DevLan/vispubs huggingface dataset:
Non-linear model fitting to parameterize diseased blood vessels
Authors: Alexandra La Cruz, Matús Straka, Arnold Köchl, Milos Srámek, M. Eduard Gröller, Dominik Fleischmann
Published at Vis, 2004

Accurate estimation of vessel parameters is a prerequisite for automated visualization and analysis of healthy and diseased blood vessels. The objective of this research is to estimate the dimensions of lower extremity arteries, imaged by computed tomography (CT). These parameters are required to get a good quality visualization of healthy as well as diseased arteries using a visualization technique such as curved planar reformation (CPR). The vessel is modeled using an elliptical or cylindrical structure with specific dimensions, orientation and blood vessel mean density. The model separates two homogeneous regions: its inner side represents a region of density for vessels, and its outer side a region for background. Taking into account the point spread function (PSF) of a CT scanner, a function is modeled with a Gaussian kernel, in order to smooth the vessel boundary in the model. A new strategy for vessel parameter estimation is presented. It stems from vessel model and model parameter optimization by a nonlinear optimization procedure, i.e., the Levenberg-Marquardt technique. The method provides center location, diameter and orientation of the vessel as well as blood and background mean density values. The method is tested on synthetic data and real patient data with encouraging results.
On the role of color in the perception of motion in animated visualizations
Authors: Daniel Weiskopf
Published at Vis, 2004

Although luminance contrast plays a predominant role in motion perception, significant additional effects are introduced by chromatic contrasts. In this paper, relevant results from psychophysical and physiological research are described to clarify the role of color in motion detection. Interpreting these psychophysical experiments, we propose guidelines for the design of animated visualizations, and a calibration procedure that improves the reliability of visual motion representation. The guidelines are applied to examples from texture-based flow visualization, as well as graph and tree visualisation.
On the Visualization of Time-Varying Structured Grids Using a 3D Warp Texture
Authors: Yuan Chen, Jonathan D. Cohen 0001, Subodh Kumar 0001
Published at Vis, 2004

We present a novel scheme to interactively visualize time-varying scalar fields defined on a structured grid. The underlying approach is to maximize the use of current graphics hardware by using 3D texture mapping. This approach commonly suffers from an expensive voxelization of each time-step as well as from large size of the voxel array approximating each step. Hence, in our scheme, instead of explicitly voxelizing each scalar field, we directly store each time-step as a three dimensional texture in its native form. We create the function that warps a voxel grid into the given structured grid. At rendering time, we reconstruct the function at each pixel using hardware-based trilinear interpolation. The resulting coordinates allow us to compute the scalar value at this pixel using a second texture lookup. For fixed grids, the function remains constant across time-steps and only the scalar field table needs to be re-loaded as a texture. Our new approach achieves excellent performance with relatively low texture memory requirements and low approximation error.
Optimal global conformal surface parameterization
Authors: Miao Jin, Yalin Wang 0001, Shing-Tung Yau, Xianfeng Gu
Published at Vis, 2004

All orientable metric surfaces are Riemann surfaces and admit global conformal parameterizations. Riemann surface structure is a fundamental structure and governs many natural physical phenomena, such as heat diffusion and electro-magnetic fields on the surface. A good parameterization is crucial for simulation and visualization. This paper provides an explicit method for finding optimal global conformal parameterizations of arbitrary surfaces. It relies on certain holomorphic differential forms and conformal mappings from differential geometry and Riemann surface theories. Algorithms are developed to modify topology, locate zero points, and determine cohomology types of differential forms. The implementation is based on a finite dimensional optimization method. The optimal parameterization is intrinsic to the geometry, preserves angular structure, and can play an important role in various applications including texture mapping, remeshing, morphing and simulation. The method is demonstrated by visualizing the Riemann surface structure of real surfaces represented as triangle meshes.
Panel 1: Can We Determine the Top Unresolved Problems of Visualization?
Authors: Theresa-Marie Rhyne, Bill Hibbard, Christopher R. Johnson 0001, Chaomei Chen, Steve Eick
Published at Vis, 2004

