This thesis presents a generic and principled solution for optimising the visual complexity of any arbitrary computer-generated virtual environment (VE). This is performed with the ultimate goal of reducing the inherent latencies of current virtual reality (VR) technology. Effectively, we wish to remove extraneous detail from an environment which the user cannot perceive, and thus modulate the graphical complexity of a VE with little or no perceptual artifacts. The work proceeds by investigating contemporary models and theories of visual perception and then applying these to the field of real-time computer graphics. Subsequently, a technique is devised to assess the perceptual content of a computer-generated image in terms of spatial frequency (c/deg), and a model of contrast sensitivity is formulated to describe a user's ability to perceive detail under various conditions in terms of this metric. This allows us to base the level of detail (LOD) of each object in a VE on a measure of the degree of spatial detail which the user can perceive at any instant (taking into consideration the size of an object, its angular velocity, and the degree to which it exists in the peripheral field). Additionally, a generic polygon simplification framework is presented to complement the use of perceptually modulated LOD. The efficient implementation of this perceptual model is discussed and a prototype system is evaluated through a suite of experiments. These include a number of low-level psychophysical studies (to evaluate the accuracy of the model), a task performance study (to evaluate the effects of the model on the user), and an analysis of system performance gain (to evaluate the effects of the model on the system). The results show that for the test application chosen, the frame rate of the simulation was manifestly improved (by four to five-fold) with no perceivable drop in image fidelity. As a result, users were able to perform the given wayfinding task more proficiently and rapidly. Finally, conclusions are drawn on the application and utility of perceptually-based optimisations; both in reference to this work, and in the wider context.

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VEMap (virtual emotion map) can be seen as an advanced application of virtual environment (VE) technology to aid with design activities in architecture and urban planning, which can assist designers to understand users’ opinions. The aim of this research and development work is to create a software application that allows designers to evaluate a user’s emotional response to virtual representations of architectural or urban planning environments. In this project, a galvanic skin response (GSR) test is adopted as an objective measurement for collecting skin conductance data representing emotional arousal. At the same time, the user’s self-reports are used as a form of subjective measurement for identifying emotional valence (i.e. positive, neutral, and negative). Finally, all of the information collected from both GSR readings (objective measurement) and self-reports (subjective measurement) are converted into coloured dots on the base map of the corresponding virtual environment (VE). According to the results of the VEmap evaluation and validation procedure, the beta-testing and evaluation of this project has been confirmed that VEmap may interpret users’ emotional changes as evoked by VE mostly. From a usability perspective, there is no obvious difficulty present for participants on all the controls. Moreover, according to participants’ comments, VEmap may increase users’ interests and promote their involvement if it is applied in architectural design and urban planning. However, gender might have influence on self-report part, and virtual reality usage or 3D game experiences might affect navigation in VE.

VEMap (virtual emotion map) can be seen as an advanced application of virtual environment (VE) technology to aid with design activities in architecture and urban planning, which can assist designers to understand users’ opinions. The aim of this research and development work is to create a software application that allows designers to evaluate a user’s emotional response to virtual representations of architectural or urban planning environments. In this project, a galvanic skin response (GSR) test is adopted as an objective measurement for collecting skin conductance data representing emotional arousal. At the same time, the user’s self-reports are used as a form of subjective measurement for identifying emotional valence (i.e. positive, neutral, and negative). Finally, all of the information collected from both GSR readings (objective measurement) and self-reports (subjective measurement) are converted into coloured dots on the base map of the corresponding virtual environment (VE). According to the results of the VEmap evaluation and validation procedure, the beta-testing and evaluation of this project has been confirmed that VEmap may interpret users’ emotional changes as evoked by VE mostly. From a usability perspective, there is no obvious difficulty present for participants on all the controls. Moreover, according to participants’ comments, VEmap may increase users’ interests and promote their involvement if it is applied in architectural design and urban planning. However, gender might have influence on self-report part, and virtual reality usage or 3D game experiences might affect navigation in VE.

