IEEE VIS Publication Dataset

We present the use of mapping functions to automatically generate levels of detail with known error bounds for polygonal models. We develop a piece-wise linear mapping function for each simplification operation and use this function to measure deviation of the new surface from both the previous level of detail and from the original surface. In addition, we use the mapping function to compute appropriate texture coordinates if the original map has texture coordinates at its vertices. Our overall algorithm uses edge collapse operations. We present rigorous procedures for the generation of local planar projections as well as for the selection of a new vertex position for the edge collapse operation. As compared to earlier methods, our algorithm is able to compute tight error bounds on surface deviation and produce an entire continuum of levels of detail with mappings between them. We demonstrate the effectiveness of our algorithm on several models: a Ford Bronco consisting of over 300 parts and 70,000 triangles, a textured lion model consisting of 49 parts and 86,000 triangles, and a textured, wrinkled torus consisting of 79,000 triangles.

Studies the topology of 2nd-order symmetric tensor fields. Degenerate points are basic constituents of tensor fields. From the set of degenerate points, an experienced researcher can reconstruct a whole tensor field. We address the conditions for the existence of degenerate points and, based on these conditions, we predict the distribution of degenerate points inside the field. Every tensor can be decomposed into a deviator and an isotropic tensor. A deviator determines the properties of a tensor field, while the isotropic part provides a uniform bias. Deviators can be 3D or locally 2D. The triple-degenerate points of a tensor field are associated with the singular points of its deviator and the double-degenerate points of a tensor field have singular local 2D deviators. This provides insights into the similarity of topological structure between 1st-order (or vectors) and 2nd-order tensors. Control functions are in charge of the occurrences of a singularity of a deviator. These singularities can further be linked to important physical properties of the underlying physical phenomena. For a deformation tensor in a stationary flow, the singularities of its deviator actually represent the area of the vortex core in the field; for a stress tensor, the singularities represent the area with no stress; for a Newtonian flow, compressible flow and incompressible flow as well as stress and deformation tensors share similar topological features due to the similarity of their deviators; for a viscous flow, removing the large, isotropic pressure contribution dramatically enhances the anisotropy due to viscosity.

Presents a new method to produce a hierarchical set of triangle meshes that can be used to blend different levels of detail in a smooth fashion. The algorithm produces a sequence of meshes M0, M1, M2..., Mn, where each mesh Mi can be transformed to mesh Mi+1 through a set of triangle-collapse operations. For each triangle, a function is generated that approximates the underlying surface in the area of the triangle, and this function serves as a basis for assigning a weight to the triangle in the ordering operation, and for supplying the point to which the triangles are collapsed. This technique allows us to view a triangulated surface model at varying levels of detail while insuring that the simplified mesh approximates the original surface well.

This paper discusses strategies for effectively portraying 3D flow using volume line integral convolution. Issues include defining an appropriate input texture, clarifying the distinct identities and relative depths of the advected texture elements, and selectively highlighting regions of interest in both the input and output volumes. Apart from offering insights into the greater potential of 3D LIC as a method for effectively representing flow in a volume, a principal contribution of this work is the suggestion of a technique for generating and rendering 3D visibility-impeding "halos" that can help to intuitively indicate the presence of depth discontinuities between contiguous elements in a projection and thereby clarify the 3D spatial organization of elements in the flow. The proposed techniques are applied to the visualization of a hot, supersonic, laminar jet exiting into a colder, subsonic coflow.

The authors introduce the contour spectrum, a user interface component that improves qualitative user interaction and provides real-time exact quantification in the visualization of isocontours. The contour spectrum is a signature consisting of a variety of scalar data and contour attributes, computed over the range of scalar values /spl omega//spl isin/R. They explore the use of surface, area, volume, and gradient integral of the contour that are shown to be univariate B-spline functions of the scalar value /spl omega/ for multi-dimensional unstructured triangular grids. These quantitative properties are calculated in real-time and presented to the user as a collection of signature graphs (plots of functions of /spl omega/) to assist in selecting relevant isovalues /spl omega//sub 0/ for informative visualization. For time-varying data, these quantitative properties can also be computed over time, and displayed using a 2D interface, giving the user an overview of the time-varying function, and allowing interaction in both isovalue and time step. The effectiveness of the current system and potential extensions are discussed.

