Search Results

Now showing 1 - 10 of 12
  • Item
    Anatomy-Guided Multi-Level Exploration of Blood Flow in Cerebral Aneurysms
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Neugebauer, Mathias; Janiga, Gabor; Beuing, Oliver; Skalej, Martin; Preim, Bernhard; H. Hauser, H. Pfister, and J. J. van Wijk
    For cerebral aneurysms, the ostium, the area of inflow, is an important anatomic landmark, since it separates the pathological vessel deformation from the healthy parent vessel. A better understanding of the inflow characteristics, the flow inside the aneurysm and the overall change of pre- and post-aneurysm flow in the parent vessel provide insights for medical research and the development of new risk-reduced treatment options. We present an approach for a qualitative, visual flow exploration that incorporates the ostium and derived anatomical landmarks. It is divided into three scopes: a global scope for exploration of the in- and outflow, an ostium scope that provides characteristics of the flow profile close to the ostium and a local scope for a detailed exploration of the flow in the parent vessel and the aneurysm. The approach was applied to five representative datasets, including measured and simulated blood flow. Informal interviews with two board-certified radiologists confirmed the usefulness of the provided exploration tools and delivered input for the integration of the ostium-based flow analysis into the overall exploration workflow.
  • Item
    PaperVis: Literature Review Made Easy
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Chou, Jia -Kai; Yang, C. -K.; H. Hauser, H. Pfister, and J. J. van Wijk
    Reviewing literatures for a certain research field is always important for academics. One could use Google-like information seeking tools, but oftentimes he/she would end up obtaining too many possibly related papers, as well as the papers in the associated citation network. During such a process, a user may easily get lost after following a few links for searching or cross-referencing. It is also difficult for the user to identify relevant/important papers from the resulting huge collection of papers. Our work, called PaperVis, endeavors to provide a user-friendly interface to help users quickly grasp the intrinsic complex citation-reference structures among a specific group of papers. We modify the existing Radial Space Filling (RSF) and Bullseye View techniques to arrange involved papers as a node-link graph that better depicts the relationships among them while saving the screen space at the same time. PaperVis applies visual cues to present node attributes and their transitions among interactions, and it categorizes papers into semantically meaningful hierarchies to facilitate ensuing literature exploration. We conduct experiments on the InfoVis 2004 Contest Dataset to demonstrate the effectiveness of PaperVis.
  • Item
    Semantic-Preserving Word Clouds by Seam Carving
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Wu, Yingcai; Provan, Thomas; Wei, Furu; Liu, Shixia; Ma, Kwan-Liu; H. Hauser, H. Pfister, and J. J. van Wijk
    Word clouds are proliferating on the Internet and have received much attention in visual analytics. Although word clouds can help users understand the major content of a document collection quickly, their ability to visually compare documents is limited. This paper introduces a new method to create semantic-preserving word clouds by leveraging tailored seam carving, a well-established content-aware image resizing operator. The method can optimize a word cloud layout by removing a left-to-right or top-to-bottom seam iteratively and gracefully from the layout. Each seam is a connected path of low energy regions determined by a Gaussian-based energy function. With seam carving, we can pack the word cloud compactly and effectively, while preserving its overall semantic structure. Furthermore, we design a set of interactive visualization techniques for the created word clouds to facilitate visual text analysis and comparison. Case studies are conducted to demonstrate the effectiveness and usefulness of our techniques.
  • Item
    A Shader Framework for Rapid Prototyping of GPU-Based Volume Rendering
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Rieder, Christian; Palmer, Stephan; Link, Florian; Hahn, Horst K.; H. Hauser, H. Pfister, and J. J. van Wijk
    In this paper, we present a rapid prototyping framework for GPU-based volume rendering. Therefore, we propose a dynamic shader pipeline based on the SuperShader concept and illustrate the design decisions. Also, important requirements for the development of our system are presented. In our approach, we break down the rendering shader into areas containing code for different computations, which are defined as freely combinable, modularized shader blocks. Hence, high-level changes of the rendering configuration result in the implicit modification of the underlying shader pipeline. Furthermore, the prototyping system allows inserting custom shader code between shader blocks of the pipeline at run-time. A suitable user interface is available within the prototyping environment to allow intuitive modification of the shader pipeline. Thus, appropriate solutions for visualization problems can be interactively developed. We demonstrate the usage and the usefulness of our framework with implementations of dynamic rendering effects for medical applications.
  • Item
    Dynamic Insets for Context-Aware Graph Navigation
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Ghani, Sohaib; Riche, N. Henry; Elmqvist, Niklas; H. Hauser, H. Pfister, and J. J. van Wijk
    Maintaining both overview and detail while navigating in graphs, such as road networks, airline route maps, or social networks, is difficult, especially when targets of interest are located far apart. We present a navigation technique called Dynamic Insets that provides context awareness for graph navigation. Dynamic insets utilize the topological structure of the network to draw a visual inset for off-screen nodes that shows a portion of the surrounding area for links leaving the edge of the screen. We implement dynamic insets for general graph navigation as well as geographical maps. We also present results from a set of user studies that show that our technique is more efficient than most of the existing techniques for graph navigation in different networks.
