Current co-op games keep collaboration virtual even when players are physically co-located in the same room, limiting embodied coordination in the shared space. We introduce MoveTogether, a novel physical co-op gameplay in which two players jointly operate a single, tracked prop, adding a shared physical communication channel on top of visual and audio cues. To explore the design space in mixed reality, we conducted a workshop with 10 professional designers, generating a physical co-op design space that encompasses prop and interaction design patterns, and how they relate to affordance and cooperative experience. In a within-subjects study of virtual vs. physical co-op experiences (n=16), we observed finer-grained task coordination, fewer collisions, and more strategy-focused communication. Players reported higher collaboration, sense of achievement, enjoyment, and overall preference for physical co-op. This work opens a new design space for co-located play and offers guidance for designing embodied co-op experiences.

We present DrivingVibe, which explores vibrotactile feedback designs around the head to enhance VR driving motion experiences. We propose two approaches that use a 360-degree vibrotactile headband: 1) mirroring and 2) 3D inertia-based. The mirroring approach extends the vibrotactile patterns of handheld controllers to actuate the entire headband uniformly. The 3D inertia-based approach uses the acceleration telemetry data that driving games/simulators export to motion platforms to generate directional vibration patterns, including: i) centrifugal forces, ii) horizontal acceleration/deceleration, and iii) vertical motion due to rough terrain. The two approaches are complementary as the mirroring approach supports all driving games because it does not require telemetry data, while the 3D inertia-based approach provides higher feedback fidelity for games that provide such data. We conducted a 24-person user experience evaluation in both passive passenger mode and active driving mode. Study results showed that both DrivingVibe designs significantly improved realism, immersion, and enjoyment (p<.01) with large effect sizes for the VR driving experiences. For overall preference, 88% (21/24) of participants preferred DrivingVibe, with a 2:1 preference for 3D inertia-based vs. mirroring designs (14 vs. 7 participants). For immersion and enjoyment, 96% (23/24) of participants preferred DrivingVibe, with nearly a 3:1 preference (17 vs. 6 participants) for the 3D inertia-based design.

Teleportation, which instantly moves users from their current location to the target location, has become the most popular locomotion technique in VR games. It enables fast navigation with reduced VR sickness but results in significantly reduced immersion. We present HeadWind, a novel approach to improve the experience of teleportation by simulating the haptic sensation of air drag when rapidly moving through the air in real life. Specifically, HeadWind modulates bursts of compressed air to the face and uses multiple nozzles to provide directional cues. To design the wearable device and to model airflow speed and duration for teleportation, we conducted three formative studies and a design session. User experience evaluation with 24 participants showed that HeadWind significantly improved realism, immersion, and enjoyment of teleportation in VR (p<.01) with large effect sizes (r>0.5), and was preferred by 96% of participants.

Virtual Reality (VR) sickness is common with symptoms such as headaches, nausea, and disorientation, and is a major barrier to using VR. We propose WalkingVibe, which applies unobtrusive vibrotactile feedback for VR walking experiences, and also reduces VR sickness and discomfort while improving realism. Feedback is delivered through two small vibration motors behind the ears at a frequency that strikes a balance in inducing vestibular response while minimizing annoyance. We conducted a 240-person study to explore how visual, audio, and various tactile feedback designs affect the locomotion experience of users walking passively in VR while seated statically in reality. Results showed timing and location for tactile feedback have significant effects on VR sickness and realism. With WalkingVibe, 2-sided step-synchronized design significantly reduces VR sickness and discomfort while significantly improving realism. Furthermore, its unobtrusiveness and ease of integration make WalkingVibe a practical approach for improving VR experiences with new and existing VR headsets.

Virtual Reality (VR) sickness occurs when exposure to a virtual environment causes symptoms that are similar to motion sickness, and has been one of the major user experience barriers of VR. To reduce VR sickness, prior work has explored dynamic field-of-view modification and galvanic vestibular stimulation (GVS) that recou-ples the visual and vestibular systems. We propose a new approach to reduce VR sickness, called PhantomLegs, that applies alternating haptic cues that are synchronized to users' footsteps in VR. Our prototype consists of two servos with padded swing arms, one set on each side of the head, that lightly taps the head as users walk in VR. We conducted a three-session, multi-day user study with 30 participants to evaluate its effects as users navigate through a VR environment while physically being seated. Results show that our approach significantly reduces VR sickness during the initial exposure while remaining comfortable to users.

