Show HN: Turn any wall into a laser graffiti canvas — all in the browser

A browser-based project recreates the old laser-tagging art installations without any native software. Point a projector at a wall as a second screen, aim a webcam at the projected area, and a laser pointer becomes your brush. After a one-click calibration that flashes corner markers so the camera can compute the camera-to-projector mapping — plus a four-second wave so the detector learns the laser’s brightness and color — the system tracks the dot each frame and paints strokes exactly where you aim. A mouse or finger works too if you don’t have hardware.

The feature set leans playful: six brush styles (round, marker, calligraphy, neon, spray, rainbow), dripping wet ink, extruded 3D spins, fade-out and kaleidoscope modes, sparkle trails, snapshot export, and even tic-tac-toe you play by drawing an X on the wall. An on-wall menu opens by holding the laser in a corner. Requirements are minimal — a laptop running Chrome, any HDMI projector, a webcam, and a laser pointer, with green recommended as the most camera-visible color.

The significance is less about novel technology than accessible execution: a real-time computer-vision pipeline (homography calibration plus per-frame blob detection) running entirely client-side, turning a classic hack into something anyone can try without installs or specialized rigs.