@InCollection{Cirscione-EGSV96-DAI, author = {Paola Criscione and Claudio Montani and Riccardo Scanteni and Roberto Scopigno}, title = {Disc{MC}: An Interactive System for Fast Fitting Isosurfaces on Volume Data}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {178--190}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {This paper describes the architecture of DiscMC, an interactive system which supports isosurfacing on regular volume datasets. DiscMC adopts a discretized fitting algorithm that considerably reduces the number of polygons generated by a Marching Cubes-like scheme while presenting shorter running times. The extracted surfaces are composed of polygons lying within a finite number of incidences, thus allowing simple merging of the output facets into large coplanar triangular facets. A pyramidal representation of the volume dataset has been adopted to speed-up isosurface fitting, by avoiding $empty$ volume traversal, and to support multiple level resolution fitting. The system has been implemented in a Unix environment, using a $de facto$ standard graphics library. The functionalities and the user interface of the system are described in detail.} } @InCollection{Weller-EGSV96-NNS, author = {Frank Weller and Robert Mencl}, title = {Nearest Neighbour Search for Visualization Using Arbitrary Triangulation}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {191--200}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {In visualization of scattered data, one is often faced with the problem of finding the nearest neighbours of a data site. This task frequently occurs in an advanced stage of the visualization process, where several data structures have been created during run time. Many applications compute a triangulation of the data for their visualization purposes. To take advantage of the previously allocated data structure we propose an algorithm for determining the $k$ nearest neighbours in a triangulated point set. As a benefit, this algorithm dynamically computes exactly as many neighbours as necessary for the specific application and does not assume a particular kind of triangulation. Furthermore, it works in any finite-dimensional, metric affine space.} } @InCollection{Sramek-EGSV96-FRT, author = {Milo{\v{s}} {\v{S}}r{\'a}mek}, title = {Fast Ray-Tracing of Rectilinear Volume Data}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {201--210}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {Tomographic devices often produce data with directionally and spatially dependent resolution. Resampling to cubic voxels is possible at the cost of significant increase of data volume and rendering time. We present an algorithm for direct ray tracing of rectilinear grids, which enables the implementation of surface rendering with subvoxel surface detection based on local interpolation, as well as different volume techniques (color compositing, re-projection, maximum intensity projection). Further we present a faster version of the basic algorithm, based on cubic macro-regions assigned to each background voxel. Each macro-region is defined by its chessboard distance to the nearest foreground voxel and can be skipped during the scene traversal. The speed-up is this gained by increasing the step along the ray, maintaining 6-connectivity of the ray in the object vicinity, which is necessary for correct surface detection.} } @InCollection{Smit-EGSV96-MVR, author = {J. Smit and M. Bosma and J. T. van Scheltinga}, title = {Metric Volume Rendering}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {211--222}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {To what extent can the exact size and form of an object be reconstructed from volume data? Why can the rendering of a 3D dataset performed with a super-resolution volume rendering algorithm be magnified beyond the dimensions of the individual voxels without introduction of artifacts and/or unsharpness? These topics are covered with clear examples and new ways tto present fundamental issues related to the reconstruction of the 3D objects from grey-values on a 3D grid. Application areas are 3D rendering of medical, seismic and geometrical data, as well as rendering of surface textures.} } @InCollection{Fruhauf-EGSV96-VVP, author = {Thomas Fr{\"u}hauf Fan Dai}, title = {Scientific Visualization and Virtual Prototyping in the Product Development Process}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {223--233}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {In this paper we introduce our work within the DMU (Digital Mock-Up) project. The focus of this project is the development of the technology for replacing physical prototypes with virtual prototypes. In particular, we discuss the integration of scientific visualization into virtual prototyping. Fraunhofer-IGD has implemented the DMU demonstrator - we describe those parts of the demonstrator where scientific visualization functionality was incorporated. Furthermore, IGD has carried out separate 'virtual prototyping' projects with two german car manufacturers where we realized 'immersive data visualization'. We describe those projects and discuss the use and usefulness of virtual reality technology for scientific visualization.} } @InCollection{Happe-EGSV96-CGF, author = {R.-T. Happe and M. Rumph}, title = {Characterizing Global Features of Simulation Data by Selected Local Icons}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {234--242}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {Large datasets that represent complex physical phenomena require advanced tools that help to recognize and study the essential features. The local behavior of the numerical data in significant areas can provide insight in its global character. We present several types of icons, geometric objects, that symbolize selected local properties of the data, notably of flow fields and of deformation fields. Furthermore we discuss the choice of points where such icons should be placed.} } @InCollection{Haase-EGSV96-DRP, author = {Helmut Haase and Christoph Dohrmann}, title = {Doing it Right: Psychological Tests to Ensure the Quality of Scientific Visualization}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {243--256}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {This paper discusses a general scheme for determining the quality of scientific visualization systems. It presents psychological tests which have been performed in order to find quantitative relationships for this scheme, and discusses why simple numerical relationships may be hard to find. Our work is motivated by research into interactive and immersive scientific visualization which pose two opposing demands: maximum image quality at sufficient frame rates. We believe that these two factors also crucial for many other applications, e.g., virtual reality. For this scheme, special focus is on the user's perception of the system. Three components of Visualization System Quality are identified: Data quality, image quality, and interaction quality. In order to migrate from merely qualitative to a more quantitative model, psychological tests were performed to measure the influence of frame rate and rendering mode on the perception on visualized three dimensional vector data. Results of the tests are presented and general suggestions for good perceptual tests are made. We believe that the experience we gained will be of benefit to many who are interested in question of visualization system quality.} } @InCollection{Liere-EGSV96-CSE, author = {Robert van Liere and Jarke J. van Wijk}, title = {{CSE} : A Modular Architecture for Computational Steering}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {257--266}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {Computational steering is the ultimate goal of interactive simulation. Steering enables users to supervise and dynamically control the computation of an out going simulation. We describe CSE: a modular architecture for a computational steering environment. The kernel of the architecture is designed to be very simple, flexible and minimalistic. All higher level system functionality is pushed into modular components outside of the kernel, resulting in a rich and powerful environment. For these modular components (called satellites) a uniform interface metaphor for users based on a tray of cards, has been used. The card tray metaphor is very simple to understand and provides users with a simple mechanism to organize and retrieve the tools. Several applications of the environment are shown.} } @InCollection{Wright-EGSV96-DVP, author = {Helen Wright and Ken Brodlie and Martin Brown}, title = {The Dataflow Visualization Pipeline as a Problem Solving Environment}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {267--276}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {Visualization systems based on the dataflow paradigm are enjoying increasing popularity in the field of scientific computation. Not only do they permit rapid construction of a display application, but they allow simulation to be incorporated, giving the scientist the opportunity to interact with the calculation as well. However, if these systems are to realise their full potential for problem solving, additional support must be given for the iterative investigation which characterises this activity. This paper will review these systems, identify some of their shortcomings as problem solving environments and describe current work which addresses these deficiencies. An implementation of our ideas for IRIS Explorer system will demonstrate their effectiveness in a study of gas turbine exhaust emissions.