Charles B. Owen

Comparative effectiveness of augmented reality in object assembly

Although there has been much speculation about the potential of Augmented Reality (AR), there are very few empirical studies about its effectiveness. This paper describes an experiment that tested the relative effectiveness of AR instructions in an assembly task. Task information was displayed in users field of view and registered with the workspace as 3D objects to explicitly demonstrate the exact execution of a procedure step. Three instructional media were compared with the AR system: a printed manual, computer assisted instruction (CAI) using a monitor-based display, and CAI utilizing a head-mounted display. Results indicate that overlaying 3D instructions on the actual work pieces reduced the error rate for an assembly task by 82%, particularly diminishing cumulative errors - errors due to previous assembly mistakes. Measurement of mental effort indicated decreased mental effort in the AR condition, suggesting some of the mental calculation of the assembly task is offloaded to the system.

Factors affecting the performance of ad hoc networks

Mobile ad hoc networks (MANETs) are an emerging class of network architectures that are characterized by their highly dynamic topology, limited resources (i.e., bandwidth and power), and lack of fixed infrastructure. The primary motivation for such networks is increased flexibility and mobility. Random node mobility along with various other factors such as network size and traffic intensity may be very dynamic, resulting in unpredictable variations in the overall network performance. This study centers on investigating and quantifying the effects of various factors and their two-way interactions on the overall performance of ad hoc networks. This study contributes to the modeling and development of adaptive ad hoc protocols (routing, medium access control, scheduling and buffer management). Using 2/sup k/r factorial experimental design, we isolate and quantify the effects of five factors: node speed, pause-time, network size, number of traffic sources, and type of routing (source versus distributed), that affect the performance of ad hoc networks. Specifically, this paper evaluates the impact of these factors on the following performance metrics: throughput, average routing overhead, and power consumption. Our study was conducted using a library-based simulator for sequential and parallel simulation of wireless networks.

What is the best fiducial

Fiducial images are a common method for supporting vision-based tracking in augmented reality systems. This paper addresses the question: what is the best fiducial? A set of criteria that are desirable in an optically tracked fiducial are presented and a new fiducial image set is designed that meets these criteria. The images in this set utilize a square black-border pattern with a 15% border width and an interior image that supports orientation determination and unique identification. The interior image is constructed from orthogonal DCT basis images chosen to minimize the probability of misidentification and to be robust to noise and occlusion. We describe how this image can be integrated into an AR software system such as ARToolKit.

Octree-based animated geometry compression

Geometry compression is the compression of the 3D geometric data that provides a computer graphics system with the scene description necessary to render images. Geometric data is quite large and, therefore, needs effective compression methods to decrease the transmission and storage bit requirements. A large amount of research has focused on static geometry compression, but only limited research has addressed animated geometry compression, the compression of temporal sequences of geometry data. This paper proposes an octree-based motion representation method that can be applied to compress animated geometric data. In our approach, 3D animated sequences can be represented with a compression factor of over 100, with slight losses in animation quality. Paper focuses on compressing vertex positions for all the frames. In the proposed approach, only two consecutive frames to generate a small set of motion vectors that represent the motion from the previous frame to the current frame is used. The motion vectors are used to predict the vertex positions for each frame except the first frame. The process generates a hierarchical octree motion representation for each frame. Quantization and an adaptive arithmetic coder are used to achieve further data reduction. The simple and efficient decompression of this approach makes it suitable for real time applications.

Display-relative calibration for optical see-through head-mounted displays

Optical see-through head-mounted displays (OSTHMDs) have many advantages in augmented reality application, but their utility in practical applications has been limited by the complexity of calibration. Because the human subject is an inseparable part of the eye-display system, previous methods for OSTHMD calibration have required extensive manual data collection using either instrumentation or manual point correspondences and are highly dependent on operator skill. This paper describes display-relative calibration (DRC) for OSTHMDs, a new two phase calibration method that minimizes the human element in the calibration process and ensures reliable calibration. Phase I of the calibration captures the parameters of the display system relative to a normalized reference frame and is performed in a jig with no human factors issues. The second phase optimizes the display for a specific user and the placement of the display on the head. Several phase II alternatives provide flexibility in a variety of applications including applications involving untrained users.

