1,720,973 research outputs found
Drawing on Surfaces
No full textVector graphics in 2D is consolidated since decades, as is supported in many design applications,
such as Adobe Illustrator, and languages, like Scalable Vector Graphics
(SVG).
In this thesis, we address the problem of designing algorithms that support the generation
of vector graphics on a discrete surface. We require such algorithm to rely on the intrinsic
geometry of the surface, and to support real time interaction on highly-tessellated meshes
(few million triangles). Both of these requirements aim at mimicking the behavior of standard
drawing systems in the Euclidean context in the following sense. Working in the intrinsic setting means
that we consider the surface as our canvas, and any quantity needed to fulfill a given task
will be computed directly on it, without resorting to any type of local/global
parametrization or projection. In this way, we are sure that, once the theoretical limitations
behind some given operation are properly handled, our result will always be consistent with the input
regardless of the surface we are working with. As we will see, in some cases, this may imply
that one geometric primitive cannot be indefinitely large, but must be contained in a proper
subset of the surface. Requiring the algorithms to support real time interaction on large meshes
makes possible to use them via a click-and-drag procedure, just as in the D case.
Both of these two requirements have several challenges. On the one hand, working with a metric
different from the Euclidean one implies that most of the properties on which one relies
on the plane are not preserved when considering a surface, so the conditions under which
geometric primitives admit a well defined counterpart in the manifold setting need to be
carefully investigated in order to ensure the robustness of our algorithms.
On the other hand, the building block of most of such algorithms are geodesic paths and distances,
which are known to be expensive operations in computer graphics, especially if one is interested
in accurate results, which is our case.
The purpose of this thesis, is to show how this problem can be addressed fulfilling all the
above requirements. The final result will be a Graphical User Interface (GUI) endowed
with all the main tools present in a D drawing system that allow the user to generate
geometric primitives on a mesh in robust manner and in real-time
b/Surf: Interactive Bzier Splines on Surface Meshes
No full textWe present a practical framework to port Bzier curves to surfaces. We support the interactive drawing and editing of Bzier splines on manifold meshes with millions of triangles, by relying on just repeated manifold averages. We show that direct extensions of the de Casteljau and Bernstein evaluation algorithms to the manifold setting are fragile, and prone to discontinuities when control polygons become large. Conversely, approaches based on subdivision are robust and can be implemented efficiently. We implement manifold extensions of the recursive de Casteljau bisection, and an open-uniform Lane-Riesenfeld subdivision scheme. For both schemes, we present algorithms for curve tracing, point evaluation, and approximated point insertion. We run bulk experiments to test our algorithms for robustness and performance, and we compare them with other methods at the state of the art, always achieving correct results and superior performance. For interactive editing, we port all the basic user interface interactions found in 2D tools directly to the mesh. We also support mapping complex SVG drawings to the mesh and their interactive editing
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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