This thesis investigates the development of a low cost, component based facial virtual conferencing system. The design is decomposed into an encoding phase and a decoding phase, which communicate with each other via a network connection. The encoding phase is composed of three components: model acquisition (which handles avatar generation), pose estimation and expression analysis. Audio is not considered part of the encoding and decoding process, and as such is not evaluated. The model acquisition component is implemented using a visual hull reconstruction algorithm that is able to reconstruct real-world objects using only sets of images of the object as input. The object to be reconstructed is assumed to lie in a bounding volume of voxels. The reconstruction process involves the following stages: - Space carving for basic shape extraction; - Isosurface extraction to remove voxels not part of the surface of the reconstruction; - Mesh connection to generate a closed, connected polyhedral mesh; - Texture generation. Texturing is achieved by Gouraud shading the reconstruction with a vertex colour map; - Mesh decimation to simplify the object. The original algorithm has complexity O(n), but suffers from an inability to reconstruct concave surfaces that do not form part of the visual hull of the object. A novel extension to this algorithm based on Normalised Cross Correlation (NCC) is proposed to overcome this problem. An extension to speed up traditional NCC evaluations is proposed which reduces the NCC search space from a 2D search problem down to a single evaluation. Pose estimation and expression analysis are performed by tracking six fiducial points on the face of a subject. A tracking algorithm is developed that uses Normalised Cross Correlation to facilitate robust tracking that is invariant to changing lighting conditions, rotations and scaling. Pose estimation involves the recovery of the head position and orientation through the tracking of the triangle formed by the subject's eyebrows and nose tip. A rule-based evaluation of points that are tracked around the subject's mouth forms the basis of the expression analysis. A user assisted feedback loop and caching mechanism is used to overcome tracking errors due to fast motion or occlusions. The NCC tracker is shown to achieve a tracking performance of 10 fps when tracking the six fiducial points. The decoding phase is divided into 3 tasks, namely: avatar movement, expression generation and expression management. Avatar movement is implemented using the base VR system. Expression generation is facilitated using a Vertex Interpolation Deformation method. A weighting system is proposed for expression management. Its function is to gradually transform from one expression to the next. The use of the vertex interpolation method allows real-time deformations of the avatar representation, achieving 16 fps when applied to a model consisting of 7500 vertices. An Expression Parameter Lookup Table (EPLT) facilitates an independent mapping between the two phases. It defines a list of generic expressions that are known to the system and associates an Expression ID with each one. For each generic expression, it relates the expression analysis rules for any subject with the expression generation parameters for any avatar model. The result is that facial expression replication between any subject and avatar combination can be performed by transferring only the Expression ID from the encoder application to the decoder application. The ideas developed in the thesis are demonstrated in an implementation using the CoRgi Virtual Reality system. It is shown that the virtual-conferencing application based on this design requires only a bandwidth of 2 Kbps. / Adobe Acrobat Pro 9.4.6 / Adobe Acrobat 9.46 Paper Capture Plug-in

The ultimate goal in the manufacturing of a part is to achieve an economic production plan with precision and accuracy in the first attempt at machining. A physics-based comprehensive modeling of the machining processes is a fundamental requirement in identifying optimal cutting conditions which result in high productivity rates without violating accuracy throughout the part production process. This thesis presents generalized virtual simulation and optimization strategies to predict and optimize performance of milling processes up to 3-axis. Computationally efficient mathematical models are introduced to predict milling process state variables such as chip load, force, torque, and cutting edge engagement at discrete cutter locations. Process states are expressed explicitly as a function of helical cutting edge - part engagement, cutting coefficient and feedrate. Cutters with arbitrary geometries are modeled parametrically, and the intersection of helical cutting edges with workpiece features are evaluated either analytically or numerically depending on geometric complexity. The dynamics of generalized milling operations are modeled and the stability of the process is predicted using both time and frequency domain based models. These algorithms enable rapid simulation of milling operations in a virtual environment as the part features vary. In an effort to reduce machining time, a constraint-based optimization scheme is proposed to maximize the material removal rate by optimally selecting the depth of cut, width of cut, spindle speed and feedrate. A variety of user defined constraints such as maximum tool deflection, torque/power demand, and chatter stability are taken into consideration. Two alternative optimization strategies are presented: pre-process optimization provides allowable depth and width of cut during part programming at the computer aided manufacturing stage using chatter constraint, whereas the post-process optimization tunes only feedrate and spindle speed of an existing part program to maximize productivity without violating physical constraints of the process. Optimized feedrates are filtered by considering machine tool axes limitations and the algorithms are tested in machining various industrial parts. The thesis contributed to the development of a novel 3-axis Virtual Milling System that has been deployed to the manufacturing industry. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