} } @InCollection{Hajek-EGSV96-UHM, author = {Daniel Hajek and Jan Nouza}, title = {Unhidding Hidden Markov Models by their Visualization (Application in Speech Processing)}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {277--285}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {The hidden Markov model (HMM) technique has become very popular in the signal and data processing areas during the last 10 years. It is not easy, however, to understand its complex nature that is 'hidden' behind a 'veil' of two probability functions, one associated with the given space of data parameters and the other with the temporal data flow. Our system, named Visual Markov, aims at removing the veil by visualizing the continuous density HMM and displaying its individual states. Moreover, it is able to show the iterative process of HMM training, step after step. In a similar way, also the HMM based classification can be presented. The system is a highly illustrative tool that is well suited both for research and teaching purposes. In the article, we demonstrate its application in the speech recognition domain.} } @InCollection{Leeuw-EGSV96-VTF, author = {Willem C. de Leeuw and Frits H. Post and Remco W. Vaatstra}, title = {Visualization of Turbulent Flow by Spot Noise}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {286--295}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {Turbulent flow is often modelled using statistical models. In these models the flow is described using average velocity at a certain level of scale, and velocity variations at smaller scale are described bny some quantity indicating turbulence intensity. In this paper several methods are described which utilize spot noise texture to visualize turbulent flow modelled in this way. With spot noise the separate fields are combined in one visualization which shows both data fields and how they are related in an intuitively clear way. Different aspects of turbulent flow can be shown using different mappings. the utility of this approach will be shown in two hydrodynamical case studies.} } @InCollection{Grosso-EGSV96-FVM, author = {Roberto Grosso and Martin Schultz and Jan Kraheberger and Thomas Ertl}, title = {Flow Visualization for Multiblock Multigrid Simulations}, booktitle = {Virtual Environments and Scientific Visualization '96}, pages = {296--307}, publisher = {Springer-Verlag Wien}, year = 1996, ISBN = {3-211-82886-9}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and J. David and P. Slavik and J. J. van Wijk}, month = {April}, comment = {Scientific Visualization '96}, URL = {http://sgi.felk.cvut.cz/EGVISC96/}, abstract = {Multiblock multigrid finite volume methods based on hexahedral control volumes are computationally efficient and widely used for solving the Navier-Stokes equations. Due to the enormous amount of data generated during an instationary 3D simulation visualization plays an important role for problem analysis and development. Two different approaches for the interactive steering of multigrid computations in combination with the IRIS Explorer visualization package are investigated. The strategies for the visualization of complex multiblock grids which are presented are based on a new visualization data type, on a concept for the reusability of available visualization modules for curvilinear grids, and on a special algorithm for particle tracing, which does not depend on the connectivity information between blocks.} } @InCollection{Pang-VSC95-MFV, author = {Alex Pang and Michael Clifton}, title = {Metaphors for Visualization}, booktitle = {Visualization in Scientific Computing '95}, pages = {1--9}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {This paper investigates the use of several common objects such as spray cans, flashlights, carving knives, and others as metaphors for visualization. The motivation behind this work is to provide an intuitive and natural 3D interface such that users will view these objects as tools during the visualization process. To help achieve this goal, the selection of the object tools are derived from expressions commonly used during visualization. For example, "let's paint this (iso)surface red"; "cut away the front part of that volume"; "look at it from this angle"; "you get similar effects from an x-ray photo"; and "let's explore this data set". In this paper, we also extend the metaphor of cutting planes to allow the users to carve non-planar cross-sectional cuts through their data sets. This extension will directly benefit applications such as medical visualization where one might want to generate curved coronal cross-sections of lumbar spines; and in oceanography where one might want to compare numerical model output against data obtained along non-planar ship tracks.} } @InCollection{Frisken-VSC95-BVM, author = {Frisken Gibson, Sarah F.}, title = {Beyond Volume Rendering: Visualization, Haptic Exploration, an Physical Modeling of Voxel-based Objects}, booktitle = {Visualization in Scientific Computing '95}, pages = {9--24}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {This paper proposes the use of a voxel-based data representation not only for visualization, but also for physical modeling of objects and structures derived from volumetric data. Work in progress that demonstrates the utility of a voxel-based data format for modeling physical interactions between virtual objects is discussed, data structures that help to optimize storage requirements and preserve object integrity during object movement are presented, and prototype systems are described. These prototypes include 2D and 3D systems that illustrate voxel-based collision detection and avoidance, a force-feedback system that enables haptic, (or tactile). exploration of virtual objects, and a 2D system that illustrates interactive modeling of deformable voxel based-objects.} } @InCollection{Schmidt-VSC95-OVA, author = {T. Schmidt and R. R{\"u}hle}, title = {On-line Visualization of Arbitrary Unstructured, Adaptive Grids}, booktitle = {Visualization in Scientific Computing '95}, pages = {25--34}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, comment = {Scientific Computing '95}, URL = {}, abstract = {Computational simulations for complex geometries nowadays often deal with unstructured grids. That's why scientific visualization must also be extended to these grid types. A visualization system is presented which work with any type of unstructured grids, i.e. arbitrary polygonal and polyhedral grids. Results from finite volume (cell-centered) and finite element methods cn be visualized. Additionally time-dependent data can be processed and interpolation between time steps is possible. This data may be transfered directly from a simulation program and therefor on-line visualized. To integrate this task into a computational simulation an object-oriented interface is presented which allows easy connection of simulation and visualization.} } @InCollection{Rumph-VSC95-OUV, author = {Martin Rumpf and Alfred Schmidt and Kunibert G. Siebert}, title = {On a Unified Visualization Approach for Data form Advanced Numerical Methods}, booktitle = {Visualization in Scientific Computing '95}, pages = {35--44}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {Recent numerical methods to solve partial differential equations in scientific computing are based on a variety of advanced kinds of domain discretizations and appropriate finite dimensional function spaces for the solutions. The scope of grids under consideration includes structured and unstructured, adaptive and hierarchical, conforming and nonconforming meshes. The functions spaces might be of Lagrangian or Hermitian type with higher polynomial degree and possibly discontinuous over element boundaries. Unfortunately, the rendering tools in scientific visualization are mostly restricted to special data structures which differ substantially from the data formats used in the numerical application. This forces users to map and interpolate their data, which is time consuming, storage extensive, and accompanied with interpolation errors. We present an interface between numerical methods on various types of grids and general visualization routines which overcome most of these disadvantages. It is based on a procedural approach managing a collection of arbitrary elements and a set of functions describing each element type.} } @InCollection{Fruhauf-VSC95-ROI, author = {Thomas Fr{\"u}hauf}, title = {Raycasting with Opaque Isosurfaces in Nonregularly Gridded {CFD} Data}, booktitle = {Visualization in Scientific Computing '95}, pages = {45--57}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {Direct volume rendering (DVR) is becoming more and more useful for graphical analysis of computational fluid dynamics (CDF) data, because of the extremely huge datasets that are generated with today's supercomputers. However, only semi-transparent visualizations have been produced via DVR from nonregularly gridded simulation data so far. Such images provide no information about the data distribution in the viewing direction. This paper reports our realisation of opaque an combined semi-transparent/opaque raycasting in nonregular grids. We emphasize on the mapping process, on the colour accumulation, and on the shading of isosurfaces. The generated images provide both holistic information and cues about spatial data distribution in the viewing direction. We use the same interpolating functions in the visualization algorithms as they are used in the data generation with the Finite Element method. Therefore, the rendered isosurfaces reveal interesting features that cannot be seen when isosurfaces are extracted directly with simplier algorithms.