@techreport{TR1862162, title = "Visual Analysis of Volume Ensembles Based on Local Features", author = "Johanna Schmidt and Bernhard Fr\"{o}hler and Reinhold Preiner and Johannes Kehrer and Eduard Gr\"{o}ller and Stefan Bruckner and Christoph Heinzl", year = "2016", abstract = "Ensemble datasets describe a specific phenomenon (e.g., a simulation scenario or a measurements series) through a large set of individual ensemble members. These individual members typically do not differ too much from each other but rather feature slightly changing characteristics. In many cases, the ensemble members are defined in 3D space, which implies severe challenges when exploring the complete ensembles such as handling occlusions, focus and context or its sheer datasize. In this paper we address these challenges and put our focus on the exploration of local features in 3D volumetric ensemble datasets, not only by visualizing local characteristics, but also by identifying connections to other local features with similar characteristics in the data. We evaluate the variance in the dataset and use the the spatial median (medoid) of the ensemble to visualize the differences in the dataset. This medoid is subsequently used as a representative of the ensemble in 3D. The variance information is used to guide users during the exploration, as regions of high variance also indicate larger changes within the ensemble members. The local characteristics of the regions can be explored by using our proposed 3D probing widgets. These widgets consist of a 3D sphere, which can be positioned at any point in 3D space. While moving a widget, the local data characteristics at the corresponding position are shown in a separate detail view, which depicts the local outliers and their surfaces in comparison to the medoid surface. The 3D probing widgets can also be fixed at a user-defined position of interest. The fixed probing widgets are arranged in a similarity graph to indicate similar local data characteristics. The similarity graph thus allows to explore whether high variances in a certain region are caused by the same dataset members or not. Finally, it is also possible to compare a single member against the rest of the ensemble. We evaluate our technique through two demonstration cases using volumetric multi-label segmentation mask datasets, two from the industrial domain and two from the medical domain.", month = may, number = "TR-186-2-16-2", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "ensemble visualization, guided local exploration, variance analysis", URL = "https://www.cg.tuwien.ac.at/research/publications/2016/TR1862162/", } @techreport{karimov-2016-SD, title = "Statistics-Driven Localization of Dissimilarities in Data", author = "Alexey Karimov and Gabriel Mistelbauer and Thomas Auzinger and Eduard Gr\"{o}ller", year = "2016", abstract = "The identification of dissimilar regions in spatial and temporal data is a fundamental part of data exploration. This process takes place in applications, such as biomedical image processing as well as climatic data analysis. We propose a general solution for this task by employing well-founded statistical tools. From a large set of candidate regions, we derive an empirical distribution of the data and perform statistical hypothesis testing to obtain p-values as measures of dissimilarity. Having p-values, we quantify differences and rank regions on a global scale according to their dissimilarity to user-specified exemplar regions. We demonstrate our approach and its generality with two application scenarios, namely interactive exploration of climatic data and segmentation editing in the medical domain. In both cases our data exploration protocol unifies the interactive data analysis, guiding the user towards regions with the most relevant dissimilarity characteristics. The dissimilarity analysis results are conveyed with a radial tree, which prevents the user from searching exhaustively through all the data.", month = apr, number = "TR-186-2-16-1", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", URL = "https://www.cg.tuwien.ac.at/research/publications/2016/karimov-2016-SD/", } @techreport{TR-186-2-08-14, title = "Smart Linking of 2D and 3D Views in Medical Applications", author = "Peter Kohlmann and Stefan Bruckner and Armin Kanitsar and Eduard Gr\"{o}ller", year = "2008", abstract = "This paper presents two techniques for the linking of 2D and 3D views in medical applications. Hereby, the goal is a better integration of 3D volume visualization into the diagnostic workflow. Until now, the main obstacle for a good integration is the time-consuming process to adjust various parameters. The LiveSync interaction metaphor is a new concept to synchronize 2D slice views and 3D volumetric views of medical data sets. A single intuitive picking interaction on anatomical structures which are detected in 2D slices results in an automatically generated 3D view. To further improve the integration contextual picking is presented as a method for the interactive identification of contextual interest points within volumetric data. Our results demonstrate how these techniques improve the efficiency to generate diagnostically relevant images and how contextual interest points can, e.g., facilitate the highlighting of relevant structures.", month = dec, number = "TR-186-2-08-14", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", URL = "https://www.cg.tuwien.ac.at/research/publications/2008/TR-186-2-08-14/", } @techreport{TR-186-2-08-12, title = "Visual Exploration for Parameter Studies of Industrial CT Dataset Series", author = "Muhammad Muddassir Malik and Christoph Heinzl and Eduard Gr\"{o}ller", year = "2008", abstract = "This paper proposes comparison and visualization techniques to carry out parameter studies for the special application area of dimensional measurement using 3D X-ray computed tomography~(ICT). A dataset series is generated by scanning a specimen multiple times by varying parameters of an industrial CT device. A high resolution series is explored using our multi-planar reformating (MPR) based exploration system. We present an evaluation system~(multi-image view) and an edge explorer for comparison