Tactile devices are prevalent in everyday life, including raised dots on computer keyboards and telephone keypads. Braille readers help to give blind users access to computers and tactile representations of maps and museum exhibits enhance blind people's experience of the world outside their houses. While computer applications and websites are often enhanced by graphics, these are difficult for blind people to access. A single haptic graphic display, aimed at presenting computer images for tactile exploration, is available for purchase, but this is based on existing Braille technology and is expensive. While there is an active research community investigating haptic graphic displays, this concentrates largely on identifying technologies that can be employed in the presentation of images, and few researchers have considered the requirements for such devices. This represents a gap in existing research. This thesis describes the development of a series of prototypes based on pin (also known as tactile elements or taxels) arrays for use within experiments aimed at specifying the requirements for a haptic graphic display. A number of experiments are documented that investigate the requirements for attributes of a display, including resolution, taxel head size, taxel height, the most natural exploration method and the required resistance force to maintain a raised image during exploration. The results suggest that a resolution of 10 taxels per inch, a taxel head size of 2mm, a taxel height of 3mm, a resistance force of 130mN and a constrained exploration style offer a promising starting point for specifying a haptic graphic display based on a pin matrix. The results of the experiments, which are presented in the form of a formal specification, suggest that the commercially available device and a limited number of the prototypes developed for prior research come close to meeting the requirements of the participants used in this study. While this research is incomplete with regard to the lack of use of blind participants, it provides a much-needed baseline specification that will enable further research to evaluate and, if necessary, amend the specification for the target user groups.

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The quest for realism in computer-generated graphics has yielded a range of algorithmic techniques, the most advanced of which are capable of rendering images at close to photorealistic quality. Due to the realism available, it is now commonplace that computer graphics are used in the creation of movie sequences, architectural renderings, medical imagery and product visualisations. This work concentrates on the photon mapping algorithm [1, 2], a physically based global illumination rendering algorithm. Photon mapping excels in producing highly realistic, physically accurate images. A drawback to photon mapping however is its rendering times, which can be significantly longer than other, albeit less realistic, algorithms. Not surprisingly, this increase in execution time is associated with a high computational cost. This computation is usually performed using the general purpose central processing unit (CPU) of a personal computer (PC), with the algorithm implemented as a software routine. Other options available for processing these algorithms include desktop PC graphics processing units (GPUs) and custom designed acceleration hardware devices. GPUs tend to be efficient when dealing with less realistic rendering solutions such as rasterisation, however with their recent drive towards increased programmability they can also be used to process more realistic algorithms. A drawback to the use of GPUs is that these algorithms often have to be reworked to make optimal use of the limited resources available. There are very few custom hardware devices available for acceleration of the photon mapping algorithm. Ray-tracing is the predecessor to photon mapping, and although not capable of producing the same physical accuracy and therefore realism, there are similarities between the algorithms. There have been several hardware prototypes, and at least one commercial offering, created with the goal of accelerating ray-trace rendering [3]. However, properties making many of these proposals suitable for the acceleration of ray-tracing are not shared by photon mapping. There are even fewer proposals for acceleration of the additional functions found only in photon mapping. All of these approaches to algorithm acceleration offer limited scalability. GPUs are inherently difficult to scale, while many of the custom hardware devices available thus far make use of large processing elements and complex acceleration data structures. In this work we make use of three novel approaches in the design of highly scalable specialised hardware structures for the acceleration of the photon mapping algorithm. Increased scalability is gained through: • The use of a brute-force approach in place of the commonly used smart approach, thus eliminating much data pre-processing, complex data structures and large processing units often required. • The use of Logarithmic Number System (LNS) arithmetic computation, which facilitates a reduction in processing area requirement. • A novel redesign of the photon inclusion test, used within the photon search method of the photon mapping algorithm. This allows an intelligent memory structure to be used for the search. The design uses two hardware structures, both of which accelerate one core rendering function. Renderings produced using field programmable gate array (FPGA) based prototypes are presented, along with details of 90nm synthesised versions of the designs which show that close to an orderof- magnitude speedup over a software implementation is possible. Due to the scalable nature of the design, it is likely that any advantage can be maintained in the face of improving processor speeds. Significantly, due to the brute-force approach adopted, it is possible to eliminate an often-used software acceleration method. This means that the device can interface almost directly to a frontend modelling package, minimising much of the pre-processing required by most other proposals.

