EdgePoints

VTKExamples/Cxx/Visualization/EdgePoints


Description

This example uses vtkEdgePoints to generat a set of points that lie on an isosurface. Points are generated along the edges of cells that starddle the given iso value. Unlike vtkMarchingCubes it does not generate normals at the points.

Question

If you have a simple question about this example contact us at VTKExamplesProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

Code

EdgePoints.cxx

#include <vtkSmartPointer.h>
#include <vtkEdgePoints.h>

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkMetaImageReader.h>
#include <vtkNamedColors.h>
#include <vtkOutlineFilter.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>

#include <array>
#include <string>

int main (int argc, char *argv[])
{
  if (argc < 2)
  {
    cout << "Usage: " << argv[0] << " file.mhd" << endl;
    return EXIT_FAILURE;
  }

  double isoValue = 0.0;
    if (argc > 2)
    {
      isoValue = std::stod(std::string(argv[2]));
    }
  vtkSmartPointer<vtkNamedColors> colors =
    vtkSmartPointer<vtkNamedColors>::New();

  std::array<unsigned char , 4> isoColor{{255, 125, 64}};
    colors->SetColor("IsoColor", isoColor.data());
  std::array<unsigned char , 4> bkg{{51, 77, 102, 255}};
    colors->SetColor("BkgColor", bkg.data());

  vtkSmartPointer<vtkRenderer> aRenderer =
    vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renWin =
    vtkSmartPointer<vtkRenderWindow>::New();
  renWin->AddRenderer(aRenderer);

  vtkSmartPointer<vtkRenderWindowInteractor> iren =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  iren->SetRenderWindow(renWin);

  vtkSmartPointer<vtkMetaImageReader> reader =
    vtkSmartPointer<vtkMetaImageReader>::New();
  reader->SetFileName (argv[1]);

  vtkSmartPointer<vtkEdgePoints> isoExtractor =
    vtkSmartPointer<vtkEdgePoints>::New();
  isoExtractor->SetInputConnection(reader->GetOutputPort());
  isoExtractor->SetValue(isoValue);

  vtkSmartPointer<vtkPolyDataMapper> isoMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  isoMapper->SetInputConnection(isoExtractor->GetOutputPort());
  isoMapper->ScalarVisibilityOff();

  vtkSmartPointer<vtkActor> iso =
    vtkSmartPointer<vtkActor>::New();
  iso->SetMapper(isoMapper);
  iso->GetProperty()->SetDiffuseColor(colors->GetColor3d("IsoColor").GetData());

  // An outline provides context around the data.
  //
  vtkSmartPointer<vtkOutlineFilter> outlineData =
    vtkSmartPointer<vtkOutlineFilter>::New();
  outlineData->SetInputConnection(reader->GetOutputPort());

  vtkSmartPointer<vtkPolyDataMapper> mapOutline =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  mapOutline->SetInputConnection(outlineData->GetOutputPort());

  vtkSmartPointer<vtkActor> outline =
    vtkSmartPointer<vtkActor>::New();
  outline->SetMapper(mapOutline);
  outline->GetProperty()->SetColor(colors->GetColor3d("Black").GetData());

  // It is convenient to create an initial view of the data. The FocalPoint
  // and Position form a vector direction. Later on (ResetCamera() method)
  // this vector is used to position the camera to look at the data in
  // this direction.
  vtkSmartPointer<vtkCamera> aCamera =
    vtkSmartPointer<vtkCamera>::New();
  aCamera->SetViewUp (0, 0, -1);
  aCamera->SetPosition (0, -1, 0);
  aCamera->SetFocalPoint (0, 0, 0);
  aCamera->ComputeViewPlaneNormal();
  aCamera->Azimuth(30.0);
  aCamera->Elevation(30.0);

  // Actors are added to the renderer. An initial camera view is created.
  // The Dolly() method moves the camera towards the FocalPoint,
  // thereby enlarging the image.
  aRenderer->AddActor(outline);
  aRenderer->AddActor(iso);
  aRenderer->SetActiveCamera(aCamera);
  aRenderer->ResetCamera ();
  aCamera->Dolly(1.5);

  // Set a background color for the renderer and set the size of the
  // render window (expressed in pixels).
  aRenderer->SetBackground(colors->GetColor3d("BkgColor").GetData());
  renWin->SetSize(640, 480);

  // Note that when camera movement occurs (as it does in the Dolly()
  // method), the clipping planes often need adjusting. Clipping planes
  // consist of two planes: near and far along the view direction. The
  // near plane clips out objects in front of the plane; the far plane
  // clips out objects behind the plane. This way only what is drawn
  // between the planes is actually rendered.
  aRenderer->ResetCameraClippingRange ();

  // Initialize the event loop and then start it.
  renWin->Render();
  iren->Initialize();
  iren->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(EdgePoints)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkFiltersGeneral
  vtkFiltersModeling
  vtkIOImage
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping EdgePoints: ${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(EdgePoints MACOSX_BUNDLE EdgePoints.cxx )
  target_link_libraries(EdgePoints PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(EdgePoints MACOSX_BUNDLE EdgePoints.cxx )
  target_link_libraries(EdgePoints PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS EdgePoints
    MODULES ${VTK_LIBRARIES}
    )
endif () 

Download and Build EdgePoints

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

cd EdgePoints/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:

./EdgePoints

WINDOWS USERS

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