3D printing technology can be used to rapidly prototype the look and feel of 3D objects. However, the objects produced are passive. There has been increasing interest in making these objects interactive, yet they often require assembling components or complex calibration. In this paper, we contribute AirTouch, a technique that enables designers to fabricate touch-sensitive objects with minimal assembly and calibration using pneumatic sensing. AirTouch-enabled objects are 3D printed as a single structure using a consumer-level 3D printer. AirTouch uses pre-trained machine learning models to identify interactions with fabricated objects, meaning that there is no calibration required once the object has completed printing. We evaluate our technique using fabricated objects with various geometries and touch sensitive locations, obtaining accuracies of at least 90% with 12 interactive locations.

Astral is a prototyping tool for authoring mobile and smart object interactive behaviours. It mirrors selected display contents of desktop applications onto mobile devices (smartphones and smartwatches), and streams/remaps mobile sensor data to desktop input events (mouse or keyboard) to manipulate selected desktop contents. This allows designers to use familiar desktop applications (e.g. PowerPoint, AfterEffects) to prototype rich interactive behaviours. Astral combines and integrates display mirroring, sensor streaming and input remapping, where designers can exploit familiar desktop applications to prototype, explore and fine-tune dynamic interactive behaviours. With Astral, designers can visually author rules to test real-time behaviours while interactions take place, as well as after the interaction has occurred. We demonstrate Astral's applicability, workflow and expressiveness within the interaction design process through both new examples and replication of prior approaches that illustrate how various familiar desktop applications are leveraged and repurposed.

We rely on our sight when manipulating objects. When objects are occluded, manipulation becomes difficult. Such occluded objects can be shown via augmented reality to re-enable visual guidance. However, it is unclear how to do so to best support object manipulation. We compare four views of occluded objects and their effect on performance and satisfaction across a set of everyday manipulation tasks of varying complexity. The best performing views were a see-through view and a displaced 3D view. The former enabled participants to observe the manipulated object through the occluder, while the latter showed the 3D view of the manipulated object offset from the object's real location. The worst performing view showed remote imagery from a simulated hand-mounted camera. Our results suggest that alignment of virtual objects with their real-world location is less important than an appropriate point-of-view and view stability.

Around-device interaction methods expand the available interaction space for mobile devices; however, there is currently no way to simultaneously track a user's input and provide haptic feedback at the tracked point away from the device. We present Magnetips, a simple, mobile solution for around-device tracking and mid-air haptic feedback. Magnetips combines magnetic tracking and electromagnetic feedback that works regardless of visual occlusion, through most common materials, and at a size that allows for integration with mobile devices. We demonstrate: (1) high-frequency around-device tracking and haptic feedback; (2) the accuracy and range of our tracking solution which corrects for the effects of geomagnetism, necessary for enabling mobile use; and (3) guidelines for maximising strength of haptic feedback, given a desired tracking frequency. We present technical and usability evaluations of our prototype, and demonstrate four example applications of its use.

Touch accuracy is not just dependent on the performance of the touch sensor itself. Instead, aspects like phone grip or occlusion of the screen have been shown to also have an influence on accuracy. Yet, these are all dependent on one underlying factor: the size and proportions of the user's hand. To better understand touch input, we investigate how 11 hand features influence accuracy. We find that thumb length in particular correlates significantly with touch accuracy and accounts for about 12% of touch error variance. Furthermore, we show that measures of some higher level interactions also correlate with hand size.

While pressing can enable a wide variety of interesting applications, most press sensing techniques operate only at close distances and rely on fragile electronics. We present EchoTube, a robust, modular, simple, and inexpensive system for sensing low-resolution press events at a distance. EchoTube works by emitting ultrasonic pulses inside a flexible tube which acts as a waveguide and detecting reflections caused by deformations in the tube. EchoTube is deployable in a wide variety of situations: the flexibility of the tubes allows them to be wrapped around and affixed to irregular objects. Because the electronic elements are located at one end of the tube, EchoTube is robust, able to withstand crushing, impacts, water, and other adverse conditions. In this paper, we detail the design, implementation, and theory behind EchoTube; characterize its performance under different configurations; and present a variety of exemplar applications that illustrate its potential.

