title: Feature detection with patent-free descriptors
body: <p>I need the feature detection algorithm. I'm fed up surfing on the web finding nothing but SURF example and <em>hints</em> how to do that, but I did not find an example with other than patented descriptors like SIFT or SURF. </p>
  
  <p>Can anybody write an example of using the <strong>free</strong> feature detection algorithm (like ORB/BRISK [as far as I understood SURF and FLAAN are <strong>nonfree</strong>]) ?</p>
  
  <p>I'm using OpenCV 3.0.0.</p>