DEPLOYING, IMPROVING AND EVALUATING EDGE BUNDLING METHODS FOR VISUALIZING LARGE GRAPHS

A tremendous increase in the scale of graphs has been witnessed in a wide range of fields, which demands efficient and effective visualization techniques to assist users in better understandings of large graphs. Conventional node-link diagrams are often used to visualize graphs, whereas excessive edge crossings can easily incur severe visual clutter in the node-link diagram of a large graph. Edge bundling can effectively remedy visual clutter and reveal high-level graph structures. Although significant efforts have been devoted to developing edge bundling, three challenging problems remain. First, edge bundling techniques are often computationally expensive and are not easy to deploy for web-based applications. The state-of-the-art edge bundling methods often require special system supports and techniques such as high-end GPU acceleration for large graphs, which makes these methods less portable, especially for ubiquitous mobile devices. Second, the quantitative quality of edge bundling results is barely assessed in the literature. Currently, the comparison of edge bundling mainly focuses on computational performance and perceptual results. Third, although the family of edge bundling techniques has a rich set of bundling layout, there is a lack of a generic method to generate different styles of edge bundling. In this research, I aim to address these problems and have made the following contributions. First, I provide an efficient framework to deploy edge bundling for web-based platforms by exploiting standard graphics hardware functions and libraries. My framework can generate high-quality edge bundling results on web-based platforms, and achieve a speedup of 50X compared to the previous state-of-the-art edge bundling method on a graph with half of a million edges. Second, I propose a new moving least squares based approach to lower the algorithm complexity of edge bundling. In addition, my approach can generate better bundling results compared to other methods based on a quality metric. Third, I provide an information-theoretic metric to evaluate the edge bundling methods. I leverage information theory in this metric. With my information-theoretic metric, domain users can choose appropriate edge bundling methods with proper parameters for their applications. Last but not least, I present a deep learning framework for edge bundling visualizations. Through a training process that learns the results of a specific edge bundling method, my deep learning framework can infer the final layout of the edge bundling method. My deep learning framework is a generic framework that can generate the corresponding results of different edge bundling methods. Adviser: Hongfeng Y

Winding Roads: Routing edges into bundles

International audienceVisualizing graphs containing many nodes and edges efficiently is quite challenging. Drawings of such graphs generally suffer from visual clutter induced by the large amount of edges and their crossings. Consequently, it is difficult to read the relationships between nodes and the high-level edge patterns that may exist in standard node- link diagram representations. Edge bundling techniques have been proposed to help solve this issue, which rely on high quality edge rerouting. In this paper, we introduce an intuitive edge bundling technique which efficiently reduces edge clutter in graphs drawings. Our method is based on the use of a grid built using the original graph to compute the edge rerouting. In comparison with previously proposed edge bundling methods, our technique improves both the level of clutter reduction and the computation performance. The second contribution of this paper is a GPU-based rendering method which helps users perceive bundles densities while preserving edge color

An Empirical Evaluation of Force-Directed Graph Layout

Force-directed graph layout is a widely used algorithm for the automatic layout of graphs. Little experimental work has been done exploring the behaviour of the algorithm under a variety of conditions. This thesis carries out three large-scale metric-based experiments. The first explores how the core algorithm behaves under changes to initial conditions. The second looks at extending the force-directed layout algorithm with additional forces to reduce overlaps. The third develops a novel symmetry metric for graphs and uses that to explore the symmetries of graphs. This thesis also carries out a user study to show that the differences reported by metrics in the graphs are reflected in a difference in user performance when using graphs for a free-form selection task

NBS monograph

From Introduction: "This is the third in a planned series of reports involving selective literature reviews of research and development requirements and areas of continuing R & D concern in the computer and information sciences and technologies.

The Origins and Evolution of Ornamental Lakes in English Designed Landscapes

The aim of this thesis is to investigate the origins and evolution of ornamental lakes in England, to establish when they first appeared, how they were constructed and what factors led to their emergence. For the purposes of this study, a lake is defined as a man-made piece of water covering one hectare or more. To aid discussion and analysis, a classification system to describe lakes has been drawn up, the two main categories being geometric and irregular lakes, with sub-divisions. The investigation begins with an appraisal of water in landscapes preceding the eighteenth century, with a focus on fishponds (vivaria), and elements such as moats, millponds and water-gardens. The appearance and development of ornamental lakes in the early eighteenth century is then explored in depth, as is the work of Lancelot Brown. The contribution of other lake-makers such as Richard Woods and William Emes is also examined. Humphry Repton�s work, and the impact of the Picturesque on lakes, are evaluated to assess their importance in the evolution of lakes, and the chronological study extends into the late nineteenth century. The construction of lakes is investigated, and related to different lake types. Also, the question of whether lakes were lined to retain water is considered. Geological and topographical factors are also studied in order to see how they might affect the construction and siting of lakes. The reasons for the emergence of ornamental lakes are also explored, and these include the fact that landscapes increased in size around 1700 and became less symmetrical, the effect of the Grand Tour, and the paintings associated with it, and the changing ways in which parks were used