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Walking is an essential means of transportation for humans. While walking to a destination, navigation through the environment requires prior knowledge of its surroundings. Different senses are used to acquire surrounding information for creating the knowledge base as well as determining one's current location. Whereas sighted people primarily rely upon vision to acquire such information, individuals with visual impairments (VI) have to rely on the remaining senses such as touch and hearing that lead to a lower mobility. For individuals with VI navigating in a new environment independently is difficult and unsafe. This results in less social activity and less job and education opportunities. This dissertation presents and evaluates an indoor navigation and information system designed to accommodate requirements of individuals with VI. This system can be deployed cost effectively in any public place such as universities or airports. As part of this dissertation a large number of indoor human navigation systems and a number of outdoor and robot navigation systems were studied and analyzed to identify research issues for different aspects of such systems for individuals with VI. While the main focus of this dissertation was to develop a navigation system for individuals with VI, the system provided here can be adopted by navigation systems for sighted individuals as well. To evaluate our approach, we conducted three user studies with sighted users and users with VI. The initial user study was conducted to help us better understand the strategies and preferences of users with VI for indoor navigation. The second study evaluated the feasibility of our approach and comparison between the designs of six alternative designs. The final study was conducted to evaluate the usability, efficiency, and accuracy of our system with users who were blind.

Virtual worlds have become very popular in the last decade and now these simu- lated environments have tens of millions of active users worldwide. Users benefit from virtual worlds in many different areas including social interaction, gaming, education and business. However, for users with visual impairments, accessing virtual worlds and benefiting from its facilities is rather challenging because of a number of important accessibility barriers. Our previous research effort, TextSL, has overcome perhaps the biggest barrier by providing a screen-reader accessible interface for individuals with visual impairments. Nevertheless, problems arising because of the limitations of a text-based desktop interface, challenges in textually describing a virtual scene and lack of reliable meta-data stand in front of our ultimate aim of enabling accessibility in virtual worlds. This thesis presents our contribution to virtual world accessibility by (1) providing a more accessible, portable and feature-rich virtual world interface; (2) proposing a method for generating efficient textual feedback for highly graphical environments; (3) analyzing and evaluating a hybrid virtual object labeling approach that benefits from machine learning and human computation.

Video games are presented to a user primary using visual feedback. Although many games contain sound and haptic feedback, these modalities are usually secondary in nature. Most secondary stimuli are used to enhance the player'€™s experience and do not contain information that will tell the user what input to provide and when. Therefore a person that has an impeded ability to perceive the primary stimuli, whether it be because of limitations of the input device (e.g. a mobile phone), a temporary sensory impairment (e.g. a noisy room), or a permanent impairment (e.g. blindness), will potentially be at a disadvantage when trying to play video games. Previous studies have shown that supplemental forms of feedback can improve the usability of so+ware and games and cues represented in multiple, simultaneous modalities can be detected faster, more accurately, and at lower thresholds than when presented separately. This thesis presents user studies of the use of supplemental feedback to reduce errors in playing Bingo, a game which is typically played by an older demographic who are more likely to suffer from sensory impairments such as low vision or hearing.

Virtual Worlds have virtually exploded in popularity and have experienced significant commercial success. People from all over the globe are experimenting on various aspects that a virtual world can provide. Virtual worlds are deemed to be the future of social networking, online advertising, distant education and potentially surfing the web closely resemble the immersive experience of virtual worlds. Individuals with visual impairments typically use screen readers to access web. Virtual Worlds like Second Life lack textual representation and are not accessible to screen readers. Because virtual worlds are completely owned and created by their users, most of their content doesn't have relevant meta information. This becomes a huge barrier to a text-extraction based approach of making virtual worlds accessible to the visually impaired. This thesis provides a framework which can be used for making virtual worlds accessible to visually impaired individuals. It presents a command based text interface which when connected to a screen reader enables the individuals with visual impairments to access Second Life. It then proposes a technique using which meaningful meta data can be added to the objects in Second Life which can then be retrieved as text and processed to make sense to the screen reader users.

As video games steadily increase in complexity and detail, game engines must also improve to be able to support both rapid and modular development while still maintaining high performance. Component-based architectures have been shown to be effective for allowing developers to rapidly create stunning games with modular components, but unfortunately come with a performance cost over traditional call-and-return systems. This thesis proposes a method that modifies existing component-based game engine architectures to automatically distribute and synchronize work in order to improve performance.

Over the last three decades, video games have evolved from an obscure pastime to a force of change that is transforming the way people perceive, learn about, and interact with the world around them. Video games are not only a popular form of entertainment, but are increasingly being used for other purposes, such as education and health, as well. Despite this increased interest, a significant number of people encounter barriers when playing games, due to a disability. This dissertation helps provide an understanding of how video games can be designed and modified to improve their accessibility features. A large number of existing, accessible games have been studied and analyzed to provide us with insights and understanding as to the importance of encouraging universal access in this field. Though our survey work covered several types of disabilities, the bulk of this dissertation focuses on improving accessibility for the visually impaired. Specific design strategies are illustrated and proven by the development and evaluation of actual blind-accessible games. Case studies are presented for each of the three games we developed during the research period. The first two case studies introduce new strategies for developing blind-accessible games and improv- ing their current state-of-the-art. The third demonstrates a new game for sighted users, the result of playing which, is improved accessibility in another existing game (Second Life). Furthermore, user studies were conducted that focused on the enjoyment, educational, and social interaction aspects of these games while evaluating their ease of access.

Accessibility research has been a part of Human-Computer Interaction since the 1970's. In recent years a small amount of this accessibility research has been applied to the area of games. This previous work applies concepts found in accessibility research to very simple games. This thesis takes the small amount of work done previously and examines it all together. Taking concepts of this work, this thesis then shows how these existing concepts were applied to newer mainstream games. The work on these newer games also led to the creation of a new mechanism that can be applied in further accessibility research, the Rotate & Extend mechanism. Finally, this thesis examines a model that represents the Trade-offs associated with making a game accessible.