This work presents HapticSphere, a wearable spherical surface enabled by bridging a finger and the head-mounted display (HMD) with a passive string. Users perceive a physical support on a finger attached to a string, when extending their arm and reaching out to the string's maximum extension. This physical support assists users in precise touch interaction in the context of stationary and walking virtual or mixed-reality experiences. We propose three methods of attachment of the haptic string (directly on the head or on the body), and illustrate a novel single-step calibration algorithm that supports these configurations by estimating a grand haptic sphere, once a head-coordinated touch interaction is established. Two user studies were conducted to validate our approach and to compare the touch performance with physical support in sitting and walking conditions in the context of mobile mixed-reality scenarios. The results show that, in the walking condition, touch interaction with physical support significantly outperformed the visual-only condition.

Drones offer camera angles that are not possible with traditional cameras and are becoming increasingly popular for videography. However, flying a drone and controlling its camera simultaneously requires manipulating 5-6 degrees of freedom (DOF) that needs significant training. We present ARPilot, a direct-manipulation interface that lets users plan an aerial video by physically moving their mobile devices around a miniature 3D model of the scene, shown via Augmented Reality (AR). The mobile devices act as the viewfinder, making them intuitive to explore and frame the shots. We leveraged AR technology to explore three 6DOF video-shooting interfaces on mobile devices: AR keyframe, AR continuous, and AR hybrid, and compared against a traditional touch interface in a user study. The results show that AR hybrid is the most preferred by the participants and expends the least effort among all the techniques, while the users' feedback suggests that AR continuous empowers more creative shots. We discuss several distinct usage patterns and report insights for further design.

Online fitness videos make it possible and popular to do exercise at home. However, it is not easy to notice the details of motions by merely watching training videos. We propose a new type of motion guidance system that simulates the way that the human body moves as driven by muscle contractions. We have designed external artificial muscles on a sleeve to create a pulling sensation that can guide the forearm's pronation (internal rotation) and the forearm's supination (external rotation). The sleeve consists of stepper motors to provide pulling force, fishing lines and elastic bands to imitate muscle contraction to drive the forearm to rotate instinctively. We present two preliminary experiments. The first one shows that this system can effectively guide the forearm to rotate in the correct direction. The second one shows that users can be guided to the targeted angle by utilizing a tactile cue. We also report users' feedback through the experiments and provide design recommendations and directions for future research.

We present FlickBoard, which combines a touchpad and a keyboard into the same interaction area to reduce hand movement between a separate keyboard and touchpad. Our main contribution is automatic mode switching between typing and pointing, and the first system capable of combining a trackpad and a keyboard into an single interaction area without the need for external switches. We developed a prototype by embedding a 58x20 capacitive sensing grid into a soft keyboard cover, and used machine learning to distinguish between moving a cursor (touchpad mode) and entering text (keyboard mode). We conducted experimental studies that show automatic mode switching classification accuracies of 98% are achievable with our technology. Finally, our prototype has a thin profile and can be placed over existing keyboards.

Current touch-based UIs commonly employ regions near the corners and/or edges of the display to accommodate essential functions. As the screen size of mobile phones is ever increasing, such regions become relatively distant from the thumb and hard to reach for single-handed use. In this paper, we present two techniques: CornerSpace and BezelSpace, designed to accommodate quick access to screen targets outside the thumb's normal interactive range. Our techniques automatically determine the thumb's physical comfort zone and only require minimal thumb movement to reach distant targets on the edge of the screen. A controlled experiment shows that BezelSpace is significantly faster and more accurate. Moreover, both techniques are application-independent, and instantly accommodate either hand, left or right.

