In this tutorial you will learn how to create an optimized effect overlay to improve realism and believability in your materials without deploying geometry. In the process you will also understand how to configure your camera and level for Real World Light values, which can be pretty handy to create stunning cinematic looks.
https://dev.epicgames.com/community/learning/tutorials/BWyk/unreal-engine-fortnite-enhancing-realism-in-pbr-materials-with-optimized-effect-overlays