QuadricDecimation

VTKExamples/Cxx/Meshes/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.

Code

QuadricDecimation.cxx

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

#include <vtkNamedColors.h>

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

  vtkSmartPointer<vtkNamedColors> colors =
    vtkSmartPointer<vtkNamedColors>::New();
  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;

  vtkSmartPointer<vtkQuadricDecimation> decimate =
    vtkSmartPointer<vtkQuadricDecimation>::New();
  decimate->SetInputData(inputPolyData);
  decimate->AttributeErrorMetricOn();
  decimate->SetTargetReduction(.9);
  decimate->VolumePreservationOn();

  decimate->Update();

  vtkSmartPointer<vtkPolyData> decimated =
    vtkSmartPointer<vtkPolyData>::New();
  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;

  vtkSmartPointer<vtkPolyDataMapper> inputMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  inputMapper->SetInputData(inputPolyData);

  vtkSmartPointer<vtkProperty> backFace =
    vtkSmartPointer<vtkProperty>::New();
  backFace->SetColor(colors->GetColor3d("gold").GetData());

  vtkSmartPointer<vtkActor> inputActor =
    vtkSmartPointer<vtkActor>::New();
  inputActor->SetMapper(inputMapper);
  inputActor->GetProperty()->SetInterpolationToFlat();
  inputActor->GetProperty()->SetColor(colors->GetColor3d("flesh").GetData());
  inputActor->SetBackfaceProperty(backFace);

  vtkSmartPointer<vtkPolyDataMapper> decimatedMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  decimatedMapper->SetInputData(decimated);

  vtkSmartPointer<vtkActor> decimatedActor =
    vtkSmartPointer<vtkActor>::New();
  decimatedActor->SetMapper(decimatedMapper);
  decimatedActor->GetProperty()->SetColor(colors->GetColor3d("flesh").GetData());
  decimatedActor->GetProperty()->SetInterpolationToFlat();
  decimatedActor->SetBackfaceProperty(backFace);

  // There will be one render window
  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->SetSize(600, 300);

  // And one interactor
  vtkSmartPointer<vtkRenderWindowInteractor> interactor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  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
  vtkSmartPointer<vtkRenderer> leftRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(leftRenderer);
  leftRenderer->SetViewport(leftViewport);
  leftRenderer->SetBackground(colors->GetColor3d("burlywood").GetData());

  vtkSmartPointer<vtkRenderer> rightRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(rightRenderer);
  rightRenderer->SetViewport(rightViewport);
  rightRenderer->SetBackground(colors->GetColor3d("slate_grey").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
  vtkSmartPointer<vtkCamera> camera =
    vtkSmartPointer<vtkCamera>::New();
  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 2.8)

PROJECT(QuadricDecimation)

find_package(VTK REQUIRED)
include(${VTK_USE_FILE})

add_executable(QuadricDecimation MACOSX_BUNDLE QuadricDecimation.cxx )

target_link_libraries(QuadricDecimation ${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.