vtkConnectivityFilter提取连通区域中的问题

1. 直接使用vtkConnectivityFilter提取连通区域，渲染上没问题，但是打印出polydata中的点数，发现跟原始数据是一致的。

    for (int i = 0; i < numRegions; ++i)
    {
    	vtkSmartPointer<vtkConnectivityFilter> connectivityFilter = vtkSmartPointer<vtkConnectivityFilter>::New();
    	connectivityFilter->SetInputData(polyData);
    	connectivityFilter->SetExtractionModeToSpecifiedRegions();
    	connectivityFilter->InitializeSpecifiedRegionList();
    	connectivityFilter->AddSpecifiedRegion(i);
    	connectivityFilter->Update();
    	cout << connectivityFilter->GetOutput()->GetNumberOfPoints() << endl;
    }

2. 正确的做法是后街一个vtkCleanPolyData过滤器

    for (int i = 0; i < numRegions; ++i)
   {
   	vtkSmartPointer<vtkConnectivityFilter> connectivityFilter = vtkSmartPointer<vtkConnectivityFilter>::New();
   	connectivityFilter->SetInputData(polyData);
   	connectivityFilter->SetExtractionModeToSpecifiedRegions();
   	connectivityFilter->InitializeSpecifiedRegionList();
   	connectivityFilter->AddSpecifiedRegion(i);
   	connectivityFilter->Update();
   	
   	// 使用vtkCleanPolyData删除孤立点
   	vtkSmartPointer<vtkCleanPolyData> cleanPolyData = vtkSmartPointer<vtkCleanPolyData>::New();
   	cleanPolyData->SetInputData(connectivityFilter->GetOutput());
   	cleanPolyData->Update();
   	
   	cout << cleanPolyData->GetOutput()->GetNumberOfPoints() << endl;
   }