VTK/Tutorials/TriangleGeometryPolygon

TrianglePolygon.cxx

<source lang="cpp">

1. include <vtkCellArray.h>
2. include <vtkSmartPointer.h>
3. include <vtkPoints.h>
4. include <vtkXMLPolyDataWriter.h>
5. include <vtkPolyData.h>
6. include <vtkTriangle.h>

int main() {

 //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" );
 writer->SetInput ( polydata );
 writer->Write();

 return 0;

}

</source>

CMakeLists.txt

<source lang="text"> cmake_minimum_required(VERSION 2.6)

PROJECT(TrianglePolygon)

FIND_PACKAGE(VTK REQUIRED) INCLUDE(${VTK_USE_FILE})

ADD_EXECUTABLE(TrianglePolygon TrianglePolygon.cxx) TARGET_LINK_LIBRARIES(TrianglePolygon vtkHybrid)

</source>