Many shape-changing interfaces use an array of actuated rods to create a display surface; each rod working as a pixel. However, this approach only supports pixel height manipulation and cannot produce more radical shape changes of each pixel (and thus of the display). Examples of such changes include non-horizontal pixels, pixels that overhang other pixels, or variable gaps between pixels. We present a concept for composing shape-changing interfaces by vertically stacking tilt-enabled modules. Together, stacking and tilting allow us to create a more diverse range of display surfaces than using arrays. We demonstrate this concept through TiltStacks, a shape-changing prototype built using stacked linear actuators and displays. Each tiltable module provides three degrees of freedom (z-movement, roll, and pitch); two more degrees of freedom are added through stacking modules (i.e., planar x- and y-movement).

Advances in sensing technologies allow for using the forearm as a touch surface to give input to off-skin displays. However, it is unclear how users perceive the mapping between an on-skin input area and an off-skin display area. We empirically describe such mappings to improve on-skin interaction. We collected discrete and continuous touch data in a study where participants mapped display content from an AR headset, a smartwatch, and a desktop display to their forearm. We model those mappings and estimate input accuracy from the spreads of touch data. Subsequently, we show how to use the models for designing touch surfaces to the forearm for a given display area, input type, and touch resolution.

Can we experience haptic textures in mid-air? Typically, the experience of texture is caused by vibration of the fingertip as it moves over the surface of an object. This object's surface also guides the finger's movement, creating an implicit motion-to-vibration mapping. If we wish to simulate a texture in mid-air, such guidance does not exist, making the choice of motion-to-vibration mapping non-obvious. We evaluate the experience of moving a pointer with four different motion-to vibration mappings in an interview study. We found that some mappings lead to a perception shift, transforming the experience. When this occurs, the pointer is no longer perceived as vibrating, interactions become more pleasurable, and users have an increased experience of agency and control. We discuss how to leverage this in the design of haptic interfaces.

We present zPatch: an eTextile patch for hover, touch, and pressure input, using both resistive and capacitive sensing. zPatches are made by layering a piezo-resistive material between silver-plated ripstop, and embedding it in non-conductive fabric to form a patch. zPatches can be easily ironed onto most fabrics, in any location, enabling easy prototyping or ad hoc modifications of existing garments. We provide open-source resources for building and programming zPatches and present measures of the achieva-ble sensing resolution of a zPatch. A pressure based targeting task demonstrated users could reliably hit pressure tar-gets at up to 13 levels, given appropriate feedback. We demonstrate that the hybrid sensing approach reduces false activations and helps distinguish between gestures. Finally, we present example applications in which we use zPatches for controlling a music player, text entry and gaming input.

This paper contributes a novel sensing approach to support on- and above-skin finger input for interaction on the move. WatchSense uses a depth sensor embedded in a wearable device to expand the input space to neighboring areas of skin and the space above it. Our approach addresses challenging camera-based tracking conditions, such as oblique viewing angles and occlusions. It can accurately detect fingertips, their locations, and whether they are touching the skin or hovering above it. It extends previous work that supported either mid-air or multitouch input by simultaneously supporting both. We demonstrate feasibility with a compact, wearable prototype attached to a user's forearm (simulating an integrated depth sensor). Our prototype---which runs in real-time on consumer mobile devices---enables a 3D input space on the back of the hand. We evaluated the accuracy and robustness of the approach in a user study. We also show how WatchSense increases the expressiveness of input by interweaving mid-air and multitouch for several interactive applications.