Haptic, or force, interaction in virtual environments can support the development of physical manipulation skills if users feel realistic forces in response to their motion in the virtual environment. The realism of the forces felt by users depends on: (i) how accurately the virtual environment simulates a real life situation such as surgery; and (ii) how faithfully the haptic controller renders the simulated interactions to users. Accurate simulations of real life situations such as surgery run at variable frequencies of the order of 20-100 Hz. However, the haptic controller needs updated stiffness and direction of contact at 1000 Hz to faithfully convey the shape and hardness of the virtual objects to the user. This thesis proposes to bridge the gap between the required fast haptic control rate and the slower virtual environment updates through a passive local model of interaction. This model comprises an approximation of the shape and stiffness of the virtual world in the area near the point of interaction. It also monitors its exchange of energy with the user to ensure its own passivity and thus, the stability of the haptic system. Lastly, the local model eliminates the spurious discontinuities that arise in contact direction at model updates by interpolating the contact normal before rendering it to the user. / Graduate

Personal Digital Assistants (PDAs) are becoming more and more powerful with advances in technology and are expanding their applications in a variety of fields. This work explores the use of PDAs in Virtual Environments (VE). The goal is to support highly interactive bi-directional user interactions in Virtual Environments in more natural and less cumbersome ways. A proxy-based approach is adopted to support a wide-range of handheld devices and have a multi-PDA interaction with the virtual world. The architecture consists of three components in the complete system, a PDA, a desktop that acts as a proxy and Virtual Environment Software Sandbox (VESS), software developed at the Institute for Simulation and Training (IST). The purpose of the architecture is to enable issuing text and voice commands from PDA to virtual entities in VESS through the proxy. The commands are a pre-defined set of simple words such as 'move forward', 'turn right', 'go', and 'stop'. These commands are matched at the proxy and sent to VESS as text in XML format. The response from VESS is received at the proxy and forwarded back to the PDA. Performance measures with respect to response time characteristics of text messages between PDA and proxy over Wi-Fi networks are conducted. The results are discussed with respect to the acceptable delays for human perception in order to have real-time interaction between a PDA and an avatar in virtual world.

Design review is a process of reviewing construction design documents to ensure that they reflect the owner's design intent, and are accurate in describing the owner's desired building or facility. Information generation becomes more intensive as the design stage progresses. The use of valuable information during design review stage can lead to a more comprehensive and high quality design, and a building or facility that is constructible, and within the intended budget. However, in current design practices, valuable design review information is scattered, ineffectively placed, and is not used efficiently. The design review process will be more efficient if this valuable information is integrated and centralized. The author developed a framework to improve the design review process by incorporating a centralized repository of design review information and 3D CAD model, in an interactive Virtual Environment (VE). To develop the framework, the author used Action Research style where he identified and confirmed the design review problem area, promoted the potential solutions to the problem, and developed a prototype. In gathering and analyzing the data for the research, the author used the synthesis of three methods. They include review of literature, a case study (interviews with industry personnel and content analysis of design review documents), and dissemination of the author's progressive findings in conferences, conference proceedings and journal publications. From his findings, the author developed the framework to improve the design review process by using information filtering based on context-aware concept, coupled with the benefits of a VE. The required design review information in the form of textual, numerical and geometric information is processed (queried, retrieved and stored). The author defined four contexts for information filtering: discipline-centric, task-centric, object-centric, and location-centric. IF-THEN rules are used to trigger the processing of the required design review information and present it to the design reviewer in a VE. A low cost 3D Game Engine is used as the enabling development tool to develop a work-in-progress (WIP) prototype design review application in a VE. / Ph. D.

Virtual reality (VR) involves an attempt to create an illusion that the user of the VR system is actually present in a synthetic (usually computer-generated) environment. Little is known about how various system parameters affect the illusion of presence in a virtual environment (VE). In particular, there seem to be very little quantitative data on which to base VR system design decisions. Also, while presence (or immersion) in VEs is a primary goal of VR, not much is known about how this variable affects task performance. The goal of this research was to provide a ratio-scale measure of perceived presence in a VE, to explore the effects of a number of environmental parameters on this measure and construct empirical models of these effects, and to relate perceived presence to user performance. This was done by manipulating eleven independent variables in a series of three experiments. The independent variables manipulated were scene update rate, visual display resolution, field of view, sound, textures, head-tracking, stereopsis, virtual personal risk, number of possible interactions, presence of a second user, and environmental detail. Participants performed a set of five tasks in the VE and rated perceived presence at the end of each set using the technique of free-modulus magnitude estimation. The amount of time spent in the VE was also recorded. The results indicate that the VR system parameters manipulated and analyzed in this research did affect participants' subjective feeling of presence in the VE. Field of view, sound, and head-tracking showed the largest effects. Other significant effects found were those of visual display resolution, texture-mapping, stereopsis, and the presence of a second user. Free-modulus magnitude estimation worked well as a measure of perceived presence. A positive relationship was found between perceived presence and task performance, but this relationship was relatively weak. Second-order empirical models were constructed that predicted perceived presence with moderate success and, with less success, task performance. / Ph. D.