Most mobile games are designed for users to only focus on their own screens thus lack of face-to-face interaction even users are sitting together. Prior work shows that the shared information space created by multiple mobile devices can encourage users to communicate to each other naturally. The aim of this work is to provide a fluent view-stitching technique for mobile phone users to establish their information-shared view. We present MagMobile: a new spatial interaction technique that allows users to stitch views by simply putting multiple mobile devices close to each other. We describe the design of spatial-aware sensor module which is low cost and easy to be obtained into phones. We also propose two collaborative games to engage social interactions in the co-located place.

We present TUIC, a technology that enables tangible interaction on capacitive multi-touch devices, such as iPad, iPhone, and 3M's multi-touch displays, without requiring any hardware modifications. TUIC simulates finger touches on capacitive displays using passive materials and active modulation circuits embedded inside tangible objects, and can be used with multi-touch gestures simultaneously. TUIC consists of three approaches to sense and track objects: spatial, frequency, and hybrid (spatial plus frequency). The spatial approach, also known as 2D markers, uses geometric, multi-point touch patterns to encode object IDs. Spatial tags are straightforward to construct and are easily tracked when moved, but require sufficient spacing between the multiple touch points. The frequency approach uses modulation circuits to generate high-frequency touches to encode object IDs in the time domain. It requires fewer touch points and allows smaller tags to be built. The hybrid approach combines both spatial and frequency tags to construct small tags that can be reliably tracked when moved and rotated. We show three applications demonstrating the above approaches on iPads and 3M's multi-touch displays.

This paper proposes convenient and useful approaches to automatically calibrate the projectors of a multi-resolution display. The proposed approaches estimate both the keystone effect and misalignment of the projections with an assistance of a color camera. Structured light patterns are employed to construct the geometric relationship between projectors and the projection surface, and then pre-warp the images so that they appear undistorted as a result. Experimental results demonstrate that the proposed approaches successfully reduce the human-effort and lower the calibration time of multi-resolution display calibration task.

Virtual keyboards and controls, commonly used on mobile multi-touch devices, occlude content of interest and do not provide tactile feedback. Clip-on Gadgets solve these issues by extending the interaction area of multi-touch devices with physical controllers. Clip-on Gadgets use only conductive materials to map user input on the controllers to touch points on the edges of screens; therefore, they are battery-free, lightweight, and low-cost. In addition, they can be used in combination with multi-touch gestures. We present several hardware designs and a software toolkit, which enable users to simply attach Clip-on Gadgets to an edge of a device and start interacting with it.

In this paper, we propose the seamless multimedia system Yongzheng Emperor's interactive tabletop, which has been incorporated into the special exhibition "Harmony and Integrity: The Yongzheng Emperor and His Times" at the National Palace Museum in Taiwan. The multimedia system features the innovative use of physical artifacts - Yongzheng figurines and a model of Yongzheng-era calendar clock as tangible user interfaces, which have been used to activate on the Surface the emperor's life at court and chronological events of his times. Museum audiences can naturally and intuitively explore the Emperor's stories by the use of hand gestures. The system vividly connects the modern world of the audiences with the emperor's virtual world, engaging museum audiences in the most interactive and compelling way to learn about the emperor. The paper aims to present the development of the seamless tabletop system in a historical museum context, including design principles, implementation, applications, and effectiveness of the system. Our contribution in this project is to demonstrate a new exhibition display model for the museum sector.

Many map systems are created to help the user finding a place or define a route to follow. Google Map extends the concept of "surfing the map" by adding a street view that allows the user to explore a place from real pictures, creating the same feeling of walking through the streets. The horizontal 2D map and vertical panoramic street view, however, cause usability problems, while operating with traditional computer mouse and keyboards and presenting by single vertical or horizontal display. This paper presents a new table system composed of a horizontal tabletop screen and a vertical screen. The map view and the street view are displayed on the horizontal and vertical displays of our system respectively. Users can place the tangible pawn on the 2D map to have direct access of the street view from the pawn's point of view. In the user study, we compare our system with a standard computer system in the navigation task. The results reported that our system improves the intuitiveness of use, efficiency of city exploring and ease of remembrance on spaces that are not familiar beforehand. We also discuss limitations of using tangible objects for map navigation.