} } @InCollection{Cignoni-VSC95-OOP, author = {P. Cignoni and C. Montani and D. Sarti and R. Scopigno}, title = {On the Optimization of Projective Volume Rendering}, booktitle = {Visualization in Scientific Computing '95}, pages = {58--71}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {How to render very complex datasets, and yet maintain interactive response times, is a hot topic in volume rendering. In this paper we focus on projective visualization of datasets represented via tetrahedral tessellations. Direct projective visualization is performed by sorting tetrahedra with respect to view direction and then by projecting them onto the screen. Different sorting algorithms and "per tetrahedra" projection techniques are reviewed and evaluated. A new method for tetrahedra projection approximation is presented. In addition, we compare the results obtained by the optimization of the rendering process with those obtained by adopting a data simplification approach.} } @InCollection{Rau-VSC95-DVR, author = {Ren{\'e} T. Rau and Wolfgang Stra{\ss}er}, title = {Direct Volume Rendering of Irregular Samples}, booktitle = {Visualization in Scientific Computing '95}, pages = {72--80}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {Visualization of concentrations and density values is one of the main tasks of volume rendering systems. Whenever the sample points are not located on any structured grid most visualization tools are not able to display the data without expensive resampling. We show that a simple forward mapping algorithm can handle this problem efficiently, whenever the reconstruction of the volume function uses spherical kernels. Different examples are discussed and we visualize a simulation of astrophysics which is based on smoothed particle hydrodynamics. Here gas dynamical processes are irregular an d vary strongly in time. We produced high quality images which display the simulation data correctly and showed that in this situation our approach is superior to resampling strategies.} } @InCollection{Grosso-VSC95-BWF, author = {Roberto Grosso and Thomas Ertl}, title = {Biorthogonal Wavelet Filters for Frequency Domain Volume Rendering}, booktitle = {Visualization in Scientific Computing '95}, pages = {81--95}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {Rendering images from three-dimensional discrete data sets usually involves interpolation between samples. In terms of signal processing theory, common interpolation methods like trilinear and cubic interpolation are equivalent to the convolution of the sampled data with a suitably chosen reconstruction filter. Frequency domain volume rendering is a technique based on the Fourier projection-slice theorem for the efficient generation of line integral projection without absorption. The quality of the images relies almost completely on the quality of the interpolation filter for the extraction of a 2D slice from the 3D frequency domain representation of the volume. This paper presents experiences we obtained when implementing frequency domain volume rendering and investigates the use of scaling functions of biorthogonal wavelets as reconstruction filters that exhibit the required compact support in space and fast decay in the frequency domain. This method generates X-ray-like images with good quality and short rendering times. In order to accelerate the rendering process without much loss of image quality we introduce wavelets as a subband filtering scheme generating a hierarchical representation of the volume data with the potential for interactive data exploration.} } @InCollection{Zhang-VSC95-OPT, author = {Hansong Zhang and Shenquan Liu}, title = {Order of Pixel Traversal and Parallel Volume Ray-tracing on the Distributed Shared Volume Buffer}, booktitle = {Visualization in Scientific Computing '95}, pages = {96--105}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {The distributed shared volume buffer (DSVB) is a software package we developed to facilitate general, parallel volume ray-tracing on networked workstations. It is internally implemented with message-passing and adopts the cache-coherent shared memory model. Thus the cache efficiency of volume data access is of utter importance to the performance of a DVSB-based ray-tracer. For a given data set, the data access behavior of a volume ray-tracer depends mostly on the way in which pixels of the image are traversed. This paper addresses the cache coherence problem and compares three kinds of pixel traversals order: one-way, two-way and along a space filling curve (e.g. a Hilbert curve) greatly enhances cache efficiency especially when size of the cache is small compared to that of the volume data, and in the meantime greatly simplifies task distribution and management.} } @InCollection{Fischel-VSC95-VLS, author = {Georg Fischel and Eduard Gr{\"o}ller}, title = {Visualization of Local Stability of Dynamical Systems}, booktitle = {Visualization in Scientific Computing '95}, pages = {106--125}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {Several methods for visualizing local stability properties of dynamical systems are presented. The calculation of the characteristic values of local stability for linear and nonlinear system is discussed. Two principles of visualizing local stability are introduced. The principle is to display the estimated stability values directly by using scaled spheres or vectors. The second principle uses numerical analysis which generates portions of sweeps, that are deformed in dependence of local stability properties.} } @InCollection{Mulder-VSC95-LCS, author = {Jurriaan D. Mulder and Jarke J. van Wijk}, title = {Logging in a Computational Steering Environment}, booktitle = {Visualization in Scientific Computing '95}, pages = {118-125}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {Logging of input and output variables s very useful in computational steering. In this paper we describe how we added logging functionality to a computational steering environment developed at CWI. We show how a 2D interface can be augmented with logging by using the third dimension for the display of the logged variables. The user specifies which graphical representations of variables must be logged, and this log is displayed together with the current state of the simulation. Two examples show that logging computational steering gives more insight in the simulation, that can be used for monitoring, and that it can be used to undo erroneous actions.} } @InCollection{Leone-VSC95-VIC, author = {Andrea O. Leone and Riccardo Scateni}, title = {Visualization of Internal Combustion Simulations in a Modular Environment}, booktitle = {Visualization in Scientific Computing '95}, pages = {126--134}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {We describe here a solution to the problem of visualizing the results of simulations of a combustion chamber in a power plant. We used for this a modular visualization environment: Iris Explorer. We sketch first the fluid-dynamics problem to solve, and then focus our attention on how to face the visualization problems, especially how to visualize several different scalar fields at the same time. Then we describe our proposed environment for the solution with the description of several new modules for Iris Explorer we implemented describing their advantages and disadvantages. Finally, we talk about the possible future evolution of the project.} } @InCollection{Leeuw-VSC95-VSE, author = {Willem C. de Leeuw and Hans-Georg Pagendarm and Frits H. Post and Brigit Waltzer}, title = {Visual Simulation of Experimental Oil-Flow Visualization by Spot Noise from Numerical Flow Simulation}, booktitle = {Visualization in Scientific Computing '95}, pages = {135--148}, publisher = {Springer-Verlag Wien}, year = 1995, ISBN = {3-211-82729-3}, ISNN = {0946-2767}, editor = {R. Scanteni and J. van Wijk and P. Zanarini}, month = {May}, abstract = {Comparative visualization of data from different sources provides useful presentations to highlight similarities or differences. Such methods are valuable for comparing results from numerical flow simulations with images taken during windtunnel experiments. The experimental flow visualization technique represents the surface flow field with oil streaks. we visualized the numerical surface flow field using the spot noise technique. The flow data are pre-processed and the parameters of the spot noise texture are tuned to enhance similarity of the resulting images. The result is a 'visual simulation', based mainly on the choice of the quantities to be visualized and the mapping of these quantities to the spot noise parameters. Analysis of the relation between pre-processing steps and the visualization parameters allows conclusions about the important mechanisms in the experimental flow visualization technique. besides the comparison of numerical data and the windtunnel experiment, the comparative visualization also provides insight into the visualization techniques involved.