VTK/Tutorials/TriangleGeometryVertices

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This example writes the coordinates of the corners of a triangle to a vtp file. There is now geometry (points) as well as topology (vertices). If you open this file in Paraview, you will now see the points immediately.

TriangleVertices.cxx

#include <vtkCellArray.h>
#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkXMLPolyDataWriter.h>
#include <vtkPolyData.h>

int main(int argc, char *argv[])
{
  //Setup point coordinates
  double X[3] = {1.0, 0.0, 0.0};
  double Y[3] = {0.0, 0.0, 1.0};
  double Z[3] = {0.0, 0.0, 0.0};

  //Create points and add a vertex at each point. Really what you are doing is adding
  //cells to the polydata, and the cells only contain 1 element, so they are, by definition,
  //0-D topology (vertices).
  vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
  vtkSmartPointer<vtkCellArray> vertices = vtkSmartPointer<vtkCellArray>::New();

  for ( unsigned int i = 0; i < 3; ++i )
    {
    //Declare a variable to store the index of the point that gets added. This behaves just like an unsigned int.
    vtkIdType pid[1];
    
    //Add a point to the polydata and save its index, which we will use to create the vertex on that point.
    pid[0] = points->InsertNextPoint ( X[i], Y[i], Z[i] );
    
    //create a vertex cell on the point that was just added.
    vertices->InsertNextCell ( 1,pid );
    }

  //create a polydata object
  vtkSmartPointer<vtkPolyData> polydata = vtkSmartPointer<vtkPolyData>::New();

  //set the points and vertices we created as the geometry and topology of the polydata
  polydata->SetPoints ( points );
  polydata->SetVerts ( vertices );

  //write the polydata to a file
  vtkSmartPointer<vtkXMLPolyDataWriter> writer = vtkSmartPointer<vtkXMLPolyDataWriter>::New();
  writer->SetFileName ( "TriangleVerts.vtp" );
#if VTK_MAJOR_VERSION <= 5
  writer->SetInput ( polydata );
#else
  writer->SetInputData ( polydata );
#endif
  writer->Write();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.6)

project(TriangleVertices)

find_package(VTK REQUIRED)
include(${VTK_USE_FILE})

add_executable(TriangleVertices TriangleVertices.cxx)
if(VTK_LIBRARIES)
  target_link_libraries(TriangleVertices ${VTK_LIBRARIES})
else()
  target_link_libraries(TriangleVertices vtkHybrid)
endif()