# DisplacementPlot

VTKExamples/Cxx/VisualizationAlgorithms/DisplacementPlot

### Description

This example shows modal lines for a vibrating rectangular beam. The vibration mode in this figure is the second torsional mode, clearly indicated by the crossing modal lines.

The default color scheme shows cool color for maximum negative motion, warm color maximum positive motion, with white at the nodes.

For other possible color maps see: Diverging Color Maps for Scientific Visualization.

Info

See Figure 6-15 in Chapter 6 the VTK Textbook.

Other Languages

See (Python)

### Code

DisplacementPlot.cxx

    // Translated from dispPlot.tcl
    /*
    Produce figure 6-15(b) from the VTK Textbook.
    Surface plot of a vibrating plane.

    The color_scheme option allows you to select a series of colour schemes.
    0: The default:- cool maximum negative motion,
                     warm maximum positive motion, white at the nodes.
    1: Alternate choice:- green maximum negative motion,
                          purple maximum positive motion, white at the nodes.
    2: The original:- white at maximum motion, black at the nodes.

    */

    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkColorTransferFunction.h>
    #include <vtkDataSetMapper.h>
    #include <vtkLookupTable.h>
    #include <vtkNamedColors.h>
    #include <vtkPolyDataNormals.h>
    #include <vtkPolyDataReader.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkSmartPointer.h>
    #include <vtkVectorDot.h>
    #include <vtkWarpVector.h>

    namespace
    {
    //! Create a lookup table.
    /*!
    @param lut - An indexed lookup table.
    */
    void MakeLUT(int const& colorScheme, vtkLookupTable* lut);
    }

    int main(int argc, char* argv[])
    {
      if (argc < 2)
      {
        std::cout << "Usage: " << argv[0] << " filename [colorScheme]" << std::endl;
        std::cout << "where: filename is the file plate.vtk." << std::endl;
        std::cout << "       colorScheme is 0, 1, or 2, default 0" << std::endl;
        std::cout << "Produces figure 6-15(b) Surface plot of vibrating plane from "
                     "the VTK Textbook."
                  << std::endl;
        return EXIT_FAILURE;
      }

      int colorScheme = 0;
      std::string fileName = argv[1];

      if (argc == 3)
      {
        colorScheme = std::abs(atoi(argv[2]));
        colorScheme = (colorScheme > 2) ? 0 : colorScheme;
      }

      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      // Read a vtk file
      //
      vtkSmartPointer<vtkPolyDataReader> plate =
        vtkSmartPointer<vtkPolyDataReader>::New();
      plate->SetFileName(fileName.c_str());
      plate->SetVectorsName("mode8");
      plate->Update();

      vtkSmartPointer<vtkWarpVector> warp = vtkSmartPointer<vtkWarpVector>::New();
      warp->SetInputConnection(plate->GetOutputPort());
      warp->SetScaleFactor(0.5);

      vtkSmartPointer<vtkPolyDataNormals> normals =
        vtkSmartPointer<vtkPolyDataNormals>::New();
      normals->SetInputConnection(warp->GetOutputPort());

      vtkSmartPointer<vtkVectorDot> color = vtkSmartPointer<vtkVectorDot>::New();
      color->SetInputConnection(normals->GetOutputPort());

      vtkSmartPointer<vtkLookupTable> lut = vtkSmartPointer<vtkLookupTable>::New();
      MakeLUT(colorScheme, lut);

      vtkSmartPointer<vtkDataSetMapper> plateMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      plateMapper->SetInputConnection(color->GetOutputPort());
      plateMapper->SetLookupTable(lut);
      plateMapper->SetScalarRange(-1, 1);

      vtkSmartPointer<vtkActor> plateActor = vtkSmartPointer<vtkActor>::New();
      plateActor->SetMapper(plateMapper);

      // Create the RenderWindow, Renderer and both Actors
      //
      vtkSmartPointer<vtkRenderer> ren = vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(ren);

