The Augmented Reality Marble Game was developed by Ohan Oda and Steve Feiner at Columbia University's Computer Graphics and User Interfaces Lab ( http://www.cs.columbia.edu/graphics/top.html ).
The player wears a video-see-through head-worn display, and tilts and translates a tracked board to guide a virtual "marble" (actually, more like a little rubber ball) through a dynamic maze of obstacles. Gravity in the game always points in the correct direction, no matter how the player's head and board are oriented relative to each other. This is possible because the game uses both optical marker tracking and a separate head-tracker built into the head-worn display. The optical marker tracker relies on a camera on the head-worn display to determine the board's relative position and orientation. The built-in head tracker determines which way is "down," which the game uses, in turn, to compute the true "down" direction for the board.
The marble game is implemented in Goblin XNA ( http://www.cs.columbia.edu/graphics/projects/goblin ), an open-source infrastructure for AR apps, built on Microsoft XNA Game Studio 3.0. Physics is supported through Newton Game Dynamics. Goblin XNA can be downloaded from http://goblinxna.codeplex.com .
Thanks to: Microsoft Research for funding the development of Goblin XNA, VTT Technical Research Centre of Finland for the ALVAR optical tracking library (which will be supported in the next Goblin XNA release), Vuzix Corporation for the iWear VR920 head-worn display and CamAR camera, and Sean White for video support.
