Show HN: Laser Graffiti

# Laser Graffiti — draw on walls with a laser pointer Source: [https://laser.consti.de/](https://laser.consti.de/) Point a projector and a webcam at any wall\. Draw with a laser pointer\. The projector paints your strokes — glowing neon, dripping ink, spinning in 3D\. Your browser doesn't support embedded video —[download the clip](https://laser.consti.de/media/howitworks.mp4)\. Inspired by[this video](https://www.youtube.com/watch?v=DKbtTPYZEig)— laser tagging buildings with a projector, done years ago and still magical\.[Read the backstory ↓](https://laser.consti.de/#backstory) ## Try it right here No projector needed for this one — your mouse \(or finger\) is the laser\. Pick a brush, flip on a mode, or play tic\-tac\-toe against the computer by drawing an X in a cell\. ## How it works Everything runs in the browser — no install, no native app\. 01 ### Set up Connect a projector as a second screen and point a webcam at the projected area\. Open the control window and the projector window \(press`F`for fullscreen\)\. 02 ### Calibrate One click flashes markers into the corners of the projection; the camera finds them and computes the camera→projector mapping\. Then wave the laser for 4 seconds so the detector learns its brightness and colour\. 03 ### Draw Every frame the camera finds the laser dot, maps it onto the projector, and the projector renders the stroke — right where you pointed\. Hold the laser in the ☰ corner to open an on\-wall menu\. ## Features - Six brushes: round, marker, calligraphy, neon, spray, rainbow - Wet ink that drips down the wall - Spin your drawing as an extruded 3D object - Fade\-out mode and kaleidoscope mirroring - Sparkle particle trail - Tic\-tac\-toe against the computer, on the wall - Coloured border around the drawable area - Snapshots: save photo \+ drawing, download as files - Laser\-operated menu — no need to touch the laptop - Reflection\-robust tracking for shiny floors - Works with green or red lasers - Zero dependencies, MIT\-licensed,[open source](https://github.com/consti/laser-graffiti) ## The backstory The inspiration came from**mzeltner**\(Michael Zeltner\) and**oneup**\(Florian Hufsky\) of[Graffiti Research Lab Vienna](https://graffitiresearchlab.at/), who around 2007 built their own laser marker and tagged buildings across Vienna with it\. They in turn were inspired by the original[Graffiti Research Lab](https://graffitiresearchlab.com/)in New York and its[L\.A\.S\.E\.R\. Tag](https://graffitiresearchlab.com/blog/projects/laser-tag/#video)project — the same idea: a camera, a projector, and a laser pointer as the pen, writ large on the side of a building\. Here's Bre Pettis talking with Michi about Laser Tag in Vienna: This project is a from\-scratch reimplementation of that idea for the browser — no Processing, no install, just a laptop, a webcam and a projector\. ## What you need A laptop with Chrome, a projector \(any HDMI projector works — it's just a second screen\), a webcam that can see the projected area \(the built\-in one is fine\), and a laser pointer\. Green shows up best on camera\. [Start Laser Graffiti →](https://laser.consti.de/app.html)