Epic recetly just released the stable version of Unreal Engine 4.22 which comes with real-time ray tracing and a fully fledged path tracer for ground truth images.
https://www.unrealengine.com/en-US/blog/real-time-ray-tracing-new-on-set-tools-unreal-engine-4-22
The path tracer is explained in more detail on this page: https://docs.unrealengine.com/en-us/Engine/Rendering/RayTracing/PathTracer
The following video is an incredible example of an architectural visualisation rendered with Unreal's real-time raytraced reflections and refractions:
https://www.unrealengine.com/en-US/blog/real-time-ray-tracing-new-on-set-tools-unreal-engine-4-22
The path tracer is explained in more detail on this page: https://docs.unrealengine.com/en-us/Engine/Rendering/RayTracing/PathTracer
The following video is an incredible example of an architectural visualisation rendered with Unreal's real-time raytraced reflections and refractions:
It's fair to say that real-time photorealism on consumer graphics card has finally arrived. In the last few years, fast and performant path tracers have become available for free (e.g. Embree, OptiX, RadeonRays, Cycles) or virtually for free (e.g Arnold, Renderman). Thanks to advances in noise reduction algorithms, their rendering speed has been accelerated from multiple hours to a few seconds per frame. The rate at which game engines, with Unreal at the forefront, are taking over the offline-rendering world is staggering. Off-line rendering for architecture will most probably disappear in the near future and be replaced by game engines with real-time ray tracing features.