# TissueLens

VTKExamples/Cxx/Medical/TissueLens

### Description

This example uses two clip filters to achieve a "tissue lens" affect. First, a sphere implicit function is used to clip a spherical hole in the extracted isosurface. Then a geometric sphere samples the original volume data using a probe filter. The resulting scalar point data is used to clip the sphere surface with the isosurface value.

### Code

TissueLens.cxx

    #include <vtkSmartPointer.h>
    #include <vtkMarchingCubes.h>
    #include <vtkMetaImageReader.h>

    #include <vtkSphereSource.h>
    #include <vtkProbeFilter.h>
    #include <vtkSphere.h>
    #include <vtkClipDataSet.h>
    #include <vtkImplicitVolume.h>
    #include <vtkUnstructuredGrid.h>
    #include <vtkLookupTable.h>

    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkDataSetMapper.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkProperty.h>

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

      // Read the volume data
      vtkSmartPointer<vtkMetaImageReader> reader =
        vtkSmartPointer<vtkMetaImageReader>::New();
      reader->SetFileName (argv[1]);
      reader->Update();

      // An isosurface, or contour value of 500 is known to correspond to the
      // skin of the patient.
      vtkSmartPointer<vtkMarchingCubes> skinExtractor =
        vtkSmartPointer<vtkMarchingCubes>::New();
      skinExtractor->SetInputConnection(reader->GetOutputPort());
      skinExtractor->SetValue(0, 500);

      // Define a spherical clip function to clip the isosurface
      vtkSmartPointer<vtkSphere> clipFunction =
        vtkSmartPointer<vtkSphere>::New();
      clipFunction->SetRadius(50);
      clipFunction->SetCenter(73, 52, 15);

      // Clip the isosurface with a sphere
      vtkSmartPointer<vtkClipDataSet> skinClip =
        vtkSmartPointer<vtkClipDataSet>::New();
      skinClip->SetInputConnection(skinExtractor->GetOutputPort());
      skinClip->SetClipFunction(clipFunction);
      skinClip->SetValue(0);
      skinClip->GenerateClipScalarsOn();
      skinClip->Update();

      vtkSmartPointer<vtkDataSetMapper> skinMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      skinMapper->SetInputConnection(skinClip->GetOutputPort());
      skinMapper->ScalarVisibilityOff();

      vtkSmartPointer<vtkActor> skin =
        vtkSmartPointer<vtkActor>::New();
      skin->SetMapper(skinMapper);
      skin->GetProperty()->SetDiffuseColor(1, .49, .25);

      vtkSmartPointer<vtkProperty> backProp =
        vtkSmartPointer<vtkProperty>::New();
      backProp->SetDiffuseColor(0.8900, 0.8100, 0.3400);
      skin->SetBackfaceProperty(backProp);

      // Define a model for the "lens". Its geometry matches the implicit
      // sphere used to clip the isosurface
      vtkSmartPointer<vtkSphereSource> lensModel =
        vtkSmartPointer<vtkSphereSource>::New();
      lensModel->SetRadius(50);
      lensModel->SetCenter(73, 52, 15);
      lensModel->SetPhiResolution(201);
      lensModel->SetThetaResolution(101);

      // Sample the input volume with the lens model geometry
      vtkSmartPointer<vtkProbeFilter> lensProbe =
        vtkSmartPointer<vtkProbeFilter>::New();
      lensProbe->SetInputConnection(lensModel->GetOutputPort());
      lensProbe->SetSourceConnection(reader->GetOutputPort());

      // Clip the lens data with the isosurface value
      vtkSmartPointer<vtkClipDataSet> lensClip =
        vtkSmartPointer<vtkClipDataSet>::New();
      lensClip->SetInputConnection(lensProbe->GetOutputPort());
      lensClip->SetValue(500);
      lensClip->GenerateClipScalarsOff();
      lensClip->Update();

      // Define a suitable grayscale lut
      vtkSmartPointer<vtkLookupTable> bwLut =
        vtkSmartPointer<vtkLookupTable>::New();
      bwLut->SetTableRange (0, 2048);
      bwLut->SetSaturationRange (0, 0);
      bwLut->SetHueRange (0, 0);
      bwLut->SetValueRange (.2, 1);
      bwLut->Build();

      vtkSmartPointer<vtkDataSetMapper> lensMapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      lensMapper->SetInputConnection(lensClip->GetOutputPort());
      lensMapper->SetScalarRange(lensClip->GetOutput()->GetScalarRange());
      lensMapper->SetLookupTable(bwLut);

      vtkSmartPointer<vtkActor> lens =
        vtkSmartPointer<vtkActor>::New();
      lens->SetMapper(lensMapper);

      // It is convenient to create an initial view of the data. The FocalPoint
      // and Position form a vector direction. Later on (ResetCamera() method)
      // this vector is used to position the camera to look at the data in
      // this direction.
      vtkSmartPointer<vtkCamera> aCamera =
        vtkSmartPointer<vtkCamera>::New();
      aCamera->SetViewUp (0, 0, -1);
      aCamera->SetPosition (0, -1, 0);
      aCamera->SetFocalPoint (0, 0, 0);
      aCamera->ComputeViewPlaneNormal();
      aCamera->Azimuth(30.0);
      aCamera->Elevation(30.0);

      // Create the renderer, the render window, and the interactor. The renderer
      // draws into the render window, the interactor enables mouse- and
      // keyboard-based interaction with the data within the render window.
      //
      vtkSmartPointer<vtkRenderer> aRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(aRenderer);

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

      // Actors are added to the renderer. An initial camera view is created.
      // The Dolly() method moves the camera towards the FocalPoint,
      // thereby enlarging the image.
      aRenderer->AddActor(lens);
      aRenderer->AddActor(skin);
      aRenderer->SetActiveCamera(aCamera);
      aRenderer->ResetCamera ();
      aCamera->Dolly(1.5);

      // Set a background color for the renderer and set the size of the
      // render window (expressed in pixels).
      aRenderer->SetBackground(.2, .3, .4);
      renWin->SetSize(640, 480);

      // Note that when camera movement occurs (as it does in the Dolly()
      // method), the clipping planes often need adjusting. Clipping planes
      // consist of two planes: near and far along the view direction. The
      // near plane clips out objects in front of the plane; the far plane
      // clips out objects behind the plane. This way only what is drawn
      // between the planes is actually rendered.
      aRenderer->ResetCameraClippingRange ();

      // Initialize the event loop and then start it.
      iren->Initialize();
      iren->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(TissueLens)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(TissueLens MACOSX_BUNDLE TissueLens.cxx)

    target_link_libraries(TissueLens ${VTK_LIBRARIES})

### Download and Build TissueLens

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

    cd TissueLens/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:

    ./TissueLens

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