One view is not enough: review of and encouragement for multiple and alternative representations in 3D and immersive visualisation

The opportunities for 3D visualisations are huge. People can be immersed inside their data, interface with it in natural ways, and see it in ways that are not possible on a traditional desktop screen. Indeed, 3D visualisations, especially those that are immersed inside head-mounted displays are becoming popular. Much of this growth is driven by the availability, popularity and falling cost of head-mounted displays and other immersive technologies. However, there are also challenges. For example, data visualisation objects can be obscured, important facets missed (perhaps behind the viewer), and the interfaces may be unfamiliar. Some of these challenges are not unique to 3D immersive technologies. Indeed, developers of traditional 2D exploratory visualisation tools would use alternative views, across a multiple coordinated view (MCV) system. Coordinated view interfaces help users explore the richness of the data. For instance, an alphabetical list of people in one view shows everyone in the database, while a map view depicts where they live. Each view provides a different task or purpose. While it is possible to translate some desktop interface techniques into the 3D immersive world, it is not always clear what equivalences would be. In this paper, using several case studies, we discuss the challenges and opportunities for using multiple views in immersive visualisation. Our aim is to provide a set of concepts that will enable developers to perform critical thinking, creative thinking and push the boundaries of what is possible with 3D and immersive visualisation. In summary developers should consider how to integrate many views, techniques and presentation styles, and one view is not enough when using 3D and immersive visualisations

Simulação numérica e visualização 3D interativa de objetos sob fluxos irrotacionais em tempo Quase-Real

Resumo: De uma maneira geral, qualquer fluxo irrotacional e incompressível é governado pela equação de Laplace. Esta não possui resolução analítica para problemas reais de engenharia, os quais possuem domínios e condições de contorno complexas, exceto para poucos casos particulares. A Dinâmica dos Fluidos Computacional (DFC) é um método utilizado para resolver numericamente a equação de Laplace, satisfazendo condições iniciais e de contorno. Porém, ao se refinar ou estender um domínio calculado, a quantidade de dados numéricos resultantes aumentará proporcionalmente e a análise destes valores pode se tornar complexa e onerosa. Complementariamente, para a compreensão dos resultados, é importante uma representação visual. A resolução numérica da equação de Laplace está descrita neste trabalho, com um algoritmo de solução inédito para as condições de contorno que atende qualquer forma geométrica em três dimensões. Desenvolveu-se um simulador que possibilita alterações geométricas de objetos 3D, calcula e visualiza interativamente velocidades, linhas de fluxo e força de sustentação para fluxos irrotacionais e incompressíveis em tempo quase-real. O sistema utiliza o método das diferenças finitas para a solução das equações. A interface gráfica foi desenvolvida utilizando, deste modo ineditamente para a DFC, a linguagem C++ e o VTK (Visualization Tool Kit). A quantidade, a origem das linhas de fluxo, a seleção do campo de velocidades, o cálculo da força de sustentação e a visualização estereoscópica são parâmetros que podem ser ajustados e selecionados para a visualização. O algoritmo passou por validações mostrando a capacidade de resolução em três dimensões. Assim, o simulador desenvolvido resolve, ao contrário dos softwares já existentes, o problema do cálculo e visualização interativa imediata ao se fazer modificações em objetos 3D. Este procedimento permitirá que se façam comparações entre formas geométricas imediatamente alteradas para que se possa escolher, entre elas, a que se adequar melhor às necessidades de um projeto

