Recent advances in material-centric personal fabrication have enabled the use of custom inks and paints with functional properties to create free-form displays. However, working with these materials, such as through airbrushing, remains a skill-intensive process that limits non-specialist access, adoption, and further development. To address these challenges, we developed Dispray, an AR-augmented airbrush tool for fabricating electroluminescent displays. The tool was shaped by insights from a study with artists and engineers and refined through iterative prototyping. We evaluated Dispray by re-engaging with the original artists and engineers and conducting a follow-up study with novice users, demonstrating its effectiveness in supporting both skill acquisition and functional fabrication. This work contributes a novel approach to connecting emerging material fabrication with accessible, user-centered tools, advancing the democratisation of interactive device creation.

Consumer-level multi-material 3D printing with conductive thermoplastics enables fabrication of interactive elements for bespoke tangible devices. However, large feature sizes, high resistance materials, and limitations of printable control circuitry mean that deployable devices cannot be printed without post-print assembly steps. To address these challenges, we present Printegrated Circuits, a technique that uses traditional electronics as material to 3D print self-contained interactive objects. Embedded PCBs are placed into recesses during a pause in the print, and through a process we term Prinjection, conductive filament is injected into their plated-through holes. This automatically creates reliable electrical and mechanical contact, eliminating the need for manual wiring or bespoke connectors. We describe the custom machine code generation that supports our approach, and characterise its electrical and mechanical properties. With our 6 demonstrations, we highlight how the Printegrated Circuits process fits into existing design and prototyping workflows as well as informs future research agendas.

Despite significant advances in interactive clothing over the past decade, e-textiles lack traditional fabric robustness and comfort. SeamSleeve provides a method for using garment seams as sensing channels while retaining the benefits of regular clothing design. We power conductive seams at low voltages to stitch together everyday fabric panels, resulting in a novel sensing mechanism capable of detecting arm movements. Our first empirical study (n=10) identifies optimal seam design and placement on the sleeve, by comparing traditional seam forms in the context of sensing capabilities. A second study (n=14) demonstrates that our minimal sensing approach is capable of successfully classifying 8 arm exercises with an accuracy of 84%. Our findings support the effectiveness of the approach in areas such as longitudinal physiotherapeutic rehabilitation beyond the clinic, enabling everyday motion capture.

Over recent years, there has been significant research within HCI towards free-form physical interactive devices. However, such devices are not straightforward to design, produce and deploy on demand. Traditional development revolves around iterative prototyping through component-based assembly, limiting device structure and implementation. Material-centric personal display fabrication (DisplayFab) opens the possibility of decentralised, configurable production by low-skill makers. Currently, DisplayFab is severely limited by its embryonic stage of development, the complexity of involved processes and materials, and the challenges around designing interactive structures. We present a development framework to provide a path for future research. DisplayFab has been developed by identifying 4 key breakpoints in the existing “Personal Fabrication” framework: Material and Deposition, Conception and Software, Feedback and Interactivity and Responsible Innovation. We use these breakpoints to form a targeted literature review of relevant work. Doing this we identify 30 challenges that act as roadmap for future research in DisplayFab.

Sonolithography is the process of directed patterning of airborne particles through the exertion of acoustic radiation forces in ultrasound fields. In this work we present a novel way to explore and gain intuition about the process through tangible interaction. We demonstrate the design and use of a physical instrument for the creation of sonolithographs. The design includes the “Orbograph”, a tangible controller that embodies key acoustic parameters through direct tactile interactions; a low-cost and open-source driving circuit; and a configurable transducer array. We demonstrate its capabilities by presenting sonolithographs made with the tool that contain linear patterns, grids, circular and more complex shapes. By using different dyes and active materials, we demonstrate sonolithography's creative application as well as suggest its potential in the fabrication of interactive devices. Through this work we encourage a playful artistic exploration of the domain to motivate future research in sonolithography for tangible material interactions.

Abstract: FabricatINK explores the personal fabrication of irregularly-shaped low-power displays using electronic ink (E ink). E ink is a programmable bicolour material used in traditional form-factors such as E readers. It has potential for more versatile use within the scope of personal fabrication of custom-shaped displays, and it has the promise to be the pre-eminent material choice for this purpose. We appraise technical literature to identify properties of E ink, suited to fabrication. We identify a key roadblock, universal access to E ink as a material, and we deliver a method to circumvent this by upcycling broken electronics. We subsequently present a novel fabrication method for irregularly-shaped E ink displays. We demonstrate our fabrication process and E ink’s versatility through ten prototypes showing different applications and use cases. By addressing E ink as a material for display fabrication, we uncover the potential for users to create custom-shaped truly bistable displays.