} } @InCollection{Jones-VSC94-FCO, author = {Mark. W. Jones and Min Chen}, title = {Fast Cutting Operations on Three Dimensional Volume Datasets}, booktitle = {Visualization in Scientific Computing}, pages = {1--8}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {This paper is concerned with high quality volume visualization with additional emphasis on real time cutting operations for displaying surface interiors. In many applications, it is necessary for a user to interactively perform cutting operations on a volume dataset in order to see different parts of the data. A method for implementing such operations. together with a direct surface rendering algorithm, has been developed and results have demonstrated its efficiency in comparison with existing methods.} } @InCollection{Ellsiepen-VSC94-PIL, author = {Peter Ellsiepen}, title = {Parallel Isosurfacing in Large Unstructured Datasets}, booktitle = {Visualization in Scientific Computing}, pages = {9--23}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {In this paper, we address the problem of constructing isosurfaces in unstructured grids as arise, for example, as results of simulations using the 3D Finite Element Method (FEM). In interactive visualization, a tradeoff always has to be made between speed and accuracy. we let the user control this tradeoff in the following way. We decompose the isosurface construction into a number of logical processing steps: at each step, the user can set parameters to control speed or accuracy. In order to keep interactivity even when handling compute-intensive actions, we propose a parallelisation/distribution scheme - applied to the construction of isosurfaces as a "test case" - featuring the distribution of work to general purpose computers (single- or multi-processor) connected to the visualization workstation via a local or wide area network (LAN/WAN), as well as an automatic dynamic load balancing scheme.} } @InCollection{Werner-VSC94-HSO, author = {Andereas Werner and Ulrich Lang}, title = {Hierarchical Splatting on a Massively Parallel System}, booktitle = {Visualization in Scientific Computing}, pages = {24--34}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {This paper presents a distributed volume rendering algorithm along with the results of an implementation on the Intel Paragon MPP system. The algorithm works with a distributed non-equidistant orthogonal dataset. It distributes most of the work to the parallel nodes to achieve fast high-quality rendering of high-resolution 3D datasets. The data fields remain unchanged so that the algorithm could use shared memory access to a distributed numerical code. The nodes render their individual data space independently and generate their own sub-images. The final image is composed by a parallel overlaying procedure.} } @InCollection{Max-VSC94-OMV, author = {Nelson Max}, title = {Optical Models for Volume Rendering}, booktitle = {Visualization in Scientific Computing}, pages = {35--40}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {This paper reviews several different models for light interaction with volume densities of absorbing, glowing, reflecting, or scattering material. They include absorption only, glow only, and multiple scattering. The models are derived from differential equations, and illustrated on a data set representing a cloud.} } @InCollection{Zahlten-VSC94-RBB, author = {Cornelia Zahlen and Hartmut J{\"u}rgens and Hans-Otto Peitgen}, title = {Reconstruction of branching blood vessels from {CT}-data}, booktitle = {Visualization in Scientific Computing}, pages = {41--53}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {A method is proposed to extract tree-like objects from sliced three dimensional data sets and to model their bifurcation structure and hierarchy. Starting from a seed voxel, the algorithm expands stepwise within the object and alignes the direction of each step with the local direction of the tree. Bifurcations are recognized from the increasing number of connected components found per step. While traversing the structure of interest, a symbolic tree is generated which corresponds to the voxel-based reconstruction and which serves for interactive identification of sub-branches, their selection and specific coloring.} } @InCollection{Leeuw-VSC94-SVV, author = {Willem C. de Leeuw and Frits H. Post}, title = {A Statistical View on Vector Fields}, booktitle = {Visualization in Scientific Computing}, pages = {53--62}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {Large vector data sets are of such complexity that reduction of the data is unavoidable, before they can be presented to the user. Common visualization techniques reducing the amount of data are: showing local data using particles or streamlines. In this paper methods for reduction available from statistics are discussed. Combined with techniques for the selection of a region in the data space, these methods can be used to present the data in a uniform way for an arbitrary subset of the data. Techniques are presented for the calculation and presentation of statistically derived quantities.} } @InCollection{Groller-VSC94-AVT, author = {Eduard Gr{\"o}ller}, title = {Application of Visualization Techniques to Chaotic Dynamical Systems}, booktitle = {Visualization in Scientific Computing}, pages = {63--71}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {Visualization provides powerful tools for investigation of dynamical systems. The application of various visualization techniques to chaotic dynamical systems is discussed.The interactive specification and modification of strange attractors allow easier understanding of the underlying dynamics. Graphical time series analysis visualizes time series and phase space reconstruction techniques. Finally advanced visualization techniques are employed to illustrate shape and chaotic properties of strange attractors.} } @InCollection{Ruprecht-VSC94-FGS, author = {Detlef Ruprecht and Heinrich M{\"u}ller}, title = {A Framework for Generalized Scattered Data Interpolation}, booktitle = {Visualization in Scientific Computing}, pages = {72--86}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {A generalization of scattered data interpolation for arbitrary sets of data is presented that allows better interpolation in situations where non-punctulate constraints are presented. A generalized point-set-metric is introduced which allows adaption of distance weighted interpolation methods to the described generalization. The usefulness of the approach is demonstrated by examples.} } @InCollection{Palamidese-VSC94-ECD, author = {Patrizia Palemides and Giuseppe Muccioli and Giovanni Lombardi}, title = {Enhancing control on decoration and visualization of art worlds}, booktitle = {Visualization in Scientific Computing}, pages = {87--94}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {Humanities, such as the history of art and archaeology, are growing fields for visualization. These fields require a variety of flexible tools to perform such tasks as building and upgrading models of works of art, acquiring and integrating new data, representing subtle decorative features, and defining the visualizations which best highlight the temporal, spatial and historical dimensions of a monument. Hence the main requirement is the availability of useful interaction mechanisms to perform various operations. Our research focuses on two particular aspects: enhancing user control firstly on shading to improve the decorative actions; and secondly on navigation to improve access to the artistic model. These issues are challenging because the exact nature of decorating and visualizing worlds of artistic interest is not completely understood.} } @InCollection{Pagendarm-VSC94-CVA, author = {Hans-Georg Pagendarm and Frits H. Post}, title = {Comparative Visualization - Approaches and Examples}, booktitle = {Visualization in Scientific Computing}, pages = {95--108}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {Today most of the work reported in the field of visualization addresses methods to transform given data into an image. Comparison, if at all, is done by placing images side by side and let the eye and brain perform the task. This paper tries to illustrate the benefits of employing scientific visualization in an deliberately comparative manner. A rage of opportunities for comparison on the data level as well as on the image level and with respect to visualization methods is illustrated. Additionally, examples from fluid dynamics applications are used to demonstrate various comparative strategies.} } @InCollection{Erbacher-VSC94-IDI, author = {Rob Erbacher and Georges Grinstein}, title = {Issues in the Development of {3D} Icons}, booktitle = {Visualization in Scientific Computing}, pages = {109--123}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {This paper reports on an extension of the two-dimensional, perception-driven iconographic approach described in [GRI89, GRI90, LEV90a, LEV90b, LEV91, PIC88, PIC90a, PIC90b] to the visualization of multidimensional dat in three dimensions through the use of 3D icons. We briefly discuss geometric and color icons, explain its parameters and features, and demonstrate how this icon produces a 3D texture from a 2D domain. Finally, we provide application examples of this new icon using a variety of multidimensional data sets.