We present the "Near Optimal IsoSurface Extraction" (NOISE) algorithm for rapidly extracting isosurfaces from structured and unstructured grids. Using the span space, a new representation of the underlying domain, we develop an isosurface extraction algorithm with a worst case complexity of o(& + c) for the search phase, where n is the size of the data set and k is the number of cells intersected by the isosurface. The memory requirement is kept at O(n) while the preprocessing step is O(n log n). We utilize the span space representation as a tool for comparing isosurface extraction methods on structured and unstructured grids. We also present a fast triangulation scheme for generating and displaying unstructured tetrahedral grids.

Radial visualization, or the practice of displaying data in a circular or elliptical pattern, is an increasingly common technique in information visualization research. In spite of its prevalence, little work has been done to study this visualization paradigm as a methodology in its own right. We provide a historical review of radial visualization, tracing it to its roots in centuries-old statistical graphics. We then identify the types of problem domains to which modern radial visualization techniques have been applied. A taxonomy for radial visualization is proposed in the form of seven design patterns encompassing nearly all recent works in this area. From an analysis of these patterns, we distill a series of design considerations that system builders can use to create new visualizations that address aspects of the design space that have not yet been explored. It is hoped that our taxonomy will provide a framework for facilitating discourse among researchers and stimulate the development of additional theories and systems involving radial visualization as a distinct design metaphor.

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Constructing distributed representations for words through neural language models and using the resulting vector spaces for analysis has become a crucial component of natural language processing (NLP). However, despite their widespread application, little is known about the structure and properties of these spaces. To gain insights into the relationship between words, the NLP community has begun to adapt high-dimensional visualization techniques. In particular, researchers commonly use t-distributed stochastic neighbor embeddings (t-SNE) and principal component analysis (PCA) to create two-dimensional embeddings for assessing the overall structure and exploring linear relationships (e.g., word analogies), respectively. Unfortunately, these techniques often produce mediocre or even misleading results and cannot address domain-specific visualization challenges that are crucial for understanding semantic relationships in word embeddings. Here, we introduce new embedding techniques for visualizing semantic and syntactic analogies, and the corresponding tests to determine whether the resulting views capture salient structures. Additionally, we introduce two novel views for a comprehensive study of analogy relationships. Finally, we augment t-SNE embeddings to convey uncertainty information in order to allow a reliable interpretation. Combined, the different views address a number of domain-specific tasks difficult to solve with existing tools.

A b s h c tinformation and minimize any mental transformations that w e present a novel Paradigm for visual correlation of network alerts from disparate logs. This paradigm facilitates and promotes situational awareness in complex network enmust be applied to the data. O u r goal is t o enable the users to quickly decide how pervasive and how severe problems vironments. Our approach is based on the notion that, by definition, a n alert must posses three attributes, namely: What, When, and Where. This fundamental premise, which WO term w 3 , provides a vehicle for comparing between seemingly disparate events. We propose a concise and scalable representation of these three attributes, that leads to a flexible visualisation tool that is also clear and intuitive t o use.Within our system, alerts can be grouped and viewed hierarchically with respect to both their type, i.e., the What, and t o their Where attributes. Further understanding is gained by displaying the temporal distribution of alerts to reveal complex attack trends. Finally, w e propose a set of visual metaphor extensions that augment the proposed paradigm and enhance users' situational awareness. These metaphors direct the attention of users t o many-t-one correlations within the current display helping them detect abnormal network activity.

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As computational engineering and science applications have grown in size and complexity, the process of analyzing and visualizing the resulting vast amounts of data has become an increasingly difficult task. Traditionally, data analysis and visualization are performed as post-processing steps after a simulation has been run. As simulations have increased in size, this task has become increasingly difficult-often requiring significant computation, high-performance machines, high capacity storage, and high bandwidth networks. Computational steering is an emerging technology that addresses this problem by "closing the loop" and providing a mechanism for integrating modeling, simulation, data analysis, and visualization. This integration allows a researcher to interactively control simulations and perform data analysis while avoiding many of the pitfalls associated with the traditional batch/post processing cycle. In this paper, we describe the application of interactive simulation and visualization as applied to the domain of computational field problems. We discuss the integration of visualization techniques within an integrated problem solving environment, SCIRun, as well as a case study of the simulation and visualization of bioelectric fields.

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