glsullivan/perterra

Perterra is a browser-based augmented reality app built for Meta Quest headsets, with a desktop preview mode too, that shows you the true direction to any place on Earth. Instead of pointing along the curved surface of the planet the way a normal compass or map would, it draws a straight line through the Earth itself. So instead of saying Hawaii is west of California, it shows you the exact angle below the horizon you would need to look, through the ground, to point straight at it. Wearing the headset, you see labeled points for landmarks, cities, and country outlines arranged around you at their true chord directions, each with a distance label. Nearby places fade out near your own location so you cannot second-guess the app against what you can see out the window, while distant places stay visible and get dimmer the farther through the Earth they are, which helps convey depth on what would otherwise look like a flat sphere. Small countries collapse into a labeled dot until you get close enough for their outline to matter, and overlapping labels fade to avoid clutter. There is also a light blue ocean fill, a grid of latitude and longitude lines, and rings marking distance every thousand miles. Inside the headset, squeezing the grip opens a menu for toggling these layers, dimming the passthrough camera feed, adjusting how quickly distant labels fade in, jumping to view the world from another location like the North Pole, and recalibrating which way is north. A desktop browser preview lets you look around with the mouse, useful for testing without a headset at all. The app is built with Three.js and has very few dependencies, using Vite for development and building a fully static site with no server required, though it must be served over HTTPS since WebXR requires it. It is open source, and the README invites people to fork it, add their own landmarks, and submit changes.