1,569 research outputs found
Sensitivity to Rate of Change in Gains Applied by Redirected Walking
Redirected walking allows for natural locomotion in virtual environments that are larger than a user’s physical environment. The mapping between real and virtual motion is modified by scaling some aspect of motion. As a user traverses the virtual environment these modifications (or gains) must be dynamically adjusted to prevent collision with physical obstacles. A significant body of work has established perceptual thresholds on rates of absolute gain, but the effect of changing gain is little understood.
We present the results of a user study on the effects of rate of gain change. A psychophysical experiment was conducted with 21 participants. Each participant completed a series of two-alternative forced choice tasks in which they determined whether their virtual motion differed from their physical motion while experiencing one of three different methods of gain change: sudden gain change, slow gain change and constant gain. Gain thresholds were determined by 3 interleaved 2-up 1-down staircases, one per condition. Our results indicate that slow gain change is significantly harder to detect than sudden gain change
ARC: Alignment-based Redirection Controller for Redirected Walking in Complex Environments
We present a novel redirected walking controller based on alignment that
allows the user to explore large and complex virtual environments, while
minimizing the number of collisions with obstacles in the physical environment.
Our alignment-based redirection controller, ARC, steers the user such that
their proximity to obstacles in the physical environment matches the proximity
to obstacles in the virtual environment as closely as possible. To quantify a
controller's performance in complex environments, we introduce a new metric,
Complexity Ratio (CR), to measure the relative environment complexity and
characterize the difference in navigational complexity between the physical and
virtual environments. Through extensive simulation-based experiments, we show
that ARC significantly outperforms current state-of-the-art controllers in its
ability to steer the user on a collision-free path. We also show through
quantitative and qualitative measures of performance that our controller is
robust in complex environments with many obstacles. Our method is applicable to
arbitrary environments and operates without any user input or parameter
tweaking, aside from the layout of the environments. We have implemented our
algorithm on the Oculus Quest head-mounted display and evaluated its
performance in environments with varying complexity. Our project website is
available at https://gamma.umd.edu/arc/
Natural Walking in Virtual Reality:A Review
Recent technological developments have finally brought virtual reality (VR) out of the laboratory and into the hands of developers and consumers. However, a number of challenges remain. Virtual travel is one of the most common and universal tasks performed inside virtual environments, yet enabling users to navigate virtual environments is not a trivial challenge—especially if the user is walking. In this article, we initially provide an overview of the numerous virtual travel techniques that have been proposed prior to the commercialization of VR. Then we turn to the mode of travel that is the most difficult to facilitate, that is, walking. The challenge of providing users with natural walking experiences in VR can be divided into two separate, albeit related, challenges: (1) enabling unconstrained walking in virtual worlds that are larger than the tracked physical space and (2) providing users with appropriate multisensory stimuli in response to their interaction with the virtual environment. In regard to the first challenge, we present walking techniques falling into three general categories: repositioning systems, locomotion based on proxy gestures, and redirected walking. With respect to multimodal stimuli, we focus on how to provide three types of information: external sensory information (visual, auditory, and cutaneous), internal sensory information (vestibular and kinesthetic/proprioceptive), and efferent information. Finally, we discuss how the different categories of walking techniques compare and discuss the challenges still facing the research community.</jats:p
Move or Push? Studying Pseudo-Haptic Perceptions Obtained with Motion or Force Input
Pseudo-haptics techniques are interesting alternatives for generating haptic
perceptions, which entails the manipulation of haptic perception through the
appropriate alteration of primarily visual feedback in response to body
movements. However, the use of pseudo-haptics techniques with a motion-input
system can sometimes be limited. This paper investigates a novel approach for
extending the potential of pseudo-haptics techniques in virtual reality (VR).
The proposed approach utilizes a reaction force from force-input as a
substitution of haptic cue for the pseudo-haptic perception. The paper
introduced a manipulation method in which the vertical acceleration of the
virtual hand is controlled by the extent of push-in of a force sensor. Such a
force-input manipulation of a virtual body can not only present pseudo-haptics
with less physical spaces and be used by more various users including
physically handicapped people, but also can present the reaction force
proportional to the user's input to the user. We hypothesized that such a
haptic force cue would contribute to the pseudo-haptic perception. Therefore,
the paper endeavors to investigate the force-input pseudo-haptic perception in
a comparison with the motion-input pseudo-haptics. The paper compared
force-input and motion-input manipulation in a point of achievable range and
resolution of pseudo-haptic weight. The experimental results suggest that the
force-input manipulation successfully extends the range of perceptible
pseudo-weight by 80\% in comparison to the motion-input manipulation. On the
other hand, it is revealed that the motion-input manipulation has 1 step larger
number of distinguishable weight levels and is easier to operate than the
force-input manipulation.Comment: This paper is now under review for IEEE Transactions on Visualization
and Computer Graphic
Advancing proxy-based haptic feedback in virtual reality
