IEEE VIS Publication Dataset

General relativistic ray tracing is presented as a tool for gravitational physics. It is shown how standard three-dimensional ray tracing can be extended to allow for general relativistic visualization. This visualization technique provides images as seen by an observer under the influence of a gravitational field and allows to probe space-time by null geodesics. Moreover, a technique is proposed for visualizing the caustic surfaces generated by a gravitational lens. The suitability of general relativistic ray tracing is demonstrated by means of two examples, namely the visualization of the rigidly rotating disk of dust and the warp drive metric.

The compression of geometric structures is a relatively new field of data compression. Since about 1995, several articles have dealt with the coding of meshes, using for most of them the following approach: the vertices of the mesh are coded in an order that partially contains the topology of the mesh. In the same time, some simple rules attempt to predict the position of each vertex from the positions of its neighbors that have been previously coded. We describe a compression algorithm whose principle is completely different: the coding order of the vertices is used to compress their coordinates, and then the topology of the mesh is reconstructed from the vertices. This algorithm achieves compression ratios that are slightly better than those of the currently available algorithms, and moreover, it allows progressive and interactive transmission of the meshes.

We present a new hierarchical clustering and visualization algorithm called H-BLOB, which groups and visualizes cluster hierarchies at multiple levels-of-detail. Our method is fundamentally different to conventional clustering algorithms, such as C-means, K-means, or linkage methods that are primarily designed to partition a collection of objects into subsets sharing similar attributes. These approaches usually lack an efficient level-of-detail strategy that breaks down the visual complexity of very large datasets for visualization. In contrast, our method combines grouping and visualization in a two stage process constructing a hierarchical setting. In the first stage a cluster tree is computed making use of an edge contraction operator. Exploiting the inherent hierarchical structure of this tree, a second stage visualizes the clusters by computing a hierarchy of implicit surfaces. We believe that H-BLOB is especially suited for the visualization of very large datasets and for visual decision making in information visualization. The versatility of the algorithm is demonstrated using examples from visual data mining.

We present a novel hardware-accelerated texture advection algorithm to visualize the motion of two-dimensional unsteady flows. Making use of several proposed extensions to the OpenGL-1.2 specification, we demonstrate animations of over 65,000 particles at 2 frames/sec on an SGI Octane with EMXI graphics. High image quality is achieved by careful attention to edge effects, noise frequency, and image enhancement. We provide a detailed description of the hardware implementation, including temporal and spatial coherence techniques, dye advection techniques, and feature extraction.

We present two beneficial rendering extensions to the projected tetrahedra (PT) algorithm proposed by Shirley and Tuchman (1990). These extensions are compatible with any cell sorting technique, for example the BSP-XMPVO sorting algorithm for unstructured meshes. Using 3D texture mapping our first extension solves the longstanding problem of hardware-accelerated but accurate rendering of tetrahedral volume cells with arbitrary transfer functions. By employing 2D texture mapping our second extension realizes the hardware-accelerated rendering of multiple shaded isosurfaces within the PT algorithm without reconstructing the isosurfaces. Additionally, two methods are presented to combine projected tetrahedral volumes with isosurfaces. The time complexity of all our algorithms is linear in the number of tetrahedra and does neither depend on the number of isosurfaces nor on the employed transfer functions.

This paper presents an efficient keyframeless image-based rendering technique. An intermediate image is used to exploit the coherences among neighboring frames. The pixels in the intermediate image are first rendered by a ray-casting method and then warped to the intermediate image at the current viewpoint and view direction. We use an offset buffer to record the precise positions of these pixels in the intermediate image. Every frame is generated in three steps: warping the intermediate image onto the frame, filling in holes, and selectively rendering a group of ”old” pixels. By dynamically adjusting the number of those ”old” pixels in the last step, the workload at every frame can be balanced. The pixels generated by the last two steps make contributions to the new intermediate image. Unlike occasional keyframes in conventional image-based rendering which need to be totally rerendered, intermediate images only need to be partially updated at every frame. In this way, we guarantee more stable frame rates and more uniform image qualities. The intermediate image can be warped efficiently by a modified incremental 3D warp algorithm. As a specific application, we demonstrate our technique with a voxel-based terrain rendering system."

We present an immersive system for exploring numerically simulated flow data through a model of a coronary artery graft. This tightly-coupled interdisciplinary project is aimed at understanding how to reduce the failure rate of these grafts. The visualization system provides a mechanism for exploring the effect of changes to the geometry, to the flow, and for exploring potential sources of future lesions. The system uses gestural and voice interactions exclusively, moving away from more traditional windows/icons/menus/point-and-click (WIMP) interfaces. We present an example session using the system and discuss our experiences developing, testing, and using it. We describe some of the interaction and rendering techniques that we experimented with and describe their level of success. Our experience suggests that systems like this are exciting to clinical researchers, but conclusive evidence of their value is not yet available.