} } @InCollection{Wijk-VSC94-TCI, author = {Jarke J. van Wijk}, title = {Time control in interactive scientific animation}, booktitle = {Visualization in Scientific Computing}, pages = {124--136}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {The use of animation in scientific visualization adds an extra dimension to the data, especially if the user steer the animation interactively. A number of applications of interactive scientific animation is presented. Scientific animation requires two types of control: refresh time control for the automatic update of the image, and user time control for the specification of the animation. Three techniques for refresh time control are presented: for data continuous in time, and for data at discrete time steps. The user interface of a typical application is discussed in detail. Three approaches are used: manipulation via a control panel, direct manipulation of a time graph, and keyboard accelerators. The combined use of a spatial and temporal views on the data proves to be very effective for the location and analysis of areas and time intervals of interest.} } @InCollection{Polthier-VSC94-CTD, author = {Konrad Polthier and Martin Rumph}, title = {A Concept for Time-Dependent Processes}, booktitle = {Visualization in Scientific Computing}, pages = {137--153}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {We develop a new concept to extend a static interactive visualization package to a time-dependent animation environment by reusing as many as possible of the existing static classes and methods. The discussion is based on an object-oriented mathematical programming environment and is applied to parameter-dependent structures, time-dependent adaptive geometries and flow computations but most of the ideas apply to other environments in scientific visualization too. We define new classes describing dynamic processes (including e.g. time-dependent adaptive geometries) and specify a protocol mechanism they must understand. This allows the definition of a class \emph{TimeNode} supervising an arbitrary dynamic processes as a time-dependent node in a formerly static data hierarchy. We discuss mechanisms such as time-dependent hierarchies, and additionally the problem of algorithms on time-dependent geometries in a number of examples.} } @InCollection{Fruhauf-VSC94-EIS, author = {Thomas Fr{\"u}hauf}, title = {Efficient {3D} Interaction With Scientific Data Using {2D} Input and Display Devices}, booktitle = {Visualization in Scientific Computing}, pages = {154--165}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {Direct user interaction with data allows to regain specific information about the data that is behind a certain part of the displayed image. Since scientific data is often three-dimensional and time-dependent, interaction and display techniques in visualization need to be adapted to 3D navigation. In this paper we present an interaction environment, called the STAGE, which has been developed with the boundary conditions of using conventional input and display devices, such as the mouse and the graphics screen without stereo rendering capabilities. Software solutions were found enabling an efficient navigation of probes through 3D data fields. Special attentions was given to the coherence of input and display signals, so that the navigation becomes 'natural' for the users. We integrated the STAGE interaction environment within a turnkey visualization system ICV (\emph{Interactive CFD Visualizer}), where it is applied in tasks like point probing or interactive particle tracing for flow visualization.} } @InCollection{Wright-VSC94-IEC, author = {Helen Wright and Gary A. Stead and Ken W. Brodie}, title = {Interactive exploration of chemical reaction mechanisms using novel visualization and integration techniques}, booktitle = {Visualization in Scientific Computing}, pages = {166--173}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {Conceptually, an evolving chemical system can be regarded as a trajectory in hyperspace, the number of dimensions of this space corresponding to the number of species taking part in the reaction. The problem of visualizing this trajectory is one perception; how many different variables can be assimilated simultaneously? This paper will describe novel visualization techniques and their incorporation into a problem solving environment, allowing the reaction chemist to obtain a qualitative view of their evolving system and to steer the calculations used to determine species' concentrations.} } @InCollection{Jern-VSC94-IRT, author = {Mikael Jern and Rae A. Earnshaw}, title = {Interactive Real-Time Visualization System using a Virtual Reality Paradigm}, booktitle = {Visualization in Scientific Computing}, pages = {174--189}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {This paper reviews existing graphics architecture software techniques for the visualization of numerical data. A new "next" generation 3D Data Visualization system based around a "Steering" and Virtual Reality paradigm is proposed, which appears to be the most promising in search for modern solution to the problem of interacting with large multi-dimensional datasets. Issues in visualization software include matching the software to the scientist's needs and requirements, integration of visualization and computation, usability of visualization software managing large datasets, handling multi-dimensional data, and real-time interaction. Also current research challenges include domain-specific data models, algorithm visualization, new visual programming paradigms, and 3D interaction techniques. The proposed new model for the scientific visualization pipeline enables the user to interact with the data displayed on the screen in real time. The user is able to explore very large data sets and interact with them directly and allow more direct exploitation in the context of virtual reality input.} } @InCollection{Arndt-VSC94-DVS, author = {Susanne Arndt and Kai Lukoschek and Heidrun Schumann}, title = {Design of a Visualization Support Tool for the Representation of Multidimensional Data Sets}, booktitle = {Visualization in Scientific Computing}, pages = {190--204}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {Lots of different methods and techniques have been developed to support the analysis, understanding and communication of models and conceptions of scientific data by means of Computer Graphics. The goal of our research was to support the user at the decision of choosing an appropriate visual representation for multi-dimensional data sets. The choice mechanism is based on the description of the visualization problem (data characteristics, interpretation aims of the user) as well as on the evaluation of the criteria expressiveness, effectiveness and appropriateness. For the representation itself we use the advantages of existing visualization systems.} } @InCollection{Saupe-VSC94-VFI, author = {Dietmar Saupe and Klaus Bayer}, title = {Visualizing Fractel Image Compression}, booktitle = {Visualization in Scientific Computing}, pages = {205--214}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {Fractal image compression makes use of self-similarity properties in the image data. The image data is segmented and for each segment a larger section of the image is sought which matches the given one as closely as possible up to some affine transformation. The collection of these transformations gives rise to a contractive image operator. The iteration of this operator starting with an arbitrary initial images converges towards a limiting image which is an approximation of the given target image. In their entirety the algorithms involved in the encoding and decoding of the image data are rather complex. The paper describes the results of our efforts to design and implement an interactive visualization system for the process of fractal image compression. The purpose of this task is twofold. The system aids the understanding of the complicated compression algorithms, thus, it is educational. On the other side it provides an interface to a current testbed for the development of fractal image compression algorithms. Thus, the action and performance of variations of algorithms can be studied visually using an algorithm animation system.} } @InCollection{Mulder-VSC94-SAG, author = {Jurriaan D. Mulder and Edo H. Dooijes}, title = {Spatial Audio in Graphical Applications}, booktitle = {Visualization in Scientific Computing}, pages = {215-229}, publisher = {Springer-Verlag Wien}, year = 1994, ISBN = {3-211-82633-5}, ISNN = {0946-2767}, editor = {M. G{\"o}bel and H. M{\"u}ller and B. Urban}, month = {May}, abstract = {The use of audio in human-computer interfaces is gaining much attention nowadays. A neglected issue in this regard is the fact that human beings perceive sounds in a spatial context. Simulated special sound presented over headphones has many potential uses in a number of fields, such as virtual reality and visualization. In this paper a simple experimental system for spatial sound simulation is presented, along with the results of several experiments that were conducted with this system. The system, called SAGA (Spatial Audio in Graphical Applications), was built to investigate the usability of spatial sound in a three-dimensional graphical applications such as visualization. Two primary uses of spatial sound in such applications are envisioned: (1) the active localization of virtual sound sources in a three-dimensional virtual environment in order to be able to move the point of view or a three-dimensional cursor two-wards this sound source, and (2) as an aid in the position determination of a cursor in a three-dimensional virtual environment. The results of the experiments conducted with the SAGA system show that the first use is very feasible, but the second will be more difficult to accomplish.