The lighting system in 'God of War III' is another one of the most noticeable pieces of gorgeous work judging just from the playable builds. Lighting is very important to the look of 'God of Wars style so it was very important for us to come up with a system that is robust and meets the many needs of the game. We have been working on the lighting since the very start of production, and four years later its still something we are tweaking. We wanted to come up with a hybrid system that would meet the demanding needs of the game. For Titan gameplay, we need a fully dynamic lighting solution and for other areas we wanted to use high resolution light maps combined with dynamic lights.
Choosing either a forward rendering system or a deferred rendering system would always depend on what the game requires and what the game system is capable of. Fortunately, the devs at Sony Santa Monica are extremely happy to be creating a game on a system as powerful as the PS3 and as a result, the rendering was never a choice of one or the other. We use a combination of both, says Feldman. The dynamic shadow system utilizes a deferred rendering solution and the dynamic lighting system uses a forward rendering solution. From the start we wanted the ability to have a lot of dynamic lights. We did not want frame rate to suffer with each light in the scene."
The programmers were able to create a system that allows the artist to use up to 50 lights per game object while not using the graphics processor. All dynamic lighting is done on the PS3s SPUs. We separate direct light (dynamic lights and baked shadowing light) from indirect (ambient, skylight, bounce). This allows us to merge baked and dynamic shadows by blocking direct light. We use Turtle for baked lighting. After testing a number of different global illumination renderers, we chose Turtle because of its feature set, lua scripting, its speed and the wonderful support offered by the Turtle guys. Turtle gives us the ability to separate direct lightmaps, or direct vertex lighting from indirect. We use all of its global illumination features including final gather. We use image based lighting or skylights and we have the ability to bake ambient occlusion to maps or verts. We also use Turtle light probes (spherical harmonics) as one of our solutions for lighting the characters.