Standard methods for ambient occlusion in games are either fully precomputed - baking AO onto vertices or lightmaps - or fully dynamic, i.e. SSAO. Both are useful, but we complement them with a hybrid approach that avoids some weaknesses of baked AO and SSAO. We present AO Fields and AO Decals, a pair of techniques developed for Sucker Punch's recent game Infamous 2. These render plausible contact shadows and self-occlusion for movable objects; rendering is fast, and only a few kilobytes per unique object are needed for precomputed data.

This talk will explain the implementation details of AO fields and decals, including the authoring model exposed to artists, how we fix up corner cases and artifacts, and what kind of texture compression we use. We will show screenshots and videos of the techniques, and report on performance and memory usage in Infamous 2.