Why this epic function- UTPortals- was not implemented in UE4 when it was in UDK?
And Epic guys, how we can create it in UE4 that easy and smooth as was in UDK? There’s a blueprint that renders to 2d plane and it’s really have big problems with perfomance, so help community, answer please.
There’s no answer to this question for 6 months already 
With best regards, Mike.
A lot of the content that came with UDK came about because of Unreal Tournament 3. UTPortals being such a thing. You won’t find any of that in UE4, as the engine is game agnostic. There are a number of people working on portal functionality already, so give it time and you will most likely have your choice, and with Unreal Tournament currently being written, Epic may release their own version. If you cannot wait, there is nothing stopping you from implementing it yourself.