"Since Epic released the full Unreal Engine 4 source to subscribers, we've had a number of questions about our dynamic global illumination tech, which Epic recently integrated into UE4. We wanted to take the opportunity to talk about why we developed this technology and how we're using it to make Fable Legends look amazing.
We made a decision early on to have fully dynamic lighting in our game. We think this is important for a number of reasons: It allows dynamic time of day, which adds variation to our world; it massively improves iteration times for artists; and it supports dynamic objects both reflecting and receiving light. Dynamic GI can also give higher quality results than baked lighting in some cases, for example, reflections, where lighting needs to take into account the view position.
Dynamic direct lighting has been around in games for a number of years, but dynamic indirect lighting (i.e bounce lighting or global illumination) – i.e. light bouncing off objects in the scene onto other objects - is a much harder problem to solve, so generally it either isn't computed dynamically, or a very simple representation is used (e.g. a single hemispherical light for the sky)."