Epic Games’ rendering team lead has brought forth some clarification on the Infiltrator demo that was revealed for Unreal Engine 4, along with the engine’s support for dynamic lighting.
In a post on the official forums, he states that, “Fully dynamic lighting and precomputed lighting are just two tools in our UE4 toolbox. We have games being made like Fortnite that are using fully dynamic lighting, no lighting build times, and the game has full flexibility to change what it desires at runtime.
“In the case of Fortnite, this is used to great effect with building and harvesting of resources. We don’t yet have a solution for dynamic GI in the fully dynamic lighting path, this is something we hope to address in the future.
On the other hand, using precomputed lighting where you don’t need dynamicness frees up a lot of processing power. The infiltrator demo that we released at GDC leverages this heavily. In short: we would have had to scale down Infiltrator massively without precomputing some of the lighting.
“There are over 1000 lights in some of the scenes, and about half of those cast shadows. Dynamic shadows have a huge cost on graphics hardware, but precomputed shadows are very cheap. Our general purpose reflection method (Reflection Environment) also relies on pre-captured probes.
“By having the general purpose reflection method be cost efficient, we were able to spend the extra GPU time on Screen Space Reflections, which provides extra detail where it is available (due to screenspace limitations).
“Precomputed lighting is also really useful for scaling down, to low end PC, 60fps, mobile, etc.
“In summary: UE4 supports multiple tiers of lighting options, and games can use what suits them best. Fully dynamic lighting provides maximum interactivity, editor workflow and game design flexibility, precomputed lighting provides maximum quality and performance.”
