152 research outputs found
Example Based Caricature Synthesis
The likeness of a caricature to the original face image is an essential and often overlooked part of caricature
production. In this paper we present an example based caricature synthesis technique, consisting of shape
exaggeration, relationship exaggeration, and optimization for likeness. Rather than relying on a large training set
of caricature face pairs, our shape exaggeration step is based on only one or a small number of examples of facial
features. The relationship exaggeration step introduces two definitions which facilitate global facial feature
synthesis. The first is the T-Shape rule, which describes the relative relationship between the facial elements in an
intuitive manner. The second is the so called proportions, which characterizes the facial features in a proportion
form. Finally we introduce a similarity metric as the likeness metric based on the Modified Hausdorff Distance
(MHD) which allows us to optimize the configuration of facial elements, maximizing likeness while satisfying a
number of constraints. The effectiveness of our algorithm is demonstrated with experimental results
ARWalker: A Virtual Walking Companion Application
Extended Reality (XR) technologies, including Augmented Reality (AR), have
attracted significant attention over the past few years and have been utilized
in several fields, including education, healthcare, and manufacturing. In this
paper, we aim to explore the use of AR in the field of biomechanics and human
movement through the development of ARWalker, which is an AR application that
features virtual walking companions (avatars). Research participants walk in
close synchrony with the virtual companions, whose gait exhibits properties
found in the gait of young and healthy adults. As a result, research
participants can train their gait to the gait of the avatar, thus regaining the
healthy properties of their gait and reducing the risk of falls. ARWalker can
especially help older adults and individuals with diseases, who exhibit
pathological gait thus being more prone to falls. We implement a prototype of
ARWalker and evaluate its systems performance while running on a Microsoft
Hololens 2 headset
Social Virtual Reality Platform Comparison and Evaluation Using a Guided Group Walkthrough Method
As virtual reality (VR) headsets become more commercially accessible, a range of social platforms have been developed that exploit the immersive nature of these systems. There is a growing interest in using these platforms in social and work contexts, but relatively little work into examining the usability choices that have been made. We developed a usability inspection method based on cognitive walkthrough that we call guided group walkthrough. Guided group walkthrough is applied to existing social VR platforms by having a guide walk the participants through a series of abstract social tasks that are common across the platforms. Using this method we compared six social VR platforms for the Oculus Quest. After constructing an appropriate task hierarchy and walkthrough question structure for social VR, we ran several groups of participants through the walkthrough process. We undercover usability challenges that are common across the platforms, identify specific design considerations and comment on the utility of the walkthrough method in this situation
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Learnersâ Experience of Presence in Virtual Worlds
This thesis explores participantsâ experiences of presence in virtual worlds as a specific case of mediated environments, and the factors that support that experience of presence, with the aim of developing practice when using these technologies in learning and teaching. The thesis begins with a framework that was created to bring together concepts from a range of disciplines that describe presence and factors that contribute to presence. Organising categories within the framework were drawn from a blend of Activity Theory and Communities of Practice.
Five case studies in Second Life (preceded by a pilot study employing webconferencing) were conducted in order to investigate learnersâ experiences in these environments. Qualitative and quantitative data were gathered from these cases. The data from the separate cases were analysed using a cross-case synthesis and the role of presence, and the factors that support it, were identified. An additional strand of investigation established a typology of different forms of resistance by students to learning in virtual worlds.
The findings of the study were that an experience of presence is strongly linked to studentsâ satisfaction with the learning activity. This experience of presence was more linked to studentsâ preparedness or ability to engage with the environment than with technological limitations. Some studentsâ resistance to learning in virtual worlds were informed by values they held about technology, but others appeared to display an inability to experience embodiment through their avatar.
The experience of presence appeared to develop over time. This can be interpreted as stages in studentsâ development of a virtual body image, body schema and virtual identity. Different learning activities are more appropriate to different stages in this development. The thesis concludes with a suggested model for supporting studentsâ development of presence. The implications of these findings for educators and for further research are discussed
Enhanced Virtuality: Increasing the Usability and Productivity of Virtual Environments
Mit stetig steigender Bildschirmauflösung, genauerem Tracking und fallenden Preisen stehen Virtual Reality (VR) Systeme kurz davor sich erfolgreich am Markt zu etablieren. Verschiedene Werkzeuge helfen Entwicklern bei der Erstellung komplexer Interaktionen mit mehreren Benutzern innerhalb adaptiver virtueller Umgebungen. Allerdings entstehen mit der Verbreitung der VR-Systeme auch zusĂ€tzliche Herausforderungen: Diverse EingabegerĂ€te mit ungewohnten Formen und Tastenlayouts verhindern eine intuitive Interaktion. DarĂŒber hinaus zwingt der eingeschrĂ€nkte Funktionsumfang bestehender Software die Nutzer dazu, auf herkömmliche PC- oder Touch-basierte Systeme zurĂŒckzugreifen. AuĂerdem birgt die Zusammenarbeit mit anderen Anwendern am gleichen Standort Herausforderungen hinsichtlich der Kalibrierung unterschiedlicher Trackingsysteme und der Kollisionsvermeidung. Beim entfernten Zusammenarbeiten wird die Interaktion durch Latenzzeiten und Verbindungsverluste zusĂ€tzlich beeinflusst. SchlieĂlich haben die Benutzer unterschiedliche Anforderungen an die Visualisierung von Inhalten, z.B. GröĂe, Ausrichtung, Farbe oder Kontrast, innerhalb der virtuellen Welten. Eine strikte Nachbildung von realen Umgebungen in VR verschenkt Potential und wird es nicht ermöglichen, die individuellen BedĂŒrfnisse der Benutzer zu berĂŒcksichtigen.