and visualization of grey values and edges of several datasets simultaneously. Visualization results and quantitative data are displayed side by side. For fast data retrieval and convenient usability we use bricking of the datasets, and efficient data structures. Graphics hardware is used for interactive visualization. We studied the applicability of our proposed visualization techniques in collaboration with our company partners. ", month = dec, number = "TR-186-2-08-12", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Multi-Datasets, Industrial Computed Tomography, MPR, Visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/2008/TR-186-2-08-12/", } @techreport{TR-186-2-08-06, title = "Variance Comparison for Volumetric Industrial CT Data", author = "Muhammad Muddassir Malik and Christoph Heinzl and Eduard Gr\"{o}ller", year = "2008", abstract = "This paper proposes a novel technique for the direct comparison of a surface model with the corresponding industrial CT volume. We do not require the generation of a mesh from the CT scan and instead perform comparison directly with the raw volume dataset. Our technique uses the information from the surface model to locate corresponding points in the CT dataset. We then compute various comparison metrics to perform distance analysis and normal analysis. The metrics are presented to the user both visually as well as quantitatively. The comparison techniques are divided into two groups namely geometry-driven comparison techniques and visual-driven comparison techniques. The geometry-driven techniques color code the datasets and render distance glyphs to provide an overview, while the visual-driven techniques can be used for a localized examination and for determining precise information about the deviation between the datasets.", month = apr, number = "TR-186-2-08-06", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Volume Rendering, Uncertainty, Variance Comparison, Industrial CT", URL = "https://www.cg.tuwien.ac.at/research/publications/2008/TR-186-2-08-06/", } @techreport{TR-186-2-07-12, title = "Variance Comparison for Volumetric Industrial CT Data", author = "Muhammad Muddassir Malik and Christoph Heinzl and Eduard Gr\"{o}ller", year = "2007", abstract = "This paper proposes a novel technique for the direct comparison of a surface model with the corresponding industrial CT volume. We do not require the generation of a mesh from the CT scan and instead perform comparison directly with the raw volume dataset. Our technique uses the information from the surface model to locate corresponding points in the CT dataset. We then compute various comparison metrics to perform distance analysis and normal analysis. The metrics are presented to the user both visually as well as quantitatively. The comparison techniques are divided into two groups namely global comparison techniques and local comparison techniques. The global techniques color code the datasets to provide an overview, while the local techniques can be used for a localized examination and for determining precise information about the deviation between datasets.", month = dec, number = "TR-186-2-07-12", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Comparison, Variance", URL = "https://www.cg.tuwien.ac.at/research/publications/2007/TR-186-2-07-12/", } @techreport{TR-186-2-07-06, title = "Surface Extraction from Multi-Material Components for Metrology using Dual Energy CT", author = "Christoph Heinzl and Johann Kastner and Eduard Gr\"{o}ller", year = "2007", abstract = "This paper describes a novel method for creating surface models of multi-material components using dual energy computed tomography (DECT). Application scenario for the presented work is metrology and dimensional measurement of multi-material components in industrial high resolution 3D X-Ray computed tomography (3DCT). The basis of this method is the dual source / dual exposure technology using the different X-Ray imaging modalities of a high precision micro-focus and a high energy macro-focus X-Ray source. The presented work aims at combining the advantages of both X-Ray modalities in order to facilitate dimensional measurement of multi-material components with high density material within low density material. We propose a pipeline model using image fusion and local surface extraction technologies: A prefiltering step reduces data inherent noise. For image fusion purposes the datasets have to be registered to each other. In the fusion step the benefits of each modality are combined. So the structure of the specimen is taken from the low precision, blurry, high energy dataset while the sharp edges are adopted and fused into the resulting image from the high precision, crisp, low energy dataset. In the final step a reliable surface model is calculated of the fused dataset, which locally adapts the surface model by moving surface vertices in the direction of the corresponding point normal to a position with maximum gradient magnitude. The major contribution of this paper is the development of a specific workflow for dimensional measurement of multi-material industrial components from high resolution industrial CT data. Several algorithms are extended to take two data sources with complementary strengths and weaknesses into account. The presented workflow is crucial for the following visual inspection of deviations.", month = may, number = "TR-186-2-07-06", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "DECT image fusion, local surface extraction, metrology, Dual Energy CT, dimensional measurement, variance comparison", URL = "https://www.cg.tuwien.ac.at/research/publications/2007/TR-186-2-07-06/", } @techreport{TR-186-2-07-08, title = "Illustrative rendering of seismic data", author = "Daniel Patel and Christopher Giertsen and John Thurmond and Eduard Gr\"{o}ller", year = "2007", abstract = "We present multi attribute texture transfer functions for the generation of seismic illustrations. We render seismic data in the style of geological textbook illustrations by combining illustratively rendered axis aligned slices with volume rendering. We have extended the transfer function concept to map volume attributes to 2D textures that flow according