VisSym99: Joint Eurographics - IEEE TCVG Symposium on Visualization

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https://diglib.eg.org/handle/10.2312/406

Link to Springer Online Library: http://link.springer.com/book/10.1007/978-3-7091-6803-5
available here: Eurographics version of papers

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Procedural Shape Generation for Multi-dimensional Data Visualization
(Springer and The Eurographics Association, 1999) Ebert, David S.; Rohrer, Randall M.; Shaw, Christopher D.; Panda, Pradyut; Kulda, James M.; Roberts, D. Aaron; Gröller, E., Löffelmann, H., Ribarsky, W.
Visualization of multi-dimensional data is a challenging task. The goal is not the display of multiple data dimensions, but user comprehension of the multi-dimensional data. This paper explores several techniques for perceptually motivated procedural generation of shapes to increase the comprehension of multi-dimensional data. Our glyph-based system allows the visualization of both regular and irregular grids of volumetric data. A glyph`s location, 3D size, color, and opacity encode up to 8 attributes of scalar data per glyph. We have extended the system's capabilities to explore shape variation as a visualization attribute. We use procedural shape generation techniques because they allow flexibility, data abstraction, and freedom from specification of detailed shapes, We have explored three procedural shape generation techniques: fractal detail generation, superquadrics, and implicit surfaces. These techniques allow front 1 to 14 additional data dimensions to be visualized using glyph shape.
Real-Time Maximum Intensity Projection
(Springer and The Eurographics Association, 1999) Mroz, Lukas; König, Andreas; Gröller, Eduard; Gröller, E., Löffelmann, H., Ribarsky, W.
Maximum Intensity Projection (MIP) is a volume rendering technique which is used to extract high-intensity structures from volumetric data. At each pixel the highest data value encountered along the corresponding viewing ray is determined. MIP is commonly used to extract vascular structures from medical MRI data sets (angiography). The usual way to compensate for the loss of spatial and occlusion information in MIP images is to view the data from different view points by rotating them. As the generation of MIP is usually non-interactive, this is done by calculating multiple images offline and playing them back as an animation. In this paper a new algorithm is proposed which is capable of interactively generating Maximum Intensity Projection images using parallel projection and templates. Voxels of the data set which will never contribute to a MIP due to their neighborhood are removed during a preprocessing step. The remaining voxels are stored in a way which guarantees optimal cache coherency regardless of the viewing direction. For use on low-end hardware, a preview-mode is included which renders only more significant parts of the volume during user interaction. Furthermore we demonstrate the usability of our data structure for extensions of the MIP technique like MIP with depth-shading and Local Maximum Intensity Projection (LMIP).
VISSION: An Object Oriented Dataflow System for Simulation and Visualization
(Springer and The Eurographics Association, 1999) Telea, Alexandru; Wijk, Jarke J. van; Gröller, E., Löffelmann, H., Ribarsky, W.
Scientific visualization and simulation speciification and monitoring are sometimes addressed by object-oriented environments. Even though object orientation powerfully and elegantly models many application domains, integration of 00 libraries in such systems remains a difficult task. The elegance and simplicity of object orientation is often lost in the integration phase, so combining 00 and dataflow concepts is usually limited. We propose a system for visualization and simulation with a generic object-oriented way to simulation design, control and interactivity, which merges 00 and dataflow modelling in a single abstraction. Advantages of the proposed system over similar tools are presented and illustrated by a comprehensive set of examples.
Analysis and Visualization of the Brain Shift Phenomenon in Neurosurgery
(Springer and The Eurographics Association, 1999) Lürig, C.; Hastreiter, P.; Nimsky, C.; Ertl, T.; Gröller, E., Löffelmann, H., Ribarsky, W.
In this paper we present a method for analyzing the brain shift. The brain shift is a brain deformation phenomenon, that occurs during surgical operations on the opened head. This deformation makes navigation within the brain very difficult for the surgeon, as preoperative magnetic resonance images invalidate very quickly after the beginning of the operation. Up to now not enough is known about this deformation phenomenon in order to come up with solutions for corrective action. The aim of the tool which is presented here is to prepare ground for a better understanding by visualizing the deformation between two 3D brain data sets, where one has been taken preoperatively and the second one during the operation after the brain shift has occured. We propose a new method for the modeling of the deformation by means of efficient distance determination of two deformable surface approximations. Color coding and semi-transparent overlay of the surfaces provides qualitative and quantitative information about the brain shift. The provided insight may lead to a prediction method in future.
