3D Model In UI ?

How would someone go about adding 3d objects with animations to a UI screen as they did in The World War Z Game
or OverWatch ill put up links to what i am talking about.

https://www.youtube.com/watch?v=8aE97H6WuR8

You would make a 3d scene where the default pawn is just a camera. In that pawn you would add your UI to the view port and set the input mode to UI. Any 3D objects you can just place in the scene and if you want them to animate due to the UI, you cant just cast to the object you are referencing.