to a deformation volume describing the buckling and discontinuites of the layers of the seismic data. Faults in the seismic layers are represented by texture disruptions. ", month = may, number = "TR-186-2-07-08", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Seismic illustration, Texture transfer function, Texture mapping", URL = "https://www.cg.tuwien.ac.at/research/publications/2007/TR-186-2-07-08/", } @techreport{TR-186-2-07-07, title = "The Event Tunnel: Interactive Visualization of Complex Event Streams for Business Process Pattern Analysis", author = "Martin Suntinger and Hannes Obweger and Josef Schuh and Eduard Gr\"{o}ller", year = "2007", abstract = "Event-based systems are gaining increasing popularity for building loosely coupled and distributed systems. Since business processes are becoming more interconnected and event-driven, event-based systems fit well for supporting and monitoring business processes. In this paper, we present an event-based business intelligence tool, the Event Tunnel framework. It provides an interactive visualization of event streams to support business analysts in exploring business cases and business processes. The visualization is based on the metaphor of considering the event stream as a cylindrical tunnel, which is presented to the user from multiple perspectives. In the Event Tunnel, relevant business events are laid out and depicted for analysts. The information of single events is encoded in event glyphs that allow for a selective mapping of event attributes to colors, size and position. Different policies for the placement of the events in the tunnel as well as a clustering mechanism generate various views on historical event data. The event tunnel is able to display the relationships between events. This facilitates users to discover root causes and causal dependencies of event patterns. Our framework couples the event-tunnel visualization with query tools that allow users to search for relevant events within a data repository. Using query, filter and highlighting operations the analyst can navigate through the Event Tunnel until the required information or event patterns become visible. We demonstrate our approach with use cases from the fraud management and logistics domain.", month = may, number = "TR-186-2-07-07", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "business process visualization, query-driven visualization, complex event processing", URL = "https://www.cg.tuwien.ac.at/research/publications/2007/TR-186-2-07-07/", } @techreport{TR-186-2-07-03, title = "Feature Peeling", author = "Muhammad Muddassir Malik and Torsten M\"{o}ller and Eduard Gr\"{o}ller", year = "2007", abstract = "We present a novel rendering algorithm that analyses the ray profile along the line of sight during rendering and cuts it into layers, according to the peaks and valleys found, which we call transition points. The sensitivity of these transition points is calibrated via two thresholds. The slope threshold influences the magnitude of a peak following a valley, while the peeling threshold measures the depth of the transition point relative to the neighboring rays. This technique separates the dataset into a number of feature layers. The user can scroll through the layers inspecting various features from the current view position. While our technique has been inspired by opacity peeling approach [14], we demonstrate that we can reveal detectable features even in the third and forth layers for both, CT and MRI datasets.", month = feb, number = "TR-186-2-07-03", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "transfer function, volume visualization, feature peeling, ray analysis", URL = "https://www.cg.tuwien.ac.at/research/publications/2007/TR-186-2-07-03/", } @techreport{GRIMM-2004-PPC, title = "Parallel Peeling of Curvilinear Grids", author = "S\"{o}ren Grimm and Michael Meissner and Armin Kanitsar and Eduard Gr\"{o}ller", year = "2004", abstract = "In this paper we present a novel hybrid CPU-GPU approach for rendering curvilinear grids. Visibility sorting is accomplished by parallel peeling cells off the grid, utilizing an active cell peeling front. In each step, we compute the ray-cell intersection coordinates on the GPU, perform accurate volume integration (CPU), and determine the set of active cells for the next iteration (GPU). The approach requires only standard graphics capabilities and can therefore be used on any commodity PC, including laptops. Furthermore, the main memory requirements are negligible since the required data structures are minimal. The main advantage of our algorithm is that we exploit hardware acceleration for the expensive visibility sorting which is bene- ficial over time due to the faster performance increase of GPUs over CPUs. Due to the simplicity of the algorithm and its low requirements on preprocessing and main memory, it is well suited for thin clients. Last but not least, the approach could easily be extended to irregular grids using tetrahedra.", month = apr, number = "TR-186-2-04-07", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Raycasting, Volume Rendering, Visibility Sorting, Curvilinear grids, Depth Sorting", URL = "https://www.cg.tuwien.ac.at/research/publications/2004/GRIMM-2004-PPC/", } @techreport{Straka-2004-TVG, title = "The VesselGlyph: Focus & Context Visualization in CT-Angiography", author = "Mat\'{u}s Straka and Michal Cervenansk\'{y} and Alexandra La Cruz and Arnold K\"{o}chl and Milo\v{s} \v{S}r\'{a}mek and Eduard Gr\"{o}ller and Dominik Fleischmann", year = "2004", abstract = "Reliable and complete blood-vessel segmentation is still a challenging problem. This is especially true in the presence of morphologic changes resulting from atherosclerotic diseases. In this paper we take advantage of partially segmented data with approximately identified vessel centerlines to comprehensively visualize the diseased peripheral arterial tree. We introduce the VesselGlyph as an abstract notation for novel focus & context visualization techniques of tubular structures such as contrast-medium enhanced arteries in CT-Angiography (CT-A). The proposed techniques combine direct volume rendering (DVR) and curved planar reformation (CPR) within a single image. The VesselGlyph consists of several regions where different rendering methods are used. Region type, the used visualization method and region parameters depend on the distance from the vessel centerline and on viewing parameters as well. By selecting proper rendering techniques for different regions, vessels are depicted in a naturally looking and undistorted anatomic context. In this paper we furthermore present a way how to implement the proposed techniques in software and by means of modern 3D graphics accelerators.", month = apr, number = "TR-186-2-04-04", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "vessel visualization., focus & context technique, curved planar reformation, direct volume rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2004/Straka-2004-TVG/", } @techreport{LaCruz-2004-NMF, title = "Non-linear Model Fitting to Parameterize Diseased Blood Vessels", author = "Alexandra La Cruz and Mat\'{u}s Straka and Arnold K\"{o}chl and Milo\v{s} \v{S}r\'{a}mek and Eduard Gr\"{o}ller and Dominik Fleischmann", year = "2004", abstract = "Accurate estimation of vessel parameters is a prerequisite for automated visualization and analysis of normal and diseased blood vessels. The objective of this research is to estimate the dimensions of lower extremity arteries, imaged by computed tomography (CT). The vessel is modeled using an elliptical or cylindrical structure with specific dimensions, orientation and blood vessel mean density. The model separates two homogeneous regions: Its inner side represents a region of density for vessels, and its outer side a region for background. Taking into account the point spread function (PSF) of a CT scanner, a function is modeled with a Gaussian kernel, in order to smooth the vessel boundary in the model. A new strategy for vessel parameter estimation is presented. It stems from vessel model and model parameter optimization by a nonlinear optimization procedure (the Levenberg-Marquardt technique). The method provides center location, diameter and orientation of the vessel as well as blood and background mean density values. The method is tested on synthetic data and real patient data with encouraging results.", month = apr, number = "TR-186-2-04-05", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Diseased Blood Vessel Detection, Segmentation, Visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/2004/LaCruz-2004-NMF/", } @techreport{Straka-2004-BSA, title = "Bone Segmentation in CT-Angiography Data Using a Probabilistic Atlas", author = "Mat\'{u}s Straka and Alexandra La Cruz and Leonid Dimitrov and Milo\v{s} \v{S}r\'{a}mek and Dominik Fleischmann and Eduard Gr\"{o}ller", year = "2004", abstract = "Automatic segmentation of bony structures in CT angiography datasets is an essential pre-processing step necessary for most visualization and analysis tasks. Since traditional density and gradient operators fail in non-trivial cases (or at least require extensive operator work), we propose a new method for segmentation of CTA data based on a probabilistic atlas. Storing densities and marks of previously manually segmented tissues to the atlas can constitute a statistical information base for latter accurate segmentation. In order to eliminate dimensional and anatomic variability of the atlas input datasets, these have to be spatially normalized (registered) first by applying a non-rigid transformation. After this transformation, densities and tissue masks are statistically processed (e.g averaged) within the atlas. Records in the atlas can be later evaluated for estimating the probability of bone tissue in a voxel of an unsegmented dataset.", month = jan, number = "TR-186-2-04-01", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Histogram Classification, Distance Fields, Thin-Plate Spline, Probabilistic Atlas, Knowledge Based Segmentation, CT Angiography", URL = "https://www.cg.tuwien.ac.at/research/publications/2004/Straka-2004-BSA/", } @techreport{Kanitsar-2004-Dia, title = "Diagnostic Relevant Visualization of Vascular Structures", author = "Armin Kanitsar and Dominik Fleischmann and Rainer Wegenkittl and Eduard Gr\"{o}ller", year = "2004", abstract = "Traditional volume visualization techniques sometimes provide incomplete clinical information needed for applications in medical visualization. In the area of vascular visualization important features such as the lumen of a diseased vessel segment may not be visible. One way to display vascular structures for diagnostic purposes is to generate longitudinal cross-sections in order to show their lumen, wall, and surrounding tissue in a curved plane. Curved planar reformation (CPR) has proven to be an acceptable practical solution. We discuss four different methods to generate CPR images from single vessel segments: Projected CPR, stretched CPR, straightened CPR, and helical CPR. Furthermore we investigate three different methods for displaying vascular trees: Multi-path projected CPR, multi-path stretched CPR, and untangled CPR. The principle concept of each method is discussed and detailed information for the realization is given. In addition the properties, advantages and disadvantages of each method are summarized.", month = jan, number = "TR-186-2-04-02", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "curved planar reformation, computed tomography angiography, vessel analysis", URL = "https://www.cg.tuwien.ac.at/research/publications/2004/Kanitsar-2004-Dia/", } @techreport{Straka-2003-CTA, title = "3D Watershed Transform Combined with a Probabilistic Atlas for Medical Image Segmentation", author = "Mat\'{u}s Straka and Alexandra La Cruz and Arnold K\"{o}chl and Milo\v{s} \v{S}r\'{a}mek and Dominik Fleischmann and Eduard Gr\"{o}ller", year = "2003", abstract = "Recent advances in medical imaging technology using multiple detector-row computed tomography (CT) provide volumetric datasets with unprecedented spatial resolution. This has allowed for CT to evolve into an excellent non-invasive vascular imaging technology, commonly referred to as CT-angiography. Visualization of vascular structures from CT datasets is demanding, however, and identification of anatomic objects in CT-datasets is highly desirable. Density and/or gradient operators have been used most commonly to classify CT data. In CT angiography, simple density/gradient operators do not allow precise and reliable classification of tissues due to the fact that different tissues (e.g. bones and vessels) possess the same density range and may lie in close spatial vicinity. We hypothesize, that anatomic classification can be achieved more accurately, if both spatial location and density properties of volume data are taken into account. We present a combination of two well-known methods for volume data processing to obtain accurate tissue classification. 