code: function(eyeVertex, horizonEdge) {
        // all the half edges are created in ccw order thus the face is always pointing outside the hull
  
        var face = Face.create(eyeVertex, horizonEdge.tail(), horizonEdge.head());
  
        this.faces.push(face);
  
        // join face.getEdge( - 1 ) with the horizon's opposite edge face.getEdge( - 1 ) = face.getEdge( 2 )
  
        face.getEdge(-1).setTwin(horizonEdge.twin);
  
        return face.getEdge(0); // the half edge whose vertex is the eyeVertex
      }
docs: Creates a face with the vertices 'eyeVertex.point', 'horizonEdge.tail' and 'horizonEdge.head' in CCW order