GreedyTerrainDecimation

VTKExamples/Cxx/PolyData/GreedyTerrainDecimation


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See (CSharp)

Question

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Code

GreedyTerrainDecimation.cxx

#include <vtkPolyData.h>
#include <vtkProperty.h>
#include <vtkMath.h>
#include <vtkSmartPointer.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkImageData.h>
#include <vtkGreedyTerrainDecimation.h>

int main(int, char *[])
{
  // Create an image
  vtkSmartPointer<vtkImageData> image =
    vtkSmartPointer<vtkImageData>::New();
  image->SetDimensions(3,3,1);
  image->AllocateScalars(VTK_UNSIGNED_CHAR,1);

  int dims[3];
  image->GetDimensions(dims);
  for(int i = 0; i < dims[0]; i++)
  {
    for(int j = 0; j < dims[1]; j++)
    {
      unsigned char* pixel = static_cast<unsigned char*>(image->GetScalarPointer(i,j,0));
      //pixel[0] = vtkMath::Round(vtkMath::Random(0, 255));
      pixel[0] = vtkMath::Round(vtkMath::Random(0, 1));
    }
  }

  vtkSmartPointer<vtkGreedyTerrainDecimation> decimation =
    vtkSmartPointer<vtkGreedyTerrainDecimation>::New();
  decimation->SetInputData(image);
  decimation->Update();

  // Visualize
  vtkSmartPointer<vtkPolyDataMapper> mapper =
      vtkSmartPointer<vtkPolyDataMapper>::New();
  mapper->SetInputConnection(decimation->GetOutputPort());

  vtkSmartPointer<vtkActor> actor =
      vtkSmartPointer<vtkActor>::New();
  actor->SetMapper(mapper);
  actor->GetProperty()->SetInterpolationToFlat();
  actor->GetProperty()->EdgeVisibilityOn();
  actor->GetProperty()->SetEdgeColor(1,0,0);

  vtkSmartPointer<vtkRenderer> renderer =
      vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renderWindow =
      vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
      vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);

  renderer->AddActor(actor);
  renderer->SetBackground(1,1,1); // Background color white

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

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(GreedyTerrainDecimation)

find_package(VTK COMPONENTS 
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersHybrid
  vtkInteractionStyle
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping GreedyTerrainDecimation: ${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(GreedyTerrainDecimation MACOSX_BUNDLE GreedyTerrainDecimation.cxx )
  target_link_libraries(GreedyTerrainDecimation PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(GreedyTerrainDecimation MACOSX_BUNDLE GreedyTerrainDecimation.cxx )
  target_link_libraries(GreedyTerrainDecimation PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS GreedyTerrainDecimation
    MODULES ${VTK_LIBRARIES}
    )
endif () 

Download and Build GreedyTerrainDecimation

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

cd GreedyTerrainDecimation/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:

./GreedyTerrainDecimation

WINDOWS USERS

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