3D watershed transform is used to partition the volume data in morphologically consistent blocks and a probabilistic anatomic atlas is used to distinguish between different kinds of tissues based on their density.", month = nov, number = "TR-186-2-03-13", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Histogram Classification, Thin-Plate-Spline, Probabilistic Atlas, Knowledge Based Segmentation, CT Angiography", URL = "https://www.cg.tuwien.ac.at/research/publications/2003/Straka-2003-CTA/", } @techreport{Kanitsar-2003-ADV, title = "Advanced Curved Planar Reformation: Flattening of Vascular Structures", author = "Armin Kanitsar and Rainer Wegenkittl and Dominik Fleischmann and Eduard Gr\"{o}ller", year = "2003", abstract = "Traditional volume visualization techniques may provide incomplete clinical information needed for many applications in medical visualization. Especially in the area of vascular visualization important features such as the patent lumen of a diseased vessel segment may not be visible. Curved Planar Reformation (CPR) has proven to be an acceptable practical solution. Existing CPR techniques, however, still have diagnostically relevant limitations. In this paper we introduce two advanced methods for efficient vessel visualization, based on the concept of CPR. Both methods benefit from relaxation of spatial coherence in favor of improved feature perception. We present a new technique to visualize the interior of a vessel in a single image. A vessel is re-sampled along a spiral around the vessel central axis. The helical spiral depicts the vessel volume. Furthermore, a method to display an entire vascular tree without mutually occluding vessels is presented. Minimal rotations around the branching points of a vessel tree eliminate occlusions. For each viewing direction the entire vessel structure is visible.", month = may, number = "TR-186-2-03-08", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "curved planar reformation, vessel analysis, computed tomography angiography", URL = "https://www.cg.tuwien.ac.at/research/publications/2003/Kanitsar-2003-ADV/", } @techreport{Mattausch-2003-SIE, title = "Strategies for Interactive Exploration of 3D Flow Using Evenly-Spaced Illuminated Streamlines", author = "Oliver Mattausch and Thomas Theu{\ss}l and Helwig Hauser and Eduard Gr\"{o}ller", year = "2003", abstract = "This paper presents several strategies to interactively explore 3D flow. Based on a fast illuminated streamlines algorithm, standard graphics hardware is sufficient to gain interactive rendering rates. Our approach does not require the user to have any prior knowledge of flow features. After the streamlines are computed in a short preprocessing time, the user can interactively change appearance and density of the streamlines to further explore the flow. Most important flow features like velocity or pressure not only can be mapped to all available streamline appearance properties like streamline width, material, opacity, but also to streamline density. To improve spatial perception of the 3D flow we apply techniques based on animation, depth cueing, and halos along a streamline if it is crossed by another streamline in the foreground. Finally, we make intense use of focus+context methods like magic volumes, region of interest driven streamline placing, and spotlights to solve the occlusion problem.", month = apr, number = "TR-186-2-03-04", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "3D flow visualization, illuminated streamlines, interactive exploration, focus+context visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/2003/Mattausch-2003-SIE/", } @techreport{Knapp-2003-SAT, title = "Semi-Automatic Topology Independent Contour-Based 2 1/2 D Segmentation Using Live-Wire", author = "Michael Knapp and Armin Kanitsar and Eduard Gr\"{o}ller", year = "2003", abstract = "In general three-dimensional segmentation algorithms assume objects to have connected homogeneous regions. However in some cases objects are defined by a fuzzy boundary surface and consist of an inhomogeneous internal structure. In the following a new three-dimensional segmentation technique exploiting the contour detection capabilities of live-wire is proposed: The algorithm consists of two basic steps. First contours are outlined by the user on a small number of planar cross-sections through the object using live-wire. Second the traced contours are used for reconstructing the object surface automatically in each slice using live-wire again. This user-friendly segmentation algorithm is independent from object topology as the topology is implicitly defined during the reconstruction process.", month = mar, number = "TR-186-2-03-06", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "connectivity graph, image processing, live-wire, segmentation", URL = "https://www.cg.tuwien.ac.at/research/publications/2003/Knapp-2003-SAT/", } @techreport{Theussl-2002-RSH, title = "Reconstruction Schemes for High Quality Raycasting of the Body-Centered Cubic Grid", author = "Thomas Theu{\ss}l and Oliver Mattausch and Torsten M\"{o}ller and Eduard Gr\"{o}ller", year = "2002", abstract = "The body-centered cubic (BCC) grid has received attention in the volume visualization community recently due to its ability to represent the same data with almost 30\% fewer samples as compared to the Cartesian cubic (CC) grid. In this paper we present several resampling strategies for raycasting BCC grids. These strategies range from 2D interpolation in planes to piece-wise linear (barycentric) interpolation in a tetrahedral