Behavior Analysis of Human Locomotion in Real World and Virtual Reality for Manufacturing Industry

Agethen P, Subramanian Sekar V, Gaisbauer F, Pfeiffer T, Otto M, Rukzio E. Behavior Analysis of Human Locomotion in Real World and Virtual Reality for Manufacturing Industry. ACM Transactions on Applied Perception (TAP). 2018;15(3): 20.With the rise of immersive visualization techniques, many domains within the manufacturing industry are increasingly validating production processes in virtual reality (VR). The validity of the results gathered in such simulations, however, is widely unknown - in particular with regard to human locomotion behavior. To bridge this gap, this paper presents an experiment, analyzing the behavioral disparity between human locomotion being performed without any equipment and in immersive virtual reality while wearing a head-mounted display (HMD). The presented study (n = 30) is split up in three sections and covers linear walking, non-linear walking and obstacle avoidance. Special care has been given to design the experiment so that findings are generally valid and can be applied to a wide range of domains beyond the manufacturing industry. The findings provide novel insights into the effect of immersive virtual reality on specific gait parameters. In total, a comprehensive sample of 18.09 km is analyzed. The results reveal that the HMD had a medium effect (up to 13%) on walking velocity, on non-linear walking towards an oriented target and on clearance distance. The overall-differences are modeled using multiple regression models, thus allowing the general usage within various domains. Summarizing, it can be concluded that VR can be used to analyze and plan human locomotion, however, specific details may have to be adjusted in order to transfer findings to the real world

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

SPATIO-TEMPORAL REGISTRATION IN AUGMENTED REALITY

The overarching goal of Augmented Reality (AR) is to provide users with the illusion that virtual and real objects coexist indistinguishably in the same space. An effective persistent illusion requires accurate registration between the real and the virtual objects, registration that is spatially and temporally coherent. However, visible misregistration can be caused by many inherent error sources, such as errors in calibration, tracking, and modeling, and system delay. This dissertation focuses on new methods that could be considered part of "the last mile" of spatio-temporal registration in AR: closed-loop spatial registration and low-latency temporal registration: 1. For spatial registration, the primary insight is that calibration, tracking and modeling are means to an end---the ultimate goal is registration. In this spirit I present a novel pixel-wise closed-loop registration approach that can automatically minimize registration errors using a reference model comprised of the real scene model and the desired virtual augmentations. Registration errors are minimized in both global world space via camera pose refinement, and local screen space via pixel-wise adjustments. This approach is presented in the context of Video See-Through AR (VST-AR) and projector-based Spatial AR (SAR), where registration results are measurable using a commodity color camera. 2. For temporal registration, the primary insight is that the real-virtual relationships are evolving throughout the tracking, rendering, scanout, and display steps, and registration can be improved by leveraging fine-grained processing and display mechanisms. In this spirit I introduce a general end-to-end system pipeline with low latency, and propose an algorithm for minimizing latency in displays (DLP DMD projectors in particular). This approach is presented in the context of Optical See-Through AR (OST-AR), where system delay is the most detrimental source of error. I also discuss future steps that may further improve spatio-temporal registration. Particularly, I discuss possibilities for using custom virtual or physical-virtual fiducials for closed-loop registration in SAR. The custom fiducials can be designed to elicit desirable optical signals that directly indicate any error in the relative pose between the physical and projected virtual objects.Doctor of Philosoph

Scene-motion- and latency-perception thresholds for head-mounted displays

A fundamental task of an immersive virtual environment (IVE) system is to present images of the virtual world that change appropriately as the user's head moves. Current IVE systems, especially those using head-mounted displays (HMDs), often produce spatially unstable scenes, resulting in simulator sickness, degraded task performance, degraded visual acuity, and breaks in presence. In HMDs, instability resulting from latency is greater than all other causes of instability combined. The primary way users perceive latency in an HMD is by improper motion of scenes that should be stationary in the world. Whereas latency-induced scene motion is well defined mathematically, less is understood about how much scene motion and/or latency can occur without subjects noticing, and how this varies under different conditions. I built a simulated HMD system with zero effective latency---no scene motion occurs due to latency. I intentionally and artificially inserted scene motion into the virtual environment in order to determine how much scene motion and/or latency can occur without subjects noticing. I measured perceptual thresholds of scene-motion and latency under different conditions across five experiments. Based on the study of latency, head motion, scene motion, and perceptual thresholds, I developed a mathematical model of latency thresholds as an inverse function of peak head-yaw acceleration. Psychophysics studies showed that measured latency thresholds correlate with this inverse function better than with a linear function. The work reported here readily enables scientists and engineers to, under their particular conditions, measure latency thresholds as a function of head motion by using an off-the-shelf projector system. Latency requirements can thus be determined before designing HMD systems

