ctor(options) {
    // initialize properties that may be required in init
    this.boids = [];
    this.obstacles = [];
    this.velocity = cc.p();
    this.targetVelocity = cc.p();
    this.randomRange = cc.p();
    this._lastPosition = cc.p();
    this._utilPoint1 = cc.p();
    this._utilPoint2 = cc.p();
    this._utilPoint3 = cc.p();
    this._utilPoint4 = cc.p();

    // do super ctor
    this._super(options);
  }
*************************************************************************
 FXFlockSprite
 var FXFlockSprite = FXProjectileSprite
 FXFlockSprite.create()
**************************************************************************