no need for those red outlined enemies, I only need to scan the environment just like in that video. searched for a similiar thing whole day and tried ton of tutorials but none gave me good results.
edit: atleast can someone tell how I can make this visible and with a different color behind objects?
Seems like a lot of post processing…
Its actually pretty simple.
You will need a 2 pass shader, pass 1 is overlay(it draws on top of everything), and transparent, it has the color of the scan. Pass 2 is the normal shader of the object. Now you only need to lerp pass1’s transparency based on something(i used a gameobject’s position) and its done 
I used unity but its generally the same in unreal.
youtube video