Dunhuang, an oasis city in the desert, preserved the flourishing, vanished and renaissance of the Silk Road in the past two thousand years. Due to the significant position located at the nodes of the routes on the Silk Road, Dunhuang has experienced a variety of cultural influences. Given its cruel desert climate where caravans were threatened by unpredictable dangers, Dunhuang became a religious center, especially for the development of Buddhism. Mogao Grotto is forever a shining pearl of Dunhuang. There are a total of 735 caves that have been identified and stretch the length of a 5578-feet cliff, which includes the 492 grottoes decorated with mural and statues in the southern section. It began being constructed around the 4th century and remained under construction for more than 1000 years. Renaissance of the Mogao Grotto is an exhibition designed to use digital media and traditional drawing to re-create the ancient cave art in Northwest China. These virtual representations enhance the experience of real visitors of the cave, allowing them to discover the history of the caves. In particular, the 3D visualization environment of Cave 275, one of the oldest existing caves in Mogao Grotto, is a strong immersive experience for audiences to appreciate the delicate Buddhist cave art. At the same time, all traditional works, such as drawing, sketching, photos, audio, and video illustrate the understanding of Mogao cave art in modern aspects. Re-exhibits powerfully demonstrate the heritage of Asian culture in multi-approaches, which are a special opportunity for visitors to experience and witness the treasure of Chinese culture. / Master of Fine Arts

Through immersive stereoscopic displays and natural user interfaces, virtual reality (VR) is capable of offering the user a sense of presence in the virtual space, and has been long expected to revolutionize how people interact with virtual content in various application scenarios. However, with many technical challenges solved over the last three decades to bring low cost and high fidelity to VR experiences, we still do not see VR technology used frequently in many seemingly suitable applications. Part of this is due to the lack of expressiveness and efficiency of traditional “simple and reality-based� 3D user interfaces (3DUIs). The challenge is especially obvious when complex interaction tasks with diverse requirements are involved, such as editing virtual objects from multiple scales, angles, perspectives, reference frames, and dimensions. A common approach to overcome such problems is through hybrid user interface (HUI) systems that combine complementary interface elements to leverage their strengths. Based on this method, the first contribution of this dissertation is the proposal of Force Extension, an interaction technique that seamlessly integrates position-controlled touch and rate-controlled force input for efficient multi-touch interaction in virtual environments. Using carefully designed mapping functions, it is capable of offering fluid transitions between the two contexts, as well as simulating shear force input realistically for multi-touch gestures. The second contribution extends the HUI concept into immersive VR by introducing a Hybrid Virtual Environment (HVE) level editing system that combines a tablet and a Head-Mounted Display (HMD). The HVE system improves user performance and experience in complex high-level world editing tasks by using a “World-In-Miniature� and 2D GUI rendered on a multi-touch tablet device to compensate for the interaction limitations of a traditional HMD- and wand-based VR system. The concept of Interaction Context (IC) is introduced to explain the relationship between tablet interaction and the immersive interaction, and four coordination mechanisms are proposed to keep the perceptual, functional, and cognitive flow continuous during IC transitions. To offer intuitive and realistic interaction experiences, most immersive 3DUIs are centered on the user’s virtual avatar, and obey the same physics rules of the real world. However, this design paradigm also employs unnecessary limitations that hinders the performance of certain tasks, such as selecting objects in cluttered space, manipulating objects in six degrees of freedom, and inspecting remote spaces. The third contribution of this dissertation proposes the Object Impersonation technique, which breaks the common assumption that one can only immerse in the VE from a single avatar, and allows the user to impersonate objects in the VE and interact from their perspectives and reference frames. This hybrid solution of avatar- and object-based interaction blurs the line between travel and object selection, creating a unique cross-task interaction experience in the immersive environment. Many traditional 3DUIs in immersive VR use simple and intuitive interaction paradigms derived from real world metaphors. But they can be just as limiting and ineffective as in the real world. Using the coordinated HUI or HVE systems presented in this dissertation, one can benefit from the complementary advantages of multiple heterogeneous interfaces (Force Extension), VE representations (HVE Level Editor), and interaction techniques (Object Impersonation). This advances traditional 3D interaction into the more powerful hybrid space, and allows future VR systems to be applied in more application scenarios to provide not only presence, but also improved productivity in people’s everyday tasks.