The paper presents a new approach for animating 2D steady flow fields. It is based on an original data structure called the motion map. The motion map contains not only a dense representation of the flow field but also all the motion information required to animate the flow. An important feature of this method is that it allows, in a natural way, cyclical variable-speed animations. As far as efficiency is concerned, the advantage of this method is that computing the motion map does not take more time than computing a single still image of the flow and the motion map has to be computed only once. Another advantage is that the memory requirements for a cyclical animation of an arbitrary number of frames amounts to the memory cost of a single still image.

Multilevel representations and mesh reduction techniques have been used for accelerating the processing and the rendering of large datasets representing scalar- or vector-valued functions defined on complex 2D or 3D meshes. We present a method based on finite element approximations which combines these two approaches in a new and unique way that is conceptually simple and theoretically sound. The main idea is to consider mesh reduction as an approximation problem in appropriate finite element spaces. Starting with a very coarse triangulation of the functional domain, a hierarchy of highly non-uniform tetrahedral (or triangular in 2D) meshes is generated adaptively by local refinement. This process is driven by controlling the local error of the piecewise linear finite element approximation of the function on each mesh element. A reliable and efficient computation of the global approximation error and a multilevel preconditioned conjugate gradient solver are the key components of the implementation. In order to analyze the properties and advantages of the adaptively generated tetrahedral meshes, we implemented two volume visualization algorithms: an iso-surface extractor and a ray-caster. Both algorithms, while conceptually simple, show significant speedups over conventional methods delivering comparable rendering quality from adaptively compressed datasets.

Different techniques have been proposed for rendering volumetric scalar data sets. Usually these approaches are focusing on orthogonal cartesian grids, but in the last years research did also concentrate on arbitrary structured or even unstructured topologies. In particular, direct volume rendering of these data types is numerically complex and mostly requires sorting the whole database. We present a new approach to direct rendering of convex, voluminous polyhedra on arbitrary grid topologies, which efficiently use hardware assisted polygon drawing to support the sorting procedure. The key idea of this technique lies in a two pass rendering approach. First, the volume primitives are drawn in polygon mode to obtain their cross sections in the VSBUFFER orthogonal to the viewing plane. Second, this buffer is traversed in front to back order and the volume integration is performed. Thus, the complexity of the sorting procedure is reduced. Furthermore, any connectivity information can be completely neglected, which allows for the rendering of arbitrary scattered, convex polyhedra.

Large simulation grids and multi-grid configurations impose many constraints on commercial visualization software. When available RAM is limited and graphics primitives are numbered in millions, alternative techniques for data access and processing are necessary. In this case study, we present our contributions to a visualization environment based on the AVS/Express software. We demonstrate how the efficient visualization of large datasets relies upon several forms of resource sharing, and alternate and efficient data access techniques.

Volume navigation is the interactive exploration of volume data sets by "flying" the view point through the data, producing a volume rendered view at each frame. The authors present an inexpensive perspective volume navigation method designed to run on a PC platform with accelerated 3D graphics hardware. They compute perspective projections at each frame, allow trilinear interpolation of sample points, and render both gray scale and RGB volumes by volumetric compositing. The implementation handles arbitrarily large volumes, by dynamically swapping data within the local depth-limited frustum into main memory as the viewpoint moves through the volume. They describe a new ray casting algorithm that takes advantage of the coherence inherent in adjacent frames to generate a sequence of approximate animated frames much faster than they could be computed individually. They also take advantage of the 3D graphics acceleration hardware to offload much of the alpha blending and resampling from the CPU.

The paper presents an algorithm, UFLIC (Unsteady Flow LIC), to visualize vector data in unsteady flow fields. Using line integral convolution (LIC) as the underlying method, a new convolution algorithm is proposed that can effectively trace the flow's global features over time. The new algorithm consists of a time-accurate value depositing scheme and a successive feedforward method. The value depositing scheme accurately models the flow advection, and the successive feedforward method maintains the coherence between animation frames. The new algorithm can produce time-accurate, highly coherent flow animations to highlight global features in unsteady flow fields. CFD scientists, for the first time, are able to visualize unsteady surface flows using the algorithm.

