How many shadow casting lights are in modern games?

Question

I'd like to know how many shadow casting lights are supported in modern games, such as Uncharted 2, Crysis 2, Modern Warfare 2, Halo: Reach, etc. Do they all limit themselves to just a couple of shadow casting lights, or do the numbers vary wildly?

Answer 1

I haven't played MW2 and Halo, but Crysis 2 and Uncharted 2 don't have lots of dynamic shadow-casting lights at the same time. I can remember mostly 2 shadow casters at the same time; naturally they wanted to keep shadow resolve quick. Generally shadows are expensive to compute, so most games will have 2-4 shadow-casting lights with several non-shadow-casting lights nearby, then shadow resolve will switch between them depending on light’s screen presence. Two shadow casters are enough for a nice visual, especially when you're targeting consoles with limited resources and have to do other lighting parts quick and beautiful, which means lots of pre-computed stuff.

I'm sure there are papers on Crysis 2 and Uncharted 2 lighting somewhere, but here is a pretty generic guess mentioning most modern techniques: detailed character shading via lighting baked into AO and diffuse maps, cascade shadows for global light source and several dynamic lights per pass via some spatial screen partitioning and a normal buffer, with the rest of the lighting baked into vertexes through some form of PRT.

That's not a very useful info for your game, you know. Number of shadow-casting lights depends on the approach to lighting, which in turn depends on lots of things like a renderer's architecture, expected scene complexity, chosen shadow maps for a global light, desired post-effects and overall "heaviness" of the shaders.

Also keep in mind that dynamic lights, shadow-casting or not, aren't the biggest part of overall lighting scheme, there are other important points to consider like character lighting/shading, opaque/alpha blend geometry and various post-processing effects.