function HalfEdge(vertex, face) {
    this.vertex = vertex;
    this.prev = null;
    this.next = null;
    this.twin = null;
    this.face = face;
  }
function HalfEdge(vertex, face) {
    this.vertex = vertex;
    this.prev = null;
    this.next = null;
    this.twin = null;
    this.face = face;
  }
function HalfEdge ( vertex , face ) { this . vertex = vertex ; this . prev = null ; this . next = null ; this . twin = null ; this . face = face ; }
Entity for a Doubly-Connected Edge List (DCEL).
Entity for a Doubly - Connected Edge List ( DCEL ) .