The K-2S0 droid character in Rogue One (voiced by Alan Tudyk) was, in fact, rendered in real-time using Unreal, then composited into shots afterwards. John Kno

The K-2S0 droid character in Rogue One (voiced by Alan Tudyk) was, in fact, rendered in real-time using Unreal, then composited into shots afterwards. John Knoll from ILM gave a talk at GDC 2017 about it. The catch, though, is that ILM took the Unreal Engine source code and modified it extensively in order to be able to render K-2S0 as he appeared in the film. It's not like they just downloaded it from the Epic Store and ran with it.