Virtual Juggling Volleyball

In 2001, I worked round the clock with the Flying Karamazov Brothers to develop a virtual juggling stage system for them. I had a ton of fun working on this project, but one of the real high points was at 4am when we first got the system up and running, we worked up a sweat playing volleyball with a ball that didn't exist.

Holding Up the Sun

The virtual Juggling system consisted of a 6000 lumen projector the size of a small Volkswagon, a 18 foot diameter rear-projection screen, a video camera, and a rack mount PC running openGL/C++.

Physics

The computer simulated the physics of planets in a gravitational field using Runge-Kutta integration written in C++ and 3-d animation written in openGL.

Edge Detection

Meanwhile, the images from the camera were digitized by a video capture card, and a simple edge detection algorithm detected the outlines of the performers.

Bouncing

When the ball approached an edge pixel, a virtual force repelled it. Actually the ball had successive layers like an onion. Layers deeper inside the ball repelled more strongly to insure that the closer it came to a performer, the more it would slow down to a stop. When the ball encountered a side wall, the sign of the horizontal component of it's velocity was reversed.

Juggling

If a ball's velocity had a downward component, and the ball touched an edge, the velocity would be set to zero so that it would come to rest easily on the performer's hand. This made it possible to "catch" the balls, enabling enough control to actually juggle multiple virtual balls.