decomposition of the grid to trilinear and sheared trilinear interpolation. We compare them to raycasting with comparable resampling techniques in the commonly used CC grid in terms of computational complexity and visual quality.", month = dec, number = "TR-186-2-02-11", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "interpolation, body-centered cubic grid, raycasting", URL = "https://www.cg.tuwien.ac.at/research/publications/2002/Theussl-2002-RSH/", } @techreport{Csebfalvi-2002-SBICG, title = "Smooth Shape-Based Interpolation using the Conjugate Gradient Method", author = "Bal\'{a}zs Cs\'{e}bfalvi and L\'{a}szl\'{o} Neumann and Armin Kanitsar and Eduard Gr\"{o}ller", year = "2002", abstract = "In this paper a novel technique for smooth shape-based interpolation of volume data is introduced. Previously simple linear interpolation of signed distance maps has been used in practice. As it will be shown, this approach results in artifacts, since sharp edges appear along the original slices. In order to obtain a smooth 3D implicit function generated by interpolating 2D distance maps, we use a global interpolation method instead of a higher order local technique. The global curvature of the implicit function representing an isosurface is minimized using an iterative conjugate gradient method. Because of the iterative approach the user can easily control the trade-off between the smoothness of the isosurface and the computational cost of the refinement. As opposed to previous techniques, like variational interpolation, our method can generate a reasonably good approximation of the ideal solution in a significantly shorter time.", month = aug, number = "TR-186-2-02-10", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "shape-based interpolation, conjugate gradient method, volume rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2002/Csebfalvi-2002-SBICG/", } @techreport{Wallisch-2002-INF, title = "Information Highlighting by Color Dependent Depth Perception with Chromo-Stereoscopy", author = "Bernd Wallisch and Wolfgang Meyer and Armin Kanitsar and Eduard Gr\"{o}ller", year = "2002", abstract = "Due to characteristics of the human visual system different colors induce different depth perception. This chromo-stereoscopy has been already used for 3D data to enhance a third spatial dimension. We propose to use chromo-stereoscopy for 2D abstract data. Color coding introduces a depth cue which encodes relevance with chromo-stereoscopy. The focus information literally stands out as compared to the context information. We applied this technique on two-dimensional graphs and multi-layer representations. Our approach can also be easily combined with other focus+context methods.", month = jul, number = "TR-186-2-02-08", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "animation, multi-layer, graphs, focus+context, chromo-stereoscopy", URL = "https://www.cg.tuwien.ac.at/research/publications/2002/Wallisch-2002-INF/", } @techreport{kanitsar-2002-CPRX, title = "CPR - Curved Planar Reformation", author = "Armin Kanitsar and Dominik Fleischmann and Rainer Wegenkittl and Petr Felkel and Eduard Gr\"{o}ller", year = "2002", abstract = "Visualization of tubular structures such as blood vessels is an important topic in medical imaging. One way to display tubular structures for diagnostic purposes is to generate longitudinal cross-sections in order to show their lumen, wall, and surrounding tissue in a curved plane. This process is called Curved Planar Reformation (CPR). We present three different methods to generate CPR images. A tube-phantom was scanned with Computed Tomography (CT) to illustrate the properties of the different CPR methods. Furthermore we introduce enhancements to these methods: thick-CPR, rotating-CPR and multi-path-CPR.", month = mar, number = "TR-186-2-02-06", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "curved planar reformation, vessel analysis, computed tomography angiography", URL = "https://www.cg.tuwien.ac.at/research/publications/2002/kanitsar-2002-CPRX/", } @techreport{kanitsar-2002-Chr, title = "Christmas Tree Case Study: Computed Tomography as a Tool for Mastering Complex Real World Objects with Applications in Computer Graphics", author = "Armin Kanitsar and Thomas Theu{\ss}l and Lukas Mroz and Milo\v{s} \v{S}r\'{a}mek and Anna Vilanova i Bartroli and Bal\'{a}zs Cs\'{e}bfalvi and Ji\v{r}\'{i} Hlad\r{u}vka and Stefan Guthe and Michael Knapp and Rainer Wegenkittl and Petr Felkel and Dominik Fleischmann and Werner Purgathofer and Eduard Gr\"{o}ller", year = "2002", abstract = "We report on using computed tomography (CT) as a model acquisition tool for complex objects in computer graphics. Unlike other modeling and scanning techniques the complexity of the object is irrelevant in CT, which naturally enables to model objects with, for example, concavities, holes, twists or fine surface details. Once the data is scanned, one can apply post-processing techniques aimed at its further enhancement, modification or presentation. For demonstration purposes we chose to scan a Christmas tree which exhibits high complexity which is difficult or even impossible to handle with other techniques. However, care has to be taken to achieve good scanning results with CT. Further, we illustrate the post-processing by means of data segmentation and photorealistic as well as non-photorealistic surface and volume rendering techniques.", month = mar, number = "TR-186-2-02-07", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "volume visualization, computed tomography, modeling", URL = "https://www.cg.tuwien.ac.at/research/publications/2002/kanitsar-2002-Chr/", } @techreport{Hauser-2002-SSI, title = "Smart surface interrogation for advanced visualization techniques", author = "Helwig Hauser and Thomas Theu{\ss}l and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "2002", abstract = "Highly elaborated visualization techniques that are based on surfaces often are independent from the origin of the surface data. Nevertheless, most of the recently presented advanced visualization methods were developed for a specific type of surface although principally applicable to generic surfaces. In this paper we discuss a unified