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QuadricClustering

vtk-examples/Cxx/Meshes/QuadricClustering


Description

The algorithm used is the one described by Peter Lindstrom in his Siggraph 2000 paper, "Out-of-Core Simplification of Large Polygonal Models." The general approach of the algorithm is to cluster vertices in a uniform binning of space, accumulating the quadric of each triangle (pushed out to the triangles vertices) within each bin, and then determining an optimal position for a single vertex in a bin by using the accumulated quadric.

Other languages

See (CSharp)

Question

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Code

QuadricClustering.cxx

#include <vtkCamera.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkQuadricClustering.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkXMLPolyDataReader.h>

int main(int argc, char* argv[])
{
  vtkSmartPointer<vtkPolyData> inputPolyData;
  if (argc > 1)
  {
    vtkNew<vtkXMLPolyDataReader> reader;
    reader->SetFileName(argv[1]);
    reader->Update();
    inputPolyData = reader->GetOutput();
  }
  else
  {
    vtkNew<vtkSphereSource> sphereSource;
    sphereSource->SetThetaResolution(30);
    sphereSource->SetPhiResolution(15);
    sphereSource->Update();
    inputPolyData = sphereSource->GetOutput();
  }

  vtkNew<vtkNamedColors> colors;

  std::cout << "Before decimation" << std::endl << "------------" << std::endl;
  std::cout << "There are " << inputPolyData->GetNumberOfPoints() << " points."
            << std::endl;
  std::cout << "There are " << inputPolyData->GetNumberOfPolys() << " polygons."
            << std::endl;

  vtkNew<vtkQuadricClustering> decimate;
  decimate->SetInputData(inputPolyData);
  decimate->UseFeatureEdgesOn();
  decimate->Update();

  vtkNew<vtkPolyData> decimated;
  decimated->ShallowCopy(decimate->GetOutput());

  std::cout << "After decimation" << std::endl << "------------" << std::endl;
  std::cout << "There are " << decimated->GetNumberOfPoints() << " points."
            << std::endl;
  std::cout << "There are " << decimated->GetNumberOfPolys() << " polygons."
            << std::endl;
  std::cout << "Reduction: "
            << static_cast<double>((inputPolyData->GetNumberOfPolys() -
                                    decimated->GetNumberOfPolys())) /
          static_cast<double>(inputPolyData->GetNumberOfPolys())
            << std::endl;

  vtkNew<vtkPolyDataMapper> inputMapper;
  inputMapper->SetInputData(inputPolyData);

  vtkNew<vtkProperty> backFace;
  backFace->SetColor(colors->GetColor3d("Gold").GetData());

  vtkNew<vtkActor> inputActor;
  inputActor->SetMapper(inputMapper);
  inputActor->GetProperty()->SetInterpolationToFlat();
  inputActor->GetProperty()->SetColor(
      colors->GetColor3d("NavajoWhite").GetData());
  inputActor->SetBackfaceProperty(backFace);

  vtkNew<vtkPolyDataMapper> decimatedMapper;
  decimatedMapper->SetInputData(decimated);

  vtkNew<vtkActor> decimatedActor;
  decimatedActor->SetMapper(decimatedMapper);
  decimatedActor->GetProperty()->SetColor(
      colors->GetColor3d("NavajoWhite").GetData());
  decimatedActor->GetProperty()->SetInterpolationToFlat();
  decimatedActor->SetBackfaceProperty(backFace);

  // There will be one render window
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetSize(600, 300);
  renderWindow->SetWindowName("QuadricClustering");

  // And one interactor
  vtkNew<vtkRenderWindowInteractor> interactor;
  interactor->SetRenderWindow(renderWindow);

  // Define viewport ranges
  // (xmin, ymin, xmax, ymax)
  double leftViewport[4] = {0.0, 0.0, 0.5, 1.0};
  double rightViewport[4] = {0.5, 0.0, 1.0, 1.0};

  // Setup both renderers
  vtkNew<vtkRenderer> leftRenderer;
  renderWindow->AddRenderer(leftRenderer);
  leftRenderer->SetViewport(leftViewport);
  leftRenderer->SetBackground(colors->GetColor3d("Peru").GetData());

  vtkNew<vtkRenderer> rightRenderer;
  renderWindow->AddRenderer(rightRenderer);
  rightRenderer->SetViewport(rightViewport);
  rightRenderer->SetBackground(colors->GetColor3d("CornflowerBlue").GetData());

  // Add the sphere to the left and the cube to the right
  leftRenderer->AddActor(inputActor);
  rightRenderer->AddActor(decimatedActor);

  // Shared camera looking down the -y axis
  vtkNew<vtkCamera> camera;
  camera->SetPosition(0, -1, 0);
  camera->SetFocalPoint(0, 0, 0);
  camera->SetViewUp(0, 0, 1);
  camera->Elevation(30);
  camera->Azimuth(30);

  leftRenderer->SetActiveCamera(camera);
  rightRenderer->SetActiveCamera(camera);

  leftRenderer->ResetCamera();
  leftRenderer->ResetCameraClippingRange();

  renderWindow->Render();
  interactor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(QuadricClustering)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkFiltersSources
  vtkIOXML
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping QuadricClustering: ${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(QuadricClustering MACOSX_BUNDLE QuadricClustering.cxx )
  target_link_libraries(QuadricClustering PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(QuadricClustering MACOSX_BUNDLE QuadricClustering.cxx )
  target_link_libraries(QuadricClustering PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS QuadricClustering
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build QuadricClustering

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

cd QuadricClustering/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:

./QuadricClustering

WINDOWS USERS

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