# InterpolateFieldDataDemo

VTKExamples/Cxx/Meshes/InterpolateFieldDataDemo

### Description

This example uses vtkPointInterpolator probe a high resolution dataset with a lower resolution dataset. Then, using vtkInterpolateDataSetAttributes, interpolate between the original low resolution data and the probed, low resolution data.

Warning

For the vtkPointInterpolator, point arrays will not be interpolated unless PassPointArrays is off. vtkPointInterpolator does not interpolate vtkFieldData. To interpolate vtkFieldData it must be added as the active scalar.

Warning

vtkInterpolateDataSetAttibutes does not interpolate vtkFieldData. To interpolate vtkFieldData it must be added as the active scalar.

Thanks

This example was inspired by Andrew E. Slaughter, Idaho National Laboratory.

### Code

InterpolateFieldDataDemo.cxx

    // This example was derived a python script created by Andrew E. Slaughter
    #include <vtkSmartPointer.h>

    #include <vtkCompositeDataGeometryFilter.h>
    #include <vtkExodusIIReader.h>
    #include <vtkGaussianKernel.h>
    #include <vtkInterpolateDataSetAttributes.h>
    #include <vtkPointInterpolator.h>
    #include <vtkStaticPointLocator.h>

    #include <vtkNamedColors.h>
    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkDataSetMapper.h>
    #include <vtkLookupTable.h>
    #include <vtkPointData.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkRenderer.h>
    #include <vtkUnstructuredGrid.h>
    #include <vtkMultiBlockDataSet.h>

    int main (int argc, char *argv[])
    {
      std::string variable = "u";
      double range[2] = {0, 10};

      if (argc < 3)
      {
        std::cout << "Usage: " << argv[0] << " coarseMesh fineMesh" << std::endl;
        return EXIT_FAILURE;
      }
      std::string file0 = argv[1];
      std::string file1 = argv[2];

      ///////////////////////////////////////////////////////////////////////////
      // FILE 0: COARSE MESH WITH SOLUTION 0
        vtkSmartPointer<vtkExodusIIReader> coarseReader =
          vtkSmartPointer<vtkExodusIIReader>::New();
        coarseReader->SetFileName(file0.c_str());
        coarseReader->UpdateInformation();
        coarseReader->SetTimeStep(0);
        coarseReader->SetAllArrayStatus(vtkExodusIIReader::NODAL, 1);
        coarseReader->Update();

        vtkSmartPointer<vtkCompositeDataGeometryFilter> coarseGeometry =
          vtkSmartPointer<vtkCompositeDataGeometryFilter>::New();
        coarseGeometry->SetInputConnection(0, coarseReader->GetOutputPort(0));
        coarseGeometry->Update();

       vtkSmartPointer<vtkPolyDataMapper> coarseMapper =
          vtkSmartPointer<vtkPolyDataMapper>::New();
        coarseMapper->SetInputConnection(coarseGeometry->GetOutputPort());
        coarseMapper->SelectColorArray(variable.c_str());
        coarseMapper->SetScalarModeToUsePointFieldData();
        coarseMapper->InterpolateScalarsBeforeMappingOn();
        coarseMapper->SetScalarRange(range);

        vtkSmartPointer<vtkActor> coarseActor =
          vtkSmartPointer<vtkActor>::New();
        coarseActor->SetMapper(coarseMapper);
        coarseActor->GetProperty()->SetEdgeVisibility(true);

        vtkSmartPointer<vtkRenderer> coarseRenderer =
          vtkSmartPointer<vtkRenderer>::New();
        coarseRenderer->AddViewProp(coarseActor);

    /////////////////////////////////////////////////////////////////////
    // FILE 1: FINE MESH WITH SOLUTION 1

        vtkSmartPointer<vtkExodusIIReader> fineReader =
          vtkSmartPointer<vtkExodusIIReader>::New();
        fineReader->SetFileName(file1.c_str());
        fineReader->UpdateInformation();
        fineReader->SetTimeStep(0);
        fineReader->SetAllArrayStatus(vtkExodusIIReader::NODAL, 1);
        fineReader->Update();

        vtkSmartPointer<vtkCompositeDataGeometryFilter> fineGeometry =
          vtkSmartPointer<vtkCompositeDataGeometryFilter>::New();
        fineGeometry->SetInputConnection(0, fineReader->GetOutputPort(0));
        fineGeometry->Update();
        fineGeometry->GetOutput()->GetPointData()->SetActiveScalars(variable.c_str());

