DevLan/vispubs huggingface dataset:
Interpolation and visualization for advected scalar fields
Authors: Shyh-Kuang Ueng, Sheng-Chuan Wang
Published at Vis, 2005

Doppler radars are useful facilities for weather forecasting. The data sampled by using Doppler radars are used to measure the distributions and densities of rain drops, snow crystals, hail stones, or even insects in the atmosphere. In this paper, we propose to build up a graphics-based software system for visualizing Doppler radar data. In the system, the reflectivity data gathered by using Doppler radars are post-processed to generate virtual cloud images which reveal the densities of precipitation in the air. An optical flow based method is adopted to compute the velocities of clouds, advected by winds. Therefore, the movement of clouds is depicted. The cloud velocities are also used to interpolate reflectivities for arbitrary time steps. Therefore, the reflectivities at any time can be produced. Our system composes of three stages. At the first stage, the raw radar data are re-sampled and filtered to create a multiple resolution data structure, based on a pyramid structure. At the second stage, a numeric method is employed to compute cloud velocities in the air and to interpolate radar reflectivity data at given time steps. The radar reflectivity data and cloud velocities are displayed at the last stage. The reflectivities are rendered by using splatting methods to produce semi-transparent cloud images. Two kinds of media are created for analyzing the reflectivity data. The first kind media consists of a group of still images of clouds which displays the distribution and density of water in the air. The second type media is a short animation of cloud images to show the formation and movement of the clouds. To show the advection of clouds, the cloud velocities are displayed by using two dimensional images. In these images, the velocities are represented by arrows and superimposed on cloud images. To enhance image quality, gradients and diffusion of the radar data are computed and used in the rendering process. Therefore the cloud structures are better portrayed. In order to achieve interactive visualization, our system is also comprised with a view-dependent visualization module. The radar data at far distance are rendered in lower resolutions, while the data closer to the eye position is rendered in details.
Marching diamonds for unstructured meshes
Authors: John C. Anderson, Janine Bennett, Kenneth I. Joy
Published at Vis, 2005

We present a higher-order approach to the extraction of isosurfaces from unstructured meshes. Existing methods use linear interpolation along each mesh edge to find isosurface intersections. In contrast, our method determines intersections by performing barycentric interpolation over diamonds formed by the tetrahedra incident to each edge. Our method produces smoother, more accurate isosurfaces. Additionally, interpolating over diamonds, rather than linearly interpolating edge endpoints. enables us to identify up to two isosurface intersections per edge. This paper details how our new technique extracts isopoints, and presents a simple connection strategy for forming a triangle mesh isosurface.
Multimodal exploration of the fourth dimension
Authors: Andrew J. Hanson, Hui Zhang 0006
Published at Vis, 2005

We present a multimodal paradigm for exploring topological surfaces embedded in four dimensions; we exploit haptic methods in particular to overcome the intrinsic limitations of 3D graphics images and 3D physical models. The basic problem is that, just as 2D shadows of 3D curves lose structure where lines cross, 3D graphics projections of smooth 4D topological surfaces are interrupted where one surface intersects another. Furthermore, if one attempts to trace real knotted ropes or a plastic models of self-intersecting surfaces with a fingertip, one inevitably collides with parts of the physical artifact. In this work, we exploit the free motion of a computer-based haptic probe to support a continuous motion that follows the local continuity of the object being explored. For our principal test case of 4D-embedded surfaces projected to 3D, this permits us to follow the full local continuity of the surface as though in fact we were touching an actual 4D object. We exploit additional sensory cues to provide supplementary or redundant information. For example, we can use audio tags to note the relative 4D depth of illusory 3D surface intersections produced by projection from 4D, as well as providing automated refinement of the tactile exploration path to eliminate jitter and snagging, resulting in a much cleaner exploratory motion than a bare uncorrected motion. Visual enhancements provide still further improvement to the feedback: by opening a view-direction-defined cutaway into the interior of the 3D surface projection, we allow the viewer to keep the haptic probe continuously in view as it traverses any touchable part of the object. Finally, we extend the static tactile exploration framework using a dynamic mode that links each stylus motion to a change in orientation that creates at each instant a maximal-area screen projection of a neighborhood of the current point of interest. This minimizes 4D distortion and permits true metric sizes to be deduced locally at any point. All these methods combine to reveal the full richness of the complex spatial relationships of the target shapes, and to overcome many expected perceptual limitations in 4D visualization.
On the optimization of visualizations of complex phenomena
Authors: Donald H. House, Alethea Bair, Colin Ware
Published at Vis, 2005