Many of us working in visualization have our own list of our top 5 or 10 unresolved problems in visualization. We have assembled a group of panelists to debate and perhaps reach concensus on the top problems in visualization that still need to be explored. We include panelists from both the information and scientific visualization domains. After our presentations, we encourage interaction with the audience to see if we can further formulate and perhaps finalize our list of top unresolved problems in visualization.
Panel 2: In the Eye of the Beholder: The Role of Perception in Scientific Visualization
Authors: Kelly P. Gaither, David S. Ebert, Bill Geisler, David H. Laidlaw
Published at Vis, 2004

The evolution of computational science over the last decade has resulted in a dramatic increase in raw problem solving capabilities. This growth has given rise to advances in scientific and engineering simulations that have put a high demand on tools for high-performance large-scale data exploration and analysis. These simulations have the potential to generate large amounts of data. Humans, however are relatively poor at gaining insight from raw numerical data, and as a result, have used visualization as a tool for understanding, interpreting and exploring data of all types and sizes. Allowing for efficient visual explorations of data, however, requires that the ratio of knowledge gained versus the cost of the visualization be maximized. This, in turn, mandates the integration of principles from human perception. Understanding perception as it relates to visualization requires that we understand not only the biology of the human visual system, but principles from vision theory, and perceptual psychology as well. This panel is the result of bringing together practioners and researchers from a broad spectrum of interests relating to the ability to maximize the amount of information that is effectively perceived from a given visualization. Position statements will be given by researchers interested in perceptual psychology and the perception of natural images, integrating art and design principles, non-photorealistic rendering techniques, and the use of global illumination methods to provide benefical perceptual cues.
Panel 3: The Future Visualization Platform
Authors: Greg Johnson, David S. Ebert, Charles D. Hansen, David Blair Kirk, Bill Mark, Hanspeter Pfister
Published at Vis, 2004

Advances in graphics hardware and rendering methods are shaping the future of visualization. For example, programmable graphics processors are redefining the traditional visualization cycle. In some cases it is now possible to run the computational simulation and associated visualization side-by-side on the same chip. Moreover, global illumination and non-photorealistic effects promise to deliver imagery which enables greater insight into high resolution, multivariate, and higher-dimensional data. The panelists will offer distinct viewpoints on the direction of future graphics hardware and its potential impact on visualization, and on the nature of advanced visualizationrelated tools and techniques. Presentation of these viewpoints will be followed by audience participation in the form of a question and answer period moderated by the panel organizer.
Panel 4: What Should We Teach in a Scientific Visualization Class?
Authors: Jon D. Genetti, Michael J. Bailey, David H. Laidlaw, Robert J. Moorhead II, Ross T. Whitaker
Published at Vis, 2004

Scientific Visualization (SciVis) has evolved past the point where one undergraduate course can cover all of the necessary topics. So the question becomes "how do we teach SciVis to this generation of students?" Some examples of current courses are: A graduate Computer Science (CS) course that prepares the next generation of SciVis researchers. An undergraduate CS course that prepares the future software architects/developers of packages such as vtk, vis5D and AVS. A class that teaches students how to do SciVis with existing software packages and how to deal with the lack of interoperability between those packages (via either a CS service course or a supercomputing center training course). An inter-disciplinary course designed to prepare computer scientists to work with the "real" scientists (via either a CS or Computational Science course). In this panel, we will discuss these types of courses and the advantages and disadvantages of each. We will also talk about some issues that you have probably encountered at your university: How do we keep the graphics/vis-oriented students from going to industry? How does SciVis fit in with evolving Computational Science programs? Is SciVis destined to be a service course at most universities? How do we deal with the diverse backgrounds of students that need SciVis?
Physically based methods for tensor field visualization
Authors: Ingrid Hotz, Louis Feng, Hans Hagen, Bernd Hamann, Kenneth I. Joy, Boris Jeremic
Published at Vis, 2004

