Browsing by Author "Rocha, Allan"
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- ItemOpen Access3De Interactive Lenses for Visualization in Virtual Environments(2018-10) Mota, Roberta Cabral Ramos; Rocha, Allan; Silva, Julio Daniel; Alim, Usman; Sharlin, EhudWe present 3De lens, a technique for focus+context 3D visualization of multiple geometric representations. Our lens fuses two categories of lenses (3D and Decal) into a single coherent entity, thus enabling flexible use of either one or the two lenses combined depending on the underlying data geometry. In addition, we incorporate our lens into virtual reality as it enables a rich and natural style of direct spatial manipulation for exploratory 3D data analysis. To demonstrate its potential use, we discuss two domain examples in which our lens technique creates customized visualizations of both surfaces and streamlines.
- ItemOpen AccessComparative Visualizations of Noisy and Filtered Blood Flow from 4D PC-MRI Cardiac Datasets(2017-10) Khan, Fahim Hasan; Rocha, Allan; Alim, UsmanModern phase-contrast magnetic resonance imaging (PC-MRI) can acquire both cardiac anatomy and flow function in a single acquisition and deliver high quality volumetric and time-varying (4D) datasets which enable better diagnosis and risk assessment of various cardiovascular diseases. A good way to visualize blood flow from 4D PC-MRI datasets is to use animated pathlines through the anatomical context for representing the trajectories of the blood particles. Artifact correction is one crucial step in the processing pipeline of 4D PC-MRI datasets for representing the cardiac flow using pathlines, which in turn can reduce the overall quality of the useful information in the dataset. In this work, an approach is presented for comparative visualization of 4D PC-MRI datasets before and after artifact correction for qualitative analysis.
- ItemOpen AccessDecal-maps: Real-time Layering of Decals on Surfaces for Multivariate Visualization(IEEE, 2017-01) Rocha, Allan; Alim, Usman; Silva, Julio Daniel; Sousa, Mario CostaWe introduce the use of decals for multivariate visualization design. Decals are visual representations that are used for communication; for example, a pattern, a text, a glyph, or a symbol, transferred from a 2D-image to a surface upon contact. By creating what we define as decal-maps, we can design a set of images or patterns that represent one or more data attributes. We place decals on the surface considering the data pertaining to the locations we choose. We propose a (texture mapping) local parametrization that allows placing decals on arbitrary surfaces interactively, even when dealing with a high number of decals. Moreover, we extend the concept of layering to allow the co-visualization of an increased number of attributes on arbitrary surfaces. By combining decal-maps,color-maps and a layered visualization, we aim to facilitate and encourage the creative process of designing multivariate visualizations. Finally, we demonstrate the general applicability of our technique by providing examples of its use in a variety of contexts.
- ItemOpen AccessIllustrative Multivariate Visualization for Geological Modelling(Wiley, 2018-07-10) Rocha, Allan; Mota, Roberta Cabral Ramos; Hamdi, Hamidreza; Alim, Usman R.; Sousa, Mario CostaIn this paper, we present a novel illustrative multivariate visualization for geological modelling to assist geologists and reservoir engineers in visualizing multivariate datasets in superimposed representations, in contrast to the single-attribute visualizations supported by commercial software. Our approach extends the use of decals from a single surface to 3D irregular grids, using the layering concept to represent multiple attributes. We also build upon prior work to augment the design and implementation of different geological attributes (namely, rock type, porosity, and permeability). More specifically, we propose a new sampling strategy to generate decals for porosity on the geological grid, a hybrid visualization for permeability which combines 2D decals and 3D ellipsoid glyphs, and a perceptually-based design that allows us to visualize additional attributes (e.g., oil saturation) while avoiding visual interference between layers. Furthermore, our visual design draws from traditional geological illustrations, facilitating the understanding and communication between interdisciplinary teams. An evaluation by domain experts highlights the potential of our approach for geological modelling and interpretation in this complex domain.
- ItemOpen AccessVisualization of Multivariate Data on Surfaces(2019-03-19) Rocha, Allan; Costa Sousa, Mario; Alim, Usman Raza; Chan, Sonny; Jacob, Christian J.; Geiger, Sebastian; Tominski, ChristianIn several domains of science and applications, the understanding of scientific data leads to technological advances and scientific discovery. Multivariate 3D data, for example, is essential for decision-making in fields such as Medicine and Geology, where experts are required to understand and correlate several spatial attributes. To simplify complexity and facilitate understanding, the 3D data is often explored through surfaces of interest. This is the reason why the visualization of multivariate data on surfaces has been a topic of interest among the visualization community. However, much work has been needed to provide visualization solutions that facilitate the multivariate visualization design, creation, and exploration. This research builds upon ideas introduced and discussed many years ago that focus on the problem of visualizing multiple attributes on surfaces in a single view. Here I present a new perspective to this problem as well as a solution that allows us to design, visualize and interact with multivariate data on surfaces. This perspective is created from the combination of several aspects born in fields such as Illustration, Perception, and Design, that have been employed and studied by the visualization community both in Information and Scientific Visualization. Therefore, this thesis lies between these two main fields, since it involves aspects from both. By building upon this multidisciplinary combination, I present a new way to visualize multivariate data on surfaces by exploiting the concept of layering. First, I introduce a new real-time rendering technique and the concept of Decal-Maps, which fills a gap in the literature and allow us to create 2D visual representations such as glyphs that follow the surface geometry. Building on this technique, I propose the layering framework to facilitate the multivariate visualization design on surfaces. The use of this concept and framework allows us to connect and generalize concepts established in flat space, such as 2D maps, to arbitrary surfaces. This thesis also demonstrates that the design of new multivariate visualizations on surfaces opens up other new possibilities such as the use of interaction techniques. Here I demonstrate this potential by introducing a new interaction technique that allows us to explore multivariate data and to create customized focus+context visualizations on surfaces. This is achieved by introducing a new category of lenses, Decal-Lenses, which extends the concept of magic-lenses from flat space to general surfaces. Finally, this thesis showcases the process of multivariate visual design and data exploration through a series of examples from several domains. Inspired by these examples, I also contribute with an in-depth application research conducted from my long-term collaboration with domain experts in the fields of Geology and Reservoir Engineering. This application illustrates how the proposed approach can support and facilitate decision-making in the complex process of Geological Modelling.