WriteLegacyLinearCells

VTKEx/Cxx/IO/WriteLegacyLinearCells

Description

This example uses vtkUnstructuredGridWriter to write each linear cell into a .vtk file. The files are written into the current directory.

Seealso

WriteXMLLinearCells writes the same files using the VTK XML format.

Cite

The VTK File Formats document discusses the XML file format.

Other languages

See (Python)

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

Code

WriteLegacyLinearCells.cxx

#include <vtkSmartPointer.h>

#include <vtkPoints.h>
#include <vtkCellArray.h>
#include <vtkUnstructuredGrid.h>
#include <vtkUnstructuredGridWriter.h>

#include <vtkVertex.h>
#include <vtkPolyVertex.h>
#include <vtkLine.h>
#include <vtkPolyLine.h>
#include <vtkTriangle.h>
#include <vtkTriangleStrip.h>
#include <vtkPolygon.h>
#include <vtkPixel.h>
#include <vtkQuad.h>
#include <vtkTetra.h>
#include <vtkVoxel.h>
#include <vtkHexahedron.h>
#include <vtkWedge.h>
#include <vtkPyramid.h>
#include <vtkPentagonalPrism.h>
#include <vtkHexagonalPrism.h>

#include <vector>
#include <string>
#include <cstdlib>

// These functions return a vtkUnstructured grid corresponding to the object.
namespace
{
template<typename T> vtkSmartPointer<vtkUnstructuredGrid> MakeUnstructuredGrid(vtkSmartPointer<T>);

vtkSmartPointer<vtkUnstructuredGrid> MakePolyVertex();
vtkSmartPointer<vtkUnstructuredGrid> MakePolyLine();
vtkSmartPointer<vtkUnstructuredGrid> MakeTriangleStrip();
vtkSmartPointer<vtkUnstructuredGrid> MakePolygon();
}

int main(int, char *[])
{
  std::vector<std::string> filenames;
  std::vector<vtkSmartPointer<vtkUnstructuredGrid> > uGrids;

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkVertex>::New()));
  filenames.push_back("Vertex.vtk");

  uGrids.push_back(MakePolyVertex());
  filenames.push_back("PolyVertex.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkLine>::New()));
  filenames.push_back("Line.vtk");

  uGrids.push_back(MakePolyLine());
  filenames.push_back("PolyLine.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkTriangle>::New()));
  filenames.push_back("Triangle.vtk");

  uGrids.push_back(MakeTriangleStrip());
  filenames.push_back("TriangleStrip.vtk");

  uGrids.push_back(MakePolygon());
  filenames.push_back("Polygon.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkPixel>::New()));
  filenames.push_back("Pixel.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkQuad>::New()));
  filenames.push_back("Quad.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkTetra>::New()));
  filenames.push_back("Tetra.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkVoxel>::New()));
  filenames.push_back("Voxel.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkHexahedron>::New()));
  filenames.push_back("Hexahedron.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkWedge>::New()));
  filenames.push_back("Wedge.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkPyramid>::New()));
  filenames.push_back("Pyramid.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkPentagonalPrism>::New()));
  filenames.push_back("PentagonalPrism.vtk");

  uGrids.push_back(MakeUnstructuredGrid(
                     vtkSmartPointer<vtkHexagonalPrism>::New()));
  filenames.push_back("HexagonalPrism.vtk");

  // Write each grid into  a file
  for (unsigned int i = 0; i < uGrids.size(); ++i)
  {
    std::cout << "Writing: " << filenames[i] << std::endl;
    vtkSmartPointer<vtkUnstructuredGridWriter> writer =
      vtkSmartPointer<vtkUnstructuredGridWriter>::New();
    writer->SetFileName(filenames[i].c_str());
    writer->SetInputData(uGrids[i]);
    writer->Write();
  }

  return EXIT_SUCCESS;
}
namespace
{
template<typename T> vtkSmartPointer<vtkUnstructuredGrid> MakeUnstructuredGrid(vtkSmartPointer<T> aCell)
{
  double *pcoords = aCell->GetParametricCoords();
  for (int i = 0; i < aCell->GetNumberOfPoints(); ++i)
  {
    aCell->GetPointIds()->SetId(i, i);
    aCell->GetPoints()->SetPoint(i,
                                     *(pcoords + 3 * i),
                                     *(pcoords + 3 * i + 1),
                                     *(pcoords + 3 * i + 2));
  }

  vtkSmartPointer<vtkUnstructuredGrid> ug =
    vtkSmartPointer<vtkUnstructuredGrid>::New();
  ug->SetPoints(aCell->GetPoints());
  ug->InsertNextCell(aCell->GetCellType(),aCell->GetPointIds());
  return ug;
}

vtkSmartPointer<vtkUnstructuredGrid> MakePolyVertex()
{
  // A polyvertex is a cell represents a set of 0D vertices
  int numberOfVertices = 6;

  vtkSmartPointer<vtkPoints> points =
    vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint(0, 0, 0);
  points->InsertNextPoint(1, 0, 0);
  points->InsertNextPoint(0, 1, 0);
  points->InsertNextPoint(0, 0, 1);
  points->InsertNextPoint(1, 0, .4);
  points->InsertNextPoint(0, 1, .6);