The physical interpretation of mathematical features of tensor fields is highly application-specific. Existing visualization methods for tensor fields only cover a fraction of the broad application areas. We present a visualization method tailored specifically to the class of tensor field exhibiting properties similar to stress and strain tensors, which are commonly encountered in geomechanics. Our technique is a global method that represents the physical meaning of these tensor fields with their central features: regions of compression or expansion. The method is based on two steps: first, we define a positive definite metric, with the same topological structure as the tensor field; second, we visualize the resulting metric. The eigenvector fields are represented using a texture-based approach resembling line integral convolution (LIC) methods. The eigenvalues of the metric are encoded in free parameters of the texture definition. Our method supports an intuitive distinction between positive and negative eigenvalues. We have applied our method to synthetic and some standard data sets, and "real" data from earth science and mechanical engineering application.
Pixel-exact rendering of spacetime finite element solutions
Authors: Yuan Zhou, Michael Garland, Robert B. Haber
Published at Vis, 2004

Computational simulation of time-varying physical processes is of fundamental importance for many scientific and engineering applications. Most frequently, time-varying simulations are performed over multiple spatial grids at discrete points in time. We investigate a new approach to time-varying simulation: spacetime discontinuous Galerkin finite element methods. The result of this simulation method is a simplicial tessellation of spacetime with per-element polynomial solutions for physical quantities such as strain, stress, and velocity. To provide accurate visualizations of the resulting solutions, we have developed a method for per-pixel evaluation of solution data on the GPU. We demonstrate the importance of per-pixel rendering versus simple linear interpolation for producing high quality visualizations. We also show that our system can accommodate reasonably large datasets - spacetime meshes containing up to 20 million tetrahedra are not uncommon in this domain.
PQuad: visualization of predicted peptides and proteins
Authors: Susan L. Havre, Mudita Singhal, Deborah A. Payne, Bobbie-Jo M. Webb-Robertson
Published at Vis, 2004

New high-throughput proteomic techniques generate data faster than biologists can analyze it. Hidden within this massive and complex data are answers to basic questions about how cells function. The data afford an opportunity to take a global or systems approach studying whole proteomes comprising all the proteins in an organism. However, the tremendous size and complexity of the high-throughput data make it difficult to process and interpret. Existing tools for studying a few proteins at a time are not suitable for global analysis. Visualization provides powerful analysis capabilities for enormous, complex data at multiple resolutions. We developed a novel interactive visualization tool, PQuad, for the visual analysis of proteins and peptides identified from high-throughput data on biological samples. PQuad depicts the peptides in the context of their source protein and DNA, thereby integrating proteomic and genomic information. A wrapped line metaphor is applied across key resolutions of the data, from a compressed view of an entire chromosome to the actual nucleotide sequence. PQuad provides a difference visualization for comparing peptides from samples prepared under different experimental conditions. We describe the requirements for such a visual analysis tool, the design decisions, and the novel aspects of PQuad.
Projecting tetrahedra without rendering artifacts
Authors: Martin Kraus, Wei Qiao, David S. Ebert
Published at Vis, 2004