The problem of perceptually optimizing complex visualizations is a difficult one, involving perceptual as well as aesthetic issues. In our experience, controlled experiments are quite limited in their ability to uncover interrelationships among visualization parameters, and thus may not be the most useful way to develop rules-of-thumb or theory to guide the production of high-quality visualizations. In this paper, we propose a new experimental approach to optimizing visualization quality that integrates some of the strong points of controlled experiments with methods more suited to investigating complex highly-coupled phenomena. We use human-in-the-loop experiments to search through visualization parameter space, generating large databases of rated visualization solutions. This is followed by data mining to extract results such as exemplar visualizations, guidelines for producing visualizations, and hypotheses about strategies leading to strong visualizations. The approach can easily address both perceptual and aesthetic concerns, and can handle complex parameter interactions. We suggest a genetic algorithm as a valuable way of guiding the human-in-the-loop search through visualization parameter space. We describe our methods for using clustering, histogramming, principal component analysis, and neural networks for data mining. The experimental approach is illustrated with a study of the problem of optimal texturing for viewing layered surfaces so that both surfaces are maximally observable.
OpenGL multipipe SDK: a toolkit for scalable parallel rendering
Authors: Praveen Bhaniramka, Philippe C. D. Robert, Stefan Eilemann
Published at Vis, 2005

We describe OpenGL multipipe SDK (MPK), a toolkit for scalable parallel rendering based on OpenGL. MPK provides a uniform application programming interface (API) to manage scalable graphics applications across many different graphics subsystems. MPK-based applications run seamlessly from single-processor, single-pipe desktop systems to large multi-processor, multipipe scalable graphics systems. The application is oblivious of the system configuration, which can be specified through a configuration file at run time. To scale application performance, MPK uses a decomposition system that supports different modes for task partitioning and implements optimized CPU-based composition algorithms. MPK also provides a customizable image composition interface, which can be used to apply post-processing algorithms on raw pixel data obtained from executing sub-tasks on multiple graphics pipes in parallel. This can be used to implement parallel versions of any CPU-based algorithm, not necessarily used for rendering. In this paper, we motivate the need for a scalable graphics API and discuss the architecture of MPK. We present MPK's graphics configuration interface, introduce the notion of compound-based decomposition schemes and describe our implementation. We present some results from our work on a couple of target system architectures and conclude with future directions of research in this area.
Opening the black box - data driven visualization of neural networks
Authors: Fan-Yin Tzeng, Kwan-Liu Ma
Published at Vis, 2005

Artificial neural networks are computer software or hardware models inspired by the structure and behavior of neurons in the human nervous system. As a powerful learning tool, increasingly neural networks have been adopted by many large-scale information processing applications but there is no a set of well defined criteria for choosing a neural network. The user mostly treats a neural network as a black box and cannot explain how learning from input data was done nor how performance can be consistently ensured. We have experimented with several information visualization designs aiming to open the black box to possibly uncover underlying dependencies between the input data and the output data of a neural network. In this paper, we present our designs and show that the visualizations not only help us design more efficient neural networks, but also assist us in the process of using neural networks for problem solving such as performing a classification task.
Opening the can of worms: an exploration tool for vortical flows
Authors: Simon Stegmaier, Ulrich Rist, Thomas Ertl
Published at Vis, 2005

Gaining a comprehensive understanding of turbulent flows still poses one of the great challenges in fluid dynamics. A well-established approach to advance this research is the analysis of the vortex structures contained in the flow. In order to be able to perform this analysis efficiently, supporting visualization tools with clearly defined requirements are needed. In this paper, we present a visualization system which matches these requirements to a large extent. The system consists of two components. The first component analyzes the flow by means of a novel combination of vortex core line detection and the /spl lambda//sub 2/ method. The second component is a vortex browser which allows for an interactive exploration and manipulation of the vortices detected and separated during the first phase. Our system improves the reliability and applicability of existing vortex detection methods and allows for a more efficient study of vortical flows which is demonstrated in an evaluation performed by experts.
Particle and texture based spatiotemporal visualization of time-dependent vector fields
Authors: Daniel Weiskopf, Frederik Schramm, Gordon Erlebacher, Thomas Ertl
Published at Vis, 2005

We propose a hybrid particle and texture based approach for the visualization of time-dependent vector fields. The underlying space-time framework builds a dense vector field representation in a two-step process: 1) particle-based forward integration of trajectories in spacetime for temporal coherence, and 2) texture-based convolution along another set of paths through the spacetime for spatially correlated patterns. Particle density is controlled by stochastically injecting and removing particles, taking into account the divergence of the vector field. Alternatively, a uniform density can be maintained by placing exactly one particle in each cell of a uniform grid, which leads to particle-in-cell forward advection. Moreover, we discuss strategies of previous visualization methods for unsteady flow and show how they address issues of spatiotemporal coherence and dense visual representations. We demonstrate how our framework is capable of realizing several of these strategies. Finally, we present an efficient GPU implementation that facilitates an interactive visualization of unsteady 2D flow on Shader Model 3 compliant graphics hardware.
Phonon tracing for auralization and visualization of sound
Authors: Martin Hering-Bertram, Eduard Deines, Jan Mohring, Jevgenijs Jegorovs, Hans Hagen
Published at Vis, 2005