One of the most fundamental interactions –pointing– is well understood on flat surfaces. However, pointing performance on tangible surfaces with physical targets is still limited for Tangible User Interfaces (TUIs). We investigate the effect of a target’s physical width, height, and distance on user pointing performance. We conducted a study using a reciprocal tapping task ( n =19) with physical rods arranged in a circle. We compared our data with five conventional interaction models designed for 2D/3D tasks rather than tangible targets. We show that variance in the movement times was only satisfactorily explained by a model established for volumetric displays ( r 2 =0.954). Analysis shows that movement direction and height should be included as parameters to this model to generalize for 3D tangible targets. Qualitative feedback from participants suggests that pointing at physical targets involves additional human factors (e.g., perception of sharpness or robustness) that need to be investigated further to understand how performance with tangible objects is affected.

Abstract: We consider how seams in clothing can be designed for interactive sensing of body movement. Conductive yarn is activated at low voltages which fluctuate as body movement varies tension across the seams. Traditional garment construction describes how fabrics, blocks and seam types are configured according to mechanical performance and historical changes in fashion. Bodice blocks span the human torso, anchoring and reflecting core body movement. We explore the stability and calibration of seam voltage in a bodice block, while performing a yoga-inspired movement sequence. Our exploratory studies test signal orthogonality between seam stitch types and seam placements for supporting reliable sensing. We use our exploratory work to consider design alternatives which balance seam requirements against sensing opportunities, including back seams for torso garments. Our findings contrast optimal seam placement and design in wearable e-textiles with those in traditional clothing.

ProtoSpray is a fabrication method that combines 3D printing and spray coating, to create interactive displays of arbitrary shapes. Our approach makes novel use of 3D printed conductive channels to create base electrodes on 3D shapes. This is then combined with spraying active materials to produce illumination. We demonstrate the feasibility and benefits of this combined approach in 6 evaluations exploring different shaped topologies. We analyze factors such as spray orientations, surface topologies and printer resolutions, to discuss how spray nozzles can be integrated into traditional 3D printers. We present a series of ProtoSprayed objects demonstrating how our technique goes beyond existing fabrication techniques by allowing creation of displays on objects with curvatures as complex as a Mobius strip. Our work provides a platform to empower makers to use displays as a fabrication material.

We present Sprayable User Interfaces: room-sized interactive surfaces that contain sensor and display elements created by airbrushing functional inks. Since airbrushing is inherently mobile, designers can create large-scale user interfaces on complex 3D geometries where existing stationary fabrication methods fail. To enable Sprayable User Interfaces, we developed a novel design and fabrication pipeline that takes a desired user interface layout as input and automatically generates stencils for airbrushing the layout onto a physical surface. After fabricating stencils from cardboard or projecting stencils digitally, designers spray each layer with an airbrush, attach a microcontroller to the user interface, and the interface is ready to be used. Our technical evaluation shows that Sprayable User Interfaces work on various geometries and surface materials, such as porous stone and rough wood. We demonstrate our system with several application examples including interactive smart home applications on a wall and a soft leather sofa, an interactive smart city application, and interactive architecture in public office spaces.

In this paper we describe an exploratory study that incorporates the design, implementation and study of a system that utilises virtual reality, tangible interaction and force feedback. The approach we take is to design a VR system that incorporates a moveable tangible interface (wheelchair), which overlaps seamlessly with a 3d counterpart in the virtual world. The user interacts with the virtual environment by pushing the physical wheelchair, which simultaneously controls the virtual avatar. In the virtual world we place objects that once collided with trigger force feedback by stopping the physical wheelchair. In this paper we discuss the design rationale and technical implementation and follow by describing the next phase of this work in progress.

