Horizon Based Ambient Occlusion
This is an OpenGL implementation of the method described in the slides available from nvidia: http://www.nvidia.co.uk/object/siggraph-2008-HBAO.html
The hbao itself is more or less a port of nvidias highly optimized DirectX version available through the SampleSDK found on https://developer.nvidia.com/
The bilateral weight function is from dice given in the slides at http://dice.se/publications/stable-ssao-in-battlefield-3-with-selective-temporal-filtering/