Low Latency Rendering with Dataflow Architectures

The research presented in this thesis concerns latency in VR and synthetic environments. Latency is the end-to-end delay experienced by the user of an interactive computer system, between their physical actions and the perceived response to these actions. Latency is a product of the various processing, transport and buffering delays present in any current computer system. For many computer mediated applications, latency can be distracting, but it is not critical to the utility of the application. Synthetic environments on the other hand attempt to facilitate direct interaction with a digitised world. Direct interaction here implies the formation of a sensorimotor loop between the user and the digitised world - that is, the user makes predictions about how their actions affect the world, and see these predictions realised. By facilitating the formation of the this loop, the synthetic environment allows users to directly sense the digitised world, rather than the interface, and induce perceptions, such as that of the digital world existing as a distinct physical place. This has many applications for knowledge transfer and efficient interaction through the use of enhanced communication cues. The complication is, the formation of the sensorimotor loop that underpins this is highly dependent on the fidelity of the virtual stimuli, including latency. The main research questions we ask are how can the characteristics of dataflow computing be leveraged to improve the temporal fidelity of the visual stimuli, and what implications does this have on other aspects of the fidelity. Secondarily, we ask what effects latency itself has on user interaction. We test the effects of latency on physical interaction at levels previously hypothesized but unexplored. We also test for a previously unconsidered effect of latency on higher level cognitive functions. To do this, we create prototype image generators for interactive systems and virtual reality, using dataflow computing platforms. We integrate these into real interactive systems to gain practical experience of how the real perceptible benefits of alternative rendering approaches, but also what implications are when they are subject to the constraints of real systems. We quantify the differences of our systems compared with traditional systems using latency and objective image fidelity measures. We use our novel systems to perform user studies into the effects of latency. Our high performance apparatuses allow experimentation at latencies lower than previously tested in comparable studies. The low latency apparatuses are designed to minimise what is currently the largest delay in traditional rendering pipelines and we find that the approach is successful in this respect. Our 3D low latency apparatus achieves lower latencies and higher fidelities than traditional systems. The conditions under which it can do this are highly constrained however. We do not foresee dataflow computing shouldering the bulk of the rendering workload in the future but rather facilitating the augmentation of the traditional pipeline with a very high speed local loop. This may be an image distortion stage or otherwise. Our latency experiments revealed that many predictions about the effects of low latency should be re-evaluated and experimenting in this range requires great care

Sonic Interactions in Virtual Environments

This open access book tackles the design of 3D spatial interactions in an audio-centered and audio-first perspective, providing the fundamental notions related to the creation and evaluation of immersive sonic experiences. The key elements that enhance the sensation of place in a virtual environment (VE) are: Immersive audio: the computational aspects of the acoustical-space properties of Virutal Reality (VR) technologies Sonic interaction: the human-computer interplay through auditory feedback in VE VR systems: naturally support multimodal integration, impacting different application domains Sonic Interactions in Virtual Environments will feature state-of-the-art research on real-time auralization, sonic interaction design in VR, quality of the experience in multimodal scenarios, and applications. Contributors and editors include interdisciplinary experts from the fields of computer science, engineering, acoustics, psychology, design, humanities, and beyond. Their mission is to shape an emerging new field of study at the intersection of sonic interaction design and immersive media, embracing an archipelago of existing research spread in different audio communities and to increase among the VR communities, researchers, and practitioners, the awareness of the importance of sonic elements when designing immersive environments

Sonic Interactions in Virtual Environments

This open access book tackles the design of 3D spatial interactions in an audio-centered and audio-first perspective, providing the fundamental notions related to the creation and evaluation of immersive sonic experiences. The key elements that enhance the sensation of place in a virtual environment (VE) are: Immersive audio: the computational aspects of the acoustical-space properties of Virutal Reality (VR) technologies Sonic interaction: the human-computer interplay through auditory feedback in VE VR systems: naturally support multimodal integration, impacting different application domains Sonic Interactions in Virtual Environments will feature state-of-the-art research on real-time auralization, sonic interaction design in VR, quality of the experience in multimodal scenarios, and applications. Contributors and editors include interdisciplinary experts from the fields of computer science, engineering, acoustics, psychology, design, humanities, and beyond. Their mission is to shape an emerging new field of study at the intersection of sonic interaction design and immersive media, embracing an archipelago of existing research spread in different audio communities and to increase among the VR communities, researchers, and practitioners, the awareness of the importance of sonic elements when designing immersive environments