# Subdivision

VTKExamples/CSharp/Meshes/Subdivision

### Description

In this example a mesh is read from a file and then subdivided using linear subdivision. The SetNumberOfSubdivisions(n) function controls how many times the mesh is subdivided. For each n, the number of triangles will increase by approximately a factor of 4. For example, if n=2, the number of triangles in the resulting mesh will be 16x the number of triangles in the original mesh.

Different types of subdivisions can be obtained by replacing vtkLinearSubdivisionFilter with either vtkLoopSubdivisionFilter or vtkButterflySubdivisionFilter.

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

Subdivision.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 {
                Subdivision(null); // you may provide a full path to a *.vtu file
             }
             catch(Exception ex) {
                MessageBox.Show(ex.Message, "Exception", MessageBoxButtons.OK);
             }
          }

          private void Subdivision(string filePath) {
             vtkPolyData originalMesh;
             if(filePath != null) {
                vtkXMLPolyDataReader reader = vtkXMLPolyDataReader.New();
                reader.SetFileName(filePath);
                // Subdivision filters only work on triangles
                vtkTriangleFilter triangles = vtkTriangleFilter.New();
                triangles.SetInputConnection(reader.GetOutputPort());
                triangles.Update();
                originalMesh = triangles.GetOutput();
             }
             else {
                vtkSphereSource sphereSource = vtkSphereSource.New();
                sphereSource.Update();
                originalMesh = sphereSource.GetOutput();
             }
             Debug.WriteLine("Before subdivision");
             Debug.WriteLine("    There are " + originalMesh.GetNumberOfPoints()
                + " points.");
             Debug.WriteLine("    There are " + originalMesh.GetNumberOfPolys()
                + " triangles.");

             int numberOfViewports = 3;

             vtkRenderWindow renderWindow = renderWindowControl1.RenderWindow;
             this.Size = new System.Drawing.Size(200 * numberOfViewports + 12, 252);
             this.Text += " - Subdivision";
             Random rnd = new Random(2);
             int numberOfSubdivisions = 2;

             // Create one text property for all
             vtkTextProperty textProperty = vtkTextProperty.New();
             textProperty.SetFontSize(14);
             textProperty.SetJustificationToCentered();

             for(int i = 0; i < numberOfViewports; i++) {
                // Note: Here we create a superclass pointer (vtkPolyDataAlgorithm) so that we can easily instantiate different
                // types of subdivision filters. Typically you would not want to do this, but rather create the pointer to be the type
                // filter you will actually use, e.g.
                // <vtkLinearSubdivisionFilter>  subdivisionFilter = <vtkLinearSubdivisionFilter>.New();
                vtkPolyDataAlgorithm subdivisionFilter;
                switch(i) {
                   case 0:
                      subdivisionFilter = vtkLinearSubdivisionFilter.New();
                      ( (vtkLinearSubdivisionFilter)subdivisionFilter ).SetNumberOfSubdivisions(numberOfSubdivisions);
                      break;
                   case 1:
                      subdivisionFilter = vtkLoopSubdivisionFilter.New();
                      ( (vtkLoopSubdivisionFilter)subdivisionFilter ).SetNumberOfSubdivisions(numberOfSubdivisions);
                      break;
                   case 2:
                      subdivisionFilter = vtkButterflySubdivisionFilter.New();
                      ( (vtkButterflySubdivisionFilter)subdivisionFilter ).SetNumberOfSubdivisions(numberOfSubdivisions);
                      break;
                   default:
                      subdivisionFilter = vtkLinearSubdivisionFilter.New();
                      ( (vtkLinearSubdivisionFilter)subdivisionFilter ).SetNumberOfSubdivisions(numberOfSubdivisions);
                      break;
                }
    #if VTK_MAJOR_VERSION_5
                subdivisionFilter.SetInputConnection(originalMesh.GetProducerPort());
    #else
                subdivisionFilter.SetInputData(originalMesh);
    #endif
                subdivisionFilter.Update();
                vtkRenderer renderer = vtkRenderer.New();
                renderWindow.AddRenderer(renderer);
                renderer.SetViewport((float)i / numberOfViewports, 0, (float)( i + 1 ) / numberOfViewports, 1);
                renderer.SetBackground(.2 + rnd.NextDouble() / 8, .3 + rnd.NextDouble() / 8, .4 + rnd.NextDouble() / 8);

                vtkTextMapper textMapper = vtkTextMapper.New();
                vtkActor2D textActor = vtkActor2D.New();
                textMapper.SetInput(subdivisionFilter.GetClassName());
                textMapper.SetTextProperty(textProperty);

                textActor.SetMapper(textMapper);
                textActor.SetPosition(100, 16);

                //Create a mapper and actor
                vtkPolyDataMapper mapper = vtkPolyDataMapper.New();
                mapper.SetInputConnection(subdivisionFilter.GetOutputPort());
                vtkActor actor = vtkActor.New();
                actor.SetMapper(mapper);
                renderer.AddActor(actor);
                renderer.AddActor(textActor);
                renderer.ResetCamera();
             }
             renderWindow.Render();
          }
       }
    }