Yeah, I mean, we've seen tons of scary pranks on youtube, but this one takes it to the next level of engineering. GWPoulos had this wonderful idea to spray-paint a transparent plexiglass with reflective transparent paint and use a projector to project his screamer video. The projector is activated with a Rasberry Pi, which in turn lurks for the victim with a PIR sensor.
The basic setup uses a projector, a PIR motion detector, raspberry pi, and a piece of plexiglass with a thin spray coating of reflective paint. A loud, startling transparent image appears when a person walks in front of it. I will go over the steps and shell script code used in creating this effect.
Follow this link to see the step-by-step guide and scare the hell out of them pranksters!