code: function chain_hull() {
     var a = arguments;
     var j = 0, closed = false;
  
     if(a[j].closed!==undefined) 
        closed = a[j++].closed;
     
     if(a[j].length) 
        a = a[j];
  
     var h = []; var n = a.length-(closed?0:1); 
     for(var i=0; i<n; i++) {
        h.push(hull(a[i],a[(i+1)%a.length]));
     }
     return union(h);
  }
docs: "Whosa whatsis" suggested "Chain Hull" as described at https://plus.google.com/u/0/105535247347788377245/posts/aZGXKFX1ACN essentially hull A+B, B+C, C+D and then union those