The human skin provides an ample, always-on surface for input to smart watches, mobile phones, and remote displays. Using touch on bare skin to issue commands, however, requires users to recall the location of items without direct visual feedback. We present an in-depth study in which participants placed 30 items on the hand and forearm and attempted to recall their locations. We found that participants used a variety of landmarks, personal associations, and semantic groupings in placing the items on the skin. Although participants most frequently used anatomical landmarks (e.g., fingers, joints, and nails), recall rates were higher for items placed on personal landmarks, including scars and tattoos. We further found that personal associations between items improved recall, and that participants often grouped important items in similar areas, such as family members on the nails. We conclude by discussing the implications of our findings for design of skin-based interfaces.

The size of information spaces often exceeds the limits of even the largest displays. This makes navigating such spaces through on-screen interactions demanding. However, if users imagine the information space extending in a plane beyond the display's boundaries, they might be able to use the space beyond the display for input. This paper investigates Off-Limits, an interaction concept extending the input space of a large display into the space beyond the screen through the use of mid-air pointing. We develop and evaluate the concept through three empirical studies in one-dimensional space: First, we explore benefits and limitations of off-screen pointing compared to touch interaction and mid-air on-screen pointing; next, we assess users' accuracy in off-screen pointing to model the distance-to-screen vs. accuracy trade-off; and finally, we show how Off-Limits is further improved by applying that model to the naïve approach. Overall, we found that the final Off-Limits concept provides significant performance benefits over on-screen and touch pointing conditions.

Remote controls facilitate interactions at-a-distance with appliances. However, the complexity, diversity, and increasing number of digital appliances in ubiquitous computing ecologies make it increasingly difficult to: (1) discover which appliances are controllable; (2) select a particular appliance from the large number available; (3) view information about its status; and (4) control the appliance in a pertinent manner. To mitigate these problems we contribute proxemic-aware controls, which exploit the spatial relationships between a person's handheld device and all surrounding appliances to create a dynamic appliance control interface. Specifically, a person can discover and select an appliance by the way one orients a mobile device around the room, and then progressively view the appliance's status and control its features in increasing detail by simply moving towards it. We illustrate proxemic-aware controls of assorted appliances through various scenarios. We then provide a generalized conceptual framework that informs future designs of proxemic-aware controls.

Often, we operate mobile devices using only one hand. The hand thereby serves two purposes: holding the device and operating the touch screen with the thumb. The current trend of increasing screen sizes however, makes it close to impossible to reach all parts of the screen (especially the top area) for users with average hand sizes. One solution is to offer adaptive user interfaces for such one-handed interactions. These modes have to be triggered manually and thus induce a critical overhead. They are further designed to bring all content closer, regardless of whether the phone is operated with the left or right hand. In this paper, we present an algorithm that allows determining the users' interacting hand from their unlocking behavior. Our algorithm correctly distinguishes one- and two-handed usage as well as left- and right handed unlocking in 98.51% of all cases. This is achieved through a k-nearest neighbor comparison of the internal sensor readings of the smartphone during the unlocking process.

Mobile gaze-based interaction with multiple displays may occur from arbitrary positions and orientations. However, maintaining high gaze estimation accuracy in such situa-tions remains a significant challenge. In this paper, we present GazeProjector, a system that combines (1) natural feature tracking on displays to determine the mobile eye tracker's position relative to a display with (2) accurate point-of-gaze estimation. GazeProjector allows for seam-less gaze estimation and interaction on multiple displays of arbitrary sizes independently of the user's position and orientation to the display. In a user study with 12 partici-pants we compare GazeProjector to established methods (here: visual on-screen markers and a state-of-the-art video-based motion capture system). We show that our approach is robust to varying head poses, orientations, and distances to the display, while still providing high gaze estimation accuracy across multiple displays without re-calibration for each variation. Our system represents an important step towards the vision of pervasive gaze-based interfaces.

