VR Headsets: How Do They See Depth?

When you put on a Meta Quest or Apple Vision Pro, you can walk around your room, and the virtual world stays locked in place. You can reach out and grab a virtual apple, and your hand is exactly where it should be. But the headset is just screens and cameras. How does it know how far away the floor is? How does it know you stepped forward 3 inches?

It uses Stereoscopic Vision and SLAM.

Two Eyes are Better Than One

Close one eye and try to touch your fingertips together quickly. It’s hard. You lost your depth perception. Humans calculate distance by comparing the slightly different image from our Left Eye and Right Eye. control center (brain) does trigonometry instantly. This is Parallax.

• Objects close to you shift a lot between eyes.
• Objects far away hardly shift at all.

Robots with Two Eyes (Stereo Cameras)

Standard webcams are “Cyclops”—they only see a flat image. They can see an orange ball, but they don’t know if it’s a huge ball far away or a tiny ball close up. To fix this, high-end robots use Stereo Cameras (like the ZED, Intel RealSense, or OAK-D).

• These cameras have two lenses spaced apart (The “Baseline”).
• The processor compares the two images millions of times a second to create a Depth Map. A map where every pixel has a distance value.

Inside-Out Tracking (SLAM)

VR headsets also use “Inside-Out Tracking.” They look at static features in your room (corners of tables, patterns on the rug, the light switch).

• “If the table moved left in the camera frame, I must have moved right.” This is SLAM (Simultaneous Localization and Mapping). The headset builds a map of the room while figuring out where it is inside that map.

FTC Application

In robotics, we use SLAM (via libraries like Vuforia or AprilTags) to navigate the field without GPS.

• Look at the wall images.
• Calculate angle and distance.
• “I am at coordinate (10, 50). I need to drive to (0, 0).” VR gaming isn’t just entertainment; it’s the pinnacle of computer vision. Every time you play Beat Saber, you are stress-testing algorithms that were originally designed for Mars rovers and autonomous cars to keep them from crashing into rocks.