Today, users are an integral part of charging their mobile and wearable computing devices, including smartphones, smartwatches, fitness trackers and music players. In this paper CoilMove is presented. CoilMove is an actuated wireless energy transfer system, envisaged as being embedded within a surface in a user's ambient environment, such as a floor or table. CoilMove transfers energy to devices located on the body and can recharge our mobile and wearable devices through inductive power transfer without the need for user input. CoilMove is capable of locating a device on a user's body through the presence of a magnet on the device. The user need not be aware of the interaction and from a user perspective devices would appear to charge themselves. Furthermore CoilMove is compliant with international guidelines on time-varying magnetic fields present in inductive power transfer systems, affording prolonged system use.

Recent improvements in ultrasound imaging enable new opportunities for hand pose detection using wearable devices. Ultrasound imaging has remained under-explored in the HCI community despite being non-invasive, harmless and capable of imaging internal body parts, with applications including smart-watch interaction, prosthesis control and instrument tuition. In this paper, we compare the performance of different forearm mounting positions for a wearable ultrasonographic device. Location plays a fundamental role in ergonomics and performance since the anatomical features differ among positions. We also investigate the performance decrease due to cross-session position shifts and develop a technique to compensate for this misalignment. Our gesture recognition algorithm combines image processing and neural networks to classify the flexion and extension of 10 discrete hand gestures with an accuracy above 98%. Furthermore, this approach can continuously track individual digit flexion with less than 5% NRMSE, and also differentiate between digit flexion at different joints.

Wearable devices for activity tracking and gesture recognition have expanded rapidly in recent years. One technique that has shown great potential for this is ultrasonic imaging [10][4]. This technique has been shown to have advantages over other techniques in accuracy, surface area, placement and importantly, continuous finger angle estimations. However, ultrasonic imaging suffers from a couple of issues: First and foremost, the propagation of ultrasound into flesh suffers greatly without a suitable coupling medium; Secondly, the complexity of the driving circuitry for medical grade imaging currently renders a wearable version of this infeasible. This paper aims to address these two problems by finding a rigid coupling medium that lasts for significantly longer periods of time; and devising a new sensor configuration to reduce the device complexity, while still retaining the benefits of the technique. Furthermore, a comparison between high and low frequency systems reveal that different devices can be created with this technique for better resolution or convenience respectively.

In this paper we present InstructiBlocks, a system for constructing ambiguously defined physical-digital models, with the role of supporting the task of early stage ideation and design space exploration. Construction blocks tagged with RFID chips allow digital labelling with the build instructions. As each label only gives partial information on how to build the model it is possible for the designer to create a wide variety of models around the particular constraints that are present in both the physical blocks available and the digital instructions contained within them. In this context ambiguity is enabled by the digital instructions and there is no master copy, rather the state of the physical-digital model is determined by the interplay between the user, the physical blocks and digital instructions. In this paper we ask: Can an ambiguously defined model lead to greater design ideation and design space exploration? Are there benefits to "human-actuated" interfaces, where a physical-digital model is constructed manually?

Gestures have become an important tool for natural interaction with computers and thus several wearables have been developed to detect hand gestures. However, many existing solutions are unsuitable for practical use due to low accuracy, high cost or poor ergonomics. We present SensIR, a bracelet that uses near-infrared sensing to infer hand gestures. The bracelet is composed of pairs of infrared emitters and receivers that are used to measure both the transmission and reflection of light through/off the wrist. SensIR improves the accuracy of existing infrared gesture sensing systems through the key idea of taking measurements with all possible combinations of emitters and receivers. Our study shows that SensIR is capable of detecting 12 discrete gestures with 93.3% accuracy. SensIR has several advantages compared to other systems such as high accuracy, low cost, robustness against bad skin coupling and thin form-factor.

Practical wearable gesture tracking requires that sensors align with existing ergonomic device forms. We show that combining EMG and pressure data sensed only at the wrist can support accurate classification of hand gestures. A pilot study with unintended EMG electrode pressure variability led to exploration of the approach in greater depth. The EMPress technique senses both finger movements and rotations around the wrist and forearm, covering a wide range of gestures, with an overall 10-fold cross validation classification accuracy of 96%. We show that EMG is especially suited to sensing finger movements, that pressure is suited to sensing wrist and forearm rotations, and their combination is significantly more accurate for a range of gestures than either technique alone. The technique is well suited to existing wearable device forms such as smart watches that are already mounted on the wrist.

