Embodiment Sensitivity to Movement Distortion and Perspective Taking in Virtual Reality

Despite recent technological improvements of immersive technologies, Virtual Reality suffers from severe intrinsic limitations, in particular the immateriality of the visible 3D environment. Typically, any simulation and manipulation in a cluttered environment would ideally require providing feedback of collisions to every body parts (arms, legs, trunk, etc.) and not only to the hands as has been originally explored with haptic feedback. This thesis addresses these limitations by relying on a cross modal perception and cognitive approach instead of haptic or force feedback. We base our design on scientific knowledge of bodily self-consciousness and embodiment. It is known that the instantaneous experience of embodiment emerges from the coherent multisensory integration of bodily signals taking place in the brain, and that altering this mechanism can temporarily change how one perceives properties of their own body. This mechanism is at stake during a VR simulation, and this thesis explores the new venues of interaction design based on these fundamental scientific findings about the embodied self. In particular, we explore the use of third person perspective (3PP) instead of permanently offering the traditional first person perspective (1PP), and we manipulate the user-avatar motor mapping to achieve a broader range of interactions while maintaining embodiment. We are guided by two principles, to explore the extent to which we can enhance VR interaction through the manipulation of bodily aspects, and to identify the extent to which a given manipulation affects the embodiment of a virtual body. Our results provide new evidence supporting strong embodiment of a virtual body even when viewed from 3PP, and in particular that voluntarily alternating point of view between 1PP and 3PP is not detrimental to the experience of ownership over the virtual body. Moreover, detailed analysis of movement quality show highly similar reaching behavior in both perspective conditions, and only obvious advantages or disadvantages of each perspective depending on the situation (e.g. occlusion of target by the body in 3PP, limited field of view in 1PP). We also show that subjects are insensitive to visuo-proprioceptive movement distortions when the nature of the distortion was not made explicit, and that subjects are biased toward self-attributing distorted movements that make the task easier

Egocentric Mapping of Body Surface Constraints

The relative location of human body parts often materializes the semantics of on-going actions, intentions and even emotions expressed, or performed, by a human being. However, traditional methods of performance animation fail to correctly and automatically map the semantics of performer postures involving self-body contacts onto characters with different sizes and proportions. Our method proposes an egocentric normalization of the body-part relative distances to preserve the consistency of self contacts for a large variety of human-like target characters. Egocentric coordinates are character independent and encode the whole posture space, i.e., it ensures the continuity of the motion with and without self-contacts. We can transfer classes of complex postures involving multiple interacting limb segments by preserving their spatial order without depending on temporal coherence. The mapping process exploits a low-cost constraint relaxation technique relying on analytic inverse kinematics; thus, we can achieve online performance animation. We demonstrate our approach on a variety of characters and compare it with the state of the art in online retargeting with a user study. Overall, our method performs better than the state of the art, especially when the proportions of the animated character deviates from those of the performer

Characterizing Embodied Interaction in First and Third Person Perspective Viewpoints

Third Person Perspective (3PP) viewpoints have the potential to expand how one perceives and acts in a virtual environment. They offer increased awareness of the posture and of the surrounding of the virtual body as compared to First Person Perspective (1PP). But from another standpoint, 3PP can be considered as less effective for inducing a strong sense of embodiment into a virtual body. Following an experimental paradigm based on full body motion capture and immersive interaction, this study investigates the effect of perspective and of visuomotor synchrony on the sense of embodiment. It provides evidence supporting a high sense of embodiment in both 1PP and 3PP during engaging motor tasks, as well as guidelines for choosing the optimal perspective depending on location of targets

Content Format and Quality of Experience in Virtual Reality

In this paper, we investigate three forms of virtual reality content production and consumption. Namely, 360 stereoscopic video, the combination of a 3D environment with a video billboard for dynamic elements, and a full 3D rendered scene. On one hand, video based techniques facilitate the acquisition of content, but they can limit the experience of the user since the content is captured from a fixed point of view. On the other hand, 3D content allows for point of view translation, but real-time photorealistic rendering is not trivial and comes at high production and processing costs. We also compare the two extremes with an approach that combines dynamic video elements with a 3D virtual environment. We discuss the advantages and disadvantages of these systems, and present the result of a user study with 24 participants. In the study, we evaluated the quality of experience, including presence, simulation sickness and participants' assessment of content quality, of three versions of a cinematic segment with two actors. We found that, in this context, mixing video and 3D content produced the best experience.Comment: 25 page