code: function ReferenceFace() {
    this.i1, this.i2; // int
    this.v1, this.v2; // v
    this.normal = Vec2.zero();
    this.sideNormal1 = Vec2.zero();
    this.sideOffset1; // float
    this.sideNormal2 = Vec2.zero();
    this.sideOffset2; // float
  }
docs: Reference face used for clipping