Delaunay2D

VTKExamples/Cxx/Filtering/Delaunay2D


Description

This example generates a set of points aligned with an XY grid with random heights (z values). The Delaunay2D filter "magically" knows how to triangulate this type of point set because it projects the points by default onto the XY axis and then performs a 2D Delaunay triangulation. The result is a mesh on the input points.

Other Languages

See (Python), (Java)

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

Delaunay2D.cxx

#include <vtkSmartPointer.h>
#include <vtkDelaunay2D.h>

#include <vtkCellArray.h>
#include <vtkPoints.h>
#include <vtkTriangle.h>
#include <vtkPolyData.h>
#include <vtkPointData.h>
#include <vtkLine.h>
#include <vtkCellLocator.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkProperty.h>
#include <vtkVertexGlyphFilter.h>
#include <vtkNamedColors.h>

int main(int, char *[])
{
  // Create a set of heighs on a grid.
  // This is often called a "terrain map".
  vtkSmartPointer<vtkPoints> points =
    vtkSmartPointer<vtkPoints>::New();

  unsigned int GridSize = 10;
  for(unsigned int x = 0; x < GridSize; x++)
  {
    for(unsigned int y = 0; y < GridSize; y++)
    {
        points->InsertNextPoint(x, y, (x+y)/(y+1));
    }
  }

  // Add the grid points to a polydata object
  vtkSmartPointer<vtkPolyData> polydata =
    vtkSmartPointer<vtkPolyData>::New();
  polydata->SetPoints(points);

  // Triangulate the grid points
  vtkSmartPointer<vtkDelaunay2D> delaunay =
  vtkSmartPointer<vtkDelaunay2D>::New();
  delaunay->SetInputData(polydata);

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

  vtkSmartPointer<vtkPolyDataMapper> meshMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  meshMapper->SetInputConnection(delaunay->GetOutputPort());

  vtkSmartPointer<vtkActor> meshActor =
    vtkSmartPointer<vtkActor>::New();
  meshActor->SetMapper(meshMapper);
  meshActor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
  meshActor->GetProperty()->EdgeVisibilityOn();

  vtkSmartPointer<vtkVertexGlyphFilter> glyphFilter =
    vtkSmartPointer<vtkVertexGlyphFilter>::New();
  glyphFilter->SetInputData(polydata);

  vtkSmartPointer<vtkPolyDataMapper> pointMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  pointMapper->SetInputConnection(glyphFilter->GetOutputPort());

  vtkSmartPointer<vtkActor> pointActor =
    vtkSmartPointer<vtkActor>::New();
  pointActor->GetProperty()->SetColor(colors->GetColor3d("Tomato").GetData());
  pointActor->GetProperty()->SetPointSize(5);
  pointActor->SetMapper(pointMapper);

  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(meshActor);
  renderer->AddActor(pointActor);
  renderer->SetBackground(colors->GetColor3d("Mint").GetData());

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

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(Delaunay2D)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkFiltersGeneral
  vtkInteractionStyle
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping Delaunay2D: ${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(Delaunay2D MACOSX_BUNDLE Delaunay2D.cxx )
  target_link_libraries(Delaunay2D PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(Delaunay2D MACOSX_BUNDLE Delaunay2D.cxx )
  target_link_libraries(Delaunay2D PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS Delaunay2D
    MODULES ${VTK_LIBRARIES}
    )
endif () 

Download and Build Delaunay2D

Click here to download Delaunay2D and its CMakeLists.txt file. Once the tarball Delaunay2D.tar has been downloaded and extracted,

cd Delaunay2D/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:

./Delaunay2D

WINDOWS USERS

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