Enhancing Visual and Gestural Fidelity for Effective Virtual Environments

A challenge for the virtual reality (VR) industry is facing is that VR is not immersive enough to make people feel a genuine sense of presence: the low frame rate leads to dizziness and the lack of human body visualization limits the human-computer interaction. In this dissertation, I present our research on enhancing visual and gestural fidelity in the virtual environment. First, I present a new foveated rendering technique: Kernel Foveated Rendering (KFR), which parameterizes foveated rendering by embedding polynomial kernel functions in log-polar space. This GPU-driven technique uses parameterized foveation that mimics the distribution of photoreceptors in the human retina. I present a two-pass kernel foveated rendering pipeline that maps well onto modern GPUs. I have carried out user studies to empirically identify the KFR parameters and have observed a 2.8x-3.2x speedup in rendering on 4K displays. Second, I explore the rendering acceleration through foveation for 4D light fields, which captures both the spatial and angular rays, thus enabling free-viewpoint rendering and custom selection of the focal plane. I optimize the KFR algorithm by adjusting the weight of each slice in the light field, so that it automatically selects the optimal foveation parameters for different images according to the gaze position. I have validated our approach on the rendering of light fields by carrying out both quantitative experiments and user studies. Our method achieves speedups of 3.47x-7.28x for different levels of foveation and different rendering resolutions. Thirdly, I present a simple yet effective technique for further reducing the cost of foveated rendering by leveraging ocular dominance - the tendency of the human visual system to prefer scene perception from one eye over the other. Our new approach, eye-dominance-guided foveated rendering (EFR), renders the scene at a lower foveation level (with higher detail) for the dominant eye than the non-dominant eye. Compared with traditional foveated rendering, EFR can be expected to provide superior rendering performance while preserving the same level of perceived visual quality. Finally, I present an approach to use an end-to-end convolutional neural network, which consists of a concatenation of an encoder and a decoder, to reconstruct a 3D model of a human hand from a single RGB image. Previous research work on hand mesh reconstruction suffers from the lack of training data. To train networks with full supervision, we fit a parametric hand model to 3D annotations, and we train the networks with the RGB image with the fitted parametric model as the supervision. Our approach leads to significantly improved quality compared to state-of-the-art hand mesh reconstruction techniques

Inattentional Blindness for Redirected Walking Using Dynamic Foveated Rendering

Redirected walking is a Virtual Reality(VR) locomotion technique which enables users to navigate virtual environments (VEs) that are spatially larger than the available physical tracked space. In this work we present a novel technique for redirected walking in VR based on the psychological phenomenon of inattentional blindness. Based on the user's visual fixation points we divide the user's view into zones. Spatially-varying rotations are applied according to the zone's importance and are rendered using foveated rendering. Our technique is real-time and applicable to small and large physical spaces. Furthermore, the proposed technique does not require the use of stimulated saccades but rather takes advantage of naturally occurring saccades and blinks for a complete refresh of the framebuffer. We performed extensive testing and present the analysis of the results of three user studies conducted for the evaluation

Space-variant picture coding

PhDSpace-variant picture coding techniques exploit the strong spatial non-uniformity of the human visual system in order to increase coding efficiency in terms of perceived quality per bit. This thesis extends space-variant coding research in two directions. The first of these directions is in foveated coding. Past foveated coding research has been dominated by the single-viewer, gaze-contingent scenario. However, for research into the multi-viewer and probability-based scenarios, this thesis presents a missing piece: an algorithm for computing an additive multi-viewer sensitivity function based on an established eye resolution model, and, from this, a blur map that is optimal in the sense of discarding frequencies in least-noticeable- rst order. Furthermore, for the application of a blur map, a novel algorithm is presented for the efficient computation of high-accuracy smoothly space-variant Gaussian blurring, using a specialised filter bank which approximates perfect space-variant Gaussian blurring to arbitrarily high accuracy and at greatly reduced cost compared to the brute force approach of employing a separate low-pass filter at each image location. The second direction is that of artifi cially increasing the depth-of- field of an image, an idea borrowed from photography with the advantage of allowing an image to be reduced in bitrate while retaining or increasing overall aesthetic quality. Two synthetic depth of field algorithms are presented herein, with the desirable properties of aiming to mimic occlusion eff ects as occur in natural blurring, and of handling any number of blurring and occlusion levels with the same level of computational complexity. The merits of this coding approach have been investigated by subjective experiments to compare it with single-viewer foveated image coding. The results found the depth-based preblurring to generally be significantly preferable to the same level of foveation blurring

How can Extended Reality Help Individuals with Depth Misperception?

Despite the recent actual uses of Extended Reality (XR) in treatment of patients, some areas are less explored. One gap in research is how XR can improve depth perception for patients. Accordingly, the depth perception process in XR settings and in human vision are explored and trackers, visual sensors, and displays as assistive tools of XR settings are scrutinized to extract their potentials in influencing users’ depth perception experience. Depth perception enhancement is relying not only on depth perception algorithms, but also on visualization algorithms, display new technologies, computation power enhancements, and vision apparatus neural mechanism knowledge advancements. Finally, it is discussed that XR holds assistive features not only for the improvement of vision impairments but also for the diagnosis part. Although, each specific patient requires a specific set of XR setting due to different neural or cognition reactions in different individuals with same the disease

