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# PolyDataConnectivityFilter SpecifiedRegion

VTKEx/CSharp/PolyData/PolyDataConnectivityFilter_SpecifiedRegion

### Description

This example creates two spheres and combines them together into one polydata. The vtkPolyDataConnectivityFilter is used to find the two spheres as they are separate regions (disconnected). If region 0 is selected, the small sphere is extracted. If region 1 is selected, the large sphere is extracted.
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

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See (Cxx)

Question

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### Code

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

          private void vtkPolyDataConnectivityFilter_SpecifiedRegion() {
             // Small sphere (first region)
             vtkSphereSource sphereSource1 = vtkSphereSource.New();
             sphereSource1.Update();

             // Large sphere (second region)
             vtkSphereSource sphereSource2 = vtkSphereSource.New();
             sphereSource2.SetRadius(10);
             sphereSource2.SetCenter(25, 0, 0);
             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.SetExtractionModeToSpecifiedRegions();
             connectivityFilter.AddSpecifiedRegion(1); //select the region to extract here
             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);
          }
       }
    }