# PolyDataConnectivityFilter LargestRegion

VTKExamples/CSharp/PolyData/PolyDataConnectivityFilter_LargestRegion

### Description

This example extracts the largest connected region of a mesh. Note that this is based on the number of points, not the actual area of the region.

- Contributed by: Jinyoung Hwang

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

### Code

PolyDataConnectivityFilter_LargestRegion.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 {
                vtkPolyDataConnectivityFilter_LargestRegion();
             }
             catch(Exception ex) {
                MessageBox.Show(ex.Message, "Exception", MessageBoxButtons.OK);
             }
          }

          private void vtkPolyDataConnectivityFilter_LargestRegion() {
             // Small sphere
             vtkSphereSource sphereSource1 = vtkSphereSource.New();
             sphereSource1.Update();

             // Large sphere
             vtkSphereSource sphereSource2 = vtkSphereSource.New();
             sphereSource2.SetRadius(10);
             sphereSource2.SetCenter(25, 0, 0);
             sphereSource2.SetThetaResolution(10);
             sphereSource2.SetPhiResolution(10);
             sphereSource2.Update();

             vtkAppendPolyData appendFilter = vtkAppendPolyData.New();
             appendFilter.AddInputConnection(sphereSource1.GetOutputPort());
             appendFilter.AddInputConnection(sphereSource2.GetOutputPort());
             appendFilter.Update();

             vtkPolyDataConnectivityFilter connectivityFilter = vtkPolyDataConnectivityFilter.New();
             connectivityFilter.SetInputConnection(appendFilter.GetOutputPort());
             connectivityFilter.SetExtractionModeToLargestRegion();
             connectivityFilter.Update();

             // Create a mapper and actor for original data
             vtkPolyDataMapper originalMapper = vtkPolyDataMapper.New();
             originalMapper.SetInputConnection(appendFilter.GetOutputPort());
             originalMapper.Update();

             vtkActor originalActor = vtkActor.New();
             originalActor.SetMapper(originalMapper);

             // Create a mapper and actor for extracted data
             vtkPolyDataMapper extractedMapper = vtkPolyDataMapper.New();
             extractedMapper.SetInputConnection(connectivityFilter.GetOutputPort());
             extractedMapper.Update();

             vtkActor extractedActor = vtkActor.New();
             extractedActor.GetProperty().SetColor(1, 0, 0);
             extractedActor.SetMapper(extractedMapper);
             // get a reference to the renderwindow of our renderWindowControl1
             vtkRenderWindow renderWindow = renderWindowControl1.RenderWindow;
             // renderer
             vtkRenderer renderer = renderWindow.GetRenderers().GetFirstRenderer();
             // set background color
             renderer.SetBackground(0.2, 0.3, 0.4);
             // add our actor to the renderer
             renderer.AddActor(originalActor);
             renderer.AddActor(extractedActor);
          }
       }
    }