Current devices have limited battery life, typically lasting less than one day. This can lead to situations where critical tasks, such as making an emergency phone call, are not possible. Other devices, supporting different functionality, may have sufficient battery life to enable this task. We present PowerShake; an exploration of power as a shareable commodity between mobile (and wearable) devices. PowerShake enables users to control the balance of power levels in their own devices (intra-personal transactions) and to trade power with others (inter-personal transactions) according to their ongoing usage requirements. This paper demonstrates Wireless Power Transfer (WPT) between mobile devices. PowerShake is: simple to perform on-the-go; supports ongoing/continuous tasks (transferring at ~3.1W); fits in a small form factor; and is compliant with electromagnetic safety guidelines while providing charging efficiency similar to other standards (48.2% vs. 51.2% in Qi). Based on our proposed technical implementation, we run a series of workshops to derive candidate designs for PowerShake enabled devices and interactions, and to bring to light the social implications of power as a tradable asset.

Wearable and smart devices are gaining in popularity, with many users now using multiple devices. Each of these devices requires individual charging and power maintenance. This paper proposes power sharing between multiple wearables to alleviate some of the burden of charging multiple devices. To achieve wearable and smart device power sharing, we propose using the garments we wear as a power distribution backbone. To allow non-contact power transfer between garments, bi-directional inductive power transfer is used. We demonstrate a novel coil topology called Feed Coils constructed from flexible materials to aid garment integration and user comfort. Our system complies with international guidelines on time-varying magnetic field exposure to human tissue, allowing the system to be operated in close proximity to the body. Three preliminary experiments are conducted to characterize the bi-directional inductive power sharing system and to investigate the feasibility and human factors impacting wearable and smart device power sharing.

This paper presents the concept of Resonant Bits, an interaction technique for encouraging engaging, slow and skilful interaction with tangible, mobile and ubiquitous devices. The technique is based on the resonant excitation of harmonic oscillators and allows the exploration of a number of novel types of tangible interaction including: ideomotor control, where subliminal micro-movements accumulate over time to produce a visible outcome; indirect tangible interaction, where a number of devices can be controlled simultaneously through an intermediary object such as a table; and slow interaction, with meditative and repetitive gestures being used for control. The Resonant Bits concept is tested as an interaction method in a study where participants resonate with virtual pendulums on a mobile device. The Harmonic Tuner, a resonance-based music player, is presented as a simple example of using resonant bits. Overall, our ambition in proposing the Resonant Bits concept is to promote skilful, engaging and ultimately rewarding forms of interaction with tangible devices that takes time and patience to learn and master.

Capturing data is a key part of archaeological practice, whether for preserving records or to aid interpretation. But the technologies used are complex and expensive, resulting in time-consuming processes associated with their use. These processes force a separation between ongoing interpretive work and capture. Through two field studies we elicit more detail as to what is important about this interpretive work and what might be gained through a closer integration of capture technology with these practices. Drawing on these insights, we go on to present a novel, portable, wireless 3D modeling system that emphasizes "quick and dirty" capture. We discuss its design rational in relation to our field observations and evaluate this rationale further by giving the system to archaeological experts to explore in a variety of settings. While our device compromises on the resolution of traditional 3D scanners, its support of interpretation through emphasis on real-time capture, review and manipulability suggests it could be a valuable tool for the future of archaeology.

Mobile devices are increasingly providing novel ways for users to engage with the spaces around them. However, there are few systematic studies of enhancing spatial ability with mobile devices, and applications such as turn-by-turn navigation systems have even been associated with a decline in spatial skills. In this paper we present a study based on the 1971 Shepard-Metzler mental rotation test but performed on a mobile-phone handset and a tablet PC. Our study extends the original experiment with the incorporation of touch and tilt interaction techniques, in order to determine if these affect the use and acquisition of spatial skills. Results suggest that the task is performed faster, and with no significant difference in accuracy, when participants rely on mental abilities rather than interaction techniques to perform 3D rotations. We also find significant differences between tablet and phone handset platforms under interactive conditions. We conclude that applications on mobile devices could be designed to enhance rather than erode spatial skills, by supporting the use of imagination to align real and virtual content.

