Multi-touch 3D positioning with the pantograph technique

One advantage of touch interaction is the sense of direct manipulation; there is perhaps no more-intuitive interface than just reaching out and touching virtual entities. However, direct manipulation is generally limited to objects located on the 2D display surface. For 3D spaces extending behind or in front of a touchscreen, the direct manipulation metaphor quickly falls apart. In these cases, gestures are needed to convert 2D finger positions into 3D cursor positions. This paper presents the pantograph technique, a simple two-finger interaction method for positioning a 3D cursor within mono and stereoscopic applications. The pantograph's pseudomechanical linkage between fingers and cursor provides helpful depth cues and maintains the sense of direct manipulation. Extensions to the technique, which integrate selection and other advanced actions, are explored within the context of real-world visual analysis applications. A series of human factors experiments showed that, while the pantograph technique outperformed other similar multitouch 3D positioning techniques, multi-touch was still inferior to other traditional, non-touch-based interfaces for sustained 3D positioning tasks.