IEEE VIS Publication Dataset

An isovalue contour of a function of two complex variables defines a surface in four-space. We present a robust technique for creating polygonal contours of complex-valued functions. The technique, contour meshing, generalizes well to larger dimensions.

Given (n-1)-dimensional parallel cross-sections of an n-dimensional body, one would like to reconstruct the n-dimensional body. The method based on Distance Field Interpolation (DFI) gives a robust solution to this problem in its ability to deal with any topology in any dimension. Still this method may give undesired solutions to the problem if the changes from one cross-section to the next are significant relative to the size of the details in the cross-sections. We consider the problem of solid reconstruction from contours, which can also be considered as a contour blending or contour morphing problem, where the third dimension is time. The method presented is based on interpolation of the distance field, guided by a warp function which is controlled by a set of corresponding anchor points. Some rules for defining a smooth least-distorting warp function are given. To reduce the distortion of the intermediate shapes, the warp function is decomposed into a rigid rotational part and an elastic part. The distance field interpolation method is modified so that the interpolation is guided by the warp function. The advantage of the new approach is that it is capable of blending between contours having different topological genus, and no correspondence between the geometric primitives should be established. The desired general correspondence is defined by the user in terms of a relatively small number of anchor points.

Comparative visualization has successfully been applied to a variety of fluid dynamic problems. Most applications rely on image level comparison such as experimental flow visualization versus computational flow imagery (CFI) which tries to simulate optical image acquisition in flow testing. When differences become difficult to distinguish or once a quantitative result is required, data level comparison provides powerful means to visualize data from multiple sources. Data level comparison and visualization turns out to be an essential tool in modern aircraft design projects. It is already successfully applied in the geometric preprocessing stage and the CFD analysis and will serve for comparison with experimental data as well.

Sampling and analysis of subsurface contaminants comprise the first steps toward environmental remediation of hazardous spills. We have developed software tools to support the analysis phase, using three different schemes for interpolating scattered 3D soil-quality data onto a grid suitable for viewing in an interactive visualization system. A good interpolation scheme is one that respects the distribution of the original data. We find that the original data can be decimated by up to seventy percent while exhibiting graceful degradation in quality. A prototype software system is being deployed to allow technicians to visually determine, while in the field with their monitoring equipment, where the highest concentrations of contaminants lie. The system is now in use by the U.S. Army Corps of Engineers.

Rendering deformable volume data currently needs separate processes for deformation and rendering, and is expensive in terms of both computational and memory costs. Recognizing the importance of unifying these processes, we present a new approach to the direct rendering of deformable volumes without explicitly constructing the intermediate deformed volumes. The volume deformation is done by a radial basis function that is piecewise linearly approximated by an adaptive subdivision of the octree encoded target volume. The octree blocks in the target volume are then projected, reverse morphed and texture mapped, using the SGI 3D texture mapping hardware, in a back-to-front order. A template-based Z-plane/block intersection method is used to expedite the block projection computation.

The paper presents interactive flow visualization methods that highlight directional information in the flow field. An added benefit of the proposed methods is that they reduce the amount of data being displayed and hence reduce clutter. The main idea behind these methods is the use of light sources to select and highlight regions in the flow field with similar directions. Varying the lighting conditions, by moving the light source and/or adding more lights, emphasizes different vector directions, set of directions, and vectors within a specified angle of a particular direction. The methods are straight forward, computationally inexpensive, and can be combined with other techniques that use glyph representation and other flow geometry such as streamlines for feature visualization. The authors apply these methods to an analytic data set to help explain how they work, and then to a simulation data set to highlight flow reversals.

Presents an algorithm for performing view-dependent simplifications of a triangulated polygonal model in real-time. The simplifications are dependent on viewing direction, lighting and visibility, and are performed by taking advantage of image-space, object-space and frame-to-frame coherences. A continuous level-of-detail representation for an object is first constructed off-line. This representation is then used at run-time to guide the selection of appropriate triangles for display. The list of displayed triangles is updated incrementally from one frame to the next. Our approach is more effective than the current level-of-detail-based rendering approaches for most scientific visualization applications where there are a limited number of highly complex objects that stay relatively close to the viewer.