We introduce spatially-aware virtual workspaces for the mobile environment. The notion of virtual workspaces was initially conceived to alleviate mental workload in desktop environments with limited display real-estate. Using spatial properties of mobile devices, we translate this approach and illustrate that mobile virtual workspaces greatly improve task performance for mobile devices. In a first study, we compare our spatially-aware prototype (mSpaces) to existing context switching methods for navigating amongst multiple tasks in the mobile environment. We show that users are faster, make more accurate decisions and require less mental and physical effort when using spatially-aware prototypes. We furthermore prototype pSpaces and m+pSpaces, two spatially-aware systems equipped with pico-projectors as auxiliary displays to provide dual-display capability to the handheld device. A final study reveals advantages of each of the different configurations and functionalities when comparing all three prototypes. Drawing on these findings, we identify design considerations to create, manipulate and manage spatially-aware virtual workspaces in the mobile environment.

An explosion in the availability of online records has led to surging interest in genealogy. In this paper we explore the present state of genealogical practice, with a particular focus on how the process of research is recorded and later accessed by other researchers. We then present our response, ChronoTape, a novel tangible interface for supporting family history research. The ChronoTape is an example of a temporal tangible interface, an interface designed to enable the tangible representation and control of time. We use the ChronoTape to interrogate the value relationships between physical and digital materials, personal and professional practices, and the ways that records are produced, maintained and ultimately inherited. In contrast to designs that support existing genealogical practice, ChronoTape captures and embeds traces of the researcher within the document of their own research, in three ways: (i) it ensures physical traces of digital research; (ii) it generates personal material around the use of impersonal genealogical data; (iii) it allows for graceful degradation of both its physical and digital components in order to deliberately accommodate the passage of information into the future.

Projector phones, handheld game consoles and many other mobile devices increasingly include more than one display, and therefore present a new breed of mobile Multi-Display Environments (MDEs) to users. Existing studies illustrate the effects of visual separation between displays in MDEs and suggest interaction techniques that mitigate these effects. Currently, mobile devices with heterogeneous displays such as projector phones are often designed without reference to visual separation issues; therefore it is critical to establish whether concerns and opportunities raised in the existing MDE literature apply to the emerging category of Mobile MDEs (MMDEs). This paper investigates the effects of visual separation in the context of MMDEs and contrasts these with fixed MDE results, and explores design factors for Mobile MDEs. Our study uses a novel eye-tracking methodology for measuring switches in visual context between displays and identifies that MMDEs offer increased design flexibility over traditional MDEs in terms of visual separation. We discuss these results and identify several design implications.

Cooperative gestures are a key aspect of human-human pro-social interaction. Thus, it is reasonable to expect that endowing humanoid robots with the ability to use such gestures when interacting with humans would be useful. However, while people are used to responding to such gestures expressed by other humans, it is unclear how they might react to a robot making them. To explore this topic, we conducted a within-subjects, video based laboratory experiment, measuring time to cooperate with a humanoid robot making interactional gestures. We manipulated the gesture type (beckon, give, shake hands), the gesture style (smooth, abrupt), and the gesture orientation (front, side). We also employed two measures of individual differences: negative attitudes toward robots (NARS) and human gesture decoding ability (DANVA2-POS). Our results show that people cooperate with abrupt gestures more quickly than smooth ones and front-oriented gestures more quickly than those made to the side, people's speed at decoding robot gestures is correlated with their ability to decode human gestures, and negative attitudes toward robots is strongly correlated with a decreased ability in decoding human gestures.

In order for anthropomorphic robots to communicate with people in a human-like way they need to produce gestures along with speech. Beat gestures are a key category of gestures, accompanying emphasis and timing of talk. The standard approach for autonomously adding gestures to speech for artificial agents to perform, is to identify when gestures should occur, and then select appropriate movements from a prewritten library. However, selecting naively from a library is unlikely to result in particularly human-like gesture sequences. In order to obtain examples of engaging human beat gestures, we studied videos of chat show hosts. Our analysis reveals rules for the creation of human-like beat gestures. We have combined these rules with hand scripted non-beat gestures, to produce a monologue with a complete set of accompanying gestures; it is designed for performance by our humanoid robot BERTI. In order to test the gestures produced we carried out a pilot study at the London Science Museum. The results of the study indicate that having correctly designed gesture sequences improves observer engagement.