Contours in Visualization

This thesis studies the visualization of set collections either via or defines as the relations among contours. In the first part, dynamic Euler diagrams are used to communicate and improve semimanually the result of clustering methods which allow clusters to overlap arbitrarily. The contours of the Euler diagram are rendered as implicit surfaces called blobs in computer graphics. The interaction metaphor is the moving of items into or out of these blobs. The utility of the method is demonstrated on data arising from the analysis of gene expressions. The method works well for small datasets of up to one hundred items and few clusters. In the second part, these limitations are mitigated employing a GPU-based rendering of Euler diagrams and mixing textures and colors to resolve overlapping regions better. The GPU-based approach subdivides the screen into triangles on which it performs a contour interpolation, i.e. a fragment shader determines for each pixel which zones of an Euler diagram it belongs to. The rendering speed is thus increased to allow multiple hundred items. The method is applied to an example comparing different document clustering results. The contour tree compactly describes scalar field topology. From the viewpoint of graph drawing, it is a tree with attributes at vertices and optionally on edges. Standard tree drawing algorithms emphasize structural properties of the tree and neglect the attributes. Adapting popular graph drawing approaches to the problem of contour tree drawing it is found that they are unable to convey this information. Five aesthetic criteria for drawing contour trees are proposed and a novel algorithm for drawing contour trees in the plane that satisfies four of these criteria is presented. The implementation is fast and effective for contour tree sizes usually used in interactive systems and also produces readable pictures for larger trees. Dynamical models that explain the formation of spatial structures of RNA molecules have reached a complexity that requires novel visualization methods to analyze these model\''s validity. The fourth part of the thesis focuses on the visualization of so-called folding landscapes of a growing RNA molecule. Folding landscapes describe the energy of a molecule as a function of its spatial configuration; they are huge and high dimensional. Their most salient features are described by their so-called barrier tree -- a contour tree for discrete observation spaces. The changing folding landscapes of a growing RNA chain are visualized as an animation of the corresponding barrier tree sequence. The animation is created as an adaption of the foresight layout with tolerance algorithm for dynamic graph layout. The adaptation requires changes to the concept of supergraph and it layout. The thesis finishes with some thoughts on how these approaches can be combined and how the task the application should support can help inform the choice of visualization modality

Festschrift zum 60. Geburtstag von Wolfgang Strasser

Die vorliegende Festschrift ist Prof. Dr.-Ing. Dr.-Ing. E.h. Wolfgang Straßer zu seinem 60. Geburtstag gewidmet. Eine Reihe von Wissenschaftlern auf dem Gebiet der Computergraphik, die alle aus der "Tübinger Schule" stammen, haben - zum Teil zusammen mit ihren Schülern - Aufsätze zu dieser Schrift beigetragen. Die Beiträge reichen von der Objektrekonstruktion aus Bildmerkmalen über die physikalische Simulation bis hin zum Rendering und der Visualisierung, vom theoretisch ausgerichteten Aufsatz bis zur praktischen gegenwärtigen und zukünftigen Anwendung. Diese thematische Buntheit verdeutlicht auf anschauliche Weise die Breite und Vielfalt der Wissenschaft von der Computergraphik, wie sie am Lehrstuhl Straßer in Tübingen betrieben wird. Schon allein an der Tatsache, daß im Bereich der Computergraphik zehn Professoren an Universitäten und Fachhochschulen aus Tübingen kommen, zeigt sich der prägende Einfluß Professor Straßers auf die Computergraphiklandschaft in Deutschland. Daß sich darunter mehrere Physiker und Mathematiker befinden, die in Tübingen für dieses Fach gewonnen werden konnten, ist vor allem seinem Engagement und seiner Ausstrahlung zu verdanken. Neben der Hochachtung vor den wissenschaftlichen Leistungen von Professor Straßer hat sicherlich seine Persönlichkeit einen entscheidenden Anteil an der spontanten Bereischaft der Autoren, zu dieser Festschrift beizutragen. Mit außergewöhnlich großem persönlichen Einsatz fördert er Studenten, Doktoranden und Habilitanden, vermittelt aus seinen reichen internationalen Beziehungen Forschungskontakte und schafft so außerordentlich gute Voraussetzungen für selbständige wissenschafliche Arbeit. Die Autoren wollen mit ihrem Beitrag Wolfgang Straßer eine Freude bereiten und verbinden mit ihrem Dank den Wunsch, auch weiterhin an seinem fachlich wie menschlich reichen und bereichernden Wirken teilhaben zu dürfen