Proxemics theory explains peoples' use of interpersonal distances to mediate their social interactions with others. Within Ubicomp, proxemic interaction researchers argue that people have a similar social understanding of their spatial relations with nearby digital devices, which can be exploited to better facilitate seamless and natural interactions. To do so, both people and devices are tracked to determine their spatial relationships. While interest in proxemic interactions has increased over the last few years, it also has a dark side: knowledge of proxemics may (and likely will) be easily exploited to the detriment of the user. In this paper, we offer a critical perspective on proxemic interactions in the form of dark patterns: ways proxemic interactions can be misused. We discuss a series of these patterns and describe how they apply to these types of interactions. In addition, we identify several root problems that underlie these patterns and discuss potential solutions that could lower their harmfulness.

Handheld displays enable flexible spatial exploration of information spaces -- users can physically navigate through three-dimensional space to access information at specific locations. Having users constantly hold the display, however, has several limitations: (1) inaccuracies due to natural hand tremors; (2) fatigue over time; and (3) limited exploration within arm's reach. We investigate autonomous, self-actuated displays that can freely move and hold their position and orientation in space without users having to hold them at all times. We illustrate various stages of such a display's autonomy ranging from manual to fully autonomous, which -- depending on the tasks -- facilitate the interaction. Further, we discuss possible motion control mechanisms for these displays and present several interaction techniques enabled by such displays. Our Hover Pad toolkit enables exploring five degrees of freedom of self-actuated and autonomous displays and the developed control and interaction techniques. We illustrate the utility of our toolkit with five prototype applications, such as a volumetric medical data explorer.

Researchers have developed interaction concepts based on mobile projectors. Yet pursuing work in this area - particularly in building projector-based interactions techniques within an application - is cumbersome and time-consuming. To mitigate this problem, we contribute ProjectorKit, a flexible open-source toolkit that eases rapid prototyping mobile projector interaction techniques.

Although there has been widespread proliferation of creative-coding programming languages, the design of many toolkits and application programming interfaces (APIs) for expression and interactivity do not take full advantages of the unique space of mobile multitouch devices. In designing a new API for this space we first consider five major problem spaces and present an architecture that attempts to address these to move beyond the low-level manipulation of graphics giving first-class status to media objects.

Portable paper calendars (i. e., day planners and organizers) have greatly influenced the design of group electronic calendars. Both use time units (hours/days/weeks/etc.) to organize visuals, with useful information (e.g., event types, locations, attendees) usually presented as - perhaps abbreviated or even hidden - text fields within those time units. The problem is that, for a group, this visual sorting of individual events into time buckets conveys only limited information about the social network of people. For example, people's whereabouts cannot be read 'at a glance' but require examining the text. Our goal is to explore an alternate visualization that can reflect and illustrate group members' calendar events. Our main idea is to display the group's calendar events as spatiotemporal activities occurring over a geographic space animated over time, all presented on a highly interactive public display. In particular, our Spalendar (Spatial Calendar) design animates people's past, present and forthcoming movements between event locations as well as their static locations. Detail of people's events, their movements and their locations is progressively revealed and controlled by the viewer's proximity to the display, their identity, and their gestural interactions with it, all of which are tracked by the public display.

Handheld optical projectors provide a simple way to overcome the limited screen real-estate on mobile devices. We present virtual projection (VP), an interaction metaphor inspired by how we intuitively control the position, size, and orientation of a handheld optical projector's image. VP is based on tracking a handheld device without an optical projector and allows selecting a target display on which to position, scale, and orient an item in a single gesture. By relaxing the optical projection metaphor, we can deviate from modeling perspective projection, for example, to constrain scale or orientation, create multiple copies, or offset the image. VP also supports dynamic filtering based on the projection frustum, creating overview and detail applications, and selecting portions of a larger display for zooming and panning. We show exemplary use cases implemented using our optical feature-tracking framework and present the results of a user study demonstrating the effectiveness of VP in complex interactions with large displays.

During a live sports event, many sports fans use social media as a part of their viewing experience, reporting on their thoughts on the event as it unfolds. In this work, we use this information stream to semantically annotate live broadcast sports games, using these annotations to select video highlights from the game. We demonstrate that this approach can be used to select highlights specific for fans of each team, and that these clips reflect the emotions of a fan during a game. Further, we describe how these clips differ from those seen on nightly sportscasts.

