normal decal

I got the problem in Blender, when I using Cycles render, the normal edge decal will show the straight shadow (it supposed to be the crack no shadow.), the decal are all one smooth group, no hard edg…

I noticed these normal decals from an Overwatch reference that somehow also allow diffuse information with a mask:From what I've experimented with, it doesn't seem possible in UE4? I was hoping …