VectorFieldNonZeroExtraction
VTKExamples/CSharp/PolyData/VectorFieldNonZeroExtraction
Description¶
This example shows how to create an imagedata object, associate scalar data with some points and visualize only nonzero scalar values
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.NETNote: 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¶
VectorFieldNonZeroExtraction.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 { VectorFieldNonZeroExtraction(); } catch(Exception ex) { MessageBox.Show(ex.Message, "Exception", MessageBoxButtons.OK); } } private void VectorFieldNonZeroExtraction() { // Create an image vtkImageData image = vtkImageData.New(); CreateVectorField(ref image); // This filter produces a vtkImageData with an array named "Magnitude" vtkImageMagnitude magnitudeFilter = vtkImageMagnitude.New(); magnitudeFilter.SetInputConnection(image.GetProducerPort()); magnitudeFilter.Update(); image.GetPointData().AddArray(magnitudeFilter.GetOutput().GetPointData().GetScalars()); image.GetPointData().SetActiveScalars("Magnitude"); vtkThresholdPoints thresholdVector = vtkThresholdPoints.New(); thresholdVector.SetInput(image); thresholdVector.SetInputArrayToProcess( 0, 0, (int)vtkDataObject.FieldAssociations.FIELD_ASSOCIATION_POINTS, (int)vtkDataSetAttributes.AttributeTypes.SCALARS, "Magnitude"); thresholdVector.ThresholdByUpper(0.00001); thresholdVector.Update(); // in case you want to save imageData //vtkXMLPolyDataWriter writer = vtkXMLPolyDataWriter.New(); //writer.SetFileName("output.vtp"); //writer.SetInputConnection(thresholdPoints.GetOutputPort()); //writer.Write(); // repesents the pixels vtkCubeSource cubeSource = vtkCubeSource.New(); cubeSource.SetXLength(2.0); cubeSource.SetYLength(2.0); cubeSource.SetZLength(2.0); vtkGlyph3D glyph = vtkGlyph3D.New(); glyph.SetInput(image); glyph.SetSourceConnection(cubeSource.GetOutputPort()); // don't scale glyphs according to any scalar data glyph.SetScaleModeToDataScalingOff(); vtkPolyDataMapper glyphMapper = vtkPolyDataMapper.New(); glyphMapper.SetInputConnection(glyph.GetOutputPort()); // don't color glyphs according to scalar data glyphMapper.ScalarVisibilityOff(); glyphMapper.SetScalarModeToDefault(); vtkActor actor = vtkActor.New(); actor.SetMapper(glyphMapper); // represent vector field vtkGlyph3D vectorGlyph = vtkGlyph3D.New(); vtkArrowSource arrowSource = vtkArrowSource.New(); vtkPolyDataMapper vectorGlyphMapper = vtkPolyDataMapper.New(); int n = image.GetPointData().GetNumberOfArrays(); for(int i = 0; i < n; i++) { Debug.WriteLine("name of array["+ i + "]: " + image.GetPointData().GetArrayName(i)); } vtkPolyData tmp = thresholdVector.GetOutput(); Debug.WriteLine("number of thresholded points: " + tmp.GetNumberOfPoints()); vectorGlyph.SetInputConnection(thresholdVector.GetOutputPort()); // in case you want the point glyphs to be oriented according to // scalar values in array "ImageScalars" uncomment the following line image.GetPointData().SetActiveVectors("ImageScalars"); vectorGlyph.SetSourceConnection(arrowSource.GetOutputPort()); vectorGlyph.SetScaleModeToScaleByVector(); vectorGlyph.SetVectorModeToUseVector(); vectorGlyph.ScalingOn(); vectorGlyph.OrientOn(); vectorGlyph.SetInputArrayToProcess( 1, 0, (int)vtkDataObject.FieldAssociations.FIELD_ASSOCIATION_POINTS, (int)vtkDataSetAttributes.AttributeTypes.SCALARS, "ImageScalars"); vectorGlyph.Update(); vectorGlyphMapper.SetInputConnection(vectorGlyph.GetOutputPort()); vectorGlyphMapper.Update(); vtkActor vectorActor = vtkActor.New(); vectorActor.SetMapper(vectorGlyphMapper); // get a reference to the renderwindow of our renderWindowControl1 vtkRenderWindow renderWindow = renderWindowControl1.RenderWindow; // renderer vtkRenderer renderer = renderWindow.GetRenderers().GetFirstRenderer(); // set background color renderer.SetBackground(.2, .6, .3); //Add the actors to the renderer, set the background and size renderer.AddActor(actor); renderer.AddActor(vectorActor); } void CreateVectorField(ref vtkImageData image) { // Specify the size of the image data image.SetDimensions(3, 3, 3); image.SetNumberOfScalarComponents(3); image.SetScalarTypeToFloat(); image.AllocateScalars(); image.SetSpacing(10.0, 10.0, 10.0); int[] dims = image.GetDimensions(); float[] pixel = new float[] {0.0f, 0.0f, 0.0f}; IntPtr pPixel; // Zero the vectors for(int z = 0; z < dims[2]; z++) { for(int y = 0; y < dims[1]; y++) { for(int x = 0; x < dims[0]; x++) { pPixel = image.GetScalarPointer(x, y, 0); Marshal.Copy(pixel, 0, pPixel, 3); } } } // Set two of the pixels to non zero values pixel[0] = 8.0f; pixel[1] = 8.0f; pixel[2] = -8.0f; pPixel = image.GetScalarPointer(0, 2, 0); Marshal.Copy(pixel, 0, pPixel, 3); pixel[0] = 8.0f; pixel[1] = -8.0f; pixel[2] = 8.0f; pPixel = image.GetScalarPointer(2, 0, 2); Marshal.Copy(pixel, 0, pPixel, 3); } } }