Error area picking with vtk and qt

[hjxy2012 (Zongyao Li)]

@hjxy2012

    QVTKOpenGLNativeWidget* vtkWidget;
    QPushButton* selectButton;
    vtkSmartPointer<vtkGenericOpenGLRenderWindow> renderWindow;
    vtkSmartPointer<vtkRenderer> renderer;
    vtkSmartPointer<vtkRenderWindowInteractor> interactor;
    vtkSmartPointer<vtkInteractorStyleTrackballCamera> defaultStyle;
    vtkSmartPointer<CustomInteractorStyle> selectionStyle;
    vtkSmartPointer<vtkXMLUnstructuredGridReader> reader;
    vtkSmartPointer<vtkActor> mainActor;

Thank you for your reply. Just like this