We present data from detailed observations of CityWall, a large multi-touch display installed in a central location in Helsinki, Finland. During eight days of installation, 1199 persons interacted with the system in various social configurations. Videos of these encounters were examined qualitatively as well as quantitatively based on human coding of events. The data convey phenomena that arise uniquely in public use: crowding, massively parallel interaction, teamwork, games, negotiations of transitions and handovers, conflict management, gestures and overt remarks to co-present people, and "marking" the display for others. We analyze how public availability is achieved through social learning and negotiation, why interaction becomes performative and, finally, how the display restructures the public space. The multi-touch feature, gesture-based interaction, and the physical display size contributed differentially to these uses. Our findings on the social organization of the use of public displays can be useful for designing such systems for urban environments.

Previous attempts to support spectators at large-scale events have concentrated separately on real-time event information, awareness cues, or media-sharing applications. CoMedia combines a group media space with event information and integrates reusable awareness elements throughout. In two field trials, one at a rally and the other at a music festival, we found that CoMedia facilitated onsite reporting to offsite members, coordination of group action, keeping up to date with others, spectating remotely, and joking. In these activities, media, awareness cues, and event information were often used in concert, albeit assuming differing roles. We show that the integrated approach better supports continuous interweaving of use with the changing interests and occurrences in large-scale events.

Most large public displays have been used for providing information to passers-by with the primary purpose of acting as one-way information channels to individual users. We have developed a large public display to which users can send their own media content using mobile devices. The display supports multi-touch interaction, thus enabling collaborative use of the display. This display called CityWall was set up in a city center with the goal of showing information of events happening in the city. We observed two user groups who used mobile phones with upload capability during two large-scale events happening in the city. Our findings are that this kind of combined use of personal mobile devices and a large public display as a publishing forum, used collaboratively with other users, creates a unique setting that extends the group's feeling of participation in the events. We substantiate this claim with examples from user data.

Upponurkka is an inexpensive immersive display system for public virtual reality installations. It is designed for public places to be robust, wireless, and light-weight. The system consists of two passive stereo screens and optical tracking. In this paper the hardware and software of Upponurkka are briefly presented. In addition, experiences of using the system in a public art exhibition are reported.

Modern general purpose processors have powerful vector processing units that can be used in infinite impulse response and finite impulse response filtering in real time. In practice, the calculations are efficient only if the filter parameters fit into the processor's cache. With long filters, the computation is slowed down since the filter data do not fit into the cache at once. By computing the filter in multiple segments, more efficient cache utilization can be achieved. The presented optimization method works when multiple samples are processed in row. The improved cache efficiency increases performance by up to almost one magnitude over direct filter implementation on modern hardware

This paper presents Kick Ass Kung-Fu, a martial arts game installation where the player fights virtual enemies with kicks and punches as well as acrobatic moves such as cartwheels. Using real-time image processing and computer vision, the video image of the user is embedded inside 3D graphics. Compared to previous work, our system uses a profile view and two displays, which allows an improved view of many martial arts techniques. We also explore exaggerated motion and dynamic slow-motion effects to transform the aesthetic of kung-fu movies into an interactive, embodied experience. The system is described and analyzed based on results from testing the game in a theater, in a television show, and in a user study with 46 martial arts practitioners.