Construct a convex hull polygon for a plane model

.. _convex_hull_2d:

Construct a convex hull polygon for a plane model

In this tutorial we will learn how to calculate a simple 2D convex hull polygon for a set of points supported by a plane.

The following video shows a demonstration of the code given below on the test dataset table_scene_mug_stereo_textured.pcd <https://raw.github.com/PointCloudLibrary/data/master/tutorials/table_scene_mug_stereo_textured.pcd>_.

.. raw:: html

<iframe title="Acquiring the convex hull of a planar surface" width="480" height="390" src="https://www.youtube.com/embed/J9CjWDgPDTM?rel=0" frameborder="0" allowfullscreen></iframe>

The code

First, download the dataset table_scene_mug_stereo_textured.pcd <https://raw.github.com/PointCloudLibrary/data/master/tutorials/table_scene_mug_stereo_textured.pcd>_ and save it somewhere to disk.

Then, create a file, let's say, convex_hull_2d.cpp in your favorite editor, and place the following inside it:

.. literalinclude:: sources/convex_hull_2d/convex_hull_2d.cpp :language: cpp :linenos:

The explanation

The only interesting part is in the lines below, where the ConvexHull object gets created and the reconstruction is performed:

.. literalinclude:: sources/convex_hull_2d/convex_hull_2d.cpp :language: cpp :lines: 49-52

Compiling and running the program

Add the following lines to your CMakeLists.txt file:

.. literalinclude:: sources/convex_hull_2d/CMakeLists.txt :language: cmake :linenos:

After you have made the executable, you can run it. Simply do::

$ ./convex_hull_2d

You will see something similar to::

PointCloud after filtering has: 139656 data points. Convex hull has: 30 data points.