Modern mobile devices allow a rich set of multi-finger interactions that combine modes into a single fluid act, for example, one finger for panning blending into a two-finger pinch gesture for zooming. Such gestures require the use of both hands: one holding the device while the other is interacting. While on the go, however, only one hand may be available to both hold the device and interact with it. This mostly limits interaction to a single-touch (i.e., the thumb), forcing users to switch between input modes explicitly. In this paper, we contribute the Fat Thumb interaction technique, which uses the thumb's contact size as a form of simulated pressure. This adds a degree of freedom, which can be used, for example, to integrate panning and zooming into a single interaction. Contact size determines the mode (i.e., panning with a small size, zooming with a large one), while thumb movement performs the selected mode. We discuss nuances of the Fat Thumb based on the thumb's limited operational range and motor skills when that hand holds the device. We compared Fat Thumb to three alternative techniques, where people had to precisely pan and zoom to a predefined region on a map and found that the Fat Thumb technique compared well to existing techniques.

Modern mobile devices rely on the screen as a primary input modality. Yet the small screen real-estate limits interaction possibilities, motivating researchers to explore alternate input techniques. Within this arena, our goal is to develop Body-Centric Interaction with Mobile Devices: a class of input techniques that allow a person to position and orient her mobile device to navigate and manipulate digital content anchored in the space on and around the body. To achieve this goal, we explore such interaction in a bottom-up path of prototypes and implementations. From our experiences, as well as by examining related work, we discuss and present three recurring themes that characterize how these interactions can be realized. We illustrate how these themes can inform the design of Body-Centric Interactions by applying them to the design of a novel mobile browser application. Overall, we contribute a class of mobile input techniques where interactions are extended beyond the small screen, and are instead driven by a person's movement of the device on and around the body.

Instant messaging systems, such as Skype, offer text, audio and video channels for one-on-one and group conversations, both for personal and professional communication. They are commonly used at a distance, i.e., across countries and continents. To avoid disrupting other tasks, they display personal states to signal others when to contact someone and when not. This mechanism, however, heavily relies on users setting their own state correctly. In an online survey with 46 participants we found that neglecting state updates leads to unwanted messages, either because the state is incorrect or others disrespect it because they assume it to be wrong anyway. We address this situation with the StaTube, a tangible object offering (1) peripheral interaction for setting one's own state and (2) peripheral awareness of selected others' state. In an in-situ evaluation we found first indicators that (1) peripheral interaction fosters more frequent state updates and more accurate state information, and (2) that our participants felt more aware of their contacts' states due to the physical ambient representation.

In the real world, touch based interaction relies on haptic feedback (e.g., grasping objects, feeling textures). Unfortunately, such feedback is absent in current tabletop systems. The previously developed Haptic Tabletop Puck (HTP) aims at supporting experimentation with and development of inexpensive tabletop haptic interfaces in a do-it-yourself fashion. The problem is that programming the HTP (and haptics in general) is difficult. To address this problem, we contribute the Haptictouch toolkit, which enables developers to rapidly prototype haptic tabletop applications. Our toolkit is structured in three layers that enable programmers to: (1) directly control the device, (2) create customized combinable haptic behaviors (e.g., softness, oscillation), and (3) use visuals (e.g., shapes, images, buttons) to quickly make use of these behaviors. In our preliminary exploration we found that programmers could use our toolkit to create haptic tabletop applications in a short amount of time.

The increasing number of media facades in urban spaces offers great potential for new forms of interaction especially for collaborative multi-user scenarios. In this paper, we present a way to directly interact with them through live video on mobile devices. We extend the Touch Projector interface to accommodate multiple users by showing individual content on the mobile display that would otherwise clutter the facade's canvas or distract other users. To demonstrate our concept, we built two collaborative multi-user applications: (1) painting on the facade and (2) solving a 15-puzzle. We gathered informal feedback during the ARS Electronica Festival in Linz, Austria and found that our interaction technique is (1) considered easy-to-learn, but (2) may leave users unaware of the actions of others.

