You have probably seen physical versions of these in children's science museums, like these ones.
This version is a quick and dirty 2-Axis, 4-Pendulum harmonograph implementation using html5 canvas.
You can also play with it live
- hit jiggle, or enter four numbers to change the shape
- hit start/stop to pause and resume, or to start with new settings
- click on the color palette to change the drawing color
- reload the page to get a different color palette
- click the little yellow triangle to hide the controls
- unselect "add layer" to start with an empty canvas
node server.js
hit localhost:8000
Click on stuff!