Your low poly should have all UV border edges set as hard edges. This should resolve your artifacting, provided you are using a cage. You should probably grab this MEL script from Jon Stewart. It automatically hardens UV borders. http://jonathonstewart.blogspot.com/search/label/Scripts
I tryed that but it doesn't work.For cage,I just duplicated the low poly and imported it into xnormal as a cage(of course adjusted the vetex to make it be a cage),and the cage is all soft edges. Is this responsible for the problem? I just found that the second picture's link is broken so I repaired it.Now you can see the…