Hi everyone,
i made a small tutorial to create a compositing with Visible in Ray Tracing Only
how to use Composure plugin in UNREAL to create compositing for nuke or after effect of the foreground and background and keep the reflection of the foreground object on the background I use an material function to add the functionality to hide the object on the camera view but keep the shadow and the reflection.
(sorry for my english 
)
https://youtube.com/watch?v=d5fbSSmFP7c
hope it’s help
have nice day
Daniel