 <tt>TH2Poly</tt> histogram, is a <tt>TH2PolyBin</tt> object.
<tt>TH2PolyBin</tt> is a very simple class containing the vertices, stored
as <tt>TGraph</tt>s and <tt>TMultiGraph</tt>s, and the content of the polygonal
bin.
<p>
Bins are defined using one of the <tt>AddBin()</tt> methods. The bins definition
should be done before filling.
<p>
<tt>TH2Poly</tt> implements a partitioning algorithm to speed up bins' filling.
The following very simple macro shows how to build and fill a <tt>TH2Poly</tt>:
<pre>
{
  