Inattentional Blindness for Redirected Walking Using Dynamic Foveated Rendering

Redirected walking is a Virtual Reality(VR) locomotion technique which enables users to navigate virtual environments (VEs) that are spatially larger than the available physical tracked space. In this work we present a novel technique for redirected walking in VR based on the psychological phenomenon of inattentional blindness. Based on the user's visual fixation points we divide the user's view into zones. Spatially-varying rotations are applied according to the zone's importance and are rendered using foveated rendering. Our technique is real-time and applicable to small and large physical spaces. Furthermore, the proposed technique does not require the use of stimulated saccades but rather takes advantage of naturally occurring saccades and blinks for a complete refresh of the framebuffer. We performed extensive testing and present the analysis of the results of three user studies conducted for the evaluation

Towards Understanding and Expanding Locomotion in Physical and Virtual Realities

Among many virtual reality interactions, the locomotion dilemma remains a significant impediment to achieving an ideal immersive experience. The physical limitations of tracked space make it impossible to naturally explore theoretically boundless virtual environments with a one-to-one mapping. Synthetic techniques like teleportation and flying often induce simulator sickness and break the sense of presence. Therefore, natural walking is the most favored form of locomotion. Redirected walking offers a more natural and intuitive way for users to navigate vast virtual spaces efficiently. However, existing techniques either lead to simulator sickness due to visual and vestibular mismatch or detract users from the immersive experience that virtual reality aims to provide. This research presents innovative techniques and applications to enhance the user experience by expanding walkable, physical space in Virtual Reality. The thesis includes three main contributions. The first contribution proposes a mobile application that uses markerless Augmented Reality to allow users to explore a life-sized virtual library through a divide-and-rule approach. The second contribution presents a subtle redirected walking technique based on inattentional blindness, using dynamic foveated rendering and natural visual suppressions like blinks and saccades. Finally, the third contribution introduces a novel redirected walking solution that leverages a deep neural network, to predict saccades in real-time and eliminate the hardware requirements for eye-tracking. Overall, this thesis offers valuable contributions to human-computer interaction, investigating novel approaches to solving the locomotion dilemma. The proposed solutions were evaluated through extensive user studies, demonstrating their effectiveness and applicability in real-world scenarios like training simulations and entertainment

Design guidelines for limiting and eliminating virtual reality-induced symptoms and effects at work: a comprehensive, factor-oriented review

Virtual reality (VR) can induce side effects known as virtual reality-induced symptoms and effects (VRISE). To address this concern, we identify a literature-based listing of these factors thought to influence VRISE with a focus on office work use. Using those, we recommend guidelines for VRISE amelioration intended for virtual environment creators and users. We identify five VRISE risks, focusing on short-term symptoms with their short-term effects. Three overall factor categories are considered: individual, hardware, and software. Over 90 factors may influence VRISE frequency and severity. We identify guidelines for each factor to help reduce VR side effects. To better reflect our confidence in those guidelines, we graded each with a level of evidence rating. Common factors occasionally influence different forms of VRISE. This can lead to confusion in the literature. General guidelines for using VR at work involve worker adaptation, such as limiting immersion times to between 20 and 30 min. These regimens involve taking regular breaks. Extra care is required for workers with special needs, neurodiversity, and gerontechnological concerns. In addition to following our guidelines, stakeholders should be aware that current head-mounted displays and virtual environments can continue to induce VRISE. While no single existing method fully alleviates VRISE, workers' health and safety must be monitored and safeguarded when VR is used at work

Perceptual Manipulations for Hiding Image Transformations in Virtual Reality

Users of a virtual reality make frequent gaze shifts and head movements to explore their surrounding environment. Saccades are rapid, ballistic, conjugate eye movements that reposition our gaze, and in doing so create large-field motion on our retina. Due to the high speed motion on the retina during saccades, the brain suppresses the visual signals from the eye, a perceptual phenomenon known as the saccadic suppression. These moments of visual blindness can help hide the display graphical updates in a virtual reality. In this dissertation, I investigated how the visibility of various image transformations differed, during combinations of saccade and head rotation conditions. Additionally, I studied how hand and gaze interaction, affected image change discrimination in an inattentional blindness task. I conducted four psychophysical experiments in desktop or head-mounted VR. In the eye tracking studies, users viewed 3D scenes, and were triggered to make a vertical or horizontal saccade. During the saccade an instantaneous translation or rotation was applied to the virtual camera used to render the scene. Participants were required to indicate the direction of these transitions after each trial. The results showed that type and size of the image transformation affected change detectability. During horizontal or vertical saccades, rotations along the roll axis were the most detectable, while horizontal and vertical translations were least noticed. In a second similar study, I added a constant camera motion to simulate a head rotation, and in a third study, I compared active head rotation with a simulated rotation or a static head. I found less sensitivity to transsaccadic horizontal compared to vertical camera shifts during simulated or real head pan. Conversely, during simulated or real head tilt observers were less sensitive to transsaccadic vertical than horizontal camera shifts. In addition, in my multi-interactive inattentional blindness experiment, I compared sensitivity to sudden image transformations when a participant used their hand and gaze to move and watch an object, to when they only watched it move. The results confirmed that when involved in a primary task that requires focus and attention with two interaction modalities (gaze and hand), a visual stimuli can better be hidden than when only one sense (vision) is involved. Understanding the effect of continuous head movement and attention on the visibility of a sudden transsaccadic change can help optimize the visual performance of gaze-contingent displays and improve user experience. Perceptually suppressed rotations or translations can be used to introduce imperceptible changes in virtual camera pose in applications such as networked gaming, collaborative virtual reality and redirected walking. This dissertation suggests that such transformations can be more effective and more substantial during active or passive head motion. Moreover, inattentional blindness during an attention-demanding task provides additional opportunities for imperceptible updates to a visual display