} } @InProceedings{David:EGvis97-1, crossref = {EGvis97-proc}, author = {Jacques David and Michel Grave}, title = {WWW and Virtual Reality for Scientific Visualization}, abstract = {Visualization in scientific computing integrates many different computer technologies. Among them two are evolving rapidly: the World Wide Web and Virtual Reality. These issues were discussed during paper presentations, and were even more precisely debated during dedicated panel sessions in the Eighth Eurographics Workshop on ViSC. This paper summarises and consolidates information that circulated among participants, but also provides additional sources of information on these topics.}, pages = {1-7}} @InProceedings{Jern:EGvis97-9, crossref = {EGvis97-proc}, author = {Mikael Jern}, title = {Information Drill-down using Web Tools}, abstract = {The paper reviews the Information Visualization and interaction techniques needed to add another dimension to surfing the Web, Information drilling and interactive data querying, sometimes also referred to as Visual Data Mining. Information Visualization can be used to explore relationships by drilling down and retrieving more data within a region of interest in the visualized data, combining data mining, direct manipulation and data visualization with 3D Web tools. It is now possible to create desktop visualization applications that let users interact with databases with larger datasets over the network using both 2D and 3D interaction metaphors. The VRML standard allows users to view and navigate through 3D information data worlds and hyperlink to new worlds. Information drilling based on HTML's Image Map, VRML's anchor node and multiple predefined viewpoints will be explained and demonstrated. The image map in 2D and 3D graphics objects (glyphs etc) will represent the Visual User Interface to the information stored in the database. Also the advantages of using distributed component techniques based on plug-ins, Java Beans and ActiveX providing client-side data manipulation will be reviewed and illustrated. Over the next couple of years, we shall see 3D visualization evolve in giant steps into interactive data drilling on the Web providing visualization technology closely integrated with the data warehouse and multidimensional abstract and geospatial data models.}, pages = {9-20}} @InProceedings{Trapp:EGvis97-21, crossref = {EGvis97-proc}, author = {J.C. Trapp and H.-G. Pagendarm}, title = {A Prototype for a WWW-based Visualization Service}, abstract = {A WWW server accepts data from a user in order to produce a visualization of the data. The user can control the visualization algorithm over the network using a JAVA-based user-interface. The visualization is transferred back to the client as a VRML world file and is pushed to the VRML Viewer. The prototype solves principal technical problems and serves as a feasibility study for an open service provided to WWW users and a platform independant access to visualization methods.}, pages = {21-30}} @InProceedings{Teitzel:EGvis97-31, crossref = {EGvis97-proc}, author = {Christian Teitzel and Roberto Grosso and Thomas Ertl}, title = {Efficient and Reliable Integration Methods for Particle Tracing in Unsteady Flows on Discrete Meshes}, abstract = {In real applications the velocity field of a flow is not available in analytical but in discrete form. One goal of this paper is to analyze particle integration methods for diseretized data defined on meshes with regard to numerical efficiency and accuracy. Careful error analysis of the particle tracing process relates the error of velocity interpolation in space and time to the error of the numerical integration. Hence, a fast integration routine which provides accuracy similar to that of interpolation is necessary. This leads to a robust integration routine with adaptive step size control and error monitoring. A second aspect of this work is the treatment of stiff problems. Stiffness occurs in flows with strong shear deformations or vorticity. To detect stiffness in a given flow field, the Jacobian of the velocity field is alialyzed. Implicit integration methods are used to handle stiff systems of ordinary differential equations.}, pages = {31-42}} @InProceedings{Jobard:EGvis97-43, crossref = {EGvis97-proc}, author = {Bruno Jobard and Wilfrid Lefer}, title = {Creating Evenly-Spaced Streamlines of Arbitrary Density}, abstract = {This paper presents a new evenly-spaced streamlines placement algorithm to visualize 2D steady flows. The main technical contribution of this work is to propose a single method to compute a wide variety of flow field images, ranging from texture-like to hand-drawing styles. Indeed the control of the density of the field is very easy since the user only needs to set the separating distance between adjacent streamlines, which is related to the overall density of the image. We show that our method produces images of a quality at least as good as other methods but that it is computationally less expensive and offers a better control on the rendering process}, pages = {43-56}} @InProceedings{Sprenger:EGvis97-71, crossref = {EGvis97-proc}, author = {T. C. Sprenger and M. H. Gross and A. Eggenberger and M. Kaufmann}, title = {A Framework for Physically-Based Information Visualization}, abstract = {The following paper describes a framework for the visualization and analysis of economic data. It can be employed in the context of risk analysis, stock prediction and other tasks being important in the context of banking. The system bases on a quantification of the similarity of related objects, which governs the parameters of a mass-spring system, organized as two concentric spheres. More specifically, we initialize all information units onto the surface of the inner sphere and attach them with springs to the outer sphere. Since the spring stiffnesses correspond to the computed similarity measures, the system converges into an energy minimum, which reveals multidimensional relations and adjacencies in terms of spatial neighborhoods. In order to simplify complex setups we propose an additional clustering algorithm for postprocessing. Furthermore, depending on the application scenario we support different topologic arrangements of related objects. In addition, we implemented various intecaction techniques allowing semantic analysis of the underlying data sets. The versatility of our approach is illustrated by two examples, namely a comparison of agricultural productivity and an analysis of the relation between interest rates and other economic data.}, pages = {71-84}} @InProceedings{Reinders:EGvis97-85, crossref = {EGvis97-proc}, author = {Freek Reinders and Frits H. Post and Hans J.W. Spoelder}, title = {Feature Extraction from Pioneer Venus OCPP Data}, abstract = {Scientific visualization provides means to explore data and highlight interesting features in the data. In this paper we will discuss the visualization of astrophysical data. Light properties of sunlight scattered by the atmosphere of Venus were measured by the Pioneer Venus Orbiter. One of the objectives of this mission was to determine the properties of the clouds and haze in the atmosphere. Given the amount and complexity of the data, it is important to be able to browse through the data and select maps with interesting features. We built a system that reads the raw data, prepares it and extracts cloud features. The feature extraction is achieved by the following steps: selection, clustering, attribute calculation and iconic mapping. After data exploration a number of consecutive images with coherent moving cloud features, is found. From the center position and the time between two frames, a qualitative measure for the cloud velocities is decived. The obtained velocities are well in correspondence with generally accepted results. Thus we have showed that visualization techniques are powerful tools to browse through the data, rcognize cloud features and determine the motions of the features in time. Keywords: scientific visualization, feature extraction, data exploration, astrophysical data.}, pages = {85-94}} @InProceedings{Klimenko:EGvis97-95, crossref = {EGvis97-proc}, author = {Stanislav Klimenko and Igor Nikitin and Martin G{\"o}bel and M. Tramberend}, title = {Visualization in topology: assembling the projective plane}, abstract = {Assembling the projective plane in 3D space from a M{\"o}bius band and a disc is animated. Various properties and representations of the projective plane are visualized.