# ColoredSphere

VTKExamples/Cxx/Rendering/ColoredSphere

### Description

This demonstrates a simple visualization pipeline. A polygonal representation of a sphere is created with the source object vtkSphereSource). The sphere is passed through a filter vtkElevationFilter) that computes the height of each point of the sphere above a plane. The plane is perpendicular to the z-axis, and passes through the point (0,0,-1). The data is finally mapped vtkDataSetMapper) through a lookup table. The mapping process converts height value into colors, and interfaces the sphere geometry to the rendering library. The mapper is assigned to an actor, and then the actor is displayed.

The execution of the pipeline occurs implicitly when we render the actor. Each actor asks its mapper to update itself. The mapper in turn asks its input to update itself. This process continues until a source object is encountered. Then the source will execute if modified since the last render.

Info

See Figure 4-19 in Chapter 4 the VTK Textbook.

Other Languages

See (Python)

### Code

ColoredSphere.cxx

    #include <vtkActor.h>
    #include <vtkCamera.h>
    #include <vtkDataSetMapper.h>
    #include <vtkElevationFilter.h>
    #include <vtkNamedColors.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkSmartPointer.h>
    #include <vtkSphereSource.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->SetPhiResolution(12); sphere->SetThetaResolution(12);

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

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

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

      renderer->AddActor(actor);
      renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());
      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(ColoredSphere)

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

### Download and Build ColoredSphere

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

    cd ColoredSphere/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:

    ./ColoredSphere

WINDOWS USERS

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