The antenna of a cellular telephone in close proximity to the human head for a variety of time periods raises questions. This research uses the finite-difference time-domain (FDTD) method to calculate the power deposition from a cellular telephone on a high-resolution model of a human head as measured by the specific absorption rates (SAR) in W/kg. Visualization has been used to verify the modeling for simulation, assisted in analyzing the data and understanding the physical aspects controlling the power absorption.

Volume ray casting is based on sampling the data along sight rays. In this technique, reconstruction is achieved by a convolution, which collects the contribution of multiple voxels to one sample point. Splatting, on the other hand, is based on projecting data points onto the screen. Here, reconstruction is implemented by an “inverted convolution” where the contribution of one data element is distributed to many sample points (i.e., pixels). Splatting produces images of a quality comparable to raycasting but at greater speed. This is achieved by precomputing the projection footprint that the interpolation kernel leaves on the image plane. However, while fast incremental schemes can bc utilized for orthographic projection, perspective projection complicates the mapping of the footprints and is therefore rather slow. In this paper, we merge the technique of splatting with principles of raycasting to yield a raydriven splatting approach. We imagine splats as being suspended in object space, a splat at every voxel. Rays are then spawned to traverse the space and intersect the splats. An efficient and accurate way of intersecting and addressing the splats is described. Not only is ray-driven splatting inherently insensitive to the complexity of the perspective viewing transform, it also offers acceleration methods such as early ray termination and bounding volumes, which are methods that traditional voxel driven splatting cannot benefit from. This results in competitive or superior performance for parallel projection, and superior performance for perspective projection.

We present new volume rendering techniques for efficiently generating high-quality stereoscopic images and propose criteria to evaluate stereo volume rendering algorithms. Specifically, we present fast stereo volume ray casting algorithms using segment composition and linearly-interpolated re-projection. A fast stereo shear-warp volume rendering algorithm is also presented and discussed.

This paper describes the Field Encapsulation Library/ (FEL), which provides a grid-independent application programmer's interface to gridded three-dimensional field data. The C++ implementation of FEL is described, stressing the way in which the class hierarchy hides the underlying grid structure in a way that allows visualization algorithms to be written in a completely grid-independent manner: Appropriately defined coordinate classes play an important role in providing this grid independence. High-petformance point location routines for data access are described and performance times are provided.

Information visualization faces challenges presented by the need to represent abstract data and the relationships within the data. Previously, we presented a system for visualizing similarities between a single DNA sequence and a large database of other DNA sequences (E.H. Chi et al., 1995). Similarity algorithms generate similarity information in textual reports that can be hundreds or thousands of pages long. Our original system visualized the most important variables from these reports. However, the biologists we work with found this system so useful they requested visual representations of other variables. We present an enhanced system for interactive exploration of this multivariate data. We identify a larger set of useful variables in the information space. The new system involves more variables, so it focuses on exploring subsets of the data. We present an interactive system allowing mapping of different variables to different axes, incorporating animation using a time axis, and providing tools for viewing subsets of the data. Detail-on-demand is preserved by hyperlinks to the analysis reports. We present three case studies illustrating the use of these techniques. The combined technique of applying a time axis with a 3D scatter plot and query filters to visualization of biological sequence similarity data is both powerful and novel.

Visualization of CFD data for turbomachinery design poses some special requirements which are often not addressed by standard flow visualization systems. The authors discuss the issues involved with this particular application and its requirements with respect to flow visualization. Aiming at a feature-based visualization for this task, they examine various existing techniques to locate vortices. The specific flow conditions for turbomachines demonstrate limitations of current methods. Visualization of turbomachinery flow thus raises some challenges and research topics, particularly regarding feature extraction.

