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VTK/Tutorials/TriangleGeometryPolygon

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TrianglePolygon.cxx

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

int main(int argc, char *argv[])
{
  //setup points (geometry)
  vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint ( 1.0, 0.0, 0.0 );
  points->InsertNextPoint ( 0.0, 0.0, 0.0 );
  points->InsertNextPoint ( 0.0, 1.0, 0.0 );

  vtkSmartPointer<vtkCellArray> triangles = vtkSmartPointer<vtkCellArray>::New();

  //create a triangle on the three points in the polydata
  vtkSmartPointer<vtkTriangle> triangle = vtkSmartPointer<vtkTriangle>::New();

  //Unfortunately in this simple example the following lines are ambiguous.
  //The first 0 is the index of the triangle vertex which is ALWAYS 0-2.
  //The second 0 is the index into the point (geometry) array, so this can range from 0-(NumPoints-1)
  //i.e. a more general statement is triangle->GetPointIds()->SetId(0, PointId);
  triangle->GetPointIds()->SetId ( 0, 0 );
  triangle->GetPointIds()->SetId ( 1, 1 );
  triangle->GetPointIds()->SetId ( 2, 2 );

  //add the triangle to the list of triangles (in this case there is only 1)
  triangles->InsertNextCell ( triangle );

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

  //add the geometry and topology to the polydata
  polydata->SetPoints ( points );
  polydata->SetPolys ( triangles );

  //write the polydata to a file
  vtkSmartPointer<vtkXMLPolyDataWriter> writer = vtkSmartPointer<vtkXMLPolyDataWriter>::New();
  writer->SetFileName ( "Triangle.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(TrianglePolygon)

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

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