Very interesting articles, once again.
The GI is a very nice visual addition to outdoor lighting, even if it has (huge) flaws. Without GI, all shaded areas have a uniform ambience... This works OK for outdoors (Crysis) but it would be nice to have some
way of simulating those low-frequency shadows you get from sunlight. I'd take even pre-rendered shadowmaps - technically calculating Terrain Occlusion does this, but it isn't very accurate and really only works for foliage shadows on terrain, not so good for brushes such as bridges, tunnels or canopies, for example.
For indoors, it would be very useful to have GI enabled for lightsources other than the sun. This is probably the best advantage of the Frostbite 2 engine GI system over CE3. The Crytek rendering tech article that described their light propagation volumes technique did mention that reflective shadowmaps are rendered for all
lightsources - yet this feature was dropped from Crysis 2, and there's not even a console variable to enable GI for all lights. I guess they decided to use Irradiance Volumes for indoors instead - performance advantage is significant in that case.
Thomy wrote:But if you want a good framerate it really depends on how much they intersect with each other and how big they are (also geometry is of an issue because of specularity if I'm not mistaken)
I think deferred rendering uses a single pass for most materials regardless of specularity - Crysis 2 has significantly fewer shaders than Crysis did (notice the lack of Metal shader) probably precisely because they want to cut down on multiple render passes required for different shaders. Shiny materials such as metals and diffuse materials such as stone are all rendered in a single pass, because they both use the Illum shader - differences are only in specular glossiness and amount, which are calculated in a single specular render target.
This narrows down material options such as anisotropy, but the metal surfaces in Crysis 2 look very nice anyway, mainly thanks to Environment Probes.