ConstrainedDelaunay2D
VTKExamples/Cxx/Filtering/ConstrainedDelaunay2D
Description¶
Perform a 2D Delaunay triangulation respecting a specified boundary. This examples constructs a 10x10 grid of points. It then defines a polygon that uses the points in the grid. We want to triangulate all of the points except the region inside the boundary of the polygon. We expect a rectangular hole of size 4x3 in the resulting triangulated plane.
Code¶
ConstrainedDelaunay2D.cxx
#include <vtkVersion.h> #include <vtkCellArray.h> #include <vtkProperty.h> #include <vtkPolyDataMapper.h> #include <vtkActor.h> #include <vtkPoints.h> #include <vtkPolyData.h> #include <vtkPolygon.h> #include <vtkSmartPointer.h> #include <vtkDelaunay2D.h> #include <vtkMath.h> #include <vtkRenderer.h> #include <vtkRenderWindow.h> #include <vtkRenderWindowInteractor.h> int main(int, char *[]) { // Generate a 10 x 10 grid of points vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New(); for(unsigned int x = 0; x < 10; x++) { for(unsigned int y = 0; y < 10; y++) { points->InsertNextPoint(x + vtkMath::Random(-.25, .25), y + vtkMath::Random(-.25,.25), 0); } } vtkSmartPointer<vtkPolyData> aPolyData = vtkSmartPointer<vtkPolyData>::New(); aPolyData->SetPoints(points); // Create a cell array to store the polygon in vtkSmartPointer<vtkCellArray> aCellArray = vtkSmartPointer<vtkCellArray>::New(); // Define a polygonal hole with a clockwise polygon vtkSmartPointer<vtkPolygon> aPolygon = vtkSmartPointer<vtkPolygon>::New(); aPolygon->GetPointIds()->InsertNextId(22); aPolygon->GetPointIds()->InsertNextId(23); aPolygon->GetPointIds()->InsertNextId(24); aPolygon->GetPointIds()->InsertNextId(25); aPolygon->GetPointIds()->InsertNextId(35); aPolygon->GetPointIds()->InsertNextId(45); aPolygon->GetPointIds()->InsertNextId(44); aPolygon->GetPointIds()->InsertNextId(43); aPolygon->GetPointIds()->InsertNextId(42); aPolygon->GetPointIds()->InsertNextId(32); aCellArray->InsertNextCell(aPolygon); // Create a polydata to store the boundary. The points must be the // same as the points we will triangulate. vtkSmartPointer<vtkPolyData> boundary = vtkSmartPointer<vtkPolyData>::New(); boundary->SetPoints(aPolyData->GetPoints()); boundary->SetPolys(aCellArray); // Triangulate the grid points vtkSmartPointer<vtkDelaunay2D> delaunay = vtkSmartPointer<vtkDelaunay2D>::New(); #if VTK_MAJOR_VERSION <= 5 delaunay->SetInput(aPolyData); delaunay->SetSource(boundary); #else delaunay->SetInputData(aPolyData); delaunay->SetSourceData(boundary); #endif delaunay->Update(); // Visualize vtkSmartPointer<vtkPolyDataMapper> meshMapper = vtkSmartPointer<vtkPolyDataMapper>::New(); meshMapper->SetInputConnection(delaunay->GetOutputPort()); vtkSmartPointer<vtkActor> meshActor = vtkSmartPointer<vtkActor>::New(); meshActor->SetMapper(meshMapper); //meshActor->GetProperty()->SetEdgeColor(0,0,1); // Why aren't the edges aren't visible unless we set the representation to wireframe? //meshActor->GetProperty()->SetInterpolationToFlat(); meshActor->GetProperty()->SetRepresentationToWireframe(); vtkSmartPointer<vtkPolyDataMapper> boundaryMapper = vtkSmartPointer<vtkPolyDataMapper>::New(); #if VTK_MAJOR_VERSION <= 5 boundaryMapper->SetInputConnection(boundary->GetProducerPort()); #else boundaryMapper->SetInputData(boundary); #endif vtkSmartPointer<vtkActor> boundaryActor = vtkSmartPointer<vtkActor>::New(); boundaryActor->SetMapper(boundaryMapper); boundaryActor->GetProperty()->SetColor(1,0,0); // Create a renderer, render window, and interactor vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New(); vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New(); renderWindow->AddRenderer(renderer); vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = vtkSmartPointer<vtkRenderWindowInteractor>::New(); renderWindowInteractor->SetRenderWindow(renderWindow); // Add the actor to the scene renderer->AddActor(meshActor); renderer->AddActor(boundaryActor); renderer->SetBackground(.3, .6, .3); // Background color green // Render and interact renderWindow->Render(); renderWindowInteractor->Start(); return EXIT_SUCCESS; }
CMakeLists.txt¶
cmake_minimum_required(VERSION 2.8) PROJECT(ConstrainedDelaunay2D) find_package(VTK REQUIRED) include(${VTK_USE_FILE}) add_executable(ConstrainedDelaunay2D MACOSX_BUNDLE ConstrainedDelaunay2D.cxx) target_link_libraries(ConstrainedDelaunay2D ${VTK_LIBRARIES})
Download and Build ConstrainedDelaunay2D¶
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Click here to download ConstrainedDelaunay2D and its CMakeLists.txt file. Once the tarball ConstrainedDelaunay2D.tar has been downloaded and extracted,
cd ConstrainedDelaunay2D/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:
./ConstrainedDelaunay2D
WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.