Wholetoning: Synthesizing Abstract Black-and-White Illustrations

Black-and-white imagery is a popular and interesting depiction technique in the visual arts, in which varying tints and shades of a single colour are used. Within the realm of black-and-white images, there is a set of black-and-white illustrations that only depict salient features by ignoring details, and reduce colour to pure black and white, with no intermediate tones. These illustrations hold tremendous potential to enrich decoration, human communication and entertainment. Producing abstract black-and-white illustrations by hand relies on a time consuming and difficult process that requires both artistic talent and technical expertise. Previous work has not explored this style of illustration in much depth, and simple approaches such as thresholding are insufficient for stylization and artistic control. I use the word wholetoning to refer to illustrations that feature a high degree of shape and tone abstraction. In this thesis, I explore computer algorithms for generating wholetoned illustrations. First, I offer a general-purpose framework, “artistic thresholding”, to control the generation of wholetoned illustrations in an intuitive way. The basic artistic thresholding algorithm is an optimization framework based on simulated annealing to get the final bi-level result. I design an extensible objective function from our observations of a lot of wholetoned images. The objective function is a weighted sum over terms that encode features common to wholetoned illustrations. Based on the framework, I then explore two specific wholetoned styles: papercutting and representational calligraphy. I define a paper-cut design as a wholetoned image with connectivity constraints that ensure that it can be cut out from only one piece of paper. My computer generated papercutting technique can convert an original wholetoned image into a paper-cut design. It can also synthesize stylized and geometric patterns often found in traditional designs. Representational calligraphy is defined as a wholetoned image with the constraint that all depiction elements must be letters. The procedure of generating representational calligraphy designs is formalized as a “calligraphic packing” problem. I provide a semi-automatic technique that can warp a sequence of letters to fit a shape while preserving their readability

Visualising multiple overlapping classification hierarchies.

The revision or reorganisation of hierarchical data sets can result in many possible hierarchical classifications composed of the same or overlapping data sets existing in parallel with each other. These data sets are difficult for people to handle and conceptualise, as they tryto reconcile the different perspectives and structures that such data represents. One area where this situation occurs is the study of botanical taxonomy, essentially the classification and naming of plants. Revisions, new discoveries and new dimensions for classifying plants lead to a proliferation of classifications over the same set of plant data. Taxonomists would like a method of exploring these multiple overlapping hierarchies for interesting information, correlations, or anomalies. The application and extension of Information Visualisation (IV) techniques, the graphical display of abstract information, is put forward as a solution to this problem. Displaying the multiple classification hierarchies in a visually appealing manner along with powerful interaction mechanisms for examination and exploration of the data allows taxonomists to unearth previously hidden information. This visualisation gives detail that previous visualisations and statistical overviews cannot offer. This thesis work has extended previous IV work in several respects to achieve this goal. Compact, yet full and unambiguous, hierarchy visualisations have been developed. Linking and brushing techniques have been extended to work on a higher class of structure, namely overlapping trees and hierarchies. Focus and context techniques have been pushed to achieve new effects across the visually distinct representations of these multiple hierarchies. Other data types, such as multidimensional data and large cluster hierarchies have also been displayed using the final version of the visualisation

Mesh-Free and Finite Element-Based Methods for Structural Mechanics Applications

The problem of solving complex engineering problems has always been a major topic in all industrial fields, such as aerospace, civil and mechanical engineering. The use of numerical methods has increased exponentially in the last few years, due to modern computers in the field of structural mechanics. Moreover, a wide range of numerical methods have been presented in the literature for solving such problems. Structural mechanics problems are dealt with using partial differential systems of equations that might be solved by following the two main classes of methods: Domain-decomposition methods or the so-called finite element methods and mesh-free methods where no decomposition is carried out. Both methodologies discretize a partial differential system into a set of algebraic equations that can be easily solved by computer implementation. The aim of the present Special Issue is to present a collection of recent works on these themes and a comparison of the novel advancements of both worlds in structural mechanics applications

XX Workshop de Investigadores en Ciencias de la Computación - WICC 2018 : Libro de actas

Actas del XX Workshop de Investigadores en Ciencias de la Computación (WICC 2018), realizado en Facultad de Ciencias Exactas y Naturales y Agrimensura de la Universidad Nacional del Nordeste, los dìas 26 y 27 de abril de 2018.Red de Universidades con Carreras en Informática (RedUNCI