Looks like you can get some really neat effects! I remember using a similar 'frustrated internal reflectance' setup with perspex + IR LEDs + an IR webcam + a pr

Looks like you can get some really neat effects! I remember using a similar 'frustrated internal reflectance' setup with perspex + IR LEDs + an IR webcam + a projector to make a large cheap multi-touch surface. You're limited by the frame rate of a camera+whatever processing needs to happen, which I imagine introduces a lot more lag than, say, an apple pencil. But it's a good cheap way to get a novel input device.