Um diese Probleme anzugehen, werden in der vorliegenden Arbeit Lösungen in den Bereichen Eingabe, Zusammenarbeit und Erweiterung von virtuellen Welten und Benutzern vorgestellt, die darauf abzielen, die Benutzerfreundlichkeit und ProduktivitĂ€t von VR zu erhöhen. ZunĂ€chst werden PC-basierte Hardware und Software in die virtuelle Welt ĂŒbertragen, um die Vertrautheit und den Funktionsumfang bestehender Anwendungen in VR zu erhalten. Virtuelle Stellvertreter von physischen GerĂ€ten, z.B. Tastatur und Tablet, und ein VR-Modus fĂŒr Anwendungen ermöglichen es dem Benutzer reale FĂ€higkeiten in die virtuelle Welt zu ĂŒbertragen. Des Weiteren wird ein Algorithmus vorgestellt, der die Kalibrierung mehrerer ko-lokaler VR-GerĂ€te mit hoher Genauigkeit und geringen Hardwareanforderungen und geringem Aufwand ermöglicht. Da VR-Headsets die reale Umgebung der Benutzer ausblenden, wird die Relevanz einer Ganzkörper-Avatar-Visualisierung fĂŒr die Kollisionsvermeidung und das entfernte Zusammenarbeiten nachgewiesen. DarĂŒber hinaus werden personalisierte rĂ€umliche oder zeitliche Modifikationen vorgestellt, die es erlauben, die Benutzerfreundlichkeit, Arbeitsleistung und soziale PrĂ€senz von Benutzern zu erhöhen. Diskrepanzen zwischen den virtuellen Welten, die durch persönliche Anpassungen entstehen, werden durch Methoden der Avatar-Umlenkung (engl. redirection) kompensiert. AbschlieĂend werden einige der Methoden und Erkenntnisse in eine beispielhafte Anwendung integriert, um deren praktische Anwendbarkeit zu verdeutlichen.
Die vorliegende Arbeit zeigt, dass virtuelle Umgebungen auf realen FĂ€higkeiten und Erfahrungen aufbauen können, um eine vertraute und einfache Interaktion und Zusammenarbeit von Benutzern zu gewĂ€hrleisten. DarĂŒber hinaus ermöglichen individuelle Erweiterungen des virtuellen Inhalts und der Avatare EinschrĂ€nkungen der realen Welt zu ĂŒberwinden und das Erlebnis von VR-Umgebungen zu steigern
Animation Fidelity in Self-Avatars: Impact on User Performance and Sense of Agency
The use of self-avatars is gaining popularity thanks to affordable VR
headsets. Unfortunately, mainstream VR devices often use a small number of
trackers and provide low-accuracy animations. Previous studies have shown that
the Sense of Embodiment, and in particular the Sense of Agency, depends on the
extent to which the avatar's movements mimic the user's movements. However, few
works study such effect for tasks requiring a precise interaction with the
environment, i.e., tasks that require accurate manipulation, precise foot
stepping, or correct body poses. In these cases, users are likely to notice
inconsistencies between their self-avatars and their actual pose. In this
paper, we study the impact of the animation fidelity of the user avatar on a
variety of tasks that focus on arm movement, leg movement and body posture. We
compare three different animation techniques: two of them using Inverse
Kinematics to reconstruct the pose from sparse input (6 trackers), and a third
one using a professional motion capture system with 17 inertial sensors. We
evaluate these animation techniques both quantitatively (completion time,
unintentional collisions, pose accuracy) and qualitatively (Sense of
Embodiment). Our results show that the animation quality affects the Sense of
Embodiment. Inertial-based MoCap performs significantly better in mimicking
body poses. Surprisingly, IK-based solutions using fewer sensors outperformed
MoCap in tasks requiring accurate positioning, which we attribute to the higher
latency and the positional drift that causes errors at the end-effectors, which
are more noticeable in contact areas such as the feet.Comment: Accepted in IEEE VR 202
Animation fidelity in self-avatars: impact on user performance and sense of agency
The use of self-avatars is gaining popularity thanks to affordable VR headsets. Unfortunately, mainstream VR devices often use a small number of trackers and provide low-accuracy animations. Previous studies have shown that the Sense of Embodiment, and in particular the Sense of Agency, depends on the extent to which the avatar's movements mimic the user's movements. However, few works study such effect for tasks requiring a precise interaction with the environment, i.e., tasks that require accurate manipulation, precise foot stepping, or correct body poses. In these cases, users are likely to notice inconsistencies between their self-avatars and their actual pose. In this paper, we study the impact of the animation fidelity of the user avatar on a variety of tasks that focus on arm movement, leg movement and body posture. We compare three different animation techniques: two of them using Inverse Kinematics to reconstruct the pose from sparse input (6 trackers), and a third one using a professional motion capture system with 17 inertial sensors. We evaluate these animation techniques both quantitatively (completion time, unintentional collisions, pose accuracy) and