This paper presents a novel approach to assist the user in exploring appropriate transfer functions for the visualization of volumetric datasets. The search for a transfer function is treated as a parameter optimization problem and addressed with stochastic search techniques. Starting from an initial population of (random or pre-defined) transfer functions, the evolution of the stochastic algorithms is controlled by either direct user selection of intermediate images or automatic fitness evaluation using user-specified objective functions. This approach essentially shields the user from the complex and tedious “trial and error” approach, and demonstrates effective and convenient generation of transfer functions.

A general volume rendering technique is described that efficiently produces images of excellent quality from data defined over irregular grids having a wide variety of formats. Rendering is done in software, eliminating the need for special graphics hardware, as well as any artifacts associated with graphics hardware. Images of volumes with about 1,000,000 cells can be produced in one to several minutes on a workstation with a 150-MHz processor. A significant advantage of this method for applications such as computational fluid dynamics is that it can process multiple intersecting grids. Such grids present problems for most current volume rendering techniques. Also, the wide range of cell sizes does not present difficulties, as it does for many techniques. A spatial hierarchical organization makes it possible to access data from a restricted region efficiently. The tree has greater depth in regions of greater detail, determined by the number of cells in the region. It also makes it possible to render useful "preview" images very quickly by displaying each region associated with a tree node as one cell. Previews show enough detail to navigate effectively in very large data sets. The algorithmic techniques include use of a k-d tree, with prefix-order partitioning of triangles, to reduce the number of primitives that must be processed for one rendering, coarse-grain parallelism for a shared-memory MIMD architecture, a new perspective transformation that achieves greater numerical accuracy, and a scanline algorithm with depth sorting and a new clipping technique.

We introduce an algorithm for reconstructing a solid model given a series of planar cross sections. The main contribution of this work is the use of knowledge obtained during the interpolation of neighboring layers while attempting to interpolate a particular layer. This knowledge is used to reconstruct a surface in which consecutive layers are connected smoothly. In most previous work, each layer is interpolated independently of what happened or will happen in the other layers. We also discuss various objective functions which aim to optimize the reconstruction, and present an evaluation of the different objective functions by using various criteria.

Transparency can be a useful device for simultaneously depicting multiple superimposed layers of information in a single image. However, in computer-generated pictures-as in photographs and in directly viewed actual objects-it can often be difficult to adequately perceive the three-dimensional shape of a layered transparent surface or its relative depth distance from underlying structures. Inspired by artists' use of line to show shape, we have explored methods for automatically defining a distributed set of opaque surface markings that intend to portray the three-dimensional shape and relative depth of a smoothly curving layered transparent surface in an intuitively meaningful (and minimally occluding) way. This paper describes the perceptual motivation, artistic inspiration and practical implementation of an algorithm for "texturing" a transparent surface with uniformly distributed opaque short strokes, locally oriented in the direction of greatest normal curvature, and of length proportional to the magnitude of the surface curvature in the stroke direction. The driving application for this work is the visualization of layered surfaces in radiation therapy treatment planning data, and the technique is illustrated on transparent isointensity surfaces of radiation dose.

We present a system where visualization and the control of the simulation are integrated to facilitate interactive exploration and modeling of large data sets. The system was developed to estimate properties of the atmosphere of Venus from comparison between measured and simulated data. Reuse of results, distributed computing, and multiple views on the data were the major ingredients to create an effective environment

A new technique for interactive vector field visualization using large numbers of properly illuminated stream lines is presented. Taking into account ambient, diffuse, and specular reflection terms as well as transparency, we employ a realistic shading model which significantly increases quality and realism of the resulting images. While many graphics workstations offer hardware support for illuminating surface primitives, usually no means for an accurate shading of line primitives are provided. However, we show that proper illumination of lines can be implemented by exploiting the texture mapping capabilities of modern graphics hardware. In this way high rendering performance with interactive frame rates can be achieved. We apply the technique to render large numbers of integral curves in a vector field. The impression of the resulting images can be further improved by making the curves partially transparent. We also describe methods for controlling the distribution of stream lines in space. These methods enable us to use illuminated stream lines within an interactive visualization environment.