VTK/Examples/Cxx/PolyData/ConvexHullShrinkWrap

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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.

Using ParaView to view to the results. Left is the sphere, centre the point cloud and right the result of wrapping the sphere around the point cloud.

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;
}

Please try the new VTKExamples website.

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)

if(VTK_LIBRARIES)
  target_link_libraries(ConvexHullShrinkWrap ${VTK_LIBRARIES})
else()
  target_link_libraries(ConvexHullShrinkWrap vtkHybrid vtkWidgets)
endif()

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.


I'm not sure the current code does what it claims to!?