysis_mode_list;


    for( i = 0; i < count; i++ )
    {
      CRhinoBrepObject* brep_object = new CRhinoBrepObject( attrib );
      if( brep_object )
      {
        brep_object->SetBrep( pieces[i] );
        if( context.m_doc.AddObject(brep_object) )
          RhinoCopyAnalysisModes( vam_list, brep_object );
        else
          delete brep_object;
      }
    }


    context.m_doc.DeleteObject( split_ref ); 
    context.m_doc.Redraw();


    return success;
  }