GVF_BY_XU

代码说明：

  XU等人做的关于GVF的小DEMO，里面比较了和传统蛇模型的不同之处以及GVF的优点，可以借此做些改进(XU and other people to do about the GVF small DEMO, which compared the traditional snake model and the differences as well as the advantages of GVF can be done to improve)