examples/vr_crop/quickhull.js
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).