This thesis advances haptic feedback for Virtual Reality (VR). Our work is guided by Sutherland's 1965 vision of the ultimate display, which calls for VR systems to control the existence of matter. To push towards this vision, we build upon proxy-based haptic feedback, a technique characterized by the use of passive tangible props. The goal of this thesis is to tackle the central drawback of this approach, namely, its inflexibility, which yet hinders it to fulfill the vision of the ultimate display. Guided by four research questions, we first showcase the applicability of proxy-based VR haptics by employing the technique for data exploration. We then extend the VR system's control over users' haptic impressions in three steps. First, we contribute the class of Dynamic Passive Haptic Feedback (DPHF) alongside two novel concepts for conveying kinesthetic properties, like virtual weight and shape, through weight-shifting and drag-changing proxies. Conceptually orthogonal to this, we study how visual-haptic illusions can be leveraged to unnoticeably redirect the user's hand when reaching towards props. Here, we contribute a novel perception-inspired algorithm for Body Warping-based Hand Redirection (HR), an open-source framework for HR, and psychophysical insights. The thesis concludes by proving that the combination of DPHF and HR can outperform the individual techniques in terms of the achievable flexibility of the proxy-based haptic feedback.Diese Arbeit widmet sich haptischem Feedback für Virtual Reality (VR) und ist inspiriert von Sutherlands Vision des ultimativen Displays, welche VR-Systemen die Fähigkeit zuschreibt, Materie kontrollieren zu können. Um dieser Vision näher zu kommen, baut die Arbeit auf dem Konzept proxy-basierter Haptik auf, bei der haptische Eindrücke durch anfassbare Requisiten vermittelt werden. Ziel ist es, diesem Ansatz die für die Realisierung eines ultimativen Displays nötige Flexibilität zu verleihen. Dazu bearbeiten wir vier Forschungsfragen und zeigen zunächst die Anwendbarkeit proxy-basierter Haptik durch den Einsatz der Technik zur Datenexploration. Anschließend untersuchen wir in drei Schritten, wie VR-Systeme mehr Kontrolle über haptische Eindrücke von Nutzern erhalten können. Hierzu stellen wir Dynamic Passive Haptic Feedback (DPHF) vor, sowie zwei Verfahren, die kinästhetische Eindrücke wie virtuelles Gewicht und Form durch Gewichtsverlagerung und Veränderung des Luftwiderstandes von Requisiten vermitteln. Zusätzlich untersuchen wir, wie visuell-haptische Illusionen die Hand des Nutzers beim Greifen nach Requisiten unbemerkt umlenken können. Dabei stellen wir einen neuen Algorithmus zur Body Warping-based Hand Redirection (HR), ein Open-Source-Framework, sowie psychophysische Erkenntnisse vor. Abschließend zeigen wir, dass die Kombination von DPHF und HR proxy-basierte Haptik noch flexibler machen kann, als es die einzelnen Techniken alleine können
Twin-photon techniques for photo-detector calibration
The aim of this review paper is to enlighten some recent progresses in
quantum optical metrology in the part of quantum efficiency measurements of
photo-detectors performed with bi-photon states. The intrinsic correlated
nature of entangled photons from Spontaneous Parametric Down Conversion
phenomenon has opened wide horizons to a new approach for the absolute
measurement of photo-detector quantum efficiency, outgoing the requirement for
conventional standards of optical radiation; in particular the simultaneous
feature of the creation of conjugated photons led to a well known technique of
coincidence measurement, deeply understood and implemented for standard uses.
On the other hand, based on manipulation of entanglement developed for Quantum
Information protocols implementations, a new method has been proposed for
quantum efficiency measurement, exploiting polarisation entanglement in
addition to energy-momentum and time ones, that is based on conditioned
polarisation state manipulation. In this review, after a general discussion on
absolute photo-detector calibration, we compare these different methods, in
order to give an accurate operational sketch of the absolute quantum efficiency
measurement state of the art
Optimizing Natural Walking Usage in VR using Redirected Teleportation
Virtual Reality (VR) has come a long way since its inception and with the recent advancements in technology, high end VR headsets are now commercially available. Although these headsets offer full motion tracking capabilities, locomotion in VR is yet to be fully solved due to space constraints, potential VR sickness and problems with retaining immersion. Teleportation is the most popular locomotion technique in VR as it allows users to safely navigate beyond the confines of the available positional tracking space without inducing VR sickness. It has been argued that the use of teleportation doesn’t facilitate the use of natural walking input which is considered to have a higher presence because teleportation is faster, requires little physical effort and uses limited available tracking space. When a user walks to the edge of the tracking space, he/she must switch to teleportation. When navigating in the same direction, available walking space does not increase, which forces users to remain stationary and continue using teleportation. We present redirected teleportation, a novel locomotion method that increases tracking space usage and natural walking input by subtle reorientation and repositioning of the user. We first analyzed the positional tendencies of the users as they played popular games implementing teleportation and found the utilization of the tracking space to be limited. We then compared redirected teleportation with regular teleportation using a navigation task in three different environments. Analysis of our data show that although redirected walking takes more time, users used significantly fewer teleports and more natural walking input while using more of the available tracking space. The increase in time is largely due to users walking more, which takes more time than using teleportation. Our results provide evidence that redirected teleportation may be a viable approach to increase the usage of natural walking input while decreasing the dependency on teleportation
Scene-motion thresholds during head yaw for immersive virtual environments
In order to better understand how scene motion is perceived in immersive virtual environments, we measured scene-motion thresholds under different conditions across three experiments. Thresholds were measured during quasi-sinusoidal head yaw, single left-to-right or right-to-left head yaw, different phases of head yaw, slow to fast head yaw, scene motion relative to head yaw, and two scene illumination levels. We found that across various conditions 1) thresholds are greater when the scene moves with head yaw (corresponding to gain 1:0), and 2) thresholds increase as head motion increases
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