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# ImplicitQuadric

VTKEx/Cxx/ImplicitFunctions/ImplicitQuadric

Create an ellipsoid by using the implicit quadric.

Question

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### Code

ImplicitQuadric.cxx

    #include <vtkQuadric.h>
    #include <vtkBox.h>
    #include <vtkImplicitBoolean.h>
    #include <vtkSampleFunction.h>
    #include <vtkContourFilter.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkNamedColors.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkCamera.h>
    #include <vtkProperty.h>
    #include <vtkColor.h>

    #include <cstdlib>

    int main(int argc, char *argv[])
    {
      // Define colors
      auto colors =
        vtkSmartPointer<vtkNamedColors>::New();
      vtkColor3d actorColor = colors->GetColor3d("AliceBlue");
      vtkColor3d  EdgeColour = colors->GetColor3d("SteelBlue");
      vtkColor3d BackgroundColour = colors->GetColor3d("Silver");

      // create a Quadric
      auto quadric = vtkSmartPointer<vtkQuadric>::New();
      quadric->SetCoefficients(0.5, 1, 0.2, 0, 0.1, 0, 0, 0.2, 0, 0);

       /*The sample function generates a distance function from the implicit
         function.This is then contoured to get a polygonal surface.*/
      auto sample =
        vtkSmartPointer<vtkSampleFunction>::New();
      sample->SetImplicitFunction(quadric);
      sample->SetModelBounds(-0.5, 0.5, -0.5, 0.5, -0.5, 0.5);
      sample->SetSampleDimensions(40, 40, 40);
      sample->ComputeNormalsOff();

      // contour
      auto surface =
        vtkSmartPointer<vtkContourFilter>::New();
      surface->SetInputConnection(sample->GetOutputPort());
      surface->SetValue(0, 0.0);

      //Create a mapper and an actor
      auto mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(surface->GetOutputPort());
      mapper->ScalarVisibilityOff();
      auto actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);
      actor->GetProperty()->EdgeVisibilityOn();
      actor->GetProperty()->SetColor(actorColor.GetData());
      actor->GetProperty()->SetEdgeColor(EdgeColour.GetData());

      // A renderer and render window
      auto renderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderer->SetBackground(BackgroundColour.GetData());
      auto renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      auto renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);
      //add the actor
      renderer->AddActor(actor);
      // Start
      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ImplicitQuadric)

    find_package(VTK COMPONENTS
      vtkvtkCommonColor
      vtkvtkCommonDataModel
      vtkvtkFiltersCore
      vtkvtkImagingHybrid
      vtkvtkInteractionStyle
      vtkvtkRenderingContextOpenGL2
      vtkvtkRenderingCore
      vtkvtkRenderingFreeType
      vtkvtkRenderingGL2PSOpenGL2
      vtkvtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ImplicitQuadric: ${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(ImplicitQuadric MACOSX_BUNDLE ImplicitQuadric.cxx )
      target_link_libraries(ImplicitQuadric PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ImplicitQuadric MACOSX_BUNDLE ImplicitQuadric.cxx )
      target_link_libraries(ImplicitQuadric PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ImplicitQuadric
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ImplicitQuadric

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

    cd ImplicitQuadric/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:

    ./ImplicitQuadric

WINDOWS USERS

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