TL;DR: Face ID does not compare standard selfies to unlock your phone. Instead, it projects 30,000 infrared laser dots onto your face to create a highly precise 3D geometry map. A neural network converts this map into a mathematical feature vector, comparing it to your saved profile to authenticate your identity. Most people think their phone unlocks by snapping a quick selfie and playing a game of spot-the-difference. I get it—from a user perspective, that’s exactly what it feels like. But under the hood, modern facial authentication relies on an entirely different stack of hardware and software. It’s not looking at your face; it’s reading your face's topography like a surveyor mapping a mountain range. Let's break down the actual engineering happening in the fraction of a second it takes to unlock your screen. How does Face ID map your face in the dark? Face ID uses infrared (IR) light instead of the visible light spectrum to detect depth.…