}, pages = {95-104}} @InProceedings{Lurig:EGvis97-105, crossref = {EGvis97-proc}, author = {Christoph L{\"u}rig and Roberto Grosso and Thomas Ertl}, title = {Combining Wavelet ansform and Graph Theory for Feature Extraction and Visualization}, abstract = {In the process of visualizing 3D MRI or CT data rzsing techniques such as isosurfacing or direct volume rendering, one is confronted with two problems. Tlze first one is that there is no distinction between important and unimportant data. The second one is the difficulty to find a meaningful mapping of the measured scalar values to the graphical attributes used for the visualization. These problems are addressed by the special segmentation procedure presented in this paper. The basic idea is to apply graph algorithms to find important structures and to assign multidimensional information to these structures with the help of wavelets. This additional information can be used to generate graphical attributes for rendering. Several aspects emerge from the interaction of both theoretical concepts.}, pages = {105-114}} @InProceedings{Subramanian:EGvis97-115, crossref = {EGvis97-proc}, author = {Kalpathi R. Subramanian and Dina M. Lawrence and M. Taghi Mostafavi}, title = {Interactive Segmentation and Analysis of Fetal Ultrasound Images}, abstract = {The ability of ultrasound scanners to image anatomical structures in real time have led to their use in two important applications of medicine, (1) for monitoring the unborn baby (fetal ultrasound), and, (2) coronary treatment of blockages in blood vessels (intravascular ultrasound). The generated images (in the form of a continuous video) are typically noisy and contain numerous artifacts, making it difficult to isolate and measure features of interest. We explore the use of two algorithms, region growing and a variant of split/merge algorithm for segmenting sequences of fetal ultrasound images. We describe an interactive system that can rapidly process and segment an arbitrary number of features. The system exploits frame to frame coherence for accelerating the segmentation process while at the same time combining ttie strengths of these algorithms and some post-processing for accurate and robust detection of features.}, pages = {115-124}} @InProceedings{Neubauer:EGvis97-125, crossref = {EGvis97-proc}, author = {R. Neubauer and M. Ohlberger and M. Rumpf and R. Schw{\"o}rer}, title = {Efficient Visualization of Large-Scale Data on Hierarchical Meshes}, abstract = {A multi-resolution approach is presented for data on a large class of hierarchical and nested grids. It is based on a procedural interface and a set of hierarchical and adaptive visualization methods. Such a method consists of a recursive traversal of mesh elements from the grid hierarchy combined with an adaptive stopping according to some error indicator which is closely related to the visual impression of data smoothness. During this traversal user data is only temporarily and locally addressed on single elements. No in advance mapping onto prescribed formats is necessary. The user only has to supply a set of element access routines as an interface to his specific data structures. As no extra storage is required, also large, economically stored computational grids can be handled on workstations with moderate local memory. Significant examples illustrate the applicability and efficiency on different types of meshes.}, pages = {125-138}} @InProceedings{Wegenkittl:EGvis97-139, crossref = {EGvis97-proc}, author = {Rainer Wegenkittl and Eduard Gr{\"o}ller}, title = {Simulation of Differential Interferometry and Comparison with Experimental Results}, abstract = {This paper presents the computational simulation of a differential interferometer in a Mach-Zehnder arrangement with objects located outside the center of the interferometer. The computer simulation corresponds well to an experimental setup. This is illustrated for several basic phase objects. The theoretical models of these objects are discussed. The concept of an interactive visualization system for the analysis of phase objects is presented and finally some results allowing a comparison between experimental and simulated interferograms are shown.}, pages = {139-154}} @InProceedings{Loffelmann:EGvis97-155, crossref = {EGvis97-proc}, author = {Helwig L{\"o}ffelmann and Lukas Mroz and Eduard Gr{\"o}ller}, title = {Hierarchical Streamarrows for the Visualization of Dynamical Systems}, abstract = {Streamarrows are a technique to enhance the use of streamsurfaces by separating arrow-shaped portions from the remaining streamsurface. We present a hierarchical streamarrows algorithm as an extension to this technique: Streamarrows are locally chosen from a stack of scaled streamarrows textures to avoid too big or small streamarrows in the rendered image. We furthermore present techniques how streamarrows can be extended into 3D, namely perpendicular to the streamsurface: streamarrows can be shifted slightly out of the streamsurface. Another extension in this category is to represent the outline of streamarrows as 3D tubes. We show a set of images which have been rendered using this technique and report about ongoing research. Keywords: Visualization, dynamical systems, streamsurfaces.}, pages = {155-164}} @InProceedings{Mulder:EGvis97-165, crossref = {EGvis97-proc}, author = {Jurriaan D. Mulder and Jarke J. van Wijk}, title = {Parametrizable Cameras for 3D Computational Steering}, abstract = {We present a method for the definition of multiple views in 3D interfaces for computational steering. The method uses the concept of a point-based parametrizable camera object. This concept enables a user to create and configure multiple views on his custom 3D interface in an intuitive graphical manner. Each view can be coupled to objects present in the interface, parametrized to (simulation) data, or adjusted through direct manipulation or user defined camera controls. Although our focus is on 3D interfaces for computational steering we think that the concept is valuable for many other 3D graphics applications as well.}, pages = {165-176}} @Proceedings{EGvis97-proc, booktitle = {Visualization in Scientific Computing '97}, title = {Visualization in Scientific Computing '97}, note = {Proc.\ Eurographics Workshop, Boulogne-sur-Mer, France, April~28--30, 1997}, year = {1997}, editor = {W. Lefer and M. Grave}, series = {Eurographics}, publisher = {Springer-Verlag Wien New York}} @InProceedings{Frank:EGvis98-3, crossref = {EGvis98-proc}, author = {Frank, Karin and Ulrich Lang}, title = {Data-Dependent Surface Simplification}, abstract = {In Scientific Visualization, surfaces have often attached data, e.g. cutting surfaces or isosurfaces in numerical simulations with multiple data components. These surfaces can be e.g. the output of a marching cubes algorithm which produces a large number of very small triangles. Existing triangle decimation algorithms use purely geometric criteria to simplify oversampled surfaces. This approach can leM-`d to coarse representations of the surface in areas with high data gradients, thus loosing important information. In this paper, a data-dependent reduction algorithm for arbitrary triangulated surfaces is presented using besides geometric criteria a gradient approximation of the data to define the order of geometric elements to be removed. Examples show that the algorithm works sufficiently fast to be used interactively in a {VR} environment and allows relatively high reduction rates keeping a good quality representation of the surface.}, pages = {3-12}} @InProceedings{Klein:EGvis98-13, crossref = {EGvis98-proc}, author = {Klein, Reinhard and Stefan Gumhald}, title = {Data Compression of Multiresolution Surfaces}, abstract = {In this paper we introduce a new compressed representation for multiresolution models ({MRM}) of triangulated surfaces of {3D}-objects. Associated with the representation we present compression and decompression algorithms. Our representation allows us to extract the surface at variable resolution in time linear in the output size. It applies to {MRMs} generated by different simplification algorithms like local vertex deletion or edge and triangle collapse. The time required to transmit models over communication lines and the space needed to store the {MRMs} is signifi cantly reduced.}, pages = {13-24}} @InProceedings{Allamandri:EGvis98-25, crossref = {EGvis98-proc}, author = {Allamandri, Fabio and Paolo Cignoni, Claudio Montani and Roberto Scopigno}, title = {Adaptively Adjusting Marching Cubes Output to Fit A Trilinear Reconstruction Filter}, abstract = {The paper focuses on the improvement of the quality of iso-surfaces fitted on volume datasets with respect to standard {MC} solutions. The new solution presented improves the precision in the reconstruction proeess using an approach based on mesh refinement and driven by the evaluation of the trilinear reconstruction filter. The iso-surface reconstruction process is adaptive, to ensure that the complexity of the fitted mesh will not become excessive. The proposed approach has been tested on many datasets; we discuss the precision of the obtained meshs and report data on fitted meshes complexity and processing times.}, pages = {25-34}} @InProceedings{Schilling:EGvis98-35, crossref = {EGvis98-proc}, author = {Schilling, Andreas and Reinhard Klein}, title = {Fast Generation of Multiresolution Surfaces from Contours}, abstract = {Surface reconstruction from contours is an important problem especially in medical applications. Other uses include reconstruction from topographic data, or isosurface generation in general. The drawback of existing reconstruction algorithms from contours is, that they are relatively complicated and often have numerical problems. Furthermore, algorithms to generate multiresolution surface models do not exploit the special situation having contours. In this paper we describe a new robust and fast reconstruction algorithm from contours that delivers a multiresolution surface with controlled distance from the original contours. Supporting selective refinement in areas of interest, this multiresolution model can be handled interactively without giving up accuracy.