surface interrogation model which provides generic access to surface properties up to degree two, i.e., surface point locations, normals, and curvature properties, (almost) regardless of the origin of the surface. Surface types and interrogation algorithms are compared and summarized. At the end of this paper we present an object-oriented implementation of this model, called SMURF.", month = jan, number = "TR-186-2-02-01", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "surface properties, surfaces, visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/2002/Hauser-2002-SSI/", } @techreport{Groeller-2001-IDV, title = "Insight into Data Through Visualization", author = "Eduard Gr\"{o}ller", year = "2001", abstract = "Computer graphics, scientific visualization, information visualization, and graph drawing are areas which deal with visual information layout. They all use the remarkable properties of the human visual perception to rapidly absorb and analyse visual information. The paper discusses important visualization aspects and gives examples of how visualization techniques facilitate insight into data characteristics. The connection between visualization and graph drawing is shortly discussed.", month = oct, number = "TR-186-2-01-20", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "graph drawing, visualization, computer graphics", URL = "https://www.cg.tuwien.ac.at/research/publications/2001/Groeller-2001-IDV/", } @techreport{Theussl-2001-RIV, title = "Reconstruction Issues in Volume Visualization", author = "Thomas Theu{\ss}l and Torsten M\"{o}ller and Ji\v{r}\'{i} Hlad\r{u}vka and Eduard Gr\"{o}ller", year = "2001", abstract = "Although volume visualization has already grown out of its infancy, the most commonly used reconstruction techniques are still trilinear interpolation for function reconstruction and central differences (most often in conjunction with trilinear interpolation) for gradient reconstruction. Nevertheless, quite some research in the last few years was devoted to improve this situation. This paper surveys the more important methods, emphasizing selected work in function and gradient reconstruction, and gives an overview over the rather new development of exploiting curvature properties for volume visualization purposes.", month = jun, number = "TR-186-2-01-14", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Taylor series expansion, frequency response, windowing, ideal reconstruction", URL = "https://www.cg.tuwien.ac.at/research/publications/2001/Theussl-2001-RIV/", } @techreport{Hladuvka-2001-DDI, title = "Direction-Driven Shape-Based Interpolation of Volume Data", author = "Ji\v{r}\'{i} Hlad\r{u}vka and Eduard Gr\"{o}ller", year = "2001", abstract = "We present a novel approach to shape-based interpolation of gray-level volume data. In contrast to the segmentation-based techniques our method directly processes the scalar volume requiring no user interaction. The key idea is to perform the interpolation in the directions given by analysis of the eigensystem of the structure tensor. Our method processes a 256 x 256 slice within a couple of seconds yielding satisfactory results. We give a quantitative and a visual comparison to the linear inter-slice interpolation. Analysis of the results lead us to the conclusion that our technique has a strong potential to compete with well-established shape-based interpolation algorithms.", month = may, number = "TR-186-2-01-12", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Eigensystem, Structure Tensor, Local Neighborhoods, Shape-based Interpolation", URL = "https://www.cg.tuwien.ac.at/research/publications/2001/Hladuvka-2001-DDI/", } @techreport{Theussl-2001-ORS, title = "Optimal Regular Volume Sampling", author = "Thomas Theu{\ss}l and Torsten M\"{o}ller and Eduard Gr\"{o}ller", year = "2001", abstract = "The classification of volumetric data sets as well as their rendering algorithms are typically based on the representation of the underlying grid. Grid structures based on a Cartesian lattice are the de-facto standard for regular representations of volumetric data. In this paper we introduce a more general concept of regular grids for the representation of volumetric data. We demonstrate that a specific type of regular lattice - the so-called body-centered cubic - is able to represent the same data set as a Cartesian grid to the same accuracy but with 29.3% less samples. This speeds up traditional volume rendering algorithms by the same ratio, which we demonstrate by adopting a splatting implementation for these new lattices. We investigate different filtering methods required for computing the normals on this lattice. The lattice representation results also in lossless compression ratios that are better than previously reported. Although other regular grid structures achieve the same sample efficiency, the body-centered cubic is particularly easy to use. The only assumption necessary is that the underlying volume is isotropic and band-limited - an assumption that is valid for most practical data sets.", month = apr, number = "TR-186-2-01-10", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "body centered cubic, hexagonal sampling, close packing, Cartesian grid, volume data", URL = "https://www.cg.tuwien.ac.at/research/publications/2001/Theussl-2001-ORS/", } @techreport{Vilanova-2001-VCU, title = "Virtual Colon Unfolding", author = "Anna Vilanova i Bartroli and Rainer Wegenkittl and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "2001", abstract = "The majority of virtual endoscopy techniques tries to simulate a real endoscopy. A real endoscopy does not always give the optimal information due to the physical limitations it is subject to. In this paper, we deal with the unfolding of the surface of the colon as a possible visualization technique for diagnosis and polyp detection. A new two-step technique is presented which deals with the problems of double appearance of polyps and nonuniform sampling that other colon unfolding techniques suffer from. In the first step, a distance map from a central path induces nonlinear rays for unambiguous parameterization of the surface. The second step compensates for locally varying distortions