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Now showing 1 - 10 of 21
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    Progressive Splatting of Continuous Scatterplots and Parallel Coordinates
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Heinrich, Julian; Bachthaler, S.; Weiskopf, Daniel; H. Hauser, H. Pfister, and J. J. van Wijk
    Continuous scatterplots and parallel coordinates are used to visualize multivariate data defined on a continuous domain. With the existing techniques, rendering such plots becomes prohibitively slow, especially for large scientific datasets. This paper presents a scalable and progressive rendering algorithm for continuous data plots that allows exploratory analysis of large datasets at interactive framerates. The algorithm employs splatting to produce a series of plots that are combined using alpha blending to achieve a progressively improving image. For each individual frame, splats are obtained by transforming Gaussian density kernels from the 3-D domain of the input dataset to the respective data domain. A closed-form analytic description of the resulting splat footprints is derived to allow pre-computation of splat textures for efficient GPU rendering. The plotting method is versatile because it supports arbitrary reconstruction or interpolation schemes for the input data and the splatting technique is scalable because it chooses splat samples independently from the size of the input dataset. Finally, the effectiveness of the method is compared to existing techniques regarding rendering performance and quality.
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    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.
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    Complete Tensor Field Topology on 2D Triangulated Manifolds embedded in 3D
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Auer, Cornelia; Hotz, Ingrid; H. Hauser, H. Pfister, and J. J. van Wijk
    This paper is concerned with the extraction of the surface topology of tensor fields on 2D triangulated manifolds embedded in 3D. In scientific visualization topology is a meaningful instrument to get a hold on the structure of a given dataset. Due to the discontinuity of tensor fields on a piecewise planar domain, standard topology extraction methods result in an incomplete topological skeleton. In particular with regard to the high computational costs of the extraction this is not satisfactory. This paper provides a method for topology extraction of tensor fields that leads to complete results. The core idea is to include the locations of discontinuity into the topological analysis. For this purpose the model of continuous transition bridges is introduced, which allows to capture the entire topology on the discontinuous field. The proposed method is applied to piecewise linear three-dimensional tensor fields defined on the vertices of the triangulation and for piecewise constant two or three-dimensional tensor fields given per triangle, e.g. rate of strain tensors of piecewise linear flow fields.
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    Uncertainty-Aware Exploration of Continuous Parameter Spaces Using Multivariate Prediction
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Berger, Wolfgang; Piringer, H.; Filzmoser, P.; Gröller, Eduard; H. Hauser, H. Pfister, and J. J. van Wijk
    Systems projecting a continuous n-dimensional parameter space to a continuous m-dimensional target space play an important role in science and engineering. If evaluating the system is expensive, however, an analysis is often limited to a small number of sample points. The main contribution of this paper is an interactive approach to enable a continuous analysis of a sampled parameter space with respect to multiple target values. We employ methods from statistical learning to predict results in real-time at any user-defined point and its neighborhood. In particular, we describe techniques to guide the user to potentially interesting parameter regions, and we visualize the inherent uncertainty of predictions in 2D scatterplots and parallel coordinates. An evaluation describes a realworld scenario in the application context of car engine design and reports feedback of domain experts. The results indicate that our approach is suitable to accelerate a local sensitivity analysis of multiple target dimensions, and to determine a sufficient local sampling density for interesting parameter regions.
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    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.
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    A View-Dependent and Inter-Frame Coherent Visualization of Integral Lines using Screen Contribution
    (The Eurographics Association, 2011) Günther, Tobias; Bürger, Kai; Westermann, Rüdiger; Theisel, Holger; Peter Eisert and Joachim Hornegger and Konrad Polthier
    In vector field visualization, integral lines like stream, path, or streak lines are often used to examine the behavior of steady and unsteady flows. In 3D, however, visualizing integral lines is problematic since the resulting geometric structures cause occlusions, often hiding relevant features in the data. For this reason one important goal is to find a minimum number of lines which can represent all relevant features in the vector field. In this paper we propose a novel approach that reduces the number of displayed lines, and occlusions thereof, by smoothly fading out lines based on their contribution to the viewport. In order to reduce visual clutter that is introduced by rendering multiple line contribution into one pixel, the blending equation is slightly modified. In addition, an interactive brushing is applied to further support exploration. Our approach attains a view-dependent visualization of integral lines that is inter-frame coherent and achieves real-time frame rates. To demonstrate the effectiveness and efficiency of our approach, we pursued a number of tests using real-world steady and unsteady vector fields.
