Chair: Bjoern Hartmann, University of California Berkeley, USA
Hand Occlusion on a Multi-Touch Tabletop
Contribution & Benefit: Presents experimental results, templates, and geometric models for the shape of hand occlusion on a multi-touch table. Can assist designers when justifying interface layouts and forms groundwork for real-time models.
Abstract » We examine the shape of hand and forearm occlusion on a multi-touch table for different touch contact types and tasks. Individuals have characteristic occlusion shapes, but with commonalities across tasks, postures, and handedness. Based on this, we create templates for designers to justify occlusion-related decisions and we propose geometric models capturing the shape of occlusion. A model using diffused illumination captures performed well when augmented with a forearm rectangle, as did a modified circle and rectangle model with ellipse "fingers" suitable when only X-Y contact positions are available. Finally, we describe the corpus of detailed multi-touch input data we generated which is available to the community.ACM
BiTouch and BiPad: Designing Bimanual Interaction for Hand-held Tablets
Contribution & Benefit: BiPad enables bimanual interaction with the support hand on multitouch tablets. With the BiTouch design space, we discuss the device-support function as an extension to Guiard's kinematic chain theory.
Abstract » Despite the demonstrated benefits of bimanual interaction, most tablets use just one hand for interaction, to free the other for support. In a preliminary study, we identified five holds that permit simultaneous support and interaction, and noted that users frequently change position to combat fatigue. We then designed the BiTouch design space, which introduces a support function in the kinematic chain model for interacting with hand-held tablets, and developed BiPad, a toolkit for creating bimanual tablet interaction with the thumb or the fingers of the supporting hand. We ran a controlled experiment to explore how tablet orientation and hand position affect three novel techniques: bimanual taps, gestures and chords. Bimanual taps outperformed our one-handed control condition in both landscape and portrait orientations; bimanual chords and gestures in portrait mode only; and thumbs outperformed fingers, but were more tiring and less stable. Together, BiTouch and BiPad offer new opportunities for designing bimanual interaction on hand-held tablets.ACM
See Me, See You: A Lightweight Method for Discriminating User Touches on Tabletop Displays
Contribution & Benefit: See Me, See You is a lightweight method that uses finger orientation for distinguishing touches from multiple users on digital tabletops. Our detection method is accurate under complex conditions.
Abstract » Tabletop systems provide a versatile space for collaboration, yet, in many cases, are limited by the inability to differentiate the interactions of simultaneous users. We present See Me, See You, a lightweight approach for discriminating user touches on a vision-based tabletop. We contribute a valuable characterization of finger orientation distributions of tabletop users. We exploit this biometric trait with a machine learning approach to allow the system to predict the correct position of users as they touch the surface. We achieve accuracies as high as 98% in simple situations and above 92% in more challenging conditions, such as two-handed tasks. We show high acceptance from users, who can self-correct prediction errors without significant costs. See Me, See You is a viable solution for providing simple yet effective support for multi-user application features on tabletops.ACM
Two-Handed Marking Menus for Multitouch Devices
Contribution & Benefit: Describes two-handed marking menu techniques. One variant reduces menu selection times over the one-handed technique and another variant doubles the number of menu items.
Abstract » We investigate multistroke marking menus for multitouch devices and we show that using two hands can improve performance. We present two new two-handed multistroke marking menu variants in which users either draw strokes with both hands simultaneously or alternate strokes between hands. In a pair of studies we find that using two hands simultaneously is faster than using a single, dominant-handed marking menu by 10-15%. Alternating strokes between hands doubles the number of accessible menu items for the same number of strokes, and is similar in performance to using a one-handed marking menu. We also examine how stroke direction affects performance. When using thumbs on an iPod Touch, drawing strokes upwards and inwards is faster than other directions. For two-handed simultaneous menus, stroke pairs that are bilaterally symmetric or share the same direction are fastest. We conclude with design guidelines and sample applications to aid multitouch application developers interested in using one- and two-handed marking menus.