# WritePolyData

VTKExamples/CSharp/IO/WritePolyData

### Description

In this example, we add 4 points to a polygonal data (polydata) object and write the result to a VTP file.
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

WritePolyData.cs

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

    using Kitware.VTK;

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

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

          private void WritePolyData() {
             // Path to vtk data must be set as an environment variable
             // VTK_DATA_ROOT = "C:\VTK\vtkdata-5.8.0"
             vtkTesting test = vtkTesting.New();
             string root = test.GetDataRoot();
             string filePath = System.IO.Path.Combine(root, @"Data\poly_test.vtp");
             // Create 4 points for a tetrahedron
             vtkPoints points = vtkPoints.New();

             points.InsertNextPoint(0, 0, 0);
             points.InsertNextPoint(0, 0, 1);
             points.InsertNextPoint(1, 0, 0);
             points.InsertNextPoint(0, 1, 0);

             // Create a polydata object and add the points to it.
             vtkPolyData polydata = vtkPolyData.New();
             polydata.SetPoints(points);

             // it's not enough only to define points
             // we need to define faces too
             // (must be defined in counter clockwise order as viewed from the outside)
             vtkTriangle face0 = vtkTriangle.New();
             face0.GetPointIds().SetId(0, 0);
             face0.GetPointIds().SetId(1, 2);
             face0.GetPointIds().SetId(2, 1);
             vtkTriangle face1 = vtkTriangle.New();
             face1.GetPointIds().SetId(0, 0);
             face1.GetPointIds().SetId(1, 3);
             face1.GetPointIds().SetId(2, 2);
             vtkTriangle face2 = vtkTriangle.New();
             face2.GetPointIds().SetId(0, 0);
             face2.GetPointIds().SetId(1, 1);
             face2.GetPointIds().SetId(2, 3);
             vtkTriangle face3 = vtkTriangle.New();
             face3.GetPointIds().SetId(0, 1);
             face3.GetPointIds().SetId(1, 2);
             face3.GetPointIds().SetId(2, 3);

             vtkCellArray faces = vtkCellArray.New();
             faces.InsertNextCell(face0);
             faces.InsertNextCell(face1);
             faces.InsertNextCell(face2);
             faces.InsertNextCell(face3);

             polydata.SetPolys(faces);

             // Write the file
             vtkXMLPolyDataWriter writer = vtkXMLPolyDataWriter.New();
             writer.SetFileName(filePath);
             writer.SetInput(polydata);

             // Optional - set the mode. The default is binary.
             //writer.SetDataModeToBinary();
             writer.SetDataModeToAscii();
             writer.Write();

             // Read and display file for verification that it was written correctly
             vtkXMLPolyDataReader reader = vtkXMLPolyDataReader.New();
             if(reader.CanReadFile(filePath) == 0) {
                MessageBox.Show("Cannot read file \"" + filePath + "\"", "Error", MessageBoxButtons.OK);
                return;
             }
             reader.SetFileName(filePath);
             reader.Update();

             vtkDataSetMapper mapper = vtkDataSetMapper.New();
             mapper.SetInputConnection(reader.GetOutputPort());

             // actor
             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(0.2, 0.3, 0.4);
             // add our actor to the renderer
             renderer.AddActor(actor);
          }
       }
    }