VTK/Tutorials/TriangleGeometryVertices

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

<source lang="cpp">

1. include "vtkCellArray.h"
2. include "vtkSmartPointer.h"
3. include "vtkPoints.h"
4. include "vtkXMLPolyDataWriter.h"
5. include "vtkPolyData.h"

int main() {

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

}

</source>

CMakeLists.txt

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

PROJECT(TriangleVertices)

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

ADD_EXECUTABLE(TriangleVertices TriangleVertices.cxx) TARGET_LINK_LIBRARIES(TriangleVertices vtkHybrid)

</source>