  vtkSmartPointer<vtkPolyVertex> polyVertex =
    vtkSmartPointer<vtkPolyVertex>::New();
  polyVertex->GetPointIds()->SetNumberOfIds(numberOfVertices);

  for (int i = 0; i < numberOfVertices; ++i)
  {
    polyVertex->GetPointIds()->SetId(i, i);
  }

  vtkSmartPointer<vtkUnstructuredGrid> ug =
    vtkSmartPointer<vtkUnstructuredGrid>::New();
  ug->SetPoints(points);
  ug->InsertNextCell(polyVertex->GetCellType(),polyVertex->GetPointIds());

  return ug;
}

vtkSmartPointer<vtkUnstructuredGrid> MakePolyLine()
{
  // A polyline is a cell that represents a set of 1D lines
  int numberOfVertices = 5;

  vtkSmartPointer<vtkPoints> points =
    vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint(0, .5, 0);
  points->InsertNextPoint(.5, 0, 0);
  points->InsertNextPoint(1, .3, 0);
  points->InsertNextPoint(1.5, .4, 0);
  points->InsertNextPoint(2.0, .4, 0);

  vtkSmartPointer<vtkPolyLine> polyline =
    vtkSmartPointer<vtkPolyLine>::New();
  polyline->GetPointIds()->SetNumberOfIds(numberOfVertices);

  for (int i = 0; i < numberOfVertices; ++i)
  {
    polyline->GetPointIds()->SetId(i, i);
  }

  vtkSmartPointer<vtkUnstructuredGrid> ug =
    vtkSmartPointer<vtkUnstructuredGrid>::New();
  ug->SetPoints(points);
  ug->InsertNextCell(polyline->GetCellType(),polyline->GetPointIds());

  return ug;
}

vtkSmartPointer<vtkUnstructuredGrid> MakeTriangleStrip()
{
  // A triangle is a cell that represents a triangle strip
  int numberOfVertices = 10;

  vtkSmartPointer<vtkPoints> points =
    vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint(0, 0, 0);
  points->InsertNextPoint(.5, 1, 0);
  points->InsertNextPoint(1, -.1, 0);
  points->InsertNextPoint(1.5, .8, 0);
  points->InsertNextPoint(2.0, -.1, 0);
  points->InsertNextPoint(2.5, .9, 0);
  points->InsertNextPoint(3.0, 0, 0);
  points->InsertNextPoint(3.5, .8, 0);
  points->InsertNextPoint(4.0, -.2, 0);
  points->InsertNextPoint(4.5, 1.1, 0);

  vtkSmartPointer<vtkTriangleStrip> trianglestrip =
    vtkSmartPointer<vtkTriangleStrip>::New();
  trianglestrip->GetPointIds()->SetNumberOfIds(numberOfVertices);
  for (int i = 0; i < numberOfVertices; ++i)
  {
    trianglestrip->GetPointIds()->SetId(i, i);
  }

  vtkSmartPointer<vtkUnstructuredGrid> ug =
    vtkSmartPointer<vtkUnstructuredGrid>::New();
  ug->SetPoints(points);
  ug->InsertNextCell(trianglestrip->GetCellType(),trianglestrip->GetPointIds());

  return ug;
}

vtkSmartPointer<vtkUnstructuredGrid> MakePolygon()
{
  // A polygon is a cell that represents a polygon
  int numberOfVertices = 6;

  vtkSmartPointer<vtkPoints> points =
    vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint(0, 0, 0);
  points->InsertNextPoint(1, -.1, 0);
  points->InsertNextPoint(.8, .5, 0);
  points->InsertNextPoint(1, 1, 0);
  points->InsertNextPoint(.6, 1.2, 0);
  points->InsertNextPoint(0, .8, 0);

  vtkSmartPointer<vtkPolygon> polygon =
    vtkSmartPointer<vtkPolygon>::New();
  polygon->GetPointIds()->SetNumberOfIds(numberOfVertices);
  for (int i = 0; i < numberOfVertices; ++i)
  {
    polygon->GetPointIds()->SetId(i, i);
  }

  vtkSmartPointer<vtkUnstructuredGrid> ug =
    vtkSmartPointer<vtkUnstructuredGrid>::New();
  ug->SetPoints(points);
  ug->InsertNextCell(polygon->GetCellType(),polygon->GetPointIds());

  return ug;
}
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(WriteLegacyLinearCells)

find_package(VTK COMPONENTS 
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkIOLegacy QUIET)
if (NOT VTK_FOUND)
  message("Skipping WriteLegacyLinearCells: ${VTK_NOT_FOUND_MESSAGE}")
  return ()
endif()
message (STATUS "VTK_VERSION: ${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
  # old system
  include(${VTK_USE_FILE})
  add_executable(WriteLegacyLinearCells MACOSX_BUNDLE WriteLegacyLinearCells.cxx )
  target_link_libraries(WriteLegacyLinearCells PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(WriteLegacyLinearCells MACOSX_BUNDLE WriteLegacyLinearCells.cxx )
  target_link_libraries(WriteLegacyLinearCells PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS WriteLegacyLinearCells
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build WriteLegacyLinearCells

Click here to download WriteLegacyLinearCells and its CMakeLists.txt file. Once the tarball WriteLegacyLinearCells.tar has been downloaded and extracted,

cd WriteLegacyLinearCells/build

If VTK is installed:

cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

make

and run it:

./WriteLegacyLinearCells

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.