Mid-Air Text Input Techniques for Very Large Wall Displays Garth Shoemaker, Leah Findlater, Jessica Q. Dawson, and Kellogg S. Booth Department of Computer Science University of British Columbia 2366 Main Mall, Vancouver, BC, Canada {garths, lkf, ksbooth}@cs.ubc.ca ABSTRACT Traditional text input modalities, namely keyboards, are often not appropriate for use when standing in front of very large wall displays. Direct interaction techniques, such as handwriting, are better, but are not well suited to situations where users are not in close physical proximity to the display. We discuss the potential of mid-air interaction techniques for text input on very large wall displays, and introduce two factors, distance-dependence and visibility-dependence, which are useful for segmenting the design space of mid-air techniques. We then describe three techniques that were designed with the goal of exploring the design space, and present a comparative evaluation of those techniques. Questions raised by the evaluation were investigated further in a second evaluation focusing on distance-dependence. The two factors of distance- and visibility-dependence can guide the design of future text input techniques, and our results suggest that distance-independent techniques may be best for use with very large wall displays. KEYWORDS: text input, wall displays, interaction techniques INDEX TERMS: H.5.2 [User Interfaces]: Input devices and strategies 1 INTRODUCTION Designers of very large interactive display environments (Figure 1) have yet to establish a standard model for interaction. Traditional devices (keyboard and mouse) and onscreen metaphors (windows, icons, menus, and pointers) long established for desktop use are often not ideal for the form factors of new wall and table displays. An ongoing effort in the research community has been to investigate different interaction possibilities, with the goal of designing better methods for input and manipulation. The development of these methods will play a critical role in the evolution of large displays from research systems to universally adopted tools. In this paper we consider English language text input techniques for very large wall displays. Text input is one of the primitives of interaction identified by Foley et al. [6], and must be supported by any general purpose interactive system, even if that system is not used for lengthy uninterrupted text input. Researchers recognize the limitations of keyboard input, the most significant being that keyboards are designed for use while sitting stationary at a desk or a table, but users of wall displays are often standing or walking. Alternative approaches have been investigated, including pen-based text input, where a user writes as on a whiteboard. This method, while natural, has the significant drawback that a user must be within physical reach of the display surface in order to write. Users of large wall displays are often not within physical reach of the display surface [21, 23]. To address this problem we identified and investigated the under-explored design space of mid-air text input techniques, those that can be used by a standing, mobile user. In this context, techniques that allow for input independent of visibility or distance to the display might be particularly important. Thus, we segment this design space along the axes of visibility-dependence and distance-dependence, both of which are useful for categorizing candidate interaction techniques. We developed three text input techniques that differ in terms of distance- and visibility-dependence: Circle, QWERTY, and Cube. For each technique the user manipulates a handheld device in mid-air, at some distance from the display surface. We conducted a controlled experiment to compare the techniques in terms of speed and accuracy for a text input task. Results suggest that the QWERTY technique is suitable for adoption, and that the other two techniques have potential for future development but need improvements to be competitive with the QWERTY technique. A second, follow-up experiment was performed with the goal of developing a deeper understanding of the distance-dependence factor of interaction techniques. We evaluated Circle and QWERTY techniques, which we hypothesized would be distance- independent and –dependent, respectively, at two different distances. Results showed that the factor of distance had a significant impact on performance. This highlights the need for further work on distance-independent techniques. The primary contributions of this paper are three-fold. First, we investigate the design space of mid-air text input techniques for large wall displays, and identify important factors segmenting this space. Second, we report a comparative analysis of three candidate text input techniques representative of the design space, and we provide conclusions regarding the usefulness of those techniques. Third, we report a second experiment that highlights the importance of distance-independence when designing interaction techniques for large wall displays. Figure 1. A mockup of collaboration around a large wall display. 231 Graphics Interface Conference 2009 25-27 May, Kelowna, British Columbia, Canada Copyright held by authors. Permission granted to CHCCS/SCDHM to publish in print form, and ACM to publish electronically.