2D Vector Field Visualization Using Furlike Texture
(Springer and The Eurographics Association, 1999) Khouas, Leila; Odet, Christophe; Friboulet, Denis; Gröller, E., Löffelmann, H., Ribarsky, W.
This paper presents a new technique for 2D vector field visualization. Our approach is based on the use of a furlike texture. For this purpose, we have first developed a texture model that allows two dimensional synthesis of 3D furlike texture. The technique is based on a non stationary two dimensional Autoregressive synthesis (2D AR). The texture generator allows local control of orientation and length of the synthesized texture (the orientation and length of filaments). This texture model is then used to represent 2D vector fields. We can use orientation, length, density and color attributes of our furlike texture to visualize local orientation and magnitude of a 2D vector field. The visual representations produced are satisfying since complete information about local orientation is easily perceived. We will show that the technique can also produce LIC-like texture. In addition, due to the AR formulation, the obtained technique is computationally efficient.
Interactive Direct Volume Rendering of Time-Varying Data
(Springer and The Eurographics Association, 1999) Clyne, John; Dennis, John M.; Gröller, E., Löffelmann, H., Ribarsky, W.
Previous efforts aimed at improving direct volume rendering performance have focused largely on time-invariant, 3D data. Little work has been done in the area of interactive direct volume rendering of timevarying data, such as is commonly found in Computational Fluid Dynamics (CFD) simulations. Until recently, the additional costs imposed by time-varying data have made consideration of interactive direct volume rendering impracticaL. We present a volume rendering system based on a parallel implementation of the Shear-Warp Factorization algorithm that is capable of rendering time-varying 128 3 data at interactive speeds.
Parallel Ray Casting of Visible Human on Distributed Memory Architectures
(Springer and The Eurographics Association, 1999) Bajaj, Chandrajit; Ihm, Insung; Koo, Gee-bum; Park, Sanghun; Gröller, E., Löffelmann, H., Ribarsky, W.
This paper proposes a new parallel ray-casting scheme for very large volume data on distributed-memory architectures. Our method, based on data compression, attempts to enhance the speedup of parallel rendering by quickly reconstructing data from local memory rather than expensively fetching them from remote memory spaces. Furthermore, it takes the advantages of both object-order and image-order traversal algorithms: It exploits object-space and image-space coherence, respectively, by traversing a min-max octrce block-wise and using a runtime quadtree which is maintained dynamically against pixels' opacity values. Our compression-based parallel volume rendering scheme minimizes conmUnications between processing elements during rendering, hence is also very appropriate for more practical distributed systems, such as dusters of PCs and/or workstations, in which data conmlUnications between processors are regarded as quite costly. We report experimental results on a Cray T3E for the Visible Man dataset.
On Simulated Annealing and the Construction of Linear Spline Approximations for Scattered Data
(Springer and The Eurographics Association, 1999) Kreylos, Oliver; Hamann, Bernd; Gröller, E., Löffelmann, H., Ribarsky, W.
We describe a method to create optimal linear spline approximations to arbitrary functions of one or two variables, given as scattered data without known connectivity.We start with an initial approximation consisting of a fixed number of vertices and improve this approximation by choosing different vertices, governed by a simulated annealing algorithm. In the case of one variable, the approximation is defined by line segments; in the case of two variables, the vertices are connected to define a Delaunay triangulation of the selected subset of sites in the plane. In a second version of this algorithm, specifically designed for the bivariate case, we choose vertex sets and also change the triangulation to achieve both optimal vertex placement and optimal triangulation. We then create a hierarchy of linear spline approximations, each one being a superset of all lower-resolution ones.
Efficient Ray Intersection for Visualization and Navigation of Global Terrain using Spheroidal Height-Augmented Quadtrees
(Springer and The Eurographics Association, 1999) Wartell, Zachary; Ribarsky, William; Hodges, Larry; Gröller, E., Löffelmann, H., Ribarsky, W.
We present an algorithm for efficiently computing ray intersections with multi-resolution global terrain partitioned by spheroidal height-augmented quadtrees. While previous methods support terrain defined on a Cartesian coordinate system, our methods support terrain defined on a two-parameter ellipsoidal coordinate system. This curvilinear system is necessary for an accurate model of global terrain. Supporting multi-resolution terrain and quadtrees on this curvilinear coordinate system raises a surprising number of complications.We describe the complex- ities and present solutions. The final algorithm is suited for interactive terrain selection, collision detection and simple LOS (line-of-site) queries on global terrain.