Currently available user interfaces for playlist generation allow creating playlists in various ways, within a spectrum from fully automatic to fully manual. However, it is not entirely clear how users interact with such systems in the field and whether different situations actually demand different interfaces. In this paper we describe Rush 2, a music interface for mobile touch-screen devices that incorporates three interaction modes with varying degrees of automation: Adding songs manually, in quick succession using the rush interaction technique or filling the playlist automatically. For all techniques various filters can be set. In a two- week diary study (with in-depth interaction logging) we gained insight into how people interact with music in their everyday lives and how much automation and interactivity are really necessary.

People naturally understand and use proxemic relationships (e.g., their distance and orientation towards others) in everyday situations. However, only few ubiquitous computing (ubicomp) systems interpret such proxemic relationships to mediate interaction (proxemic interaction). A technical problem is that developers find it challenging and tedious to access proxemic information from sensors. Our Proximity Toolkit solves this problem. It simplifies the exploration of interaction techniques by supplying fine-grained proxemic information between people, portable devices, large interactive surfaces, and other non-digital objects in a room-sized environment. The toolkit offers three key features. 1) It facilitates rapid prototyping of proxemic-aware systems by supplying developers with the orientation, distance, motion, identity, and location information between entities. 2) It includes various tools, such as a visual monitoring tool, that allows developers to visually observe, record and explore proxemic relationships in 3D space. (3) Its flexible architecture separates sensing hardware from the proxemic data model derived from these sensors, which means that a variety of sensing technologies can be substituted or combined to derive proxemic information. We illustrate the versatility of the toolkit with proxemic-aware systems built by students.

In 1992, Tani et al. proposed remotely operating machines in a factory by manipulating a live video image on a computer screen. In this paper we revisit this metaphor and investigate its suitability for mobile use. We present Touch Projector, a system that enables users to interact with remote screens through a live video image on their mobile device. The handheld device tracks itself with respect to the surrounding displays. Touch on the video image is projected onto the target display in view, as if it had occurred there. This literal adaptation of Tani's idea, however, fails because handheld video does not offer enough stability and control to enable precise manipulation. We address this with a series of improvements, including zooming and freezing the video image. In a user study, participants selected targets and dragged targets between displays using the literal and three improved versions. We found that participants achieved highest performance with automatic zooming and temporary image freezing.

We present rush as a recommendation-based interaction and visualization technique for repeated item selection from large data sets on mobile touch screen devices. Proposals and choices are intertwined in a continuous finger gesture navigating a two-dimensional canvas of recommended items. This provides users with more flexibility for the resulting selections. Our design is based on a formative user study regarding orientation and occlusion aspects. Subsequently, we implemented a version of rush for music playlist creation. In an experimental evaluation we compared different types of recommendations based on similarity, namely the top 5 most similar items, five random selections from the list of similar items and a hybrid version of the two. Participants had to create playlists using each condition. Our results show that top 5 was too restricting, while random and hybrid suggestions had comparable results.

The choices we take when listening to music are expressions of our personal taste and character. Storing and accessing our listening histories is trivial due to services like Last.fm, but learning from them and understanding them is not. Existing solutions operate at a very abstract level and only produce statistics. By applying techniques from information visualization to this problem, we were able to provide average people with a detailed and powerful tool for accessing their own musical past. LastHistory is an interactive visualization for displaying music listening histories, along with contextual information from personal photos and calendar entries. Its two main user tasks are (1) analysis, with an emphasis on temporal patterns and hypotheses related to musical genre and sequences, and (2) reminiscing, where listening histories and context represent part of one's past. In this design study paper we give an overview of the field of music listening histories and explain their unique characteristics as a type of personal data. We then describe the design rationale, data and view transformations of LastHistory and present the results from both a lab- and a large-scale online study. We also put listening histories in contrast to other lifelogging data. The resonant and enthusiastic feedback that we received from average users shows a need for making their personal data accessible. We hope to stimulate such developments through this research.