GetWork nace para atender tres segmentos de mercado enlazados entre sí. En primer lugar, empresas que necesiten cubrir plazas dentro de su equipo de trabajo y buscan a los profesionales más capacitados y sobretodo que les aseguren la creación de valor con su permanencia, atendiendo una problemática como la rotación de personal, y crecimiento dentro de la empresa. Por otro lado, profesionales con dificultades para encontrar el trabajo soñado, o simplemente con dificultades para integrarse al mercado laboral. Ante ello, GetWork garantiza apoyo y asesoría completa, inducción en diversos temas, consejos para la elaboración de CVs y presentación personal, etc. La meta final es que los profesionales se unan a empresas en las que puedan establecerse en una relación de beneficio mutuo. Por último, empresas dedicadas a la educación y capacitaciones para profesionales que se encuentran en la búsqueda de empleo, o que desean mejorar sus habilidades y aptitudes para alcanzar mayores rendimientos en sus centros de trabajo. Para ello, GetWork le sirve de ventana a estas instituciones para darse a conocer por medio de publicidad y conseguir nuevos clientes que eventualmente crearán valor no solo para las empresas en las que laboran, sino también para nosotros incrementado las posibilidades de nuestro servicio. / GetWork was created to serve the three following market segments: companies, users and institutions dedicated to education and training. First place, companies, with open jobs openings who look for the most qualified professionals and above all to ensure the creation of value with their retention. Also, GetWork helps professionals with difficulties to find jobs, land an adequate job opportunity. GetWork guarantees full support and advice, induction on various topics, advices for the preparation of resume and personal presentation, etc. The ultimate goal is for professionals to join companies in which they can establish a mutually beneficial relationship. Finally, GetWork aids companies dedicated to education and training professionals who want to improve their skills and abilities to achieve higher performance in their workplaces. For this, GetWork serves as a link to these institutions to become known through advertising and increase their posibilities for networking. / Trabajo de investigación

One of the oft cited reasons for virtual environments is that they provide experiences with places one would never be able to visit and to perform tasks that would otherwise be dangerous, or inaccessible. The ability to become transported to another environment, such that you think you are "there," is known as presence. Existing presence literature focuses largely on the sensory aspects of virtual environment experiences. However, there is more to experience than what is sensed. This dissertation investigates the theoretical components of holistic experiences in virtual environments. In order to explore the relationship between experiential design and presence, a new evaluation tool was needed. This ultimately led to the development of the Virtual Experience Test. To validate the Virtual Experience Test, an experiment was designed that utilized subjective evaluations regarding game-play in the commercial game Mirror's Edge. Measures of experiential design, flow, and presence were taken and the relationships between the measures analyzed. The results of this research showed that environments utilizing holistic designs result in significantly higher presence. Furthermore, this study produced a validated measure of holistic experience that designers could use to evaluate their virtual environments.

Conventional analysis of atmospheric data includes three-dimensional desktop-computer displays. One disadvantage is that it can reduce the ability to zoom in and see small-scale features while concurrently viewing other faraway features. This research intends to determine if using virtual environments to examine atmospheric data can improve a meteorologist's ability to analyze the given information. In addition to possibly enhancing small-scale analysis, virtual environments technology offers an array of possible improvements. Presented is the theory on developing an experiment to establish the extent to which virtual environments assist meteorologists in analysis. Following is the details of an implementation of such an experiment. Based on the quantitative results obtained, the conclusion is that immersion can significantly increase the accuracy of a meteorologist's analysis of an atmospheric data set.

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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.

A Distributed Virtual Environment (DVE) system provides a shared virtual environment where physically separated users can interact and collaborate over a computer network. More simultaneous DVE users could result in intolerable system performance degradation. We address the three major challenges to improve DVE scalability: effective DVE system performance measurement, understanding the controlling factors of system performance/quality and determining the consequences of DVE system changes. We propose a DVE Scalability Engineering (DSE) process that addresses these three major challenges for DVE design. DSE allow us to identify, evaluate, and leverage trade-offs among DVE resources, the DVE software, and the virtual environment. DSE has three stages. First, we show how to simulate different numbers and types of users on DVE resources. Collected user study data is used to identify representative user types. Second, we describe a modeling method to discover the major trade-offs between quality of service and DVE resource usage. The method makes use of a new instrumentation tool called ppt. ppt collects atomic blocks of developer-selected instrumentation at high rates and saves it for offline analysis. Finally, we integrate our load simulation and modeling method into a single process to explore the effects of changes in DVE resources. We use the simple Asteroids DVE as a minimal case study to describe the DSE process. The larger and commercial Torque and Quake III DVE systems provide realistic case studies and demonstrate DSE usage. The Torque case study shows the impact of many users on a DVE system. We apply the DSE process to significantly enhance the Quality of Experience given the available DVE resources. The Quake III case study shows how to identify the DVE network needs and evaluate network characteristics when using a mobile phone platform. We analyze the trade-offs between power consumption and quality of service. The case studies demonstrate the applicability of DSE for discovering and leveraging tradeoffs between Quality of Experience and DVE resource usage. Each of the three stages can be used individually to improve DVE performance. The DSE process enables fast and effective DVE performance improvement. / Ph. D.

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