  • Item
    Comparison of Multiple Weighted Hierarchies: Visual Analytics for Microbe Community Profiling
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Dinkla, Kasper; Westenberg, M. A.; Timmerman, H. M.; Hijum, S.A.F.T. van; Wijk, J. J. van; H. Hauser, H. Pfister, and J. J. van Wijk
    We propose visual analytics techniques to support concurrent comparison of hundreds of cumulatively weighted instances of a single hierarchy. This includes a node-link representation of the hierarchy where nodes depict the weights of all instances with high-density heat maps that are grouped and aligned to ease cross-referencing. Hierarchy exploration is facilitated by smoothly animated expansion and collapse of its branches. Detailed infor- mation about hierarchy structure, weights, and meta-data is provided by secondary linked visualizations. These techniques have been implemented in a prototype tool, in which the computational analysis concerns have been strictly separated from the visualization concerns. The analysis algorithms are extensible via a script engine. We discuss the effectiveness of our techniques for the visual analytic process of microbe community profiling experts.
  • Item
    Prostate Cancer Visualization from MR Imagery and MR Spectroscopy
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Marino, Joseph; Kaufman, Arie; H. Hauser, H. Pfister, and J. J. van Wijk
    Prostate cancer is one of the most prevalent cancers among males, and the use of magnetic resonance imaging (MRI) has been suggested for its detection. A framework is presented for scoring and visualizing various MR data in an efficient and intuitive manner. A classification method is introduced where a cumulative score volume is created which takes into account each of three acquisition types. This score volume is integrated into a volume rendering framework which allows the user to view the prostate gland, the multi-modal score values, and the sur- rounding anatomy. A visibility persistence mode is introduced to automatically avoid full occlusion of a selected score and indicate overlaps. The use of GPU-accelerated multi-modal single-pass ray casting provides an inter- active experience. User driven importance rendering allows the user to gain insight into the data and can assist in localization of the disease and treatment planning. We evaluate our results against pathology and radiologists' determinations.
  • Item
    A Gradient-Based Comparison Measure for Visual analysis of Multifield Data
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Nagaraj, Suthambhara; Natarajan, Vijay; Nanjundiah, Ravi S.; H. Hauser, H. Pfister, and J. J. van Wijk
    We introduce a multifield comparison measure for scalar fields that helps in studying relations between them. The comparison measure is insensitive to noise in the scalar fields and to noise in their gradients. Further, it can be computed robustly and efficiently. Results from the visual analysis of various data sets from climate science and combustion applications demonstrate the effective use of the measure.
  • Item
    Visual Boosting in Pixel-based Visualizations
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Oelke, Daniela; Janetzko, Halldor; Simon, Svenja; Neuhaus, Klaus; Keim, Daniel A.; H. Hauser, H. Pfister, and J. J. van Wijk
    Pixel-based visualizations have become popular, because they are capable of displaying large amounts of data and at the same time provide many details. However, pixel-based visualizations are only effective if the data set is not sparse and the data distribution not random. Single pixels - no matter if they are in an empty area or in the middle of a large area of differently colored pixels - are perceptually difficult to discern and may therefore easily be missed. Furthermore, trends and interesting passages may be camouflaged in the sea of details. In this paper we compare different approaches for visual boosting in pixel-based visualizations. Several boosting techniques such as halos, background coloring, distortion, and hatching are discussed and assessed with respect to their effectiveness in boosting single pixels, trends, and interesting passages. Application examples from three different domains (document analysis, genome analysis, and geospatial analysis) show the general applicability of the techniques and the derived guidelines.
  • Item
    Perceptual Evaluation of Ghosted View Techniques for the Exploration of Vascular Structures and Embedded Flow
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Baer, Alexandra; Gasteiger, Rocco; Cunningham, Douglas; Preim, Bernhard; H. Hauser, H. Pfister, and J. J. van Wijk
    This paper presents three controlled perceptual studies investigating the visualization of the cerebral aneurysm anatomy with embedded flow visualization. We evaluate and compare the common semitransparent visualization technique with a ghosted view and a ghosted view with depth enhancement technique. We analyze the techniques' ability to facilitate and support the shape and spatial representation of the aneurysm models as well as evaluating the smart visibility characteristics. The techniques are evaluated with respect to the participants accuracy, response time and their personal preferences. We used as stimuli 3D aneurysm models of five clinical datasets. There was overwhelming preference for the two ghosted view techniques over the semitransparent technique. Since smart visibility techniques are rarely evaluated, this paper may serve as orientation for further studies.