Skeletal Images as Visual Cues in Graph Visualization
(Springer and The Eurographics Association, 1999) Herman, I.; Marshall, M.S.; Melancon, G.; Duke, D.J.; Delest, M.; Domenger, J.-P.; Gröller, E., Löffelmann, H., Ribarsky, W.
The problem of graph layout and drawing is fundamental to many approaches to the visualization of relational information structures. As the data set grows, the visualization problem is compounded by the need to reconcile the user's need for orientation cues with the danger of information overload. Put simply: How can we limit the number of visual elements on the screen so as not to overwhelm the user yet retain enough information that the user is able to navigate and explore the data set confidently? How can we provide orientational cues so that a user can understand the location of the current viewpoint in a large data set? These are problems inherent not only to graph drawing but information visualization in general. We propose a method which extracts the significant features of a directed acyclic graph as the basis for navigation.
Attribute-Based Feature Tracking
(Springer and The Eurographics Association, 1999) Reinders, Freek; Post, Frits H.; Spoelder, Hans J. W.; Gröller, E., Löffelmann, H., Ribarsky, W.
Visualization of time-dependent data is an enormous task because of the vast amount of data involved. However, most of the time the scientist is mainly interested in the evolution of certain features. Therefore, it suffices to show the evolution of these features. The task of the visualization system is to extract the features from all frames, to track the features, i.e. to determine the correspondences between features in successive frames, and finally to visualize the tracking results. This paper describes a tracking system that uses feature data to track the features and to determine their evolution in time. The feature data consists of basic attributes such as position, size, and mass. For each set of attributes a number of correspondence functions can be tested which results in a correspondence factor. This factor makes it possible to quantify the goodness of the match between two features in successive time frames. Since the algorithm uses only the feature data instead of the grid data, it is feasible to perform an extensive multi-pass search for continuing paths.
Parallel Multipipe Rendering for Very Large Isosurface Visualization
(Springer and The Eurographics Association, 1999) Udeshi, Tushar; Hansen, Charles D.; Gröller, E., Löffelmann, H., Ribarsky, W.
In exploratory scientific visualization, isosurfaces are typi- cally created with an explicit polygonal representation for the surface using a technique such as Marching Cubes. For even moderate data sets, Marchching Cubes can generate an extraordinary number of poly- gons, which take time to construct, and to render. To address the ren- dering bottleneck, we have developed a multipipe strategy for parallel rendering using a combination of CPUs and parallel graphics adaptors. The multipipe system uses multiple graphics adapters in parallel, the so called SGI Onyx2 Reality Monster. In this paper, we discuss the issues of using the multiple pipes in a Sort-Last fashion which out performs a single graphics adaptor for a surprisingly low number of polygons.
Exploring Instationary Fluid Flows by Interactive Volume Movies
(Springer and The Eurographics Association, 1999) Glau, Thomas; Gröller, E., Löffelmann, H., Ribarsky, W.
Volume rendering offers the unique ability to represent inner object data and to realize enclosed structures ""at first glance"". Unlike software-based methods, the use of more and more available specialpurpose hardware allows volume rendering at interactive frame rates - a crucial criterion for acceptance in industrial applications,e,g. CFD analysis, Careful optimizations and the exclusive use of hardware-accelerated data manipulation facilities even enable volume rendered movies supporting real time interactivity. This article presents the most important features and implementation issues of an OpenInventor-based stereoscopic, VR-featured volume rendering system for instationary datasets.
Efficiently Rendering Large Volume Data Using Texture Mapping Hardware
(Springer and The Eurographics Association, 1999) Tong, Xin; Wang, Wenping; Tsang, Waiwan; Tang, Zesheng; Gröller, E., Löffelmann, H., Ribarsky, W.
Volume rendering with texture mapping hardware is a fast volume rendering method available on high-end workstations. However, limited texture memory often prevents the method from being used to render large volume data efficiently. In this paper, we propose a new approach to fast rendering of large volume data with texture mapping hardware. Based on a new volume-loading pipeline, the volume data is preprocessed in such a way that only the volume data that contains object voxels are loaded into texture memory and resampled for rendering. Moreover, if classification threshold is changed, our algorithm classifies and processes the raw volume data accordingly nearly in real time. Our tests show that about 40% to 60% rendering time is saved in our method for large volume data.
A Client-side Approach towards Platform Independent Molecular Visualization over the World Wide Web
(Springer and The Eurographics Association, 1999) Bender, Michael; Hagen, Hans; Seck, Axel; Gröller, E., Löffelmann, H., Ribarsky, W.
