title: Create concave polygon passing through all given points
body: <p>Given a set of points, I want to create a concave non-intersecting polygon using these points. A convex hull would negate the concave part, while arranging them by x/y coordinates or angles from centre would create spiky artefacts. Is there a simple way to do this?</p>
  
  <p>An example of the kind of polygon I want to create:</p>
  
  <p><a href="https://i.stack.imgur.com/rppJt.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rppJt.png" alt="example"></a></p>