Intrinsic frames of reference and egocentric viewpoints in scene recognition

Three experiments investigated the roles of intrinsic directions of a scene and observers viewing direction in recognizing the scene. Participants learned the locations of seven objects along an intrinsic direction that was different from their viewing direction and then recognized spatial arrangements of three or six of these objects from different viewpoints. The results showed that triplets with two objects along the intrinsic direction (intrinsic triplets) were easier to recognize than triplets with two objects along the study viewing direction (non-intrinsic triplets), even when the intrinsic triplets were presented at a novel test viewpoint and the non-intrinsic triplets were presented at the familiar test viewpoint. The results also showed that configurations with the same three or six objects were easier to recognize at the familiar test viewpoint than other viewpoints. These results support and develop the model of spatial memory and navigation proposed by Mou, McNamara, Valiquette, and Rump [Mou, W., McNamara, T. P., Valiquiette C. M., & Rump, B. (2004). Allocentric and egocentric updating of spatial memories. Journal of Experimental Psychology: Learning, Memory, and Cognition, 30, 142-157].

Review on cybersickness in applications and visual displays

Cybersickness is an affliction common to users of virtual environments. Similar in symptoms to motion sickness, cybersickness can result in nausea, headaches, and dizziness. With these systems becoming readily available to the general public, reports of cybersickness have increased and there is a growing concern about the safety of these systems. This review presents the current state of research methods, theories, and known aspects associated with cybersickness. Current measurements of incidence of cybersickness are questionnaires, postural sway, and physiological state. Varying effects due to display and rendering modes, such as visual display type and stereoscopic or monoscopic rendering, are compared. The known and suspected application aspects that induce cybersickness are discussed. There are numerous potential contributing application design aspects, many of which have had limited study, but field of view and navigation are strongly correlated with cybersickness. The effect of visual displays is not well understood, and application design may be of greater importance.

Design of the PromoPad: An Automated Augmented-Reality Shopping Assistant

Augmented reality technologies as a new way of human computer interaction make possible real-time modification of our perception of reality without active user interference. This paper introduces the prototype of an augmented reality shopping assistant device, the PromoPad, based on a hand-held Tablet PC allowing see-through vision with augmentations. While this new interaction utilizing augmented reality that places products into contextual settings can enhance shopping experience and suggest complementary products, it also has challenges and issues to be used in a public environment such as a store setting. This paper discusses the design and implementation of the PromoPad, and addresses the issues and possible solutions. The concept of dynamic contextualization is further investigated in this setting with a list of possible context modifications and their relation to advertising and the psychology of consumer purchasing.

Attention Issues in Spatial Information Systems: Directing Mobile Users' Visual Attention Using Augmented Reality

Knowledge of objects, situations, or locations in the environment can be productive, useful, or even life-critical for mobile augmented reality (AR) users. Users may need assistance with (1) dangers, obstacles, or situations requiring attention; (2) visual search; (3) task sequencing; and (4) spatial navigation. The omnidirectional attention funnel is a general purpose AR interface technique that rapidly guides attention to any tracked object, person, or place in the space. The attention funnel dynamically directs user attention with strong bottom-up spatial attention cues. In a study comparing the attention funnel to other attentional techniques such as highlighting and audio cueing, search speed increased by over 50 percent, and perceived cognitive load decreased by 18 percent. The technique is a general three-dimensional cursor in a wide array of applications requiring visual search, emergency warning, and alerts to specific objects or obstacles, or for three-dimensional navigation to objects in space.

Evaluation of calibration procedures for optical see-through head-mounted displays

Optical see-through head-mounted displays (HMDs) are less commonly used because they are difficult to accurately calibrate. In this article, we report a user study to compare the accuracy of 4 variants of the SPAAM calibration method. Among the 4 variants, Stylus-marker calibration, where the user aligns a crosshair projected in the HMD with a tracked stylus tip, achieved the most accurate result. A decomposition and analysis of the calibration matrices from the trials is performed and the characteristics of the computed calibration matrices are examined. A physiological engineering point of view is also discussed to explain why calibrating optical see-through HMD is so difficult for users.