Interacting efficiently and comfortably with Augmented Reality (AR) headsets remains a major issue. We investigate the concept of mid-air pads as an alternative to gaze or direct hand input to control a cursor in windows anchored in the environment. ARPads allow users to control the cursor displayed in the headset screen through movements on a mid-air plane, which is not spatially aligned with the headset screen. We investigate a design space for ARPads, which takes into account the position of the pad relative to the user's body, and the orientation of the pad relative to that of the headset screen. Our study suggests that 1) indirect input can achieve the same performance as direct input while causing less fatigue than hand raycast, 2) an ARPad should be attached to the wrist or waist rather than to the thigh, and 3) the ARPad and the screen should have the same orientation.

Spatial presence encompasses the user's ability to experience a sense of "being there". While particular attention was given to assess spatial presence in real and virtual environments, few have been interested in measuring it in telepresence situations. To bridge this gap, the present work introduces a study that compares the execution of a task in three conditions: a real physical environment, a remote environment via a telepresence system, and a virtual simulation of the real environment. Following a within-subject design, 27 participants performed a navigation task consisting in following a route while avoiding obstacles. Spatial presence and five related factors (affordance, enjoyment, attention allocation, reality, and cybersickness) were evaluated using a presence questionnaire. In addition, performance measures were gathered regarding environment recollection and task execution. The evaluation also included a behavioral metric measured by obstacle avoidance distance extracted from participants' trajectories. Results indicated a higher presence in the real environment, along with the best performance measures. No difference was found in spatial presence between the remote and the virtual conditions, although a higher degree of affordance and enjoyment was attributed to the virtual environment, and a higher degree of reality was attributed to the remote environment. The number of collisions was found to be lower in the remote condition compared to the virtual condition. Similarly, the avoidance distance was also bigger (and almost similar) in the real and the remote environments compared to the virtual environment indicating a greater caution of participants. These cues highlight that the behavior of participants in the remote condition was closer to their behavior in the real situation than it was in the virtual condition. Furthermore, positive correlations were found between the reality factor and two of the three performance measures, as well as with the behavioral metric. This suggests that the degree of physical existence of the space in which participants operate can influence their performance and behavior.

This paper presents an experiment assessing the feeling of spatial presence in both real and remote environments (respectively the socalled “natural presence” and “telepresence”). Twenty-eight (28) participants performed a 3D-pointing task while being located in a real office and the same office remotely rendered over HMD. The spatial presence was evaluated by means of the ITC-SOPI questionnaire and users' behaviour analysis (trajectories of head during the task). The analysis also included the effect of different levels of immersion of the system - visual-only versus visual and audio - rendering in such environments. The results show a higher sense of spatial presence for the remote condition, regardless of the degree of immersion, and for the “visual and audio” condition regardless of the environment. Additionally, trajectory analysis of users' heads reveals that participants behaved similarly in both environments.

Relativity, as introduced by Einstein, is regarded as one of the most important revolutions in the history of physics. Nevertheless, the observation of direct outcomes of this theory on mundane objects is impossible because they can only be witnessed when travelling at relative speeds approaching the velocity of light c. These effects are so counterintuitive and contradicting with our daily understanding of space and time that physics students find it hard to learn relativity beyond mathematical equations and to understand the deep implications of the theory. Advances in Computer Graphics and Interaction Technology now make it possible to actually experiment the effects of relativity in a 3D immersive environment. We propose a Virtual Reality framework to study and learn relativity as well as to develop some intuition of the relativistic effects and the quadri-dimensional reality of space-time. More precisely, an innovative rendering engine and a non-Newtonian physics engine are combined to compute relativistic effects. Experiments are proposed within a game-oriented carom billiard environment. Our work improves over previous efforts in the ability i) to render in real-time multiple relativistic objects, each moving with a different velocity vector ii) to enable interactions between objects and iii) to enable the user to interact with the objects and modify the scene dynamically. The originality of our 4D rendering engine lies in its capacity to efficiently store and retrieve non-simultaneous past space-time events that are visible by an observer at a specific location and at a given instant of his proper time.

This paper presents an approach to shape and motion estimation that integrates heterogeneous knowledge into a unique model-based framework. We describe the observed scenes in terms of structured geometric elements (points, line segments, rectangles, 3D corners) sharing explicitly Euclidean relationships (orthogonality, parallelism, colinearity, coplanarity). Camera trajectories are represented with adaptative models which account for the regularity of usual camera motions. Two different strategies of automatic model building lead us to reduced models for shape and motion estimation with a minimal number of parameters. These models increase the robustness to noise and occlusions, improve the reconstruction, and provide a high-level representation of the observed scene. The parameters are optimally computed within a sequential Bayesian estimation procedure that gives accurate and reliable results on synthetic and real video imagery.

In this paper, the problem of constructing geometric models from data provided by 3-D imaging sensors is addressed. Such techniques allow for rapid modeling of sculptured free-form shapes and generation of geometric models for existing parts. In order for a complete data set to be obtained, multiple images, each from a different viewpoint, have to be merged. A technique stemming from the Iterative Closest Point (ICP) method for estimating the relative transformations among the viewpoints is developed. Computational solutions are provided for estimating shape from noisy sensory measurements using representations that conform with commonly used representations from Computer Aided Geometric Design (CAGD). In particular, NURBS and triangular surface representations are applied in shape estimation. The surface approximations are refined by the algorithms to meet a user-defined tolerance value.

This paper introduces new techniques for interactive piecewise flattening of parametric 3-D surfaces, leading to a non-distorted, hence realistic, texture mapping. Cuts are allowed on the mapped texture and we make a compromise between discontinuities and distortions. These techniques are based on results from differential geometry, more precisely on the notion of "geodesic curvature": isoparametric curves of the surface are mapped, in a constructive way, onto curves in the texture plane with preservation of geodesic curvature at each point. As an application, we give a concrete example which is a first step towards an efficient and robust CAD tool for shoe modeling.