I’d like to know the feasibility of a system for dynamic lights (static or moveable) to contribute color to the indirect lighting environment when illuminating static geometry.
Basically I guess I’m wondering about the possibility for something like Ubisoft’s Deferred Radiance Transfer Volumes in UE4 (link below). Unlike SVOGI, which had too big of a performance impact, this dynamic GI managed to ship on both the PC and console versions of Far Cry 3 (PC also allowed point lights to influence the GI as well as the sun). As far as I can tell, it’s a proven system optimized to run and allows dynamic GI from everything except dynamic actors, which is a fair trade and considerably better than no dynamic GI at all.
Link: http://www.gdcvault.com/play/1015326/Deferred-Radiance-Transfer-Volumes-Global
A couple examples of where this could be used:
A flashlight or flickering/swinging light in an otherwise dark environment that can bounce and reflect ambient light back based on the color of the environment illuminated by the flashlight.
Day/night cycles where the color for all static objects are taken into account, and when the sun/moon light strikes them, they bounce ambient light back into the scene.
The reflection capture isn’t really what I’m talking about. See the recent Snowdrop Engine video below, specifically 0:25 through 0:29. Basically it’s a system similar to the Light Cache that updates dynamically based on lighting changes to give you dynamic GI bounces. In reality it’s not truly dynamic since the probes and color of the environment around them are precaclulated and static, but whether they contribute to the scene’s ambient GI is based on the direction and shadowing of fully dynamic lights.
In that video they use the system to give ‘dynamic’ GI to the sun, but previous videos showed the same system giving GI bounces to dynamic point lights in interior scenes. Right now, if you bake GI with lightmass and then turn off a light or move it behind an object so it’s casting shadows, the scene is still brightly illuminated by the static, baked lightmass GI (or alternatively you don’t bake GI with any dynamic lights so the ambient lighting is simply black).