ShepardMethod

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkCellArray.h>
#include <vtkColorTransferFunction.h>
#include <vtkContourFilter.h>
#include <vtkFloatArray.h>
#include <vtkPointData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkShepardMethod.h>
#include <vtkSmartPointer.h>
#include <vtkUnsignedCharArray.h>
#include <vtkVertexGlyphFilter.h>

// For compatibility with new VTK generic data arrays
#ifdef vtkGenericDataArray_h
#define InsertNextTupleValue InsertNextTypedTuple
#endif

int main(int, char *[])
{
  // Create a set of vertices (polydata)
  vtkSmartPointer<vtkPoints> points =
      vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint(100.0, 0.0, 0.0);
  points->InsertNextPoint(300.0, 0.0, 0.0);

  // Setup colors
  unsigned char white[3] = {255, 255, 255};
  unsigned char black[3] = {0, 0, 0};

  vtkSmartPointer<vtkUnsignedCharArray> vertexColors =
    vtkSmartPointer<vtkUnsignedCharArray>::New();
  vertexColors->SetNumberOfComponents(3);
  vertexColors->SetName("Colors");
  vertexColors->InsertNextTupleValue(black);
  vertexColors->InsertNextTupleValue(white);

  // Create a scalar array for the pointdata, each value represents the distance
  // of the vertices from the first vertex
  vtkSmartPointer<vtkFloatArray> values =
      vtkSmartPointer<vtkFloatArray>::New();
  values->SetNumberOfComponents(1);
  values->SetName("Values");
  values->InsertNextValue(0.0);
  values->InsertNextValue(1.0);

  // We must make two objects, because the ShepardMethod uses the ActiveScalars, as does the renderer!
  vtkSmartPointer<vtkPolyData> polydataToProcess =
      vtkSmartPointer<vtkPolyData>::New();
  polydataToProcess->SetPoints(points);
  polydataToProcess->GetPointData()->SetScalars(values);

  vtkSmartPointer<vtkPolyData> polydataToVisualize =
    vtkSmartPointer<vtkPolyData>::New();
  polydataToVisualize->SetPoints(points);
  polydataToVisualize->GetPointData()->SetScalars(vertexColors);

  vtkSmartPointer<vtkVertexGlyphFilter> vertexGlyphFilter =
    vtkSmartPointer<vtkVertexGlyphFilter>::New();
  vertexGlyphFilter->AddInputData(polydataToVisualize);
  vertexGlyphFilter->Update();

  //Create a mapper and actor
  vtkSmartPointer<vtkPolyDataMapper> vertsMapper =
      vtkSmartPointer<vtkPolyDataMapper>::New();
  //vertsMapper->ScalarVisibilityOff();
  vertsMapper->SetInputConnection(vertexGlyphFilter->GetOutputPort());

  vtkSmartPointer<vtkActor> vertsActor =
    vtkSmartPointer<vtkActor>::New();
  vertsActor->SetMapper(vertsMapper);
  vertsActor->GetProperty()->SetColor(1,0,0);
  vertsActor->GetProperty()->SetPointSize(3);

  // Create a shepard filter to interpolate the vertices over a regularized image grid
  vtkSmartPointer<vtkShepardMethod> shepard = vtkSmartPointer<vtkShepardMethod>::New();
  shepard->SetInputData(polydataToProcess);
  shepard->SetSampleDimensions(2,2,2);
  shepard->SetModelBounds(100,300,-10,10,-10,10);
  shepard->SetMaximumDistance(1);

  // Contour the shepard generated image at 3 isovalues
  // The accuracy of the results are highly dependent on how the shepard filter is set up
  vtkSmartPointer<vtkContourFilter> contourFilter = vtkSmartPointer<vtkContourFilter>::New();
  contourFilter->SetNumberOfContours(3);
  contourFilter->SetValue(0, 0.25);
  contourFilter->SetValue(1, 0.50);
  contourFilter->SetValue(2, 0.75);
  contourFilter->SetInputConnection(shepard->GetOutputPort());
  contourFilter->Update();

  //Create a mapper and actor for the resulting isosurfaces
  vtkSmartPointer<vtkPolyDataMapper> contourMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  contourMapper->SetInputConnection(contourFilter->GetOutputPort());
  contourMapper->ScalarVisibilityOn();
  contourMapper->SetColorModeToMapScalars();

  vtkSmartPointer<vtkActor> contourActor =
    vtkSmartPointer<vtkActor>::New();
  contourActor->SetMapper(contourMapper);
  contourActor->GetProperty()->SetAmbient(1);
  contourActor->GetProperty()->SetSpecular(0);
  contourActor->GetProperty()->SetDiffuse(0);

  // Report the results of the interpolation
  double *range = contourFilter->GetOutput()->GetScalarRange();

  std::cout << "Shepard interpolation:" << std::endl;
  std::cout << "contour output scalar range: " << range[0] << ", " << range[1] << std::endl;

  vtkIdType nCells = contourFilter->GetOutput()->GetNumberOfCells();
  double bounds[6];
  for( vtkIdType i = 0; i < nCells; ++i )
  {
    if(i%2) // each isosurface value only has 2 cells to report on the odd ones
    {
      contourFilter->GetOutput()->GetCellBounds(i,bounds);
      std::cout << "cell " << i << ", x position: " << bounds[0] << std::endl;
    }
  }

  // Create a transfer function to color the isosurfaces
  vtkSmartPointer<vtkColorTransferFunction> lut =
    vtkSmartPointer<vtkColorTransferFunction>::New();
  lut->SetColorSpaceToRGB();
  lut->AddRGBPoint(range[0],0,0,0);//black
  lut->AddRGBPoint(range[1],1,1,1);//white
  lut->SetScaleToLinear();

  contourMapper->SetLookupTable( lut );

  // Create a renderer, render window and interactor
  vtkSmartPointer<vtkRenderer> renderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderer->GradientBackgroundOn();
  renderer->SetBackground(0,0,1);
  renderer->SetBackground2(1,0,1);

  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  renderer->AddActor(contourActor);
  renderer->AddActor(vertsActor);

  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);

  // Position the camera so that the image produced is viewable
  vtkCamera* camera = renderer->GetActiveCamera();
  camera->SetPosition(450, 100, 100);
  camera->SetFocalPoint(200, 0, 0);
  camera->SetViewUp(0, 0, 1);

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

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ShepardMethod)

find_package(VTK COMPONENTS 
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkFiltersCore
  vtkvtkFiltersGeneral
  vtkvtkImagingHybrid
  vtkvtkInteractionStyle
  vtkvtkRenderingContextOpenGL2
  vtkvtkRenderingCore
  vtkvtkRenderingFreeType
  vtkvtkRenderingGL2PSOpenGL2
  vtkvtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping ShepardMethod: ${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(ShepardMethod MACOSX_BUNDLE ShepardMethod.cxx )
  target_link_libraries(ShepardMethod PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(ShepardMethod MACOSX_BUNDLE ShepardMethod.cxx )
  target_link_libraries(ShepardMethod PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS ShepardMethod
    MODULES ${VTK_LIBRARIES}
    )
endif ()

cd ShepardMethod/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./ShepardMethod