Possible to blend materials on edge of two separate plane objects?

Unreal Engine Rendering
#1

UE4Editor_20180802_110717.jpg
UE4Editor_20180802_110717.jpg1206×577 101 KB

How do I go about smoothly blending the edges of two separate objects?

#2

Objects should share a material, then vertex paint along the seam of both objects. It would help if the textures were aligned, either by lining up the uv edges, or by using world aligned texturing