We present a new particle tracing approach for the simulation of mid- and high-frequency sound. Inspired by the photorealism obtained by methods like photon mapping, we develop a similar method for the physical simulation of sound within rooms. For given source and listener positions, our method computes a finite-response filter accounting for the different reflections at various surfaces with frequency-dependent absorption coefficients. Convoluting this filter with an anechoic input signal reproduces a realistic aural impression of the simulated room. We do not consider diffraction effects due to low frequencies, since these can be better computed by finite elements. Our method allows the visualization of a wave front propagation using color-coded blobs traversing the paths of individual phonons.
Prefiltered Gaussian reconstruction for high-quality rendering of volumetric data sampled on a body-centered cubic grid
Authors: Balázs Csébfalvi
Published at Vis, 2005

In this paper a novel high-quality reconstruction scheme is presented. Although our method is mainly proposed to reconstruct volumetric data sampled on an optimal body-centered cubic (BCC) grid, it can be easily adapted lo the conventional regular rectilinear grid as well. The reconstruction process is decomposed into two steps. The first step, which is considered to be a preprocessing, is a discrete Gaussian deconvolution performed only once in the frequency domain. Afterwards, the second step is a spatial-domain convolution with a truncated Gaussian kernel, which is used to interpolate arbitrary samples for ray casting. Since the preprocessing is actually a discrete prefiltering, we call our technique prefiltered Gaussian reconstruction (PGR). It is shown that the impulse response of PGR well approximates the ideal reconstruction kernel. Therefore the quality of PGR is much higher than that of previous reconstruction techniques proposed for optimally sampled data, which are based on linear and cubic box splines adapted to the BCC grid. Concerning the performance, PGR is slower than linear box-spline reconstruction but significantly faster than cubic box-spline reconstruction.
Profile Flags: a novel metaphor for probing of T₂ maps
Authors: Matej Mlejnek, Pierre Ermes, Anna Vilanova, Rob van der Rijt, Harrie van den Bosch, Frans A. Gerritsen, M. Eduard Gröller
Published at Vis, 2005

This paper describes a tool for the visualization of T/sub 2/ maps of knee cartilage. Given the anatomical scan, and the T/sub 2/ map of the cartilage, we combine the information on the shape and the quality of the cartilage in a single image. The Profile Flag is an intuitive 3D glyph for probing and annotating of the underlying data. It comprises a bulletin board pin-like shape with a small flag on top of it. While moving the glyph along the reconstructed surface of an object, the curve data measured along the pin's needle and in its neighborhood are shown on the flag. The application area of the Profile Flag is manifold, enabling the visualization of profile data of dense but in-homogeneous objects. Furthermore, it extracts the essential part of the data without removing or even reducing the context information. By sticking Profile Flags into the investigated structure, one or more significant locations can be annotated by showing the local characteristics of the data at that locations. In this paper we are demonstrating the properties of the tool by visualizing T/sub 2/ maps of knee cartilage.
Quality mesh generation for molecular skin surfaces using restricted union of balls
Authors: Ho-Lun Cheng, Xinwei Shi
Published at Vis, 2005

Quality surface meshes for molecular models are desirable in the studies of protein shapes and functionalities. However, there is still no robust software that is capable to generate such meshes with good quality. In this paper, we present a Delaunay-based surface triangulation algorithm generating quality surface meshes for the molecular skin model. We expand the restricted union of balls along the surface and generate an /spl epsiv/-sampling of the skin surface incrementally. At the same time, a quality surface mesh is extracted from the Delaunay triangulation of the sample points. The algorithm supports robust and efficient implementation and guarantees the mesh quality and topology as well. Our results facilitate molecular visualization and have made a contribution towards generating quality volumetric tetrahedral meshes for the macromolecules.
Query-driven visualization of large data sets
Authors: Kurt Stockinger, John Shalf, Kesheng Wu, E. Wes Bethel
Published at Vis, 2005