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    Curve Density Estimates
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Lampe, Ove Daae; Hauser, Helwig; H. Hauser, H. Pfister, and J. J. van Wijk
    In this work, we present a technique based on kernel density estimation for rendering smooth curves. With this approach, we produce uncluttered and expressive pictures, revealing frequency information about one, or, multiple curves, independent of the level of detail in the data, the zoom level, and the screen resolution. With this technique the visual representation scales seamlessly from an exact line drawing, (for low-frequency/low-complexity curves) to a probability density estimate for more intricate situations. This scale-independence facilitates displays based on non-linear time, enabling high-resolution accuracy of recent values, accompanied by long historical series for context. We demonstrate the functionality of this approach in the context of prediction scenarios and in the context of streaming data.
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    Direct Visualization of Particle-Partition of Unity Data
    (The Eurographics Association, 2011) Üffinger, Markus; Schweitzer, Marc Alexander; Sadlo, Filip; Ertl, Thomas; Peter Eisert and Joachim Hornegger and Konrad Polthier
    Direct visualization of higher-order data provides manifold advantages over the traditional approach, which is based on resampling and subsequent visualization by interpolation-based techniques. Most important, it avoids excessive computation and consumption of memory, and prevents artifacts by pixel-accurate visualization at interactive rates. This work addresses particle-partition of unity simulation data, where fields are modeled both using cell-based analytic representations together with enrichment functions centered at individual points. This combination of bases allows for superior simulation convergence rates and is able to capture high field variations with comparably small sets of basis functions. In this paper we propose direct visualization of such data from 2D simulations, providing accurate insight. We additionally visualize solver performance, allowing for more directed simulation design, and exemplify our technique using a GPU-based prototype on crack simulation examples.
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    Pathway Preserving Representation of Metabolic Networks
    (The Eurographics Association and Blackwell Publishing Ltd., 2011) Lambert, Antoine; Dubois, J.; Bourqui, Romain; H. Hauser, H. Pfister, and J. J. van Wijk
    Improvements in biological data acquisition and genomes sequencing now allow to reconstruct entire metabolic networks of many living organisms. The size and complexity of these networks prohibit manual drawing and thereby urge the need of dedicated visualization techniques. An efficient representation of such a network should preserve the topological information of metabolic pathways while respecting biological drawing conventions. These constraints complicate the automatic generation of such visualization as it raises graph drawing issues. In this paper we propose a method to lay out the entire metabolic network while preserving the pathway information as much as possible. That method is flexible as it enables the user to define whether or not node duplication should be performed, to preserve or not the network topology. Our technique combines partitioning, node placement and edge bundling to provide a pseudo-orthogonal visualization of the metabolic network. To ease pathway information retrieval, we also provide complementary interaction tools that emphasize relevant pathways in the entire metabolic context.
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    A Clustering-based Visualization Technique to Emphasize Meaningful Regions of Vector Fields
    (The Eurographics Association, 2011) Kuhn, Alexander; Lehmann, Dirk J.; Gaststeiger, Rocco; Neugebauer, Matthias; Preim, Bernhard; Theisel, Holger; Peter Eisert and Joachim Hornegger and Konrad Polthier
    This paper proposes a vector field visualization approach that extracts and visualizes grouped regions of static 3D vector fields of similar curvature behavior. These regions are argued to ease the recognition of regions of potential interest and accelerate the general exploration process of vector fields. Our approach detects regions of similar geometric stream properties such as integral curvature and visualizes them by means of compact cluster boundaries. To supplement existing approaches our method combines information on relevant scales to extract meaningful semantical aspects of the overall field structure. For proof of concept we illustrate our results based on real and synthetic data sets.