Better Blurring

This shows a softer blur with reduced temporal artifacts, used in Call of Duty Advanced Warfare. 
http://www.iryoku.com/next-generation-post-processing-in-call-of-duty-advanced-warfare

This is just a single pass per mipmap level, so it's easier to manage than separate horizontal / vertical passes, and it works better with multiple mip levels for roughness.

Thanks to Benjamin Rosseaux for pointing out the technique.