VTK/Examples/Cxx/Meshes/Decimation

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VTK Examples Baseline Meshes TestDecimation.png

This example decimates a mesh. The SetTargetReduction function specifies how many triangles should reduced by specifying the percentage ([0,1]) of triangles to be removed. For example, if the mesh contains 100 triangles and SetTargetReduction(.90) is called, after the decimation there will be approximately 10 triangles - a 90% reduction.

Decimation.cxx

#include <vtkVersion.h>
#include <vtkPolyData.h>
#include <vtkSphereSource.h>
#include <vtkDecimatePro.h>
#include <vtkSmartPointer.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
 
int main(int, char *[])
{
  vtkSmartPointer<vtkSphereSource> sphereSource =
    vtkSmartPointer<vtkSphereSource>::New();
  sphereSource->Update();
 
  vtkSmartPointer<vtkPolyData> input =
    vtkSmartPointer<vtkPolyData>::New();
  input->ShallowCopy(sphereSource->GetOutput());
 
  std::cout << "Before decimation" << std::endl << "------------" << std::endl;
  std::cout << "There are " << input->GetNumberOfPoints() << " points." << std::endl;
  std::cout << "There are " << input->GetNumberOfPolys() << " polygons." << std::endl;
 
  vtkSmartPointer<vtkDecimatePro> decimate =
    vtkSmartPointer<vtkDecimatePro>::New();
#if VTK_MAJOR_VERSION <= 5
  decimate->SetInputConnection(input->GetProducerPort());
#else
  decimate->SetInputData(input);
#endif
  //decimate->SetTargetReduction(.99); //99% reduction (if there was 100 triangles, now there will be 1)
  decimate->SetTargetReduction(.10); //10% reduction (if there was 100 triangles, now there will be 90)
  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;
 
  vtkSmartPointer<vtkPolyDataMapper> inputMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
#if VTK_MAJOR_VERSION <= 5
  inputMapper->SetInputConnection(input->GetProducerPort());
#else
  inputMapper->SetInputData(input);
#endif
  vtkSmartPointer<vtkActor> inputActor =
    vtkSmartPointer<vtkActor>::New();
  inputActor->SetMapper(inputMapper);
 
  vtkSmartPointer<vtkPolyDataMapper> decimatedMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
#if VTK_MAJOR_VERSION <= 5
  decimatedMapper->SetInputConnection(decimated->GetProducerPort());
#else
  decimatedMapper->SetInputData(decimated);
#endif
  vtkSmartPointer<vtkActor> decimatedActor =
    vtkSmartPointer<vtkActor>::New();
  decimatedActor->SetMapper(decimatedMapper);
 
  // 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(.6, .5, .4);
 
  vtkSmartPointer<vtkRenderer> rightRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(rightRenderer);
  rightRenderer->SetViewport(rightViewport);
  rightRenderer->SetBackground(.4, .5, .6);
 
  // Add the sphere to the left and the cube to the right
  leftRenderer->AddActor(inputActor);
  rightRenderer->AddActor(decimatedActor);
 
  leftRenderer->ResetCamera();
 
  rightRenderer->ResetCamera();
 
  renderWindow->Render();
  interactor->Start();
 
  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
 
PROJECT(Decimation)
 
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
 
add_executable(Decimation MACOSX_BUNDLE Decimation.cxx)
 
if(VTK_LIBRARIES)
  target_link_libraries(Decimation ${VTK_LIBRARIES})
else()
  target_link_libraries(Decimation vtkHybrid vtkWidgets)
endif()

Download and Build Decimation

Click here to download Decimation. and its CMakeLists.txt file.

Once the tarball Decimation.tar has been downloaded and extracted,

cd Decimation/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:

./Decimation

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