The human sciences have demonstrated that gesture is a critical element of human communication. While existing graphical solutions are appropriate for virtual agents, solving arm trajectories for physically embodied robots requires that we consider the challenges of robot dynamics within a realtime gesture framework. We explore and evaluate a low computational-cost gesture production algorithm that can generate adequate gesture trajectories in a humanoid torso, as judged by participants in Human-Robot gesturing studies presented in this paper. Our approach produces a constrained inverse-kinematic solution for the start and end points, and generates appropriate wrist angles. Gesture time is used to calculate the joint accelerations to give a smooth, direct hand movement. Selecting open hand gestures as an example gesture sub-domain, we implement our controller on BERTI, a bespoke upper-torso humanoid robot (Fig. 2). A qualitative pilot study highlights gesture features salient to users: gesture shape, timing, naturalness and smoothness. A controlled experimental study then demonstrates that, by these metrics, our algorithm performs well; despite some dissimilarities with users' own gestures. We establish some salient points of robot gestures based on these studies.

Designing for embodied physical interaction is just as important at a coarse level of spatial navigation as in the minutiae of object exploration. We created interactive embedded interfaces called 'Navitiles' that can be suspended in a floor to support navigation of a building. Our design uses capacitance and RFID sensors to determine users' location and LEDs to indicate possible directions. We determine whether Navitile cues could help users understand spatial relationships between points of interest. We based our study on a previous experiment that used a simulated VR maze to test whether users were able to exhibit 'shortcut' behaviour that would indicate the formation of spatial maps. Our hypothesis was that the physicality of embodied spatial navigation directed by the Navitiles in a real maze would enable users to achieve similar spatial shortcut behaviours to those found in the virtual task. We found significant evidence that sufficient spatial knowledge was acquired to enable successful shortcut performance between unexplored routes. However, further work is required to measure the effect of physical body movement on spatial skills development.

Vehicular Ad hoc networks (VANETs) are the relevant form of ubiquitous computing. Several protocols are being developed for V2R (vehicle to road side) and V2V (Vehicle to Vehicle) communication and the notion of intelligent vehicles is nurturing very rapidly. We have tested the existing WIFI protocol for V2V communication especially at high speed. We have proved, with the help of real life experiments and analytical justification, that WIFI is a successful means of communication between vehicles even at very high speed (i.e. 120 mph relative). Furthermore, several useful and novel applications (like parking, tourist information center, congestion control, advertisement campaign, shortest route, weather reporting, file sharing and on-board gaming) are suggested.

Location-aware systems have traditionally left mobility to the user through carrying, supporting and manipulating the device itself. This design choice has limited the scale and style of device to corresponding weight and form constraints. This paper presents a project introducing school children to location aware systems. We observed that it is hard to notice, physically grasp and simultaneously share these small personal devices in groups. These behaviours are partly grounded in the physical device design, but also in the location awareness model itself, which provides information 'right here' while the children are looking around and about them. These observations lead us to suggest the alternative model of pointing at locations so that they can be noticed and experienced by groups in public places. We further build this location model into the device itself by introducing actuated components from robotics to make a location-aware device called 'Limbot' that can be physically pointed. A preliminary study of the Limbot with the school children indicates rich sharing behaviours, but that user control of actuation at all points is critical to the ultimate success of our approach, and further exploration of our location model is required.

Pauses in distributed groupware activity can indicate anything from technical latency through infrastructure failure to a participant's thoughtful contemplation. Unraveling these ambiguities highlights mismatches between unseen off-screen activities and on-screen cursor behaviors. In this paper we suggest that groupware systems have typically been poor at representing off-screen activities, and introduce the concept of display trajectories to bridge the sensor gap between the display and its surrounding space. We consider requirements for display trajectories using the distributed social scientific analysis of video data as an example domain. Drawing on these requirements, we prototype a freeform whiteboard pen tracking and visualization technique around displays using ultrasound. We describe an experiment which inspects the impact of display trajectories on remote response efficiency. Our findings show that visualization of the display trajectory improves participants' ability to coordinate their actions by one second per interaction turn, reducing latency in organizing turn taking by a 'standard maximum' conversation pause.

