# CarotidFlow

VTKExamples/Cxx/VisualizationAlgorithms/CarotidFlow

### Description

This example generates streamtubes of blood velocity. an isosurface of speed provides context. The starting positions for the streamtubes were determined by experimenting with the data. Because of the way the data was measured and the resolution of the velocity field, many streamers travel outside the artery. This is because the boundary layer of the blood flow is not captured due to limitations in data resolution. Consequently, as the blood flows around curves, there is a component of the velocity field that directs the streamtube outside the artery. As a result it is hard to find starting positions for the streamtubes that yield interesting results. The examples uses the source object vtkPointSource in combination with vtkThresholdPoints to work around this problem. vtkPointSource generates random points centered around a sphere of a specified radius. We need only find an approximate position for the starting points of the streamtubes and then generate a cloud of random seed points. vtkThresholdPoints is used to cull points that may be generated outside the regions of high flow velocity.

Cite

See 3D Phase Contrast MRI of Cerebral Blood Flow and Surface Anatomy for background.

Info

See Figure 6-44 in Chapter 6 the VTK Textbook.

Other Languages

See (Python)

### Code

CarotidFlow.cxx

    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkContourFilter.h>
    #include <vtkLookupTable.h>
    #include <vtkNamedColors.h>
    #include <vtkOutlineFilter.h>
    #include <vtkPointData.h>
    #include <vtkPointSource.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkStreamTracer.h>
    #include <vtkStructuredPointsReader.h>
    #include <vtkThresholdPoints.h>
    #include <vtkTubeFilter.h>

    int main (int argc, char *argv[])
    {
      if (argc < 2)
      {
        std::cout << "Usage: " << argv[0] << " carotid.vtk" << std::endl;
        return EXIT_FAILURE;
      }

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

      vtkSmartPointer<vtkRenderer> ren1 =
        vtkSmartPointer<vtkRenderer>::New();

      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(ren1);

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

    // create pipeline
    //
      vtkSmartPointer<vtkStructuredPointsReader> reader =
        vtkSmartPointer<vtkStructuredPointsReader>::New();
      reader->SetFileName(argv[1]);

      vtkSmartPointer<vtkPointSource> psource =
        vtkSmartPointer<vtkPointSource>::New();
      psource->SetNumberOfPoints(25);
      psource->SetCenter(133.1, 116.3, 5.0);
      psource->SetRadius(2.0);

      vtkSmartPointer<vtkThresholdPoints> threshold =
        vtkSmartPointer<vtkThresholdPoints>::New();
      threshold->SetInputConnection(reader->GetOutputPort());
      threshold->ThresholdByUpper(275);

      vtkSmartPointer<vtkStreamTracer> streamers =
        vtkSmartPointer<vtkStreamTracer>::New();
      streamers->SetInputConnection(reader->GetOutputPort());
      streamers->SetSourceConnection(psource->GetOutputPort());
    //  streamers->SetMaximumPropagationUnitToTimeUnit();
      streamers->SetMaximumPropagation(100.0);
    //  streamers->SetInitialIntegrationStepUnitToCellLengthUnit();
      streamers->SetInitialIntegrationStep(0.2);
      streamers->SetTerminalSpeed(.01);
      streamers->Update();
      double range[2];
      range[0] = streamers->GetOutput()->GetPointData()->GetScalars()->GetRange()[0];
      range[1] = streamers->GetOutput()->GetPointData()->GetScalars()->GetRange()[1];

      vtkSmartPointer<vtkTubeFilter> tubes =
        vtkSmartPointer<vtkTubeFilter>::New();
      tubes->SetInputConnection(streamers->GetOutputPort());
      tubes->SetRadius(0.3);
      tubes->SetNumberOfSides(6);
      tubes->SetVaryRadius(0);

      vtkSmartPointer<vtkLookupTable> lut =
        vtkSmartPointer<vtkLookupTable>::New();
      lut->SetHueRange(.667, 0.0);
      lut->Build();

      vtkSmartPointer<vtkPolyDataMapper> streamerMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      streamerMapper->SetInputConnection(tubes->GetOutputPort());
      streamerMapper->SetScalarRange(range[0], range[1]);
      streamerMapper->SetLookupTable(lut);

      vtkSmartPointer<vtkActor> streamerActor =
        vtkSmartPointer<vtkActor>::New();
      streamerActor->SetMapper(streamerMapper);

    // contours of speed
      vtkSmartPointer<vtkContourFilter> iso =
        vtkSmartPointer<vtkContourFilter>::New();
      iso->SetInputConnection(reader->GetOutputPort());
      iso->SetValue(0, 175);

      vtkSmartPointer<vtkPolyDataMapper> isoMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      isoMapper->SetInputConnection(iso->GetOutputPort());
      isoMapper->ScalarVisibilityOff();

      vtkSmartPointer<vtkActor> isoActor =
        vtkSmartPointer<vtkActor>::New();
      isoActor->SetMapper(isoMapper);
      isoActor->GetProperty()->SetRepresentationToWireframe();
      isoActor->GetProperty()->SetOpacity(0.25);

    // outline
      vtkSmartPointer<vtkOutlineFilter> outline =
        vtkSmartPointer<vtkOutlineFilter>::New();
      outline->SetInputConnection(reader->GetOutputPort());

      vtkSmartPointer<vtkPolyDataMapper> outlineMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      outlineMapper->SetInputConnection(outline->GetOutputPort());

      vtkSmartPointer<vtkActor> outlineActor =
        vtkSmartPointer<vtkActor>::New();
      outlineActor->SetMapper(outlineMapper);
      outlineActor->GetProperty()->SetColor(colors->GetColor3d("Black").GetData());

    // Add the actors to the renderer, set the background and size
    //
      ren1->AddActor(outlineActor);
      ren1->AddActor(streamerActor);
      ren1->AddActor(isoActor);
      ren1->SetBackground(colors->GetColor3d("Wheat").GetData());
      renWin->SetSize(640, 480);

      vtkSmartPointer<vtkCamera> cam1 =
        vtkSmartPointer<vtkCamera>::New();
      cam1->SetClippingRange(17.4043, 870.216);
      cam1->SetFocalPoint(136.71, 104.025, 23);
      cam1->SetPosition(204.747, 258.939, 63.7925);
      cam1->SetViewUp(-0.102647, -0.210897, 0.972104);
      cam1->Zoom(1.6);
      ren1->SetActiveCamera(cam1);

    // render the image
    //
      renWin->Render();
      iren->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(CarotidFlow)

    find_package(VTK COMPONENTS
      vtkCommonColor
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersCore
      vtkFiltersFlowPaths
      vtkFiltersModeling
      vtkFiltersSources
      vtkIOLegacy
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping CarotidFlow: ${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(CarotidFlow MACOSX_BUNDLE CarotidFlow.cxx )
      target_link_libraries(CarotidFlow PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(CarotidFlow MACOSX_BUNDLE CarotidFlow.cxx )
      target_link_libraries(CarotidFlow PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS CarotidFlow
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build CarotidFlow

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

    cd CarotidFlow/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:

    ./CarotidFlow

WINDOWS USERS

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