vtkSTLWriter存储了cell相关的点，而vtkXMLPolyDataWriter保存了原始polydata中所有的点，不管它有没有被cell使用到。所以保存数据之后要看一下效果，最好用 vtkXMLPolyDataWriter，保存不丢失数据；

常用，这里记录一下

#include <vtkActor.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSTLReader.h>
#include <vtkSTLWriter.h>
#include <vtkSphereSource.h>

int main(int argc, char* argv[])
{
  vtkNew<vtkNamedColors> colors;
  if (argc != 2)
  {
    std::cout << "Required parameters: filename.stl" << std::endl;
    return EXIT_FAILURE;
  }

  std::string filename = argv[1];

  vtkNew<vtkSphereSource> sphereSource;
  sphereSource->Update();

  vtkNew<vtkSTLWriter> stlWriter;
  stlWriter->SetFileName(filename.c_str());
  stlWriter->SetInputConnection(sphereSource->GetOutputPort());
  stlWriter->Write();

  // Read and display for verification
  vtkNew<vtkSTLReader> reader;
  reader->SetFileName(filename.c_str());
  reader->Update();

  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputConnection(sphereSource->GetOutputPort());

  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->SetColor(colors->GetColor3d("MistyRose").GetData());

  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("WriteSTL");

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("cobalt_green").GetData());

  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

// VTK 保存
--cpp
vtkSmartPointer<vtkPolyDataWriter> vtkWriter = vtkSmartPointer<vtkPolyDataWriter>::New();
vtkWriter->SetInput(skinExtractor->GetOutput());
vtkWriter->SetFileName("test.vtk");
vtkWriter->Write();
 -------
  // Write the unstructured grid
```cpp
  vtkNew<vtkXMLUnstructuredGridWriter> writer;
  writer->SetFileName("test.vtu");
  writer->SetInputData(unstructuredGrid);
  writer->Write();

vtkSmartPointer<vtkUnstructuredGridReader> reader =
    vtkSmartPointer<vtkUnstructuredGridReader>::New();
  reader->SetFileName("test.vtk");
  //    delete[] fileName;
  reader->Update();
 --------------

数据旋转后保存 STL

void SaveSTL(char* name, vtkPolyData* data)
{
  vtkNew<vtkTransform> transform;

  double * bounds = data->GetBounds();
  // Compute the center of the image
  double center[3];
  center[0] = (bounds[1] + bounds[0]) / 2.0;
  center[1] = (bounds[3] + bounds[2]) / 2.0;
  center[2] = (bounds[5] + bounds[4]) / 2.0;

  // Rotate about the center
  transform->Translate(center[0], center[1], center[2]);
  transform->RotateWXYZ(180, 1, 0, 0);
  transform->Translate(-center[0], -center[1], -center[2]);

  vtkSmartPointer<vtkTransform> pTransform = vtkSmartPointer<vtkTransform>::New();
  // pTransform->SetInput(actor->GetUserTransform());
  pTransform->SetMatrix(transform->GetMatrix());
  pTransform->Update();

  vtkSmartPointer<vtkTransformPolyDataFilter> pTransformPolyDataFilterSTL = vtkSmartPointer<vtkTransformPolyDataFilter>::New();
  pTransformPolyDataFilterSTL->SetInputData(data);
  pTransformPolyDataFilterSTL->SetTransform(pTransform);
  pTransformPolyDataFilterSTL->Update();

  vtkNew<vtkSTLWriter> stlWriter;
  stlWriter->SetFileName(name);
  stlWriter->SetInputData(pTransformPolyDataFilterSTL->GetOutput());
  stlWriter->Update();
  stlWriter->Write();
}

使用 vtkSTLWriter 保存数据，发现和实际显示的数据有差异，查资料发现，
vtkSTLWriter存储了cell相关的点，而vtkXMLPolyDataWriter保存了原始polydata中所有的点，不管它有没有被cell使用到。

char filename[128] = "./a.vtp";
  vtkNew<vtkXMLPolyDataWriter> stlWriter;
  stlWriter->SetFileName(filename);
  stlWriter->SetInputData(pigPoly);
  stlWriter->Update();
  stlWriter->Write();

或者保存成 obj

vtkSmartPointer<vtkOBJExporter> porter = vtkSmartPointer<vtkOBJExporter>::New();
  porter->SetFilePrefix("./qiu.obj");
  porter->SetInput(renderWindow);
  porter->Write();

读；

std::string filename = "aa.obj";
  vtkSmartPointer<vtkOBJReader> reader1 =
    vtkSmartPointer<vtkOBJReader>::New();
  reader1->SetFileName(filename.c_str());
  reader1->Update();