Interaction is increasingly a public affair, taking place in our theatres, galleries, museums, exhibitions and on the city streets. This raises a new design challenge for HCI - how should spectators experience a performer's interaction with a computer? We classify public interfaces (including examples from art, performance and exhibition design) according to the extent to which a performer's manipulations of an interface and their resulting effects are hidden, partially revealed, fully revealed or even amplified for spectators. Our taxonomy uncovers four broad design strategies: 'secretive,' where manipulations and effects are largely hidden; 'expressive,' where they tend to be revealed enabling the spectator to fully appreciate the performer's interaction; 'magical,' where effects are revealed but the manipulations that caused them are hidden; and finally 'suspenseful,' where manipulations are apparent but effects are only revealed as the spectator takes their turn.

Delay is an unavoidable reality in collaborative environments. We propose an approach to dealing with delay in which 'decorators' are introduced into the interface. Decorators show the presence, magnitude and effects of delay so that participants can better understand its consequences and adopt their own natural coping strategies. Two experiments with different decorators show that this approach can significantly reduce errors in specific collaborative activities. We conclude that revealing delays is one way in which groupware can benefit from accepting and working with the reality of distributed systems, rather than trying to maintain the illusion of copresent interaction.

The augurscope is a portable mixed reality interface for outdoors. A tripod-mounted display is wheeled to different locations and rotated and tilted to view a virtual environment that is aligned with the physical background. Video from an onboard camera is embedded into this virtual environment. Our design encompasses physical form, interaction and the combination of a GPS receiver, electronic compass, accelerometer and rotary encoder for tracking. An initial application involves the public exploring a medieval castle from the site of its modern replacement. Analysis of use reveals problems with lighting, movement and relating virtual and physical viewpoints, and shows how environmental factors and physical form affect interaction. We suggest that problems might be accommodated by carefully constructing virtual and physical content

We present four contrasting interfaces to allow multiple viewers to explore 3D recordings of dramas in on-line virtual worlds. The first is an on-line promenade performance to an audience of avatars. The second is a form of immersive cinema, with multiple simultaneous viewpoints. The third is a tabletop projection surface that allows viewers to select detailed views from a bird's-eye overview. The fourth is a linear television broadcast created by a director or editor. A comparison of these examples shows how a viewing audience can exploit four general resources - interactivity, influence, space, and time - to make sense of complex, non-linear virtual drama. These resources provide interaction designers with a general framework for defining the relationship between the audience and the 3D content.

A study of a professional touring mixed reality performance called Desert Rain yields insights into how performers orchestrate players' engagement in an interactive experience. Six players at a time journey through an extended physical and virtual set. Each sees a virtual world projected onto a screen made from a fine water spray. This acts as a traversable interface, supporting the illusion that performers physically pass between real and virtual worlds. Live and video-based observations of Desert Rain, coupled with interviews with players and the production team, have revealed how the performers create conditions for the willing suspension of disbelief, and how they monitor and intervene in the players experience without breaking their engagement. This involves carefully timed performances and “off-face” and “virtual” interventions. In turn, these are supported by the ability to monitor players' physical and virtual activity through asymmetric interfaces.

This paper explores and evaluates the support for object-focused interaction provided by a desktop Collaborative Virtual Environment. An experimental “design” task was conducted, and video recordings of the participants' activities facilitated an observational analysis of interaction in, and through, the virtual world. Observations include: problems due to “fragmented” views of embodiments in relation to shared objects; participants compensating with spoken accounts of their actions; and difficulties in understanding others' perspectives. Implications and proposals for the design of CVEs drawn from these observations are: the use of semidistorted views to support peripheral awareness; more explicit or exaggerated representations of actions than are provided by pseudohumanoid avatars; and navigation techniques that are sensitive to the actions of others. The paper also presents some examples of the ways in which these proposals might be realized.

This paper explores interfaces to virtual environments supporting multiple users. An interface to an environment allowing interaction with virtual artefacts is constructed, drawing on previous proposals for 'desktop' virtual environments. These include the use of Peripheral Lenses to support peripheral awareness in collaboration; and extending the ways in which users' actions are represented for each other. Through a qualitative analysis of a design task, the effect of the proposals is outlined. Observations indicate that, whilst these designs go some way to re-constructing physical co-presence in terms of awareness and interaction through the environment, some issues remain. Notably, peripheral distortion in supporting awareness may cause problematic interactions with and through the virtual world; and extended representations of actions may still allow problems in re-assembling the composition of others' actions. We discuss the potential for: designing representations for distorted peripheral perception; and explicitly displaying the course of action in object-focused interaction.

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