QuadricDecimation

Description¶

This example uses Quadric Clustering, based on the work of Garland and Heckbert who first presented the quadric error measure at Siggraph '97 "Surface Simplification Using Quadric Error Metrics". For details of the algorithm Michael Garland's Ph.D. thesis is also recommended. Hughues Hoppe's Vis '99 paper, "New Quadric Metric for Simplifying Meshes with Appearance Attributes" is also a good take on the subject especially as it pertains to the error metric applied to attributes.

Seealso

QuadricClustering and Decimation.

Other languages

See (CSharp)

Question

If you have a question about this example, please use the VTK Discourse Forum

Code¶

QuadricDecimation.cxx

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

int main(int argc, char* argv[])
{
  vtkSmartPointer<vtkPolyData> inputPolyData;
  if (argc > 1)
  {
    vtkNew<vtkXMLPolyDataReader> reader;
    reader->SetFileName(argv[1]);
    vtkNew<vtkTriangleFilter> triangles;
    triangles->SetInputConnection(reader->GetOutputPort());
    triangles->Update();
    inputPolyData = triangles->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<vtkQuadricDecimation> decimate;
  decimate->SetInputData(inputPolyData);
  decimate->AttributeErrorMetricOn();
  decimate->SetTargetReduction(.9);
  decimate->VolumePreservationOn();

  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("QuadricDecimation");

  // 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 3.12 FATAL_ERROR)

project(QuadricDecimation)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonDataModel
  FiltersCore
  FiltersSources
  IOXML
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "QuadricDecimation: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(QuadricDecimation MACOSX_BUNDLE QuadricDecimation.cxx )
  target_link_libraries(QuadricDecimation PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS QuadricDecimation
  MODULES ${VTK_LIBRARIES}
)

Download and Build QuadricDecimation¶

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

cd QuadricDecimation/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:

./QuadricDecimation

WINDOWS USERS

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