# ConvexHullShrinkWrap

VTKExamples/Cxx/PolyData/ConvexHullShrinkWrap

### Description

This example creates a point cloud, and a sphere larger than the point cloud which fully contains the cloud. It then "shrink wraps" the sphere onto the points. This produces approximately a convex hull.

### Code

ConvexHullShrinkWrap.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPolyData.h>
    #include <vtkSphereSource.h>
    #include <vtkPointSource.h>
    #include <vtkSmoothPolyDataFilter.h>
    #include <vtkXMLPolyDataWriter.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetRadius(10);
      sphereSource->SetPhiResolution(50);
      sphereSource->SetThetaResolution(50);
      sphereSource->Update();

      vtkSmartPointer<vtkPointSource> pointSource =
        vtkSmartPointer<vtkPointSource>::New();
      pointSource->SetNumberOfPoints(40);
      pointSource->SetRadius(2);
      pointSource->Update();

      {
      vtkSmartPointer<vtkXMLPolyDataWriter> writer =
        vtkSmartPointer<vtkXMLPolyDataWriter>::New();
      writer->SetFileName("input.vtp");
      writer->SetInputConnection(sphereSource->GetOutputPort());
      writer->Write();
      }

      {
      vtkSmartPointer<vtkXMLPolyDataWriter> writer =
        vtkSmartPointer<vtkXMLPolyDataWriter>::New();
      writer->SetFileName("points.vtp");
      writer->SetInputConnection(pointSource->GetOutputPort());
      writer->Write();
      }

      vtkSmartPointer<vtkSmoothPolyDataFilter> smoothFilter =
        vtkSmartPointer<vtkSmoothPolyDataFilter>::New();
      smoothFilter->SetInputConnection(0, sphereSource->GetOutputPort());
      smoothFilter->SetInputConnection(1, pointSource->GetOutputPort());
      smoothFilter->Update();

      vtkSmartPointer<vtkXMLPolyDataWriter> writer =
        vtkSmartPointer<vtkXMLPolyDataWriter>::New();
      writer->SetFileName("output.vtp");
      writer->SetInputConnection(smoothFilter->GetOutputPort());
      writer->Write();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ConvexHullShrinkWrap)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(ConvexHullShrinkWrap MACOSX_BUNDLE ConvexHullShrinkWrap.cxx )

    target_link_libraries(ConvexHullShrinkWrap ${VTK_LIBRARIES})

### Download and Build ConvexHullShrinkWrap

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

    cd ConvexHullShrinkWrap/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:

    ./ConvexHullShrinkWrap

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.