# Delaunay2D

vtk-examples/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

### Code¶

Delaunay2D.cxx

#include <vtkActor.h>
#include <vtkCellArray.h>
#include <vtkCellLocator.h>
#include <vtkDelaunay2D.h>
#include <vtkLine.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkTriangle.h>
#include <vtkVertexGlyphFilter.h>

int main(int, char*[])
{
vtkNew<vtkNamedColors> colors;

// Create a set of heights on a grid.
// This is often called a "terrain map".
vtkNew<vtkPoints> points;

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
vtkNew<vtkPolyData> polydata;
polydata->SetPoints(points);

// Triangulate the grid points
vtkNew<vtkDelaunay2D> delaunay;
delaunay->SetInputData(polydata);

// Visualize
vtkNew<vtkPolyDataMapper> meshMapper;
meshMapper->SetInputConnection(delaunay->GetOutputPort());

vtkNew<vtkActor> meshActor;
meshActor->SetMapper(meshMapper);
meshActor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
meshActor->GetProperty()->EdgeVisibilityOn();

vtkNew<vtkVertexGlyphFilter> glyphFilter;
glyphFilter->SetInputData(polydata);

vtkNew<vtkPolyDataMapper> pointMapper;
pointMapper->SetInputConnection(glyphFilter->GetOutputPort());

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

vtkNew<vtkRenderer> renderer;
vtkNew<vtkRenderWindow> renderWindow;
vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
renderWindowInteractor->SetRenderWindow(renderWindow);

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

renderWindow->SetWindowName("Delaunay2D");
renderWindow->Render();
renderWindowInteractor->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(Delaunay2D)

find_package(VTK COMPONENTS
CommonColor
CommonCore
CommonDataModel
FiltersCore
FiltersGeneral
InteractionStyle
RenderingContextOpenGL2
RenderingCore
RenderingFreeType
RenderingGL2PSOpenGL2
RenderingOpenGL2
)

if (NOT VTK_FOUND)
message(FATAL_ERROR "Delaunay2D: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
target_link_libraries(Delaunay2D PRIVATE ${VTK_LIBRARIES} ) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS Delaunay2D MODULES${VTK_LIBRARIES}
)


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.