试图用vtkHardwareSelector或其他类选择可见的单元格。我不知道如何在vtk中做到这一点，而且我无法获取我选择的数据

Question

我想在模型中选择视点ID（这是一个bdf文件，并显示使用unstructuregrid）。我复制一个人的代码。但是我无法使用vtkHardwareSelector获取数据。我不知道为什么。

使用vtk8.2; vtkInteractorStyleRubberBandPick和vtkHardwareSelector。

void vtkRubberBandPickInteractorStyle::OnLeftButtonUp()
{
    vtkSmartPointer<vtkWarpVector> warpVector = vtkSmartPointer<vtkWarpVector>::New();
    warpVector->SetInputData(m_Grid);
    // Forward events
    vtkInteractorStyleRubberBandPick::OnLeftButtonUp();
    int* posUp = this->GetInteractor()->GetEventPosition();
    SetEndPos(posUp);
    vtkSmartPointer<vtkHardwareSelector> selector = vtkSmartPointer<vtkHardwareSelector>::New();
    selector->SetRenderer(this->Interactor->GetRenderWindow()->GetRenderers()->GetFirstRenderer());
    unsigned int windowSize[4]
    windowSize[0] = m_StartPosition[0] < m_EndPosition[0] ? m_StartPosition[0] : m_EndPosition[0];  // xmin
    windowSize[1] = m_StartPosition[1] < m_EndPosition[1] ? m_StartPosition[1] : m_EndPosition[1];  // ymin
    windowSize[2] = m_StartPosition[0] < m_EndPosition[0] ? m_EndPosition[0]   : m_StartPosition[0]; // xmax
    windowSize[3] = m_StartPosition[1] < m_EndPosition[1] ? m_EndPosition[1]   : m_StartPosition[1]; // ymax

    selector->SetArea(windowSize);
    selector->SetFieldAssociation(vtkDataObject::FIELD_ASSOCIATION_CELLS);
    selector->CaptureBuffers();
    vtkSmartPointer<vtkSelection> selection = vtkSmartPointer<vtkSelection>::New();
    selection = selector->GenerateSelection();
    vtkSmartPointer<vtkExtractSelection> extractSelection = vtkSmartPointer<vtkExtractSelection>::New();
    extractSelection->SetInputData(selection);
    extractSelection->Update();
    vtkSmartPointer<vtkUnstructuredGrid> selected1 = vtkSmartPointer<vtkUnstructuredGrid>::New();
    selected1->ShallowCopy(extractSelection->GetOutput());
    vtkSmartPointer<vtkPolyData> selected2 = vtkSmartPointer<vtkPolyData>::New();
    selected2->ShallowCopy(extractSelection->GetOutput());
    vtkIdType type = selected2->GetNumberOfCells();


    vtkSmartPointer<vtkPolyDataMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
    mapper->SetInputData(selected2);
    vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
    actor->SetMapper(mapper);
    actor->GetProperty()->SetPointSize(10.0);
    actor->GetProperty()->SetColor(1,0,0);
    this->Interactor->GetRenderWindow()->GetRenderers()->GetFirstRenderer()->AddActor(actor);
    this->Interactor->GetRenderWindow()->GetRenderers()->GetFirstRenderer()->Render();
    vtkInteractorStyleTrackballCamera::OnLeftButtonUp();

vtkIdType type = selected2->GetNumberOfCells();

该值为0；所以我找不到选择的任何数据。