Epic Games, in collaboration with NVIDIA and ILMxLAB, today gave the first public demonstration of real-time ray tracing in Unreal Engine. Real-time ray tracing is considered to be a holy grail for those creating high-end cinematic imagery, and one that signifies a leap forward in the convergence of film and games.

https://www.unrealengine.com/en-US/blog/epic-games-demonstrates-real-time-ray-tracing-in-unreal-engine-4-with-ilmxlab-and-nvidia