This paper reports our recent finding that a laser that is radiated on a thin light-absorbing elastic medium attached on the skin can elicit a tactile sensation of mechanical tap. Laser radiation to the elastic medium creates inner elastic waves on the basis of thermoelastic effects, which subsequently move the medium and stimulate the skin. We characterize the associated stimulus by measuring its physical properties. In addition, the perceptual identity of the stimulus is confirmed by comparing it to mechanical and electrical stimuli by means of perceptual spaces. All evidence claims that indirect laser radiation conveys a sensation of short mechanical tap with little individual difference. To the best of our knowledge, this is the first study that discovers the possibility of using indirect laser radiation for mid-air tactile rendering.

We propose a new action-transferred design approach by which the benefits of embodied cognition and activity can be realized to enhance spatial learning and usability for navigating virtual spaces. The action-transferred design approach is supported by theories of learning, action-perception, and neuropsychology. These theories help us understand how human action can be transferred to different body parts for improving the usability of interaction techniques and why the acquired spatial knowledge using the transferred action may remain the same independent of the used body parts. The finger-walking-in-place (FWIP) navigation technique is used as a design example to demonstrate the concept of the action-transferred design approach. Leveraging 3D immersive virtual reality technology, we performed an empirical study to evaluate the performance of the action-transferred FWIP navigation technique in terms of spatial knowledge acquisition. The FWIP navigation technique was compared with a full-body-based walking-like (sensor-fusion walking-in-place; SF-WIP) navigation technique and a well-known, convenient (Joystick) navigation technique using a common input device, that is, a wand with a joystick. Both the action-transferred and the full-body-based navigation techniques were more effective for spatial learning than the navigation technique using the common input device. However, only the action-transferred FWIP navigation technique can provide users with the convenience of navigating with their fingers. These results suggest that the action-transferred design approach is useful in designing a navigation technique supporting users' spatial learning performance more effectively and conveniently. Possible design implications for broader applications are discussed and indicate that the action-transferred design approach is worth further study.

Comparative studies involving CAVE systems inevitably have some confounding factors. Except for the six-sided CAVE systems, the missing back wall(s) of a CAVE system can be a confounding factor when virtual and physical navigation interaction techniques are compared, regarding the viewpoint rotation. We introduce a virtual black wall as a way to avoid a possible confounding factor in comparative studies. Based on our pilot study, we found that the virtual black wall can provide the comparable experimental condition for the two types of navigation interaction techniques and that the wall can play a dual role as an obstacle and a landmark during navigation. These findings provide a stepping stone for further investigation of the virtual black wall.

This paper describes a sensor-fusion-based wireless walking-in-place (WIP) interaction technique. We devised a new human-walking detection algorithm that is based on a sensor-fusion using both acceleration and magnetic sensors integrated within a smart phone. Our sensor-fusion approach can be useful for the cases when the detection capability of a single sensor is limited to a certain range of walking speeds, when a system power source is limited, and/or when computation power is limited. The proposed algorithm is versatile enough to handle possible data-loss and random delay in the wireless communication environment, resulting in reduced wireless communication load and computation overhead. The initial study demonstrated that the algorithm can detect dynamic speeds of human walking. The algorithm can be implemented on any mobile device equipped with magnetic and acceleration sensors.

iPhone and iPod Touch are multi-touch handheld devices that provide new possibilities for interaction techniques. We describe iPhone/iPod Touch implementation of a navigation interaction technique originally developed for a larger multi-touch device (i.e. Lemur). The interaction technique implemented on an iPhone/iPod Touch was used for navigation tasks in a CAVE virtual environment. We performed a pilot study to measure the control accuracy and to observe how human subjects respond to the interaction technique on the iPhone and iPod Touch devices. We used the preliminary results to improve the design of the interaction technique.

This paper describes a 3D, tangible user interface system and related interaction techniques for the CAVE environment. The developed system is based on off-the shelf software and hardware components to provide 3D input data for CAVE applications. A CAVE with four sides (three walls and a floor) is used as a display and interaction space. Interaction tasks (selection, manipulation, navigation) are performed using interaction techniques based on manipulation of physical objects (props). All virtual objects are directly manipulated using the corresponding props to which Augmented Reality physical markers are attached. Each physical marker corresponds to a specific virtual object. The floor projection (a white rectangle overlaid on top of the application generated video stream) or a directional light create illumination necessary for computer vision based marker detection using ARToolKit. Initial evaluation results are positive and provide directions for future research.