# TransformSphere

VTKExamples/Cxx/Rendering/TransformSphere

### Description

This example extends the pipeline of the ColoredSphere.cxx example and shows the effects of type checking on the connectivity of process objects. We add a transform filter vtkTransformFilter) to nonuniformly scale the sphere in the x-y-z directions. The transform filter only operates on objects with explicit point coordinate representation (i.e., a subclass of vtkPointSet ). However, the elevation filter generates the more general form vtkDataSet as output. Hence we cannot connect the transform filter to the elevation filter. But we can connect the transform filter to the sphere source, and then the elevation filter to the transform filter. (Note: an alternative method is to use vtkCastToConcrete to perform run-time casting.)

Info

See Figure 4-20 in Chapter 4 the VTK Textbook.

Other Languages

See (Python)

### Code

TransformSphere.cxx

    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkDataSetMapper.h>
    #include <vtkElevationFilter.h>
    #include <vtkLookupTable.h>
    #include <vtkNamedColors.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkSphereSource.h>
    #include <vtkTransform.h>
    #include <vtkTransformFilter.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);

      vtkSmartPointer<vtkSphereSource> sphere =
        vtkSmartPointer<vtkSphereSource>::New();
      sphere->SetThetaResolution(12); sphere->SetPhiResolution(12);

      vtkSmartPointer<vtkTransform> aTransform =
        vtkSmartPointer<vtkTransform>::New();
      aTransform->Scale(1,1.5,2);

      vtkSmartPointer<vtkTransformFilter> transFilter =
        vtkSmartPointer<vtkTransformFilter>::New();
      transFilter->SetInputConnection(sphere->GetOutputPort());
      transFilter->SetTransform(aTransform);

      vtkSmartPointer<vtkElevationFilter> colorIt =
        vtkSmartPointer<vtkElevationFilter>::New();
      colorIt->SetInputConnection(transFilter->GetOutputPort());
      colorIt->SetLowPoint(0,0,-1);
      colorIt->SetHighPoint(0,0,1);

      vtkSmartPointer<vtkLookupTable> lut =
        vtkSmartPointer<vtkLookupTable>::New();
      lut->SetHueRange(0.667, 0);
      lut->SetSaturationRange(1,1);
      lut->SetValueRange(1,1);

      vtkSmartPointer<vtkDataSetMapper> mapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      mapper->SetLookupTable(lut);
      mapper->SetInputConnection(colorIt->GetOutputPort());

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

      renderer->AddActor(actor);
      renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());
      renderer->ResetCamera();
      renderer->GetActiveCamera()->Elevation(60.0);
      renderer->GetActiveCamera()->Azimuth(30.0);
      renderer->ResetCameraClippingRange();

      renWin->SetSize(640, 480);

      renWin->Render();

      // interact with data
      iren->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(TransformSphere)

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

### Download and Build TransformSphere

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

    cd TransformSphere/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:

    ./TransformSphere

WINDOWS USERS

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