The authors present a visualization system for interactive real time animation and visualization of simulation results from a parallel Particle-in-Cell code. The system was designed and implemented for the Onyx2 Infinite Reality hardware. A number of different visual objects, such as volume rendered particle density functionals were implemented. To provide sufficient frame rates for interactive visualization, the system was designed to provide performance close to the hardware specifications both in terms of the I/O and graphics subsystems. The presented case study applies the developed system to the evolution of an instability that gives rise to a plasma surfatron, a mechanism which rapidly can accelerate particles to very high velocities and thus be of great importance in the context of electron acceleration in astrophysical shocks, in the solar corona and in particle accelerators. The produced visualizations have allowed us to identify a previously unknown saturation mechanism for the surfatron and direct research efforts into new areas of interest.

The study of time dependent characteristics of proteins is important for gaining insight into many biological processes. However, visualizing protein dynamics by animating atom trajectories does not provide satisfactory results. When the trajectory is sampled with large times steps, the impression of smooth motion will be destroyed due to the effects of temporal aliasing. Sampling with small time steps will result in the camouflage of interesting motions. In this case study, we discuss techniques for the interactive 3D visualization of the dynamics of the photoactive yellow protein. We use essential dynamics methods to filter out uninteresting atom motions from the larger concerted motions. In this way, clear and concise 3D animations of protein motions can be produced. In addition, we discuss various interactive techniques that allow exploration of the essential subspace of the protein. We discuss the merits of these techniques when applied to the analysis of the yellow protein.

We present an algorithm for automatically classifying the interior and exterior parts of a polygonal model. The need for visualizing the interiors of objects frequently arises in medical visualization and CAD modeling. The goal of such visualizations is to display the model in a way that the human observer can easily understand the relationship between the different parts of the surface. While there exist excellent methods for visualizing surfaces that are inside one another (nested surfaces), the determination of which parts of the surface are interior is currently done manually. Our automatic method for interior classification takes a sampling approach using a collection of direction vectors. Polygons are said to be interior to the model if they are not visible in any of these viewing directions from a point outside the model. Once we have identified polygons as being inside or outside the model, these can be textured or have different opacities applied to them so that the whole model can be rendered in a more comprehensible manner. An additional consideration for some models is that they may have holes or tunnels running through them that are connected to the exterior surface. Although an external observer can see into these holes. It is often desirable to mark the walls of such tunnels as being part of the interior of a model. In order to allow this modified classification of the interior, we use morphological operators to close all the holes of the model. An input model is used together with its closed version to provide a better classification of the portions of the original model.

Visualization algorithms have seen substantial improvements in the past several years. However, very few algorithms have been developed for directly studying data in dimensions higher than three. Most algorithms require a sampling in three-dimensions before applying any visualization algorithms. This sampling typically ignores vital features that may be present when examined in oblique cross-sections, and places an undo burden on system resources when animation through additional dimensions is desired. For time-varying data of large data sets, smooth animation is desired at interactive rates. We provide a fast Marching Cubes like algorithm for hypercubes of any dimension. To support this, we have developed a new algorithm to automatically generate the isosurface and triangulation tables for any dimension. This allows the efficient calculation of 4D isosurfaces, which can be interactively sliced to provide smooth animation or slicing through oblique hyperplanes. The former allows for smooth animation in a very compressed format. The latter provide better tools to study time-evolving features as they move downstream. We also provide examples in using this technique to show interval volumes or the sensitivity of a particular isovalue threshold.

The display of iso-surfaces in medical data sets is an important visualization technique used by radiologists for the diagnosis of volumetric density data sets. The demands put by radiologists on such a display technique are interactivity, multiple stacked transparent surfaces and cutting planes that allow an interactive clipping of the surfaces. This paper presents a Java based, platform independent implementation of a very fast surface rendering algorithm which combines the advantages of explicit surface representation, splatting, and shear-warp projection to fulfill all these requirements. The algorithm is implemented within the context of J-Vision, an application for viewing and diagnosing medical images which is currently in use at various hospitals.

Virtual endoscopy presents the cross-sectional acquired 3D-data of a computer tomograph as an endoluminal view. The common approach for the visualization of a virtual endoscopy is surface rendering, yielding images close to a real endoscopy. If external structures are of interest, volume rendering techniques have to be used. These methods do not display the exact shape of the inner lumen very well. For certain applications, e.g. operation planning of a transbronchial biopsy, both the shape of the inner lumen as well as outer structures like blood vessels and the tumor have to be delineated. A method is described, that allows a quick and easy hybrid visualization using overlays of different visualization methods like different surfaces or volume renderings with different transfer functions in real time on a low-end PC. To achieve real time frame rates, image based rendering techniques have been used.

