Changes

[[Ray tracing]]

[[Deep learning]]

[[Pixel density]] and [[retinal resolution]] - [http://www.roadtovr.com/understanding-pixel-density-retinal-resolution-and-why-its-important-for-vr-and-ar-headsets/ ref 1]

[[Focal Surface Display]] - [http://www.roadtovr.com/oculus-research-demonstrate-groundbreaking-focal-surface-display/ ref 1]