examples/vr_crop/quickhull.js
function(target, vertex) {
      vertex.prev = target.prev;
      vertex.next = target;

      if (vertex.prev === null) {
        this.head = vertex;
      } else {
        vertex.prev.next = vertex;
      }

      target.prev = vertex;

      return this;
    }
function(target, vertex) {
      vertex.prev = target.prev;
      vertex.next = target;

      if (vertex.prev === null) {
        this.head = vertex;
      } else {
        vertex.prev.next = vertex;
      }

      target.prev = vertex;

      return this;
    }
Inserts a vertex before the target vertex