Barry A. Po

Collaborative coupling over tabletop displays

Designing collaborative interfaces for tabletops remains difficult because we do not fully understand how groups coordinate their actions when working collaboratively over tables. We present two observational studies of pairs completing independent and shared tasks that investigate collaborative coupling, or the manner in which collaborators are involved and occupied with each others work. Our results indicate that individuals frequently and fluidly engage and disengage with group activity through several distinct, recognizable states with unique characteristics. We describe these states and explore the consequences of these states for tabletop interface design.

Physical and Digital Artifact-Mediated Coordination in Building Design

We conducted an ethnographic field study examining how a building design team used representational artifacts to coordinate the design of building systems, structure, and architecture. The goals of this study were to characterize the different interactions meeting participants had with design artifacts, to identify bottlenecks in the design coordination process, and to develop design considerations for CSCW technology that will support in-person design coordination meetings of building design teams. We found that gesturing, navigation, annotation, and viewing were the four primary interactions meeting participants had with design artifacts. The form of the design information (2D vs. 3D, digital vs. physical) had minimal impact on gesture interactions, although navigation varied significantly with different representations of design information. Bottlenecks in the design process were observed when meeting participants attempted to navigate digital information, interact with wall displays, and access information individually and as a group. Based on our observations, we present some possible directions for future CSCW technologies, including new mechanisms for digital bookmarking, interacting with 2D and 3D design artifacts simultaneously, and enriched pointing techniques and pen functionality.

Comparing cursor orientations for mouse, pointer, and pen interaction

Most graphical user interfaces provide visual cursors to facilitate interaction with input devices such as mice, pointers, and pens. These cursors often include directional cues that could influence the stimulus-response compatibility of user input. We conducted a controlled evaluation of four cursor orientations and an orientation-neutral cursor in a circular menu selection task. Mouse interaction on a desktop, pointer (i.e. wand) interaction on a large screen, and pen interaction on a Tablet PC were evaluated. Our results suggest that choosing appropriate cursors is especially important for pointer interaction, but may be less important for mice or pens. Cursors oriented toward the lower-right corner of a display yielded the poorest performance overall while orientation-neutral cursors were generally the best. Advantages were found for orientations aligned with the direction of movement. We discuss these results and suggest guidelines for the appropriate use of cursors in various input and display configurations.

Comparing CAVE, wall, and desktop displays for navigation and wayfinding in complex 3D models

Computer-aided design (CAD) and 3D visualization techniques are at the heart of many engineering processes such as aircraft, ship, and automobile design. These visualization tasks require users to navigate or wayfind through complex 3D geometric models consisting of millions of parts. Despite numerous studies, it remains unclear whether large-screen displays improve user performance for such activities. We present a user study comparing standard desktop, immersive room (i.e., CAVE), and wall displays with 3D stereo/head-tracking, and mono/no head-tracking. We observed individual differences between users and found that the presence of contextual structure greatly impacted performance, suggesting that providing structure and developing interaction techniques accommodating a wide range of users yields better performance than focusing on display characteristics alone

Mouse and touchscreen selection in the upper and lower visual fields

Neuroanatomical evidence indicates the human eyes visual field can be functionally divided into two vertical hemifields, each specialized for specific functions. The upper visual field (UVF) is specialized to support perceptual tasks in the distance, while the lower visual field (LVF) is specialized to support visually-guided motor tasks, such as pointing. We present a user study comparing mouse- and touchscreen-based pointing for items presented in the UVF and LVF on an interactive display. Consistent with the neuroscience literature, we found that mouse and touchscreen pointing were faster and more accurate for items presented in the LVF when compared to pointing at identical targets presented in the UVF. Further analysis found previously unreported performance differences between the visual fields for touchscreen pointing that were not observed for mouse pointing. This indicates that a placement of interactive items favorable to the LVF yields superior user performance, especially for systems dependent on direct touch interactions.

Pointing and visual feedback for spatial interaction in large-screen display environments

The two visual systems hypothesis in neuroscience suggests that pointing without visual feedback may be less affected by spatial visual illusions than cognitive interactions such as judged target location. Our study examined predictions of this theory for target localization on a large-screen display. We contrasted pointing interactions under varying levels of visual feedback with location judgments of targets that were surrounded by an offset frame. As predicted by the theory, the frame led to systematic errors in verbal report of target location but not in pointing without visual feedback for some participants. We also found that pointing with visual feedback produced a similar level of error as location judgments, while temporally lagged visual feedback appeared to reduce these errors somewhat. This suggests that pointing without visual feedback may be a useful interaction technique in situations described by the two visual systems literature, especially with large-screen displays and immersive environments.

Exploring collaboration with group pointer interaction

Enabling group collaboration is important in computer graphics today. We have developed a framework that supports multiple pointing devices to explore the collaborative utility of multiple mice and laser pointer interaction in graphical environments. Because most pointing device comparisons are done in the context of single user performance, very little is known about the affordances of collaborating with multiple pointing devices. We present an experimental comparison of mouse pointer to laser pointer interaction in a problem-solving task involving groups of one, two, and three people. We show that collaborative performance is largely orthogonal to motor performance and that the interaction patterns are dependent on the task and on the group size. This suggests that the collaborative characteristics of a pointing device are just as important as the physical characteristics that are usually given the most attention, such as precision and accuracy

Causes of depth perception errors in stereo displays

The use of stereo wall displays for applications that require strong versimilitude has shown that individual differences in depth and size perception remain a significant obstacle. One cue in the real world that is different in stereo displays is the ratio betweeen vergence and accomodation. To date, there is no consensus as to how much of an effect this difference has. In this study, we compare subject’s size and distance estimation of spheres in the virtual and real world, to try to quantify the impact of extraretinal inflow.