This thesis examines how the properties of visualisation user interfaces (Uls) can augment cognition during individual and collaborative problem solving activities. Claims pertaining to the benefits of visualisation UIs are well documented. In order to inform their application with respect to the context of use. this research aims to identify the particular properties that can support cognition, and to explore the different communicative and representational conditions under which these properties operate. The principal focus for investigation concerns issues surrounding the benefits of promoting visualisation Uls in distributed systems. This emphasis stems from a practical requirement for the design of visualisation UIs to support the analysis of telecommunication customer behavioural datasets within a collaborative environment. The design activities in this thesis followed a human-centred approach, realising a novel set of 20 and 30 graphical representations which were evaluated in a series of three task-based studies. Study I investigated the effects of 20 and 3D displays exhibiting different representational properties on individual problem solving. The results indicated a performance advantage for the 2D display and a subjective user preference for the 3D displays. However, overall. the comparable benefits were confounded by differences in representational characteristics. Studies 2 and 3 adopted 3D displays with equivalent representational characteristics to examine the effects of different communication mediums and representational configurations on collaborative problem solving behaviours. Study 2 confirmed the prediction that visually shared representations offers a more optimal setting for collaboration compared to audio only contexts. Study 3 substantiated previous findings by highlighting that collaborative activities are better supported by sharing representations with identical rather than complementary datasets. Overall, the thesis has implications for informing two key areas: I) visualisations for supporting individual and collaborative problem solving activities, and 2) the optimal configurations of visualisation Uis for supporting remote collaborations.

As the technologies of computing have advanced to become ubiquitous and pervasive in our everyday life, our way of interacting with computers is also changing. Most existing research, particularly on Tangible User Interfaces (TUI), has focused on enhancing and augmenting physical artefacts to be digitally-linked to underlying computational functionalities. This research focuses on physical devices and reports an investigation into what makes interaction natural and fluid.

Capturing meaningful interactions between a user and an application is useful. A meaningful interaction is an interaction that causes a change in state of one of the participants. Meaningful interaction capture is well established for console based applications. No techniques exist that capture only the meaningful interactions with a graphical interface. Data collected by such a system could be used for a variety of applications, such as HCI studies, authorship identification, cognitive modelling and screen recording. A methodology for capturing the meaningful interactions between a user and a graphical application is described. An implementation of this methodology has been developed, together with a supporting tool-set. A new corpus consisting of captured interactions between users and two applications with contrasting graphical interfaces has been collected and published. This corpus is analysed and used for authorship attribution.

Interacting with a computer game using only a simple web camera has seen a great deal of success in the computer games industry, as demonstrated by the numerous computer vision based games available for the Sony PlayStation 2 and PlayStation 3 game consoles. Computational efficiency is important for these human computer inter- action applications, so for simple interactions a fast background subtraction approach is used that incorporates a new local descriptor which uses a novel temporal coding scheme that is much more robust to noise than the standard formulations. Results are presented that demonstrate the effect of using this method for code label stability. Detecting local image changes is sufficient for basic interactions, but exploiting high-level information about the player's actions, such as detecting the location of the player's head, the player's body, or ideally the player's pose, could be used as a cue to provide more complex interactions. Following an object detection approach to this problem, a combined detection and segmentation approach is explored that uses a face detection algorithm to initialise simple shape priors to demonstrate that good real-time performance can be achieved for face texture segmentation. Ultimately, knowing the player's pose solves many of the problems encountered by simple local image feature based methods, but is a difficult and non-trivial problem. A detection approach is also taken to pose estimation: first as a binary class problem for human detection, and then as a multi-class problem for combined localisation and pose detection. For human detection, a novel formulation of the standard chamfer matching algo- rithm as an SVM classifier is proposed that allows shape template weights to be learnt automatically. This allows templates to be learnt directly from training data even in the presence of background and without the need to pre-process the images to extract their silhouettes. Good results are achieved when compared to a state of the art human detection classifier. For combined pose detection and localisation, a novel and scalable method of ex- ploiting the edge distribution in aligned training images is presented to select the most potentially discriminative locations for local descriptors that allows a much higher space of descriptor configurations to be utilised efficiently. Results are presented that show competitive performance when compared to other combined localisation and pose detection methods.

This research investigates the feasibility and effectiveness of assessing students programming solutions to Graphical User Interface exercises in an automated fashion. Automated marking systems ease the burden on the staff involved in running a course and allow students to get results and feedback in a timely fashion. Several automated marking systems exist but are currently unable to mark GUIs. The inherent complexity of GUIs and the need for aesthetic analysis has rendered GUIs beyond the scope of most marking systems. The marking approach described in this thesis implements a number of novel concepts. By exploiting language design properties such as the hierarchical relationship between components, it was possible to develop a framework capable of testing and marking students' GUI programs. Introspectively analysing the interface enables the marking system to obtain access to the intrinsic elements contained within the GUI. Once access has been obtained, the tests can be performed on the actual interface components themselves rather than a mere representation. GUI assessment is more than functional testing, aesthetics play a major role in the creation of an interface. Existing aesthetic metrics do not provide the analytical capabilities required due to their failure to include colour. The distractive effects that colours have were quantified and incorporated into the metrics. The results of the dynamic and aesthetic testing show that through the implementation of the novel components detailed, the creation of a GUI marking system is feasible and its marking both consistent and effective. The design enables the system to return results in a timely fashion and the effects that colour has can be seen in the results of basic aesthetic testing.