PointsProjectedHull
VTKExamples/Cxx/PolyData/PointsProjectedHull
Description¶
This example demonstrates how to find the 2D convex hull of a point set projected onto any of the coordinate planes (in this case, we choose the YZ plane (projection along the x axis) ).
Code¶
PointsProjectedHull.cxx
#include <vtkVersion.h> #include <vtkSmartPointer.h> #include <vtkActor.h> #include <vtkCamera.h> #include <vtkCellArray.h> #include <vtkPointSource.h> #include <vtkPoints.h> #include <vtkPointsProjectedHull.h> #include <vtkPolyData.h> #include <vtkPolyDataMapper.h> #include <vtkPolyLine.h> #include <vtkRenderWindow.h> #include <vtkRenderWindowInteractor.h> #include <vtkRenderer.h> #include <vtkXMLPolyDataWriter.h> int main(int, char *[]) { vtkSmartPointer<vtkPointSource> pointSource = vtkSmartPointer<vtkPointSource>::New(); pointSource->SetNumberOfPoints(40); pointSource->Update(); //setup actor and mapper vtkSmartPointer<vtkPolyDataMapper> pointMapper = vtkSmartPointer<vtkPolyDataMapper>::New(); pointMapper->SetInputConnection(pointSource->GetOutputPort()); vtkSmartPointer<vtkActor> pointActor = vtkSmartPointer<vtkActor>::New(); pointActor->SetMapper(pointMapper); vtkSmartPointer<vtkPointsProjectedHull> points = vtkSmartPointer<vtkPointsProjectedHull>::New(); points->DeepCopy(pointSource->GetOutput()->GetPoints()); int xSize = points->GetSizeCCWHullX(); std::cout << "xSize: " << xSize << std::endl; double* pts = new double[xSize*2]; points->GetCCWHullX(pts,xSize); vtkSmartPointer<vtkPoints> xHullPoints = vtkSmartPointer<vtkPoints>::New(); for(int i = 0; i < xSize; i++) { double yval = pts[2*i]; double zval = pts[2*i + 1]; std::cout << "(y,z) value of point " << i << " : (" << yval << " , " << zval << ")" << std::endl; xHullPoints->InsertNextPoint(0.0, yval, zval); } // Insert the first point again to close the loop xHullPoints->InsertNextPoint(0.0, pts[0], pts[1]); // Display the x hull vtkSmartPointer<vtkPolyLine> xPolyLine = vtkSmartPointer<vtkPolyLine>::New(); xPolyLine->GetPointIds()->SetNumberOfIds(xHullPoints->GetNumberOfPoints()); for(vtkIdType i = 0; i < xHullPoints->GetNumberOfPoints(); i++) { xPolyLine->GetPointIds()->SetId(i,i); } // Create a cell array to store the lines in and add the lines to it vtkSmartPointer<vtkCellArray> cells = vtkSmartPointer<vtkCellArray>::New(); cells->InsertNextCell(xPolyLine); // Create a polydata to store everything in vtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New(); // Add the points to the dataset polyData->SetPoints(xHullPoints); // Add the lines to the dataset polyData->SetLines(cells); // Setup actor and mapper vtkSmartPointer<vtkPolyDataMapper> xHullMapper = vtkSmartPointer<vtkPolyDataMapper>::New(); #if VTK_MAJOR_VERSION <= 5 xHullMapper->SetInput(polyData); #else xHullMapper->SetInputData(polyData); #endif vtkSmartPointer<vtkActor> xHullActor = vtkSmartPointer<vtkActor>::New(); xHullActor->SetMapper(xHullMapper); // Setup render window, renderer, 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); renderer->AddActor(xHullActor); renderer->AddActor(pointActor); // Rotate camera renderer->GetActiveCamera()->Azimuth(90); renderer->ResetCamera(); renderWindow->Render(); renderWindowInteractor->Start(); return EXIT_SUCCESS; }
CMakeLists.txt¶
cmake_minimum_required(VERSION 2.8) PROJECT(PointsProjectedHull) find_package(VTK REQUIRED) include(${VTK_USE_FILE}) add_executable(PointsProjectedHull MACOSX_BUNDLE PointsProjectedHull.cxx) target_link_libraries(PointsProjectedHull ${VTK_LIBRARIES})
Download and Build PointsProjectedHull¶
Danger
The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.
Click here to download PointsProjectedHull and its CMakeLists.txt file. Once the tarball PointsProjectedHull.tar has been downloaded and extracted,
cd PointsProjectedHull/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:
./PointsProjectedHull
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.