This paper describes our experiences with using the Virtual Reality Modeling Language (VRML) to view files in the Initial Graphics Exchange Specification (IGES) format using a Java-based translator from IGES to VRML and HTML (Hypertext Markup Language). The paper examines the conversion problems between IGES and VRML and presents some results of the process.

Virtualized reality is a modeling technique that constructs full 3D virtual representations of dynamic events from multiple video streams. Image-based stereo is used to compute a range image corresponding to each intensity image in each video stream. Each range and intensity image pair encodes the scene structure and appearance of the scene visible to the camera at that moment, and is therefore called a visible surface model (VSM). A single time instant of the dynamic event can be modeled as a collection of VSMs from different viewpoints, and the full event can be modeled as a sequence of static scenes-the 3D equivalent of video. Alternatively, the collection of VSMs at a single time can be fused into a global 3D surface model, thus creating a traditional virtual representation out of real world events. Global modeling has the added benefit of eliminating the need to hand-edit the range images to correct errors made in stereo, a drawback of previous techniques. Like image-based rendering models, these virtual representations can be used to synthesize nearly any view of the virtualized event. For this reason, the paper includes a detailed comparison of existing view synthesis techniques with the authors' own approach. In the virtualized representations, however, scene structure is explicitly represented and therefore easily manipulated, for example by adding virtual objects to (or removing virtualized objects from) the model without interfering with real event. Virtualized reality, then, is a platform not only for image-based rendering but also for 3D scene manipulation.

This paper investigates the visualization and animation of geometric computing in a distributed electronic classroom. We show how focusing in a well-defined domain makes it possible to develop a compact system that is accessible to even naive users. We present a conceptual model and a system, GASP-II (Geometric Animation System, Princeton, II), that realizes this model in the geometric domain. The system allows the presentation and interactive exploration of 3D geometric algorithms over a network.

The paper discusses a unique way to visualize height field data-the use of solid fabricated parts with a photomapped texture to display scalar information. In this process, the data in a height field are turned into a 3D solid representation through solid freeform fabrication techniques, in this case laminated object manufacturing. Next, that object is used as a 3D "photographic plate" to allow a texture image representing scalar data to be permanently mapped onto it. The paper discusses this process and how it can be used in different visualization situations.

Presents an algorithm for the visualization of vector field topology based on Clifford algebra. It allows the detection of higher-order singularities. This is accomplished by first analysing the possible critical points and then choosing a suitable polynomial approximation, because conventional methods based on piecewise linear or bilinear approximation do not allow higher-order critical points and destroy the topology in such cases. The algorithm is still very fast, because of using linear approximation outside the areas with several critical points.

The authors describe a software system supporting interactive visualization of large terrains in a resource-limited environment, i.e. a low-end client computer accessing a large terrain database server through a low-bandwidth network. By "large", they mean that the size of the terrain database is orders of magnitude larger than the computer RAM. Superior performance is achieved by manipulating both geometric and texture data at a continuum of resolutions, and, at any given moment, using the best resolution dictated by the CPU and bandwidth constraints. The geometry is maintained as a Delaunay triangulation of a dynamic subset of the terrain data points, and the texture compressed by a progressive wavelet scheme. A careful blend of algorithmic techniques enables the system to achieve superior rendering performance on a low-end computer by optimizing the number of polygons and texture pixels sent to the graphics pipeline. It guarantees a frame rate depending only on the size and quality of the rendered image, independent of the viewing parameters and scene database size. An efficient paging scheme minimizes data I/O, thus enabling the use of the system in a low-bandwidth client/server data-streaming scenario, such as on the Internet.

The measurement, analysis and visualization of plant growth is of primary interest to plant biologists. We are developing software tools to support such investigations. There are two parts in this investigation, namely growth visualization of (i) a plant root and (ii) a plant stem. For both domains, the input data is a stream of images taken by cameras. The tools being developed make it possible to measure various time-varying quantities, such as differential growth. For both domains, the plant is modeled by using flexible templates to represent non-rigid motions.

We define a rotation field by extending the notion of a vector field to rotations. A vector field has a vector as a value at each point of its domain; a rotation field has a rotation as a value at each point of its domain. Rotation fields result from mapping the orientation error of tracking systems. We build upon previous methods for the visualization of vector fields, tensor fields and rotations at a point, to visualize a rotation field resulting from calibration of a commonly-used magnetic tracking system.