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# ShrinkCube

VTKEx/Cxx/GeometricObjects/ShrinkCube

### Description

Generates a cube using vtkCubeSource, then a shrink filter is applied. vtkShrinkFilter object shrinks cells composing an arbitrary data set towards their centroid. The centroid of a cell is computed as the average position of the cell points. Shrinking results in disconnecting the cells from one another.

Seealso

TessellatedBoxSource generates multiple quads or triangles per side.

Info

See Figure 5-17 in Chapter 5 the VTK Textbook.

Other languages

See (Python), (Java)

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

ShrinkCube.cxx

    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkCubeSource.h>
    #include <vtkDataSetMapper.h>
    #include <vtkNamedColors.h>
    #include <vtkPolyData.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkShrinkFilter.h>
    #include <vtkSmartPointer.h>

    int main(int, char *[])
    {
      // Create a cube.
      vtkSmartPointer<vtkCubeSource> cubeSource =
        vtkSmartPointer<vtkCubeSource>::New();

      vtkSmartPointer<vtkShrinkFilter> shrink =
        vtkSmartPointer<vtkShrinkFilter>::New();
      shrink->SetInputConnection(cubeSource->GetOutputPort());
      shrink->SetShrinkFactor(.9);

      // Create a mapper and actor.
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      vtkSmartPointer<vtkDataSetMapper> mapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      mapper->SetInputConnection(shrink->GetOutputPort());

      vtkSmartPointer<vtkProperty> back =
        vtkSmartPointer<vtkProperty>::New();
      back->SetColor(colors->GetColor3d("Tomato").GetData());

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);
      actor->GetProperty()->EdgeVisibilityOn();
      actor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
      actor->SetBackfaceProperty(back);

      // 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 actors to the scene
      renderer->AddActor(actor);
      renderer->SetBackground(colors->GetColor3d("Silver").GetData());

      renderer->ResetCamera();
      renderer->GetActiveCamera()->Azimuth(30);
      renderer->GetActiveCamera()->Elevation(30);
      renderer->ResetCameraClippingRange();

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ShrinkCube)

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

### Download and Build ShrinkCube

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

    cd ShrinkCube/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:

    ./ShrinkCube

WINDOWS USERS

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