We present a practical and general-purpose approach to large and complex visual data analysis where visualization processing, rendering and subsequent human interpretation is constrained to the subset of data deemed interesting by the user. In many scientific data analysis applications, "interesting" data can be defined by compound Boolean range queries of the form (temperature&gt;1000) AND (70&lt;pressure&lt;90). As data sizes grow larger, a central challenge is to answer such queries as efficiently as possible. Prior work in the visualization community has focused on answering range queries for scalar fields within the context of accelerating the search phase of isosurface algorithms. In contrast, our work describes an approach that leverages state-of-the-art indexing technology from the scientific data management community called "bitmap indexing". Our implementation, which we call "DEX" (short for dextrous data explorer), uses bitmap indexing to efficiently answer multivariate, multidimensional data queries to provide input to a visualization pipeline. We present an analysis overview and benchmark results that show bitmap indexing offers significant storage and performance improvements when compared to previous approaches for accelerating the search phase of isosurface algorithms. More importantly, since bitmap indexing supports complex multidimensional, multivariate range queries, it is more generally applicable to scientific data visualization and analysis problems. In addition to benchmark performance and analysis, we apply DEX to a typical scientific visualization problem encountered in combustion simulation data analysis.
Reconstructing manifold and non-manifold surfaces from point clouds
Authors: Jianning Wang, Manuel Menezes de Oliveira Neto, Arie E. Kaufman
Published at Vis, 2005

This paper presents a novel approach for surface reconstruction from point clouds. The proposed technique is general in the sense that it naturally handles both manifold and non-manifold surfaces, providing a consistent way for reconstructing closed surfaces as well as surfaces with boundaries. It is also robust in the presence of noise, irregular sampling and surface gaps. Furthermore, it is fast, parallelizable and easy to implement because it is based on simple local operations. In this approach, surface reconstruction consists of three major steps: first, the space containing the point cloud is subdivided, creating a voxel representation. Then, a voxel surface is computed using gap filling and topological thinning operations. Finally, the resulting voxel surface is converted into a polygonal mesh. We demonstrate the effectiveness of our approach by reconstructing polygonal models from range scans of real objects as well as from synthetic data.
Reflection nebula visualization
Authors: Marcus A. Magnor, Kristian Hildebrand, Andrei Lintu, Andrew J. Hanson
Published at Vis, 2005

Stars form in dense clouds of interstellar gas and dust. The residual dust surrounding a young star scatters and diffuses its light, making the star's "cocoon" of dust observable from Earth. The resulting structures, called reflection nebulae, are commonly very colorful in appearance due to wavelength-dependent effects in the scattering and extinction of light. The intricate interplay of scattering and extinction cause the color hues, brightness distributions, and the apparent shapes of such nebulae to vary greatly with viewpoint. We describe an interactive visualization tool for realistically rendering the appearance of arbitrary 3D dust distributions surrounding one or more illuminating stars. Our rendering algorithm is based on the physical models used in astrophysics research. The tool can be used to create virtual fly-throughs of reflection nebulae for interactive desktop visualizations, or to produce scientifically accurate animations for educational purposes, e.g., in planetarium shows. The algorithm is also applicable to investigate on-the-fly the visual effects of physical parameter variations, exploiting visualization technology to help gain a deeper and more intuitive understanding of the complex interaction of light and dust in real astrophysical settings.
Rendering tetrahedral meshes with higher-order attenuation functions for digital radiograph reconstruction
Authors: Ofri Sadowsky, Jonathan D. Cohen 0001, Russell H. Taylor
Published at Vis, 2005

This paper presents a novel method for computing simulated x-ray images, or DRRs (digitally reconstructed radiographs), of tetrahedral meshes with higher-order attenuation functions. DRRs are commonly used in computer assisted surgery (CAS), with the attenuation function consisting of a voxelized CT study, which is viewed from different directions. Our application of DRRs is in intra-operative "2D-3D" registration, i.e., finding the pose of the CT dataset given a small number of patient radiographs. We register 2D patient images with a statistical tetrahedral model, which encodes the CT intensity numbers as Bernstein polynomials, and includes knowledge about typical shape variation modes. The unstructured grid is more suitable for applying deformations than a rectilinear grid, and the higher-order polynomials provide a better approximation of the actual density than constant or linear models. The infra-operative environment demands a fast method for creating the DRRs, which we present here. We demonstrate this application through the creation and use of a deformable atlas of human pelvis bones. Compared with other works on rendering unstructured grids, the main contributions of this work are: 1) Simple and perspective-correct interpolation of the thickness of a tetrahedral cell. 2) Simple and perspective-correct interpolation of front and back barycentric coordinates with respect to the cell. 3) Computing line integrals of higher-order functions. 4) Capability of applying shape deformations and variations in the attenuation function without significant performance loss. The method does not depend on for pre-integration, and does not require depth-sorting of the visualized cells. We present imaging and timing results of implementing the algorithm, and discuss the impact of using higher-order functions on the quality of the result and the performance.