从 polydata 中获取数组 及 vtkDoubleArray、vtkIntArray互转

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开发环境：

1. Windows 11 家庭中文版
2. Microsoft Visual Studio Community 2019
3. VTK-9.3.0.rc0
4. vtk-example

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demo解决问题：示范冲polydata中获取命名数组，并转换数组数据类型

关键点：

1. 从 polydata 中获取数组，我们必须使用 SafeDownCast 转换为我们想要的类型。

  // Get the distances from the polydata.
  vtkDoubleArray* array = dynamic_cast<vtkDoubleArray*>(
      polydata->GetPointData()->GetArray("Distances"));

2. vtkDoubleArray->vtkIntArray

 // Cast the double distances to ints.
  vtkDoubleArray* doubleDistances = dynamic_cast<vtkDoubleArray*>(
      polydata->GetPointData()->GetArray("Distances"));
  vtkIntArray* intDistances = dynamic_cast<vtkIntArray*>

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prj name: Casting

#include 
#include 
#include 
#include 
#include 
#include 

int main(int, char*[])
{
  // Create points.
  vtkNew<vtkPoints> points;

  unsigned int numberOfPoints = 3;
  points->InsertNextPoint(0.0, 0.0, 0.0);
  points->InsertNextPoint(1.0, 0.0, 0.0);
  points->InsertNextPoint(0.0, 1.0, 0.0);

  // Add the points to a polydata
  vtkNew<vtkPolyData> polydata;
  polydata->SetPoints(points);

  // Add distances to each point
  vtkNew<vtkDoubleArray> distances;
  distances->SetNumberOfComponents(1);
  distances->SetName("Distances");

  distances->InsertNextValue(1.1);
  distances->InsertNextValue(2.2);
  distances->InsertNextValue(3.3);

  polydata->GetPointData()->AddArray(distances);

  // Get the distances from the polydata.
  vtkDoubleArray* array = dynamic_cast<vtkDoubleArray*>(
      polydata->GetPointData()->GetArray("Distances"));

  if (array)
  {
    for (unsigned int i = 0; i < numberOfPoints; i++)
    {
      double dist;
      dist = array->GetValue(i);
      std::cout << "Distance: " << dist << std::endl;
    }
  }

  // Cast the double distances to ints.
  vtkDoubleArray* doubleDistances = dynamic_cast<vtkDoubleArray*>(
      polydata->GetPointData()->GetArray("Distances"));
  vtkIntArray* intDistances = dynamic_cast<vtkIntArray*>(doubleDistances);

  if (intDistances)
  {
    for (unsigned int i = 0; i < numberOfPoints; i++)
    {
      int dist;
      dist = intDistances->GetValue(i);
      std::cout << "Distance: " << dist << std::endl;
    }
  }
  else
  {
    std::cout << "invalid cast." << std::endl;
  }

  return EXIT_SUCCESS;
}