      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);

      // Add the actors to the renderer, set the background and size
      //
      ren->AddActor(plateActor);
      ren->SetBackground(colors->GetColor3d("Wheat").GetData());
      renWin->SetSize(512, 512);

      ren->GetActiveCamera()->SetPosition(13.3991, 14.0764, 9.97787);
      ren->GetActiveCamera()->SetFocalPoint(1.50437, 0.481517, 4.52992);
      ren->GetActiveCamera()->SetViewAngle(30);
      ren->GetActiveCamera()->SetViewUp(-0.120861, 0.458556, -0.880408);
      ren->GetActiveCamera()->SetClippingRange(12.5724, 26.8374);
      // Render the image.
      renWin->Render();

      iren->Start();

      return EXIT_SUCCESS;
    }

    namespace
    {
    void MakeLUT(int const& colorScheme, vtkLookupTable* lut)
    {
      // See: [Diverging Color Maps for Scientific Visualization]
      //      (http://www.kennethmoreland.com/color-maps/)
      auto nc = 256;
      vtkSmartPointer<vtkColorTransferFunction> ctf =
        vtkSmartPointer<vtkColorTransferFunction>::New();
      switch (colorScheme)
      {
        case 0:
        default:
          // Cool to warm diverging.
          ctf->SetColorSpaceToDiverging();
          ctf->AddRGBPoint(0.0, 0.230, 0.299, 0.754);
          ctf->AddRGBPoint(1.0, 0.706, 0.016, 0.150);
          lut->SetNumberOfTableValues(nc);
          lut->Build();
          for (auto i = 0; i < nc; ++i)
          {
            double rgb[4] = {0.0, 0.0, 0.0, 1.0};
            ctf->GetColor(static_cast<double>(i) / nc, rgb);
            lut->SetTableValue(i, rgb);
          }
          break;
        case 1:
          // Green to purple diverging.
          ctf->SetColorSpaceToDiverging();
          ctf->AddRGBPoint(0.0, 0.085, 0.532, 0.201);
          ctf->AddRGBPoint(1.0, 0.436, 0.308, 0.631);
          lut->SetNumberOfTableValues(nc);
          lut->Build();
          for (auto i = 0; i < nc; ++i)
          {
            double rgb[4] = {0.0, 0.0, 0.0, 1.0};
            ctf->GetColor(static_cast<double>(i) / nc, rgb);
            lut->SetTableValue(i, rgb);
          }
          break;
        case 2:
        {
          // Make a lookup table, black in the centre with bright areas
          //   at the beginning and end of the table.
          // This is from the original code.
          auto nc2 = nc / 2;
          lut->SetNumberOfColors(nc);
          lut->Build();
          for (auto i = 0; i < nc2; ++i)
          {
            // White to black.
            auto v = (double(nc2) - i) / double(nc2);
            lut->SetTableValue(i, v, v, v, 1);
          }
          for (auto i = nc2; i < nc; ++i)
          {
            // Black to white.
            auto v = (i - double(nc2)) / double(nc2);
            lut->SetTableValue(i, v, v, v, 1);
          }
          break;
        }
      }
    }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(DisplacementPlot)

    find_package(VTK COMPONENTS
      vtkCommonColor
      vtkCommonCore
      vtkFiltersCore
      vtkFiltersGeneral
      vtkIOLegacy
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping DisplacementPlot: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(DisplacementPlot MACOSX_BUNDLE DisplacementPlot.cxx )
      target_link_libraries(DisplacementPlot PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(DisplacementPlot MACOSX_BUNDLE DisplacementPlot.cxx )
      target_link_libraries(DisplacementPlot PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS DisplacementPlot
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build DisplacementPlot

Click here to download DisplacementPlot and its CMakeLists.txt file. Once the tarball DisplacementPlot.tar has been downloaded and extracted,

    cd DisplacementPlot/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

    cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

    make

and run it:

    ./DisplacementPlot

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.