Hello. I have the same problem,exactly like here http://eat3d.com/forum/questions-and-feedback/how-create-displacement-map But advice, i gave adamzeliasz does not work for me now. xNormal version 3.19.2
I set up smooth shading for both LP and HP meshes, subdivide LP mesh two times, load in xNormal, set up cage, everything looks fine. Normal maps bake perfect, but no matter how many tiimes i subdivide LP mesh, even four times,i still have this black lines issue on displacement texture. It there any solution or tip?