Thesis (doctoral)--Göteborg University, 2000. / Includes bibliographical references (p. 141-142).

Thesis (Ph. D.)--University of Missouri-Columbia, 2004. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (June 29, 2006) Vita. Includes bibliographical references.

There is much research in the literature regarding the construction of distributed virtual reality implementations. After evaluating some well-known virtual reality systems, it was determined that several problems exist that need to be solved. In particular: network efficiency, object distribution and coherency, inadequate system resource management, and overall performance. In order to properly address these issues, a holistic design approach is taken. The entire system is examined, rather than focusing on a specific problem area (such as the human-computer interface). The major component of this work, the Newtonian Architecture for Virtual Landscapes (NAVL), is presented to respond to the problems areas discovered. Highlights of the architecture include: (1) A distributed client/server network that addressed the networking issues. (2) Autonomous objects encapsulate control and object state into a single entity. Using autonomous objects avoids lengthy synchronization processes (e.g., full database locking). (3) ForceLets, a novel synchronization method, minimize the network bandwidth required to keep an object synchronized at remote locations. In addition, ForceLets provide much improved synchronization of the object at the remote locations in the presence of network lag. Implementation details of the NAVL prototype are also presented. The implementation consists of an object simulation and execution unit, rendering and collision detection unit, and network subsystem and protocols. An evaluation of the NAVL system architecture examines the efficiency of the key architectural components: (1) A bandwidth and latency analysis examines the efficiency of the distributed client/server network. (2) The object distribution and coherency components are tested directly from the prototype. Profiles of actual prototype execution are used to show the efficiency gains of the ForceLet approach as compared to the commonly used stream-of-data coherency mechanism. (3) The rendering and collision detection unit is tested by examining the effects on CPU utilization and frame rate with increases in the number of virtual objects. / Graduate

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<p dir="ltr">In recent years, VR technology has significantly enhanced video immersion and efficiency. Numerous studies have delved into analyzing user panning, a head or body movement executed by an individual engaging with a 360-degree video, to improve video buffering by predicting such movements. However, this perspective tends to isolate user panning behavior as a distinct signal for modeling and prediction, neglecting the intrinsic value of the content and the user's engagement with it, thereby leaving a gap in comprehending the motives behind users' panning in these immersive settings.</p><p dir="ltr">Our research endeavors to bridge this gap by investigating the underlying reasons for viewers' panning behavior (head movements) in 360-degree content, employing thematic analysis of self-reported user intentions. This thesis illuminates the driving motivations for pans during 360-degree video interactions, as expressed by participants. Through categorizing the viewer's behavior with detailed annotations, we establish a structured framework for understanding viewer engagement.</p><p dir="ltr">Furthermore, we explore the feasibility of predicting viewer intentions based solely on video content, thus providing insights into content-driven viewer panning behavior. This work also introduces a meticulously compiled dataset that merges pan action data with corresponding user-reported motivations, presenting a valuable asset for subsequent VR viewer behavior research. Lastly, we unveil a user-friendly system compatible with any head-mounted device, designed to ease the replication of our study and enable real-time collection of user panning data, free from desktop tethering constraints. This system not only facilitates data gathering but also broadens the accessibility and utility of our research outcomes, significantly advancing the comprehension of human interaction within VR contexts.</p>

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