        vtkSmartPointer<vtkPolyDataMapper> fineGeometryMapper =
          vtkSmartPointer<vtkPolyDataMapper>::New();
        fineGeometryMapper->SetInputConnection(fineGeometry->GetOutputPort());
        fineGeometryMapper->SelectColorArray(variable.c_str());
        fineGeometryMapper->SetScalarModeToUsePointFieldData();
        fineGeometryMapper->InterpolateScalarsBeforeMappingOn();
        fineGeometryMapper->SetScalarRange(range);

        vtkSmartPointer<vtkActor> fineGeometryActor =
          vtkSmartPointer<vtkActor>::New();
        fineGeometryActor->SetMapper(fineGeometryMapper);
        fineGeometryActor->GetProperty()->SetEdgeVisibility(true);

        vtkSmartPointer<vtkRenderer> fineGeometryRenderer =
          vtkSmartPointer<vtkRenderer>::New();
        fineGeometryRenderer->AddViewProp(fineGeometryActor);

    //////////////////////////////////////////////////////////////////////
    // PROJECT SOLUTION FROM FILE 0 to GRID FROM FILE 1

        // Build the structure to interpolate onto
        vtkSmartPointer<vtkUnstructuredGrid> coarseInterpolatedGrid = // output to be interpolated on to
          vtkSmartPointer<vtkUnstructuredGrid>::New();

        vtkMultiBlockDataSet *coarseMultiBlock =
          vtkMultiBlockDataSet::SafeDownCast(coarseReader->GetOutput()->GetBlock(0));
        coarseInterpolatedGrid->DeepCopy(vtkUnstructuredGrid::SafeDownCast(coarseMultiBlock->GetBlock(0)));

        vtkSmartPointer<vtkStaticPointLocator> locator =
          vtkSmartPointer<vtkStaticPointLocator>::New();
        locator->SetDataSet(fineGeometry->GetOutput());
        locator->BuildLocator();

        vtkSmartPointer<vtkGaussianKernel> kernel =
          vtkSmartPointer<vtkGaussianKernel>::New();
        kernel->SetSharpness(4);
        kernel->SetKernelFootprintToNClosest();
        kernel->SetNumberOfPoints(10);
        kernel->SetSharpness(4.0);

        // Probe the fine geometry with the course geometry.
        // NOTE: The point arrays will not be interpolated unless PassPointArrays is off.
        vtkSmartPointer<vtkPointInterpolator> coarseInterpolator =
          vtkSmartPointer<vtkPointInterpolator>::New();
        coarseInterpolator->SetSourceData(fineGeometry->GetOutput()); // Pc data set to be probed by input points P
        coarseInterpolator->SetInputData(coarseGeometry->GetOutput());
        coarseInterpolator->SetKernel(kernel);
        coarseInterpolator->SetLocator(locator);
        coarseInterpolator->SetNullPointsStrategyToClosestPoint();
        coarseInterpolator->PassPointArraysOff();
        coarseInterpolator->Update();

        vtkSmartPointer<vtkDataSetMapper> coarseInterpolatorMapper =
          vtkSmartPointer<vtkDataSetMapper>::New();
        coarseInterpolatorMapper->SetInputConnection(coarseInterpolator->GetOutputPort());
        coarseInterpolatorMapper->SelectColorArray(variable.c_str());
        coarseInterpolatorMapper->SetScalarModeToUsePointFieldData();
        coarseInterpolatorMapper->InterpolateScalarsBeforeMappingOn();
        coarseInterpolatorMapper->SetScalarRange(range);

        vtkSmartPointer<vtkActor> coarseInterpolatorActor =
          vtkSmartPointer<vtkActor>::New();
        coarseInterpolatorActor->SetMapper(coarseInterpolatorMapper);
        coarseInterpolatorActor->GetProperty()->SetEdgeVisibility(true);

        vtkSmartPointer<vtkRenderer> coarseInterpolatorRenderer =
          vtkSmartPointer<vtkRenderer>::New();
        coarseInterpolatorRenderer->AddActor(coarseInterpolatorActor);

