# ExtractEdges

VTKExamples/CSharp/Meshes/ExtractEdges

### Description

This example shows how to extract the edges from a PolyData. In this case, we convert a sphere into a wireframe sphere. We demonstrate how to traverse the resulting edges.

A tutorial on how to setup a Windows Forms Application utilizing ActiViz.NET can be found here: Setup a Windows Forms Application to use ActiViz.NET
Note: As long as ActiViz.NET is not build with VTK version 6.0 or higher you must define the preprocessor directive VTK_MAJOR_VERSION_5.

### Code

ExtractEdges.cs

    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Windows.Forms;
    using System.Diagnostics;

    using Kitware.VTK;

    namespace ActiViz.Examples {
       public partial class Form1 : Form {
          public Form1() {
             InitializeComponent();
          }

          private void renderWindowControl1_Load(object sender, EventArgs e) {
             try {
                ExtractEdges();
             }
             catch(Exception ex) {
                MessageBox.Show(ex.Message, "Exception", MessageBoxButtons.OK);
             }
          }

          private void ExtractEdges() {
             vtkSphereSource sphereSource = vtkSphereSource.New();
             sphereSource.Update();

             Debug.WriteLine("Sphere" + Environment.NewLine + "----------");
             Debug.WriteLine("There are " + sphereSource.GetOutput().GetNumberOfCells() + " cells.");
             Debug.WriteLine("There are " + sphereSource.GetOutput().GetNumberOfPoints() + " points.");

             vtkExtractEdges extractEdges = vtkExtractEdges.New();
    #if VTK_MAJOR_VERSION_5
             extractEdges.SetInputConnection(sphereSource.GetOutputPort());
    #else
             extractEdges.SetInputData(sphereSource);
    #endif
             extractEdges.Update();

             vtkCellArray lines = extractEdges.GetOutput().GetLines();
             vtkPoints points = extractEdges.GetOutput().GetPoints();

             Debug.WriteLine(Environment.NewLine + "Edges" + Environment.NewLine + "----------" );
             Debug.WriteLine("There are " + lines.GetNumberOfCells() + " cells." );
             Debug.WriteLine("There are " + points.GetNumberOfPoints() + " points." );

             // Traverse all of the edges
             for(int i = 0; i < extractEdges.GetOutput().GetNumberOfCells(); i++) {
                //Debug.WriteLine("Type: " + extractEdges.GetOutput().GetCell(i).GetClassName() );
                vtkLine line = vtkLine.SafeDownCast(extractEdges.GetOutput().GetCell(i));
                Debug.WriteLine("Line " + i + " : " + line );
             }

             // Visualize the edges

             // Create a mapper and actor
             vtkPolyDataMapper mapper = vtkPolyDataMapper.New();
    #if VTK_MAJOR_VERSION_5
             mapper.SetInputConnection(extractEdges.GetOutputPort());
    #else
             mapper.SetInputData(extractEdges);
    #endif
             vtkActor actor = vtkActor.New();
             actor.SetMapper(mapper);
             // get a reference to the renderwindow of our renderWindowControl1
             vtkRenderWindow renderWindow = renderWindowControl1.RenderWindow;
             // renderer
             vtkRenderer renderer = renderWindow.GetRenderers().GetFirstRenderer();
             // set background color
             renderer.SetBackground(1, 1, 1);
             // add our actor to the renderer
             renderer.AddActor(actor);
          }
       }
    }