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# ColoredElevationMap

VTKEx/Cxx/Meshes/ColoredElevationMap

Other languages

See (Python), (CSharp)

Question

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### Code

ColoredElevationMap.cxx

    #include <vtkSmartPointer.h>

    #include <vtkActor.h>
    #include <vtkDelaunay2D.h>
    #include <vtkLookupTable.h>
    #include <vtkMath.h>
    #include <vtkPointData.h>
    #include <vtkPoints.h>
    #include <vtkPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkVertexGlyphFilter.h>
    #include <vtkXMLPolyDataWriter.h>

    // For compatibility with new VTK generic data arrays
    #ifdef vtkGenericDataArray_h
    #define InsertNextTupleValue InsertNextTypedTuple
    #endif

    int main(int, char *[])
    {
      // Create a grid of points (height/terrian map)
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();

      unsigned int GridSize = 20;
      double xx, yy, zz;
      for(unsigned int x = 0; x < GridSize; x++)
      {
        for(unsigned int y = 0; y < GridSize; y++)
        {
          xx = x + vtkMath::Random(-.2, .2);
          yy = y + vtkMath::Random(-.2, .2);
          zz = vtkMath::Random(-.5, .5);
          points->InsertNextPoint(xx, yy, zz);
        }
      }

      // Add the grid points to a polydata object
      vtkSmartPointer<vtkPolyData> inputPolyData =
        vtkSmartPointer<vtkPolyData>::New();
      inputPolyData->SetPoints(points);

      // Triangulate the grid points
      vtkSmartPointer<vtkDelaunay2D> delaunay =
        vtkSmartPointer<vtkDelaunay2D>::New();
      delaunay->SetInputData(inputPolyData);
      delaunay->Update();
      vtkPolyData* outputPolyData = delaunay->GetOutput();

      double bounds[6];
      outputPolyData->GetBounds(bounds);

      // Find min and max z
      double minz = bounds[4];
      double maxz = bounds[5];

      std::cout << "minz: " << minz << std::endl;
      std::cout << "maxz: " << maxz << std::endl;

      // Create the color map
      vtkSmartPointer<vtkLookupTable> colorLookupTable =
        vtkSmartPointer<vtkLookupTable>::New();
      colorLookupTable->SetTableRange(minz, maxz);
      colorLookupTable->Build();

      // Generate the colors for each point based on the color map
      vtkSmartPointer<vtkUnsignedCharArray> colors =
        vtkSmartPointer<vtkUnsignedCharArray>::New();
      colors->SetNumberOfComponents(3);
      colors->SetName("Colors");

      std::cout << "There are " << outputPolyData->GetNumberOfPoints()
                << " points." << std::endl;

      for(int i = 0; i < outputPolyData->GetNumberOfPoints(); i++)
      {
        double p[3];
        outputPolyData->GetPoint(i,p);

        double dcolor[3];
        colorLookupTable->GetColor(p[2], dcolor);
        std::cout << "dcolor: "
                  << dcolor[0] << " "
                  << dcolor[1] << " "
                  << dcolor[2] << std::endl;
        unsigned char color[3];
        for(unsigned int j = 0; j < 3; j++)
        {
          color[j] = static_cast<unsigned char>(255.0 * dcolor[j]);
        }
        std::cout << "color: "
                  << (int)color[0] << " "
                  << (int)color[1] << " "
                  << (int)color[2] << std::endl;

        colors->InsertNextTupleValue(color);
      }

      outputPolyData->GetPointData()->SetScalars(colors);

      // Create a mapper and actor
      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputData(outputPolyData);

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);

      // Create a renderer, render window, and interactor
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      // Add the actor to the scene
      renderer->AddActor(actor);
      renderer->SetBackground(.1, .2, .3);

      // Render and interact
      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ColoredElevationMap)

    find_package(VTK COMPONENTS
      vtkvtkCommonCore
      vtkvtkCommonDataModel
      vtkvtkFiltersCore
      vtkvtkFiltersGeneral
      vtkvtkIOXML
      vtkvtkInteractionStyle
      vtkvtkRenderingContextOpenGL2
      vtkvtkRenderingCore
      vtkvtkRenderingFreeType
      vtkvtkRenderingGL2PSOpenGL2
      vtkvtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ColoredElevationMap: ${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(ColoredElevationMap MACOSX_BUNDLE ColoredElevationMap.cxx )
      target_link_libraries(ColoredElevationMap PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ColoredElevationMap MACOSX_BUNDLE ColoredElevationMap.cxx )
      target_link_libraries(ColoredElevationMap PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ColoredElevationMap
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ColoredElevationMap

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

    cd ColoredElevationMap/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:

    ./ColoredElevationMap

WINDOWS USERS

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