GTAO
A screen-space ambient occlusion that was fitted to a path-traced reference so it stops over-darkening creases.
GTAO (Ground-Truth Ambient Occlusion) reformulated the horizon approach so its output matches a path-traced "ground truth", and added a cheap multi-bounce term — multiscatter — so dark corners don't come out blacker than reality. Older AO methods tended to exaggerate shading in tight folds; GTAO fixed that without getting more expensive.
Developed by Activision in 2016 (Jimenez et al.) and used in Call of Duty. It quickly became a common default, Unreal Engine among others, succeeding HBAO as the reference screen-space method.