title: A point CGAL transformation between two coordinate systems
body: <p>Using CGAL, how to determine the coordinates of a point from one system to another? 
  Suppose we have:  </p>
  
  <pre><code>Point p1(1.0, 1.0, 1.0);  
  </code></pre>
  
  <p>which is expressed in the typical coordinate system determined by the vectors:  </p>
  
  <pre><code>Vector vx1(1.0, 0.0, 0.0);  
  Vector vy1(0.0, 1.0, 0.0);  
  Vector vz1(0.0, 0.0, 1.0);  
  </code></pre>
  
  <p>representing the coordinate axis. 
  Now taking the vectors of the coordinate axis of another system, how do I determine the coordinates of p1 in that system?  </p>
  
  <pre><code>Vector vx2(1.0, -1.0, -1.0);  
  Vector vy2(-1.0, 1.0, -1.0);  
  Vector vz2(1.0, 1.0, 0.0);  
  </code></pre>
  
  <p>I think I must determine a matrix for pass it to an object of <code>CGAL::Aff_transformation_3</code>, but I don't know how.  </p>
  
  <pre><code>Vector p2 = p1.transform(??);  
  </code></pre>
  
  <p>Any tips?</p>