IEEE VIS Publication Dataset

This work briefly describes our approach to visualize results of transient flow simulations in the application areas of groundwater flow and pollutant transport as well as compressible fluid flow in engine parts. The simulations use finite element data structures and can have geometries which change over time. We designed a client-server model to handle the huge amount of data that can be obtained either directly from the simulation process or from files on disk. As standard visualization packages are not able to cope with transient unstructured data, we implemented streamlines, stream surfaces and particle systems as our main visualization methods. Our experiences and results with these techniques are discussed in this paper

We present a 3-D antialiasing algorithm for voxel-based geometric models. The technique band-limits the continuous object before sampling it at the desired 3-D raster resolution. By precomputing tables of filter values for different types and sizes of geometric objects, the algorithm is very efficient and has a complexity that is linear with the number of voxels generated. The algorithm not only creates voxel models which are free from object space aliasing, but it also incorporates the image space antialiasing information as part of the view independent voxel model. The resulting alias-free voxel models have been used to model synthetic scenes, for discrete ray tracing applications. The discrete ray-traced image is superior in quality to the image generated with a conventional surface-based ray tracer, since silhouettes of objects, shadows, and reflections appear smooth (jaggy-less). In addition, the alias-free models are also suitable for intermixing with sampled datasets, since they can be treated uniformly as one common data representation

A methodology has been developed for constructing streamlines and particle paths in numerically generated fluid velocity fields. A graphical technique is used to convert the discretely defined flow within a cell into one represented by two three-dimensional stream functions. Streamlines are calculated by tracking constant values of each stream function, a process which corresponds to finding the intersection of two stream surfaces. The tracking process is mass conservative and does not use a time stepping method for integration, thus eliminating a computationally intensive part of traditional tracking algorithms. The method can be applied generally to any three-dimensional compressible or incompressible steady flow. Results presented compare the performance of the new method to the most commonly used scheme and show that calculation times can be reduced by an order of magnitude

It is shown how data visualization fits into the broader process of scientific data analysis. Scientists from several disciplines were observed while they analyzed their own data. Examination of the observations exposed process elements outside conventional image viewing. For example, analysts queried for quantitative information, made a variety of comparisons, applied math, managed data, and kept records. The characterization of scientific data analysis reveals activity beyond that traditionally supported by computer. It offers an understanding which has the potential to be applied to many future designs, and suggests specific recommendations for improving the support of this important aspect of scientific computing

While scientific visualization systems share many requirements with other graphical applications, they also have special requirements that make solutions based on standard rendering hardware or software not entirely satisfactory. Those requirements are illustrated by describing the renderer used in a production scientific visualization system, Data Explorer. The requirements for a visualization renderer are discussed. Implementation techniques used to meet the requirements of parallelism, volume rendering of irregular data, clipping, and integration of rendering modalities are described. The renderer described is a software renderer, but it is hoped that the requirements and implementation presented might influence the design of future generations of rendering hardware

A voxel-based, forward projection algorithm with a pipeline architecture for real-time applications is presented. The multisensor capabilities (electrooptical, or visual, and infrared) currently implemented in software have also been applied to non-real-time imaging applications on workstations and minicomputers. Most suited for terrain-based applications, the system features haze, imbedded targets, moving objects, smooth shading, and specular reflections

The architecture of the Data Explorer, a scientific visualization system, is described. Data Explorer supports the visualization of a wide variety of data by means of a flexible set of visualization modules. A single powerful data model common to all modules allows a wide range of data types to be imported and passed between modules. There is integral support for parallelism, affecting the data model and the execution model. The visualization modules are highly interoperable, due in part to the common data model, and exemplified by the renderer. An execution model facilitates parallelization of modules and incorporates optimizations such as caching. The two-process client-server system structure consists of a user interface that communicates with an executive via a dataflow language

A fast range search algorithm for visualizing extrema of d-dimensional volume data in real time as the user interactively moves the query range is presented. The algorithm is based on an efficient data structure, called index heap, which needs only O(N/log N) space and O(d2 dN) preprocessing time to be set up, where N is the size of the d-dimensional data volume. The algorithm can answer an extremum query in O(4d) expected time, and its worst-case time complexity is O(2d log N) per query. For dimensions two and three, the range search for extrema is effected in average O(1) time per query independently of the size of query range. Unlike previous range query algorithms in the computational geometry literature, the proposed algorithm is very simple and can be easily implemented.

