VTK笔记——寻找最近点(vtkKdTree，vtkKdTreePointLocator，vtkOctreePointLocator，vtkCellLocator)

1.使用vtkKdTree，可以找到多个，或一个
 

// Create the tree
    vtkSmartPointer<vtkKdTree> pointTree =
      vtkSmartPointer<vtkKdTree>::New();
    pointTree->BuildLocatorFromPoints(points);

    // Find the 2 closest points to (0.5,0。5,0.5)
    vtkIdType k = 2;
    double inPutPoint[3] = {0.5,0。5,0.5};
    vtkSmartPointer<vtkIdList> result =
      vtkSmartPointer<vtkIdList>::New();
    pointTree->FindClosestNPoints(k, inPutPoint, result);



//   or
  //Create the tree
  vtkSmartPointer<vtkKdTree> kDTree = 
    vtkSmartPointer<vtkKdTree>::New();
  kDTree->BuildLocatorFromPoints(points);

  double inPutPoint[3] = {0.5,0。5,0.5};

  //Find the closest points to inPutPoint
  double closestPointDist;
  vtkIdType id = kDTree->FindClosestPoint(inPutPoint, closestPointDist); //vtkKdTree::FindClosestPoint: must build locator first
  std::cout << "The closest point is point " << id << std::endl;

2.使用vtkKdTreePointLocator 可以找到多个，或一个

//Create the tree
    vtkSmartPointer<vtkKdTreePointLocator> pointTree =
        vtkSmartPointer<vtkKdTreePointLocator>::New();
    pointTree->SetDataSet(pointSource->GetOutput());
    pointTree->BuildLocator();

    // Find the k closest points to (0.5, 0.5, 0.5)
    unsigned int k = 3;
    double inPutPoint[3] = {0.5, 0.5, 0.5};
    vtkSmartPointer<vtkIdList> result =
        vtkSmartPointer<vtkIdList>::New();

    pointTree->FindClosestNPoints(k, inPutPoint, result);

3.使用vtkCellLocator  找到最近的cell id 和点 id

// Create the tree
  auto cellLocator = vtkSmartPointer<vtkCellLocator>::New();
  cellLocator->SetDataSet(sphereSource->GetOutput());
  cellLocator->BuildLocator();
  
  double inPutPoint[3] = {0.6, 0.5, 0.0};
  
  //Find the closest points to inPutPoint
  auto assistCell = vtkSmartPointer<vtkGenericCell>::New();
  double closestPoint[3];//the coordinates of the closest point will be returned here
  double closestPointDist2; //the squared distance to the closest point will be returned here
  vtkIdType cellId; //the cell id of the cell containing the closest point will be returned here
  int subId;
  cellLocator->FindClosestPoint(inPutPoint, closestPoint, assistCell, cellId, subId, closestPointDist2);