qualitatively (Sense of Embodiment). Our results show that the animation quality affects the Sense of Embodiment. Inertial-based MoCap performs significantly better in mimicking body poses. Surprisingly, IK-based solutions using fewer sensors outperformed MoCap in tasks requiring accurate positioning, which we attribute to the higher latency and the positional drift that causes errors at the end-effectors, which are more noticeable in contact areas such as the feet.This project has received funding from the European Unionâs Horizon 2020 research and innovation programme under the Marie SkĆodowska-Curie grant agreement No. 860768 (CLIPE project) and from MCIN/AEI/10.13039/501100011033/FEDER, UE (PID2021-122136OB-C21). Jose Luis Ponton was also funded by the Spanish Ministry of Universities (FPU21/01927).Peer ReviewedPostprint (author's final draft
Learners' experience of presence in virtual worlds
This thesis explores participants' experiences of presence in virtual worlds as a specific case of
mediated environments, and the factors that support that experience of presence, with the aim of
developing practice when using these technologies in learning and teaching. The thesis begins with
a framework that was created to bring together concepts from a range of disciplines that describe
presence and factors that contribute to presence. Organising categories within the framework were
drawn from a blend of Activity Theory and Communities of Practice.
Five case studies in Second Life (preceded by a pilot study employing webconferencing) were
conducted in order to investigate learners' experiences in these environments. Qualitative and
quantitative data were gathered from these cases. The data from the separate cases were analysed
using a cross-case synthesis and the role of presence, and the factors that support it, were
identified. An additional strand of investigation established a typology of different forms of
resistance by students to learning in virtual worlds.
The findings of the study were that an experience of presence is strongly linked to students'
satisfaction with the learning activity. This experience of presence was more linked to students'
preparedness or ability to engage with the environment than with technological limitations. Some
students' resistance to learning in virtual worlds were informed by values they held about
technology, but others appeared to display an inability to experience embodiment through their
avatar.
The experience of presence appeared to develop over time. This can be interpreted as stages in
students' development of a virtual body image, body schema and virtual identity. Different learning
activities are more appropriate to different stages in this development. The thesis concludes with a
suggested model for supporting students' development of presence. The implications of these
findings for educators and for further research are discussed
Ankle-Actuated Human-Machine Interface for Walking in Virtual Reality
This thesis work presents design, implementation and experimental study of an impedance type ankle haptic interface for providing users with the immersive navigation experience in virtual reality (VR). The ankle platform enables the use of foot-tapping gestures to reproduce realistic walking experience in VR and to haptically render different types of walking terrains. The system is designed to be used by seated users allowing more comfort, causing less fatigue and motion sickness. The custom-designed ankle interface is composed of a single actuator-sensors system making it a cost-efficient solution for VR applications. The designed interface consists of a single degree of freedom actuated platform which can rotate around the ankle joint of the user. The platform is impedance controlled around the horizontal position by an electric motor and capstan transmission system. to perform walking in a virtual scene, a seated user is expected to perform walking gestures in form of ankle plantar-flexion and dorsiflexion movements causing the platform to tilt forward and backward. We present three algorithms for simulating the immersive locomotion of a VR avatar using the platform movement information. We also designed multiple impedance controllers to render haptic feedback for different virtual terrains during walking. We carried out experiments to understand how quickly users adapt to the interface, how well they can control their locomotion speed in VR, and how well they can distinguish different types of terrains presented through haptic feedback. We implemented qualitative questionnaires on the usability of the device and the task load of the experimental procedures. The experimental studies demonstrated that the interface can be easily used to navigate in VR and it is capable of rendering dynamic multi-layer complex terrains containing structures with different stiffness and brittleness properties
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