The MOST bus is a current bus technology for connecting multimedia components in cars, such as radios, navigation systems, or media players. The bus functionality is described in a large hierarchically structured catalog of some 4psila000 entries. Browsing this catalog has become infeasible on paper as well as with currently used textual database interfaces. An observation of current work practices has revealed many problems and inefficiencies. We describe the (iteratively developed) design of MostVis, a visual tool for exploring MOST function catalogs, as well as an evaluation of our implemented prototype. Our design carefully adapts existing visualization techniques and combines them in a multiple coordinated view (MCV) approach to satisfy the specific needs of our target group. With this paper, we hope to provide a living example of how existing general-purpose techniques can be successfully trimmed and tailored for a very specific audience.

As mobile and tangible devices are getting smaller and smaller it is desirable to extend the interaction area to their whole surface area. The HandSense prototype employs capacitive sensors for detecting when it is touched or held against a body part. HandSense is also able to detect in which hand the device is held, and how. The general properties of our approach were confirmed by a user study. HandSense was able to correctly classify over 80 percent of all touches, discriminating six different ways of touching the device (hold left/right, pick up left/right, pick up at top/bottom). This information can be used to implement or enhance implicit and explicit interaction with mobile phones and other tangible user interfaces. For example, graphical user interfaces can be adjusted to the user's handedness.

This paper documents the demonstration showcasing the ScreenSpot resource discovery framework and the Mobile-Vue social media sharing application. The key points of the demonstration include: requesting multidimensional resource availability information from a smart space and visualizing this inform

Big challenge related to the contemporary research on ubiquitous and pervasive computing is that of seamless integration. For the next generation of ubiquitous and distributed applications to emerge, disruptive functionality towards opportunistic and heterogeneous device ensembles is required on all

Collaborative creativity is traditionally supported by formal techniques, such as brainstorming. These techniques improve the idea-generation process by creating group synergies, but also suffer from a number of negative effects. Current electronic tools to support collaborative creativity overcome some of these problems, but introduce new ones, by either losing the benefits of face-to-face communication or the immediacy of simultaneous contribution. Using an interactive environment as a test bed, we are investigating how collaborative creativity can be supported electronically while maintaining face-to-face communication. What are the design-factors influencing such a system? We have designed a brainstorming application that uses an interactive table and a large wall display, and compared the results of using it to traditional paper-based brainstorming in a user study with 30 participants. From the considerations that went into the design and the observations during the study we derive a number of design guidelines for collaborative systems in interactive environments.

In this paper we present a wall-sized input system with high accuracy input in the center and lower precision tracking on the remaining parts of the wall. This work complements the concept of focus plus context displays where output quality in the center is better than in the periphery. Our contribution is to realize a similar concept for the input direction. A high precision tracking unit in the center provides a workspace with high interactivity, while four additional cameras placed in the corners of the wall provide lower precision tracking and hence much coarser interactivity on the entire wall. In our prototype this multi-precision input solution is combined with a focus plus context display, thus providing two levels of interactivity in both the input and output direction. With this setup, we have implemented two example applications to demonstrate the benefits of variable precision input

In this paper we present a toolkit for realizing capacitive sensing applications for human-computer interaction in pervasive computing systems. We argue that capacitive sensors - due to their unique properties - are well suited for many pervasive and ubiquitous computing applications and scenarios. We describe the CapToolKit designed to rapidly realize prototypes and systems that are able to detect the presence of humans and objects. Our toolkit also allows the integration of 3D interaction with everyday objects as well as instrumented environments. We illustrate its capabilities by presenting several applications implemented using CapToolKit. The entire system will be open-sourced to allow utilization of our technology within other research projects. By building on the existing toolkit researchers are provided a foundation for developing their own sensor systems, algorithms, and applications