How to combine decal normal and underlying mesh normal?

Technical & Engine Help Unreal Engine Help
#1

Any help would be very much appreciated. I am trying to make a animated blood decal by using animated opacity mask. but the problem is when i am using a normal map to show the blood pool depth, it is not taking the normal of the wood floor mesh, unless i dont use the decal normal. in that case, the blood is totally flat.
please check the problem here : https://youtu.be/B0vWNM5-ef0

I am trying to achieve this look of Last of us 2 blood fx : https://www.artstation.com/artwork/xJz82E

#2

Are you sure they have Normal Map on blood puddle? It can be only roughness and color decal then normal doesn’t get overridden.

Decal normal will override, but you can do something like this:

Basically to sample D-Bufffer Normal in Surface material and blend them manually.