A web-based, entirely platform independent Molecular Visualization System has been developed using state of the Internet programming techniques. This system offers the visualization of various molecular models, molecular surfaces and molecular properties which can be displayed at the same time . The system itself has been developed using the Java programming language, which alIows flexible and platform independent use, perfect integration with the World Wide Web and due to its object-oriented structure easy extension and maintenance. All necessary calculations, e.g. the calculation of a Richards' Contact Surface or an lsosurface, take place on the client's side exploiting the computational power of modern desktop workstations and personal computers.
Geometric Methods for Vortex Extraction
(Springer and The Eurographics Association, 1999) Sadarjoen, I. Ari; Post, Frits H.; Gröller, E., Löffelmann, H., Ribarsky, W.
This paper presents two vortex detection methods which are based on the geometric properties of streamlines. Unlike traditional vortex detection methods, which are based on point-samples of physical quantities, one of our methods is also effective in detecting weak vortices. In addition, it allows for quantitative feature extraction by calculating numerical attributes of vortices. Results are presented of applying these methods to CFD simulation data sets.
New Approaches for Particle Tracing on Sparse Grids
(Springer and The Eurographics Association, 1999) Teitzel, Christian; Ertl, Thomas; Gröller, E., Löffelmann, H., Ribarsky, W.
Flow visualization tools based on particle methods continue to be an important utility of flow simulation. Additionally, sparse grids are of increasing interest in numerical simulations. In [14] we presented the advontages of particle tracing on uniform sparse grids. Here we present and compare two different approaches to accelerate particle tracing on sparse grids. Furthermore, a new approach is presented in order to perform particle tracing on curvilinear sparse grids. The method for curvilinear sparse grids consists of a modified Stencil Walk algorithm and especially adapted routines to compute, store, and handle the required Jacobians. The accelerating approaches are on the on hand an adaptive method, where an error criterion is used to skip basis functions with minor contribution coefficients, and on the other hand the so-called combination technique, which uses a specific selection of small full grids to emulate sparse grids.
Where Weather Meets the Eye - A Case Study on a Wide Range of Meteorological Visualizations for Diverse Audiences
(Springer and The Eurographics Association, 1999) Haase, H.; Bock, M.; Hergenröther, E.; Knöpfle, C.; Koppert, H.-J.; Schröder, F.; Trembilski, A.; Weidenhausen, J.; Gröller, E., Löffelmann, H., Ribarsky, W.
Sophisticated visualisation enables experts as well as lay persons to extract knowledge from complex data. This is particularly true for visualising the massive amounts of data involved in meteorological observations and simulations. These are of interest to scientists, to forecasters, and to the general public. The paper presents and discusses a range of solutions for meteorlogical visualisation. Topics covered include systems for the production of TV weather forecasts, for the analysis of simulation output by experts, for personalised weather information in the Web, and for meteorological visualisation using Virtual Studio and Augmented Reality technology.
Advances in Quality Control of Intraoperative Radiotherapy
(Springer and The Eurographics Association, 1999) Walter, Stefan; Straßmann, Gerd; Schmitt, Marco; Gröller, E., Löffelmann, H., Ribarsky, W.
Intraoperative radiotherapy is the kind of radiotherapy where the remains of a surgically not completely removed tumour are irradiated at the open situ of the patient. The current main drawback of this radiotherapy is the insufficient documentation of the applied radiation and the lack of a possibility for an individual treatment planning. This work presents a system that is a conmlon development of Fraunhofer IGD, Städtische Klinik Offenbach and MedCom GmbH which offers a possibility for supervision of the placement of the irradiation flabs through interactive navigation in eT data acquired from the patient, the creation of a documentation of the applied isodose as well as the possibility for an individual treatment planning.
Fast Volume Rotation using Binary Shear-Warp Factorization
(Springer and The Eurographics Association, 1999) Csebfalvi, Balazs; Gröller, E., Löffelmann, H., Ribarsky, W.
This paper presents a fast volume rotation technique based on binary shear-warp factorization. Unlike many acceleration algorithms this method does not trade image quality for speed and does not require any specialized hardware either. In order to skip precisciy the empty regions along the rays to be evaluated a binary volume is generated indicating the locations of the transparent cells. This mask is rotated by an incremental binary shear transformation, executing bitwisc boolean operations on integers storing the bits of the binary volume. The ray casting is accelerated using the transformed mask and an appropriate lookup-table technique for finding the first non-transparent cell along each ray.

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