Michael Abrash has a good overview of some AR challenges here, also discusses why that doesn't work: http://blogs.valvesoftware.com/abrash/why-you-wont-see-ha

Michael Abrash has a good overview of some AR challenges here, also discusses why that doesn't work: http://blogs.valvesoftware.com/abrash/why-you-wont-see-hard-ar-anytime-soon/ http://blogs.valvesoftware.com/abrash/why-you-wont-see-hard-...