# Decimate

VTKExamples/CSharp/Meshes/Decimate

### Description

This example decimates a mesh. The SetTargetReduction function specifies how many triangles should reduced by specifying the percentage ([of triangles to be removed. For example, if the mesh contains 100 triangles and SetTargetReduction(.90) is called, after the decimation there will be approximately 10 triangles - a 90% reduction.

A tutorial on how to setup a Windows Forms Application utilizing ActiViz.NET can be found here: http://www.vtk.org/Wiki/VTK/CSharp/ActiViz.NET 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

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

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

             vtkPolyData input = vtkPolyData.New();
             input.ShallowCopy(sphereSource.GetOutput());

             Debug.WriteLine("Before decimation" + Environment.NewLine + "------------" );
             Debug.WriteLine("There are " + input.GetNumberOfPoints() + " points." );
             Debug.WriteLine("There are " + input.GetNumberOfPolys() + " polygons." );

             vtkDecimatePro decimate = vtkDecimatePro.New();
    #if VTK_MAJOR_VERSION_5
             decimate.SetInputConnection(input.GetProducerPort());
    #else
             decimate.SetInputData(input);
    #endif
             //decimate.SetTargetReduction(.99); //99% reduction (if there was 100 triangles, now there will be 1)
             decimate.SetTargetReduction(.10); //10% reduction (if there was 100 triangles, now there will be 90)
             decimate.Update();

             vtkPolyData decimated = vtkPolyData.New();
             decimated.ShallowCopy(decimate.GetOutput());

             Debug.WriteLine("After decimation" + Environment.NewLine + "------------" );

             Debug.WriteLine("There are " + decimated.GetNumberOfPoints() + " points." );
             Debug.WriteLine("There are " + decimated.GetNumberOfPolys() + " polygons." );

             vtkPolyDataMapper inputMapper = vtkPolyDataMapper.New();
    #if VTK_MAJOR_VERSION_5
             inputMapper.SetInputConnection(input.GetProducerPort());
    #else
             inputMapper.SetInputData(input);
    #endif
             vtkActor inputActor = vtkActor.New();
             inputActor.SetMapper(inputMapper);

             vtkPolyDataMapper decimatedMapper = vtkPolyDataMapper.New();
    #if VTK_MAJOR_VERSION_5
             decimatedMapper.SetInputConnection(decimated.GetProducerPort());
    #else
             decimatedMapper.SetInputData(decimated);
    #endif
             vtkActor decimatedActor = vtkActor.New();
             decimatedActor.SetMapper(decimatedMapper);

             vtkRenderWindow renderWindow = renderWindowControl1.RenderWindow;
             this.Size = new System.Drawing.Size(612, 352);

             // Define viewport ranges
             // (xmin, ymin, xmax, ymax)
             double[] leftViewport = new double[] { 0.0, 0.0, 0.5, 1.0 };
             double[] rightViewport = new double[] { 0.5, 0.0, 1.0, 1.0 };

             // Setup both renderers
             vtkRenderer leftRenderer = vtkRenderer.New();
             renderWindow.AddRenderer(leftRenderer);
             leftRenderer.SetViewport(leftViewport[0], leftViewport[1], leftViewport[2], leftViewport[3]);
             leftRenderer.SetBackground(.6, .5, .4);

             vtkRenderer rightRenderer = vtkRenderer.New();
             renderWindow.AddRenderer(rightRenderer);
             rightRenderer.SetViewport(rightViewport[0], rightViewport[1], rightViewport[2], rightViewport[3]);
             rightRenderer.SetBackground(.4, .5, .6);

             // Add the sphere to the left and the cube to the right
             leftRenderer.AddActor(inputActor);
             rightRenderer.AddActor(decimatedActor);
             leftRenderer.ResetCamera();
             rightRenderer.ResetCamera();
             renderWindow.Render();
          }
       }
    }