Indirect input techniques allow users to quickly access all parts of tabletop workspaces without the need for physical access; however, indirect techniques restrict the available social cues that are seen on direct touch tables. This reduced awareness results in impoverished coordination; for example, the number of conflicts might increase since users are more likely to interact with objects that another person is planning to use. Conflicts may also arise because indirect techniques reduce territorial behavior, expanding the interaction space of each collaborator. In this paper, we introduce three new tabletop coordination techniques designed to reduce conflicts arising from indirect input, while still allowing users the flexibility of distant object control. Two techniques were designed to promote territoriality and to allow users to protect objects when they work near their personal areas, and the third technique lets users set their protection levels dynamically. We present the results of an evaluation, which shows that people prefer techniques that automatically provide protection for personal territories, and that these techniques also increase territorial behavior. Author Keywords Tabletop, groupware, interaction techniques, territoriality,

Pico projectors attached to mobile phones allow users to view phone content using a large display. However, to provide input to projector phones, users have to look at the device, diverting their attention from the projected image. Additionally, other collocated users have no way of interacting with the device. We present ShadowPuppets, a system that supports collocated interaction with mobile projector phones. Shadow-Puppets allows users to cast hand shadows as input to mobile projector phones. Most people understand how to cast hand shadows, which provide an easy input modality. Additionally, they implicitly support collocated usage, as nearby users can cast shadows as input and one user can see and understand another user’s hand shadows. We describe the results of three user studies. The first study examines what hand shadows users expect will cause various effects. The second study looks at how users perceive hand shadows, examining what effects they think various hand shadows will cause. Finally, we present qualitative results from a study with our functional prototype and discuss design implications for systems using shadows as input. Our findings suggest that shadow input can provide a natural and intuitive way of interacting with projected interfaces and can support collocated collaboration. Author Keywords Projector-camera system, mobile projector phone, shadow,

Abstract. Deictic gestures are ubiquitous when people work over tables and whiteboards, but when collaboration occurs across distributed surfaces, the embodiments used to represent other members of the group often fail to convey the details of these gestures. Although both gestures and embodiments have been well studied, there is still little information available to groupware designers about what components and characteristics of deictic gesture are most important for conveying meaning through remote embodiments. To provide this information, we conducted three observational studies in which we recorded and analysed more than 450 deictic gestures. We considered four issues that are important for the design of embodiments on surfaces: what parts of the body are used to produce a deictic gesture, what atomic movements make up deixis, where gestures occur in the space above the surface, and what other characteristics deictic gestures exhibit in addition to pointing. Our observations provide a new design understanding of deictic gestures. We use our results to identify the limitations of current embodiment techniques in supporting deixis, and to propose new hybrid designs that can better represent the range of behavior seen in real-world settings.

Abstract. The rising popularity of digital table surfaces has spawned considerable interest in new interaction techniques. Most interactions fall into one of two modalities: 1) direct touch and multi-touch (by hand and by tangibles) directly on the surface, and 2) hand gestures above the surface. The limitation is that these two modalities ignore the rich interaction space between them. To move beyond this limitation, we first contribute a unification of these discrete interaction modalities called the continuous interaction space. The idea is that many interaction techniques can be developed that go beyond these two modalities, where they can leverage the space between them. That is, we believe that the underlying system should treat the space on and above the surface as a continuum, where a person can use touch, gestures, and tangibles anywhere in the space and naturally move between them. Our second contribution illustrates this, where we introduce a variety of interaction categories that exploit the space between these modalities. For example, with

effect of representation location on interaction in a

When people work face-to-face, they use multiple cues like gesture, orientation and visual attention to co-ordinate interaction, maintain awareness and negotiate meaning (e.g. Gutwin and Greenberg, 1998). Tabletop interfaces are often said to support these multiple cues: people are able to see each other across the table; interface manipulations require large movements and so are more visible than when using a mouse; and hands are free to gesture (e.g. Scott et al., 2003). However, there are often multiple breakdowns of awareness, failures of co-ordination and clashes even when working face-to-face and on shared collaborative task (Hornecker et al., 2008). Figure 1: the blind folded subject (right) tracks the approaching orange ball by sensing its movement as vibration on his abdomen. This demonstration took place at

Abstract This chapter discusses empirical and theoretical investigations of the practice of tabletop territoriality in order to understand how to exploit such social interaction practices that people have developed over years of collaborating in traditional tabletop environments in the design of digital tabletops. These investigations reveal that collaborators at traditional tabletop workspaces use three types of tabletop territories to help coordinate their interactions within the shared tabletop workspace: personal, group, and storage territories. These tabletop territories facilitate collaborative interactions on a table by providing commonly understood social protocols that help people to share a tabletop workspace by clarifying which regions are available for individual or joint task work, to delegate task responsibilities, to coordinate access to task resources by providing lightweight mechanisms to reserve and share task resources, and to organize the task resources in the workspace.

The advent of touch-sensitive and camera-based digital surfaces has spawned considerable development in two types of hand-based interaction techniques. In particular, people can interact: 1) directly on the surface via direct touch, or 2) above the surface via hand motions. While both types have value on their own, we believe much more potent interactions are achievable by unifying interaction techniques across this space. That is, the underlying system should treat this space as a continuum, where a person can naturally move from gestures over the surface to touches directly on it and back again. We illustrate by example, where we unify actions such as selecting, grabbing, moving, reaching, and lifting across this continuum of space.

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