A framework for the generation of atlases of the human body based on the linkage of volume data to a knowledge base is presented. The model has a two layer structure. The lower level is a volume model with a set of semantic attributes belonging to each voxel. Its spatial representation is derived from data sets of magnetic resonance imaging (MRI) and computer tomography. The semantic attributes are assigned by an anatomist using a volume editor. The upper level is a set of relations between these attributes which are also specified by the expert. Interactive visualization tools, such as multiple surface display, transparent rendering, and cutting, are provided. It is shown that the combination of this object-oriented data structure with advanced volume visualization tools provides the look and feel of a real dissection

A method is presented to obtain a unique shape description of an object by using wavelet transforms. Wavelet transform is a signal analysis technique which decomposes a signal using a family of functions having a local property in both time and frequency domains. A multiresolution expression of 3D volume data was first obtained by applying 3D orthogonal wavelet transforms, with the shape then being approximated with a relatively small number of 3D orthogonal functions using only the significant functions. In addition, the resolution of the approximation can be varied point by point using the local property of the wavelets. The method is applied to real volume data, i.e. facial range data and MR images of a human head, and typical results are shown

Interactive visualization systems provide a powerful means to explore complex data, especially when coupled with 3-D interaction and display devices to produce virtual worlds. While designing a quality static 2-D visualization is already a difficult task for most users, designing an interactive 3-D one is even more challenging. To address this problem, AutoVisual, a research system that designs interactive virtual worlds for visualizing and exploring multivariate relations of arbitrary arity, is being developed. AutoVisual uses worlds within worlds, an interactive visualization technique that exploits nested, heterogeneous coordinate systems to map multiple variables onto each spatial dimension. AutoVisual's designs are guided by user-specified visualization tasks, and by a catalog of design principles encoded using a rule-based language

A brief example of the visualization and quantification of a complex fluid interaction is presented in order to give one a feeling for the difficulty of dealing with geometrical and topological questions in three dimensions and time. To obtain a quantitative understanding, visiometric techniques, including thresholding, object isolation, ellipsoid fitting, abstraction, vector field line generation and data juxtaposition, were used

Calico, a dynamic tool for the creation and manipulation of color mappings for the exploration of multivariate, quantitative data, was used to study the effects of user control and smooth change on user preference, accuracy, and confidence. The results of the study, as well as other user experiences with Calico, support the hypothesis that dynamic manipulation of color mappings is a useful feature of systems for the exploration of quantitative data using color. The main effect observed is a clear user preference for representations providing control over the mapping, a small but significant increase in accuracy, and greater confidence in information gleaned from manipulable displays. A smaller and less consistent effect showed greater user preference for an confidence in representations which provided smooth change between images

Maintenance of a front of particles, an efficient method of generating a set of sample points over a two-dimensional stream surface, is described. The particles are repeatedly advanced a short distance through the flow field. New polygons are appended to the downstream edge of the surface. The spacing of the particles is adjusted to maintain an adequate sampling across the width of the growing surface. Curve and ribbon methods of vector field visualization are reviewed

The need for direct volume visualization display devices is discussed, as well as some specifics of the Texas Instruments OmniView technology. The topics discussed include the concept of operations, the rotating surface, the display volume, the transport theory model, the image quality in the display, and applications. The outlook for future volumetric displays is addressed

A technique for defining graphical depictions for all the data types defined in an algorithm is presented. The ability to display arbitrary combinations of an algorithm's data objects in a common frame of reference, coupled with interactive control of algorithm execution, provides a powerful way to understand algorithm behavior. Type definitions are constrained so that all primitive values occurring in data objects are assigned scalar types. A graphical display, including user interaction with the display, is modeled by a special data type. Mappings from the scalar types into the display model type provide a simple user interface for controlling how all data types are depicted, without the need for type-specific graphics logic

Issues and difficulties involved in the practical implementation of flow visualization techniques based on a database generated in numerical simulations of unsteady square jets are addressed. Instantaneous visualizations provide basic information on the topological features of the flow, while animation of these visualizations gives an insight into the detailed dynamics of formation, development, and interaction of the coherent structures controlling the entrainment and mixing processes

Scalar functions of three variables, w=f(x , y, z), are common in many types of scientific and medical applications. Such 3D scalar fields can be understood as elevation maps in four dimensions, with three independent variables (x, y, z) and a fourth, dependent, variable w that corresponds to the elevations. It is shown how techniques developed originally for the display of 3-manifolds in 4D Euclidean space can be adapted to visualize 3D scalar fields in a variety of ways

The generation of smooth surfaces from a mesh of three-dimensional data points is an important problem in geometric modeling. Apart from the pure construction of these curves and surfaces, the analysis of their quality is equally important in the design and manufacturing process. Generalized focal surfaces are presented as a new surface interrogation tool

Discusses issues relating to the complexity of scientific visualization software system implementation. It is argued that the complexity of current implementations of such systems may limit the utility for users because the interfaces typically require significant knowledge of the data being studied and the applicable visualization algorithms, as well as its infrastructure of graphics, imaging and data handling technology. The issues, unknowns, and possible solutions associated with building effective scientific visualization software are discussed