Hardware-accelerated direct volume rendering of unstructured volumetric meshes is often based on tetrahedral cell projection, in particular, the projected tetrahedra (PT) algorithm and its variants. Unfortunately, even implementations of the most advanced variants of the PT algorithm are very prone to rendering artifacts. In this work, we identify linear interpolation in screen coordinates as a cause for significant rendering artifacts and implement the correct perspective interpolation for the PT algorithm with programmable graphics hardware. We also demonstrate how to use features of modern graphics hardware to improve the accuracy of the coloring of individual tetrahedra and the compositing of the resulting colors, in particular, by employing a logarithmic scale for the preintegrated color lookup table, using textures with high color resolution, rendering to floating-point color buffers, and alpha dithering. Combined with a correct visibility ordering, these techniques result in the first implementation of the PT algorithm without objectionable rendering artifacts. Apart from the important improvement in rendering quality, our approach also provides a test bed for different implementations of the PT algorithm that allows us to study the particular rendering artifacts introduced by these variants.
Quick-VDR: interactive view-dependent rendering of massive models
Authors: Sung-Eui Yoon, Brian Salomon, Russell Gayle, Dinesh Manocha
Published at Vis, 2004

We present a novel approach for interactive view-dependent rendering of massive models. Our algorithm combines view-dependent simplification, occlusion culling, and out-of-core rendering. We represent the model as a clustered hierarchy of progressive meshes (CHPM). We use the cluster hierarchy for coarse-grained selective refinement and progressive meshes for fine-grained local refinement. We present an out-of-core algorithm for computation of a CHPM that includes cluster decomposition, hierarchy generation, and simplification. We make use of novel cluster dependencies in preprocess to generate crack-free, drastic simplifications at runtime. The clusters are used for occlusion culling and out-of-core rendering. We add a frame of latency to the rendering pipeline to fetch newly visible clusters from the disk and to avoid stalls. The CHPM reduces the refinement cost for view-dependent rendering by more than an order of magnitude as compared to a vertex hierarchy. We have implemented our algorithm on a desktop PC. We can render massive CAD, isosurface, and scanned models, consisting of tens or a few hundreds of millions of triangles at 10-35 frames per second with little loss in image quality.
Radial hermite operators for scattered point cloud data with normal vectors and applications to implicitizing polygon mesh surfaces for generalized CSG operations and smoothing
Authors: Gregory M. Nielson
Published at Vis, 2004

We describe a new technique for fitting scattered point cloud data. Given a scattered point cloud of 3D data points and associated normal vectors, our new method produces an implicit volume model whose zero level isosurface interpolates the given points and associated normal vectors. We concentrate on certain application of these new volume modeling techniques. We take existing polygon mesh surfaces and use the present methods to construct implicit volume models for these surfaces. Implicit models allow for the application of Boolean operations on these surfaces through the techniques of constructive solid geometry. Also, standard wavelet and filter operators can be applied to the implicit volume model leading to effective smoothing and filtering algorithms, which are simple to implement.
Real-time motion estimation and visualization on graphics cards
Authors: Robert Strzodka, Christoph S. Garbe
Published at Vis, 2004

We present a tool for real-time visualization of motion features in 2D image sequences. The motion is estimated through an eigenvector analysis of the spatio-temporal structure tensor at every pixel location. This approach is computationally demanding but allows reliable velocity estimates as well as quality indicators for the obtained results. We use a 2D color map and a region of interest selector for the visualization of the velocities. On the selected velocities we apply a hierarchical smoothing scheme which allows the choice of the desired scale of the motion field. We demonstrate several examples of test sequences in which some persons are moving with different velocities than others. These persons are visually marked in the real-time display of the image sequence. The tool is also applied to angiography sequences to emphasize the blood flow and its distribution. An efficient processing of the data streams is achieved by mapping the operations onto the stream architecture of standard graphics cards. The card receives the images and performs both the motion estimation and visualization, taking advantage of the parallelism in the graphics processor and the superior memory bandwidth. The integration of data processing and visualization also saves on unnecessary data transfers and thus allows the real-time analysis of 320/spl times/240 images. We expect that on the newest generation of graphics hardware our tool could run in real time for the standard VGA format.
Real-Time Volume Rendering of Four Channel Data Sets
Authors: Jürgen P. Schulze, Alexander Rice
Published at Vis, 2004