        // Set the active scalar for the two inputs.
        // NOTE: InterpolateDataSetAttibutes does not interpolate field data.
        // To interpolate field data it must be added as the active scalar
        coarseInterpolatedGrid->GetPointData()->SetActiveScalars(variable.c_str());
        coarseInterpolator->GetOutput()->GetPointData()->SetActiveScalars(variable.c_str());

        vtkSmartPointer<vtkInterpolateDataSetAttributes> coarseInterpolateAttributes =
          vtkSmartPointer<vtkInterpolateDataSetAttributes>::New();
        coarseInterpolateAttributes->AddInputData(0, coarseInterpolatedGrid);
        coarseInterpolateAttributes->AddInputData(0, coarseInterpolator->GetOutput());
        coarseInterpolateAttributes->SetT(0.5);
        coarseInterpolateAttributes->Update();

        vtkSmartPointer<vtkDataSetMapper> coarseInterpolateAttibutesMapper =
          vtkSmartPointer<vtkDataSetMapper>::New();
        coarseInterpolateAttibutesMapper->SetInputConnection(coarseInterpolateAttributes->GetOutputPort());
        coarseInterpolateAttibutesMapper->SelectColorArray(variable.c_str());
        coarseInterpolateAttibutesMapper->SetScalarModeToUsePointFieldData();
        coarseInterpolateAttibutesMapper->InterpolateScalarsBeforeMappingOn();
        coarseInterpolateAttibutesMapper->SetScalarRange(range);

        vtkSmartPointer<vtkActor> coarseInterpolateAttributesActor =
          vtkSmartPointer<vtkActor>::New();
        coarseInterpolateAttributesActor->SetMapper(coarseInterpolateAttibutesMapper);
        coarseInterpolateAttributesActor->GetProperty()->SetEdgeVisibility(true);

        vtkSmartPointer<vtkRenderer> coarseInterpolateAttributesRenderer =
          vtkSmartPointer<vtkRenderer>::New();
        coarseInterpolateAttributesRenderer->AddActor(coarseInterpolateAttributesActor);

    /////////////////////////
    //  Window and Interactor

        vtkSmartPointer<vtkRenderWindow> window =
          vtkSmartPointer<vtkRenderWindow>::New();

        // Use the same camera for each renderer
        fineGeometryRenderer->SetActiveCamera(coarseRenderer->GetActiveCamera());
        coarseInterpolatorRenderer->SetActiveCamera(coarseRenderer->GetActiveCamera());
        coarseInterpolateAttributesRenderer->SetActiveCamera(coarseRenderer->GetActiveCamera());

        // Set each renderer color
        vtkSmartPointer<vtkNamedColors> colors =
          vtkSmartPointer<vtkNamedColors>::New();
        coarseRenderer->SetBackground(
          colors->GetColor3d("Gainsboro").GetData());
        coarseInterpolatorRenderer->SetBackground(
          colors->GetColor3d("LightGrey").GetData());
        coarseInterpolateAttributesRenderer->SetBackground(
          colors->GetColor3d("Silver").GetData());
        fineGeometryRenderer->SetBackground(
          colors->GetColor3d("DarkGray").GetData());

        // Set the viewport for each renderer
        coarseRenderer->SetViewport(0, 0, 0.25, 1);
        coarseInterpolatorRenderer->SetViewport(0.25, 0, 0.5, 1);
        coarseInterpolateAttributesRenderer->SetViewport(0.5, 0, 0.75, 1);
        fineGeometryRenderer->SetViewport(0.75, 0, 1, 1);

        // Add the renderers
        window->AddRenderer(coarseRenderer);                      // low res
        window->AddRenderer(coarseInterpolatorRenderer);          // interpolated geometry
        window->AddRenderer(coarseInterpolateAttributesRenderer); // interpolated attributes
        window->AddRenderer(fineGeometryRenderer);                // hi res with point data

        // The size the window to hold 4 viewports of width 320
        window->SetSize(1280, 320);

        // Create the interactor
        vtkSmartPointer<vtkRenderWindowInteractor> interactor =
          vtkSmartPointer<vtkRenderWindowInteractor>::New();
        interactor->SetRenderWindow(window);
        window->Render();
        interactor->Initialize();

        // Reset the camera to a default view, shared by all
        coarseRenderer->ResetCamera();
        interactor->Start();

        return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(InterpolateFieldDataDemo)

    find_package(VTK COMPONENTS
      vtkCommonColor
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersGeneral
      vtkFiltersGeometry
      vtkFiltersPoints
      vtkIOExodus
      vtkInteractionStyle
      vtkRenderingContextOpenGL2
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingGL2PSOpenGL2
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping InterpolateFieldDataDemo: ${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(InterpolateFieldDataDemo MACOSX_BUNDLE InterpolateFieldDataDemo.cxx )
      target_link_libraries(InterpolateFieldDataDemo PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(InterpolateFieldDataDemo MACOSX_BUNDLE InterpolateFieldDataDemo.cxx )
      target_link_libraries(InterpolateFieldDataDemo PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS InterpolateFieldDataDemo
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build InterpolateFieldDataDemo

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

    cd InterpolateFieldDataDemo/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:

    ./InterpolateFieldDataDemo

WINDOWS USERS

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