Pinch-to-zoom-plus: an enhanced pinch-to-zoom that reduces clutching and panning

Despite its popularity, the classic pinch-to-zoom gesture used in modern multi-touch interfaces has drawbacks: specifically, the need to support an extended range of scales and the need to keep content within the view window on the display can result in the need to clutch and pan. In two formative studies of unimanual and bimanual pinch-to-zoom, we found patterns: zooming actions follows a predictable ballistic velocity curve, and users tend to pan the point-of-interest towards the center of the screen. We apply these results to design an enhanced zooming technique called Pinch-to-Zoom-Plus (PZP) that reduces clutching and panning operations compared to standard pinch-to-zoom behaviour.