We present a novel method to encode four data channels in a volumetric data set, and render it at interactive frame rates with maximum intensity projection (MIP) using textured polygons. The first three channels are stored in the volume texture’s red, green, and blue components. The fourth channel is stored in the alpha channel. To achieve real-time rendering speed we are using a pixel shader.
Rendering implicit flow volumes
Authors: Daqing Xue, Caixia Zhang, Roger Crawfis
Published at Vis, 2004

Traditional flow volumes construct an explicit geometrical or parametrical representation from the vector field. The geometry is updated interactively and then rendered using an unstructured volume rendering technique. Unless a detailed refinement of the flow volume is specified for the interior, information inside the underlying flow volume is lost in the linear interpolation. These disadvantages can be avoided and/or alleviated using an implicit flow model. An implicit flow is a scalar field constructed such that any point in the field is associated with a termination surface using an advection operator on the flow. We present two techniques, a slice-based three-dimensional texture mapping and an interval volume segmentation coupled with a tetrahedron projection-based renderer, to render implicit stream flows. In the first method, the implicit flow representation is loaded as a 3D texture and manipulated using a dynamic texture operation that allows the flow to be investigated interactively. In our second method, a geometric flow volume is extracted from the implicit flow using a high dimensional isocontouring or interval volume routine. This provides a very detailed flow volume or set of flow volumes that can easily change topology, while retaining accurate characteristics within the flow volume. The advantages and disadvantages of these two techniques are compared with traditional explicit flow volumes.
Rendering planar cuts through quadratic and cubic finite elements
Authors: Michael Brasher, Robert Haimes
Published at Vis, 2004

Coloring higher order scientific data is problematic using standard linear methods as found in OpenGL. The visual results are inaccurate when there is a large scalar gradient over an element or when the scalar field is nonlinear. In addition to shading nonlinear data, last and accurate rendering of planar cuts through parametric elements can be implemented using programmable shaders on current graphics hardware. The intersection of a planar cut with geometrically curved volume elements can be rendered using a combination of selective refinement and programmable shaders. This hybrid algorithm also handles curved 2D planar triangles.
Rough interface reconstruction using the level set method
Authors: Yootai Kim, Raghu Machiraju, David S. Thompson
Published at Vis, 2004

We present a new level set method for reconstructing interfaces from point aggregations. Although level-set-based methods are advantageous because they can handle complicated topologies and noisy data, most tend to smooth the inherent roughness of the original data. Our objective is to enhance the quality of a reconstructed surface by preserving certain roughness-related characteristics of the original dataset. Our formulation employs the total variation of the surface as a roughness measure. The algorithm consists of two steps: a roughness-capturing flow and a roughness-preserving flow. The roughness capturing step attempts to construct a surface for which the original roughness is captured - distance flow is well suited for roughness capturing. Surface reconstruction is enhanced by using a total variation preserving (TVP) scheme for the roughness-preserving flow. The shock filter formulation of Osher and Rudin is exploited to achieve this goal. In practice, we have found that better results arc obtained by balancing the TVP term with a smoothing term based on curvature. The algorithm is applied to both fractal surface growth simulations and scanned data sets to demonstrate the efficacy of our approach.
Scout: a hardware-accelerated system for quantitatively driven visualization and analysis
Authors: Patrick S. McCormick, Jeff T. Inman, James P. Ahrens, Charles D. Hansen, Greg Roth
Published at Vis, 2004

Quantitative techniques for visualization are critical to the successful analysis of both acquired and simulated scientific data. Many visualization techniques rely on indirect mappings, such as transfer functions, to produce the final imagery. In many situations, it is preferable and more powerful to express these mappings as mathematical expressions, or queries, that can then be directly applied to the data. We present a hardware-accelerated system that provides such capabilities and exploits current graphics hardware for portions of the computational tasks that would otherwise be executed on the CPU. In our approach, the direct programming of the graphics processor using a concise data parallel language, gives scientists the capability to efficiently explore and visualize data sets.