}, pages = {35-46}} @InProceedings{Reinders:EGvis98-49, crossref = {EGvis98-proc}, author = {Reinders, Freek and Hans J.W. Spoelder and Frits H. Post}, title = {Experiments on the Accuracy of Feature Extraction}, abstract = {Feature extraction is an approach to visualization that extracts important regions or objects of interest algorithmically from large data sets. In our feature extraction process, high-level attributes are calculated for the features, thus resulting in averaged quantitative measures. The usability of these measures depends on their robustness with noise and their dependency on parameters like the density of the grid that is used. In this paper experiments are described to investigate the accuracy and robustness of the feature extraction method. Synthetic data is generated with predefined features, this data is used in the feature extraction procedure, and the obtained attributes of the feature are compared to the input attributes. This has been done for several grid resolutions, for different noise levels, and with different feature extraction parameters. We present the results of the experiments, and also derive a number of guidelines for setting the extraction parameters. Keywords: feature extraction, attribute calculation, experimental accuracy estimation.}, pages = {49-58}} @InProceedings{Loeffelmann:EGvis98-59, crossref = {EGvis98-proc}, author = {L{\"o}ffelmann, Helwig and Eduard Gr{\"o}ller}, title = {Enhancing the Visualization of Characteristic Structures in Dynamical Systems}, abstract = {We present a thread of streamlets as a new technique to visualize dynamical systems in three-dimensional space. A trade-off is made between solely visualizing a mathematical abstraction through lower-dimensional manifolds, i.e., characteristic structures such as fixed points, separatrices, etc., and directly encoding the flow through stream lines or stream surfaces. Bundles of streamlets are selectively placed near characteristic trajectories. An over-population of phase space with occlusion problems as a consequence is omitted. On the other hand, information loss is minimized since characteristic structures of the flow are still illustrated in the visualization. Keywords: visualization, dynamieal systems.}, pages = {59-68}} @InProceedings{Sadarjoen:EGvis98-71, crossref = {EGvis98-proc}, author = {Sadarjoen, I. Ari and Alex J. de Boer and Frits H. Post and Arthur E. Mynett }, title = {Patricle Tracing in {$\sigma$}-Transformed Grids using Tetrahedral 6-Decomposition}, abstract = {Particle tracing in curvilinear grids often employs decomposition, of hexahedral cells into 5 tetrahedra. This method has shortcomings when applied to {$\sigma$}-transformed grids; a grid type having strongly sheared cells, commonly used in hydrodynamic simulations. This paper describes an improved decomposition method into 6 tetrahedra. It is shown that this method is robust in {$\sigma$}-transformed grids, however large the shearing. Results are presented of applying the technique to a real world simulation. Comparisons are made between the accuracy and speed of the 5-decomposition and the 6-decomposition methods.}, pages = {71-80}} @InProceedings{Teitzel:EGvis98-81, crossref = {EGvis98-proc}, author = {Teitzel, Christian and Roberto Grosso and Thomas Ertl}, title = {Particle Tracing on Sparse Grids}, abstract = {These days sparse grids are of increasing interest in numerical simulations. Based upon hierarchical tensor product bases, the sparse grid approach is a very efficient one improving the ratio of invested storage and computing time to the achieved accuracy for many problems in the area of numerical solution of differential equations, for instance in numerical fluid mechanics. The particle tracing algorithms that are available so far cannot cope with sparse grids. Now we present an approach that directly works on sparse grids. As a second aspect in this paper, we suggest to use sparse grids as a data compression method in order to visualize huge data sets even on small workstations. Because the size of data sets used in numerical simulations is still growing, this feature makes it possible that workstations can continue to handle these data sets.}, pages = {81-90}} @InProceedings{Becker:EGvis98-91, crossref = {EGvis98-proc}, author = {Becker, Joachim and Martin Rumpf}, title = {Visualization of Time-Dependent Velocity Fields by Texture Transport}, abstract = {Vector field visualization is an important topic in scientific visualization. The aim is to graphically represent field data in an intuitively understandable and precise way, which should be closely related to the physical interpretation. A new tool, the texture transport method is presented, which especially applies to time-dependent velocity fields. It is based on an accurate numerical scheme for convection equations, which is used to compute Lagrangian coordinates in space time. These coordinates are then used as texture coordinates referring to some prescribed texture in the Lagrangian reference space. The method is combined with a reliability indicator. This indicator influences the final appearance of the texture and thereby leads to reliable visual information. At first the method applies to {2D} problems. It can be generalized to {3D}.}, pages = {91-102}} @InProceedings{Hubbold:EGvis98-105, crossref = {EGvis98-proc}, author = {Hubbold, Roger J. and David J. Hancock and Christopher J. Moore}, title = {Stereoscopic Volume Rendering}, abstract = {In this paper we describe the extension of a parallel, distributed, direct volume renderer for use with a novel auto-stereoscopic display. We begin by briefly describing the target application of our research, radiation therapy planning, why we believe that stereoscopic viewing may be helpful for this, and the design of our {DVR} system. We then report on some of the problems we have encountered, and the results we have obtained in experiments. These demonstrate that stereoscopic viewing is beneficial for perceiving depth in transparent {DVR} images. We illustrate the application of the system to the visualisation of prostate cancer treatment plans. Finally, we describe the use of head-tracking to implement {3D} stereo look-around.}, pages = {105-116}} @InProceedings{Haase:EGvis98-117, crossref = {EGvis98-proc}, author = {Haase, Helmut}, title = {Mirror, Mirror on the Wall, Who Has the Best Visualization of All? -- A Reference Model for Visualization Quality}, abstract = {What is a 'good' visualization, one which leads to desired insights? How can wei evaluate the quality of a scientific visualization or compare two visualizations (or visualization systems) to each other? In the following, the importance of considering the 'visualization context' is stressed. It consists of the prior knowledge of the user; the aims of the user; the application domain; amount, structure, and distribution of the data; and the available hardware and software. Then, six subqualities are identified: data resolution quality, semantic quality, mapping quality, image quality, presentation and interaction quality, and multi-user quality. The {$Q_{vis}$} reference model defines a weight value C (i.e., importance) and a quality value {$Q$} for each subquality. The {$Q_{vis}$} graph is introduced as a compact, easy to perceive representation of the so-defined visualization quality. An example illustrates all concepts. The reference model and the graph can help to evaluate visualizations and thus to further improve the quality of scientific visualizations.}, pages = {117-128}} @InProceedings{Sroubek:EGvis98-129, crossref = {EGvis98-proc}, author = {{\v{S}}roubek, Filip and Pavel Slav{\'\i}k}, title = {Three-Dimensional Visualization of Atomic Collision Cascades}, abstract = {The paper describes a new approach to the visualization of atomic collision cascades and using the interaction with visualized data. The collision cascade is a physical phenomenon initiated by bombarding the surface of a solid with accelerated atomic particles. The process evolves in time and therefore it is necessary to develop some tools that would allow to investigate and visualize the dynamics of the process. Such tools are classifiers (filters) that enable to select and visualize objects with specific dynamic properties. As the visualization has been done in a {3D} environment a question arises how to specify effectively and user friendly both the properties and the objects in the {3D} space. Several techniques are available that allow interaction in the {3D} space. It has been necessary to test some of these techniques and to determine which one is the most suitable for the given application class.}, pages = {129-138}} @Proceedings{EGvis98-proc, booktitle = {Visualization in Sientific Computing '98}, title = {Visualization in Sientific Computing '98}, note = {Proc.\ Eurographics Workshop, Blaubeuren, Germany, April~20--22, 1998}, year = {1998}, editor = {Bartz, D.}, series = {Eurographics}, publisher = {Springer-Verlag Wien New York}}