Doom 3 BFG screenshot with Oculus Rift distortion at Quakecon 2012. The Oculus Rift is a Head mounted display that simulates a virtual reality kind of world. To increase the perceived field of view it uses a non standard optic that will deform what is on the screen (making it a non planar projection anymore). The Doom 3 BFG engine has been modified to do the inverse of that deformation so that the end result looks "okay" to the player. This screenshot shows the output of the engine before the optics deformation has been applied (so that it is straight again).