Multi-resolution techniques and models have been shown to be effective for the display and transmission of large static geometric object. Dynamic environments with internally deforming models and scientific simulations using dynamic meshes pose greater challenges in terms of time and space, and need the development of similar solutions. We introduce the T-DAG, an adaptive multi-resolution representation for dynamic meshes with arbitrary deformations including attribute, position, connectivity and topology changes. T-DAG stands for time-dependent directed acyclic graph which defines the structure supporting this representation. We also provide an incremental algorithm (in time) for constructing the T-DAG representation of a given input mesh. This enables the traversal and use of the multi-resolution dynamic model for partial playback while still constructing new time-steps.

Scaling of simulations challenges the effectiveness of conventional visualization methods. This problem becomes two-fold for mesoscale weather models that operate in near-real-time at cloud-scale resolution. For example, typical approaches to vector field visualization (e.g., wind) are based upon global methods, which may not illustrate detailed structure. In addition, such computations employ multi-resolution meshes to capture small-scale phenomena, which are not properly reflected in both vector and scalar realizations. To address the former critical point analysis and simple bandpass filtering of wind fields is employed for better seed point identification of streamline calculations. For the latter, an encapsulation of nested computational meshes is developed for general realization. It is then combined with the seed point calculation for an improved vector visualization of multi-resolution weather forecasting data.

In this paper we are presenting a novel architecture which allows rendering of large-shared dataset at interactive rates on an inexpensive workstation. The idea is based on view-dependent rendering on a client-server network. The server stores the large dataset and manages the selection of the various levels of detail while the inexpensive clients receive a stream of update operations that generate the appropriate level of detail in an incremental fashion. These update operations are based on changes in the clients’ view-parameters. Our approach dramatically reduces the amount of memory needed by each client and the entire computing system since the dataset is stored only once on the server’s local memory. In addition, it decreases the load on the network as results of the incremental update contributed by view-dependent rendering.

Throughout the design cycle, visualization, whether a sketch scribbled on the back of a spare piece of paper or a fully detailed drawing, has been the mainstay of design: we need to see the product. One of the most important stages of the design cycle is the initial, or concept, stage and it is here that design variants occur in large numbers to be vetted quickly. At this initial stage the human element, the designer is crucial to the success of the product. We describe an interactive environment for concept design which recognises the needs of the designer, not only to see the product and make rapid modifications, but also to monitor the progress of their design towards some preferred solution. This leads to the notion of a design parameter space, typically high-dimensional, which must also be visualized in addition to the product itself. Using a module developed for IRIS Explorer design steering is presented as a navigation of this space in order to search for optimal designs, either manually or by local optimisation.

We present a novel approach to surface reconstruction based on the Delaunay complex. First we give a simple and fast algorithm that picks locally a surface at each vertex. For that, we introduce the concept of ╬╗-intervals. It turns out that for smooth regions of the surface this method works very well and at difficult parts of the surface yields an output well-suited for postprocessing. As a postprocessing step we propose a topological clean up and a new technique based on linear programming in order to establish a topologically correct surface. These techniques should be useful also for many other reconstruction schemes.

Very large irregular-grid data sets are represented as tetrahedral meshes and may incur significant disk I/O access overhead in the rendering process. An effective way to alleviate the disk I/O overhead associated with rendering a large tetrahedral mesh is to reduce the I/O bandwidth requirement through compression. Existing tetrahedral mesh compression algorithms focus only on compression efficiency and cannot be readily integrated into the mesh rendering process, and thus demand that a compressed tetrahedral mesh be decompressed before it can be rendered into a 2D image. This paper presents an integrated tetrahedral mesh compression and rendering algorithm called Gatun, which allows compressed tetrahedral meshes to be rendered incrementally as they are being decompressed, thus leading to an efficient irregular grid rendering pipeline. Both compression and rendering algorithms in Gatun exploit the same local connectivity information among adjacent tetrahedra, and thus can be tightly integrated into a unified implementation framework. Our tetrahedral compression algorithm is specifically designed to facilitate the integration with an irregular grid renderer without any compromise in compression efficiency. A unique performance advantage of Gatun is its ability to reduce the runtime memory footprint requirement by releasing memory allocated to tetrahedra as early as possible.

Concerns the development of non-photorealistic rendering techniques for volume visualisation. In particular, we present two pen-and-ink rendering methods, a 3D method based on non-photorealistic solid textures, and a 2+D method that involves two rendering phases in the object space and the image space respectively. As both techniques utilize volume- and image-based data representations, they can be built upon a traditional volume rendering pipeline, and can be integrated with the photorealistic methods available in such a pipeline. We demonstrate that such an integration facilitates an effective mechanism for enhancing visualisation and its interpretation.