of the unfolded surface. A technique similar to magnification fields in information visualization is hereby applied. The technique produces a single view of a complete virtually dissected colon.", month = apr, number = "TR-186-2-01-08", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Virtual Endoscopy, Volume Rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2001/Vilanova-2001-VCU/", } @techreport{Csebfalvi-2001-NPVR, title = "Fast Visualization of Object Contours by Non-Photorealistic Volume Rendering", author = "Bal\'{a}zs Cs\'{e}bfalvi and Lukas Mroz and Helwig Hauser and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "2001", abstract = "In this paper we present a fast visualization technique for volumetric data, which is based on a recent non-photorealistic rendering technique. Our new approach enables alternative insights into 3D data sets (compared to traditional approaches such as direct volume rendering or iso-surface rendering). Object contours, which usually are characterized by locally high gradient values, are visualized regardless of their density values. Cumbersome tuning of transfer functions, as usually needed for setting up DVR views is avoided. Instead, a small number of parameters is available to adjust the non-photorealistic display. Based on the magnitude of local gradient information as well as on the angle between viewing direction and gradient vector, data values are mapped to visual properties (color, opacity), which then are combined to form the rendered image (MIP is proposed as the default compositing stragtegy here). Due to the fast implementation of this alternative rendering approach, it is possible to interactively investigate the 3D data, and quickly learn about internal structures. Several further extensions of our new approach, such as level lines are also presented in this paper.", month = apr, number = "TR-186-2-01-09", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "shear-warp projection, non-photorealistic rendering, interactive volume rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2001/Csebfalvi-2001-NPVR/", } @techreport{Kanitsar-2001-PVI, title = "Peripheral Vessel Investigation For Routine Clinical Use", author = "Armin Kanitsar and Rainer Wegenkittl and Petr Felkel and Dominik Fleischmann and Dominique Sandner and Eduard Gr\"{o}ller", year = "2001", abstract = "This paper is about computed tomography angiography based vessel exploration. Large image sequences of the lower extremities are investigated in a clinical environment. Two different approaches for peripheral vessel diagnosis dealing with stenosis and calcification detection are introduced. The paper presents an automated vessel-tracking tool for curved planar reformation. A user interactive segmentation tool for bone removal is proposed.", month = mar, number = "TR-186-2-01-13", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "optimal path computation, semi automated segmentation, CTA", URL = "https://www.cg.tuwien.ac.at/research/publications/2001/Kanitsar-2001-PVI/", } @techreport{Csebfalvi-2000-IVRBM, title = "Interactive Volume Rendering based on a ''Bubble Model''", author = "Bal\'{a}zs Cs\'{e}bfalvi and Eduard Gr\"{o}ller", year = "2000", abstract = "In this paper an interactive volume rendering technique is presented which is based on a novel visualization model. We call the basic method ``bubble model'' since iso-surfaces are rendered as thin semi-transparent membranes similarly to blown soap bubbles. The primary goal is to develop a fast previewing technique for volumetric data which does not require a time consuming transfer function specification to visualize internal structures. Our approach uses a very simple rendering model controlled by only two parameters. We also present an interactive rotation technique which does not rely on any specialized hardware, therefore it can be widely used even on low-end machines. Due to the interactive display, fine tuning is also supported since the modification of the rendering parameters has an immediate visual feedback.", month = dec, number = "TR-186-2-00-23", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Shear-Warp Factorization., Previewing, Direct Volume Rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Csebfalvi-2000-IVRBM/", } @techreport{Hladuvka-2000-Exp, title = "Salient Representation of Volume Data", author = "Ji\v{r}\'{i} Hlad\r{u}vka and Eduard Gr\"{o}ller", year = "2000", abstract = "We introduce a novel approach for identification of objects of interest in volume data. Our approach tries to convey the information contained in two essentially different concepts, the object's boundaries and the narrow solid structures, in an easy and uniform way. The second order derivative operators in directions reaching minimal response are involved for this task. To show the superior performance of our method, we provide a comparison to its main competitor -- surface extraction from areas of maximal gradient magnitude. We show that our approach provides the possibility to represent volume data by its subset of a nominal size.", month = dec, number = "TR-186-2-00-26", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Gradient vector, Hessian matrix, Feature Extraction, Sufrace Extraction, Volume Rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Hladuvka-2000-Exp/", } @techreport{Vilanova-2000-VCF, title = "Virtual Colon Flattening", author = "Anna Vilanova i Bartroli and Rainer Wegenkittl and Andreas K\"{o}nig and Eduard Gr\"{o}ller and E. Sorantin", year = "2000", abstract = "We present a new method to visualize virtual endoscopic views. We propose to flatten the organ by the direct projection of the surface onto a set of cylinders. Two sampling strategies are presented and the introduced distortions are studied. A non-photorealistic technique is presented to enhance the perception of the images. Finally, an approximate but real-time endoscopic fly-through is possible by using the data obtained by the projection technique.", month = dec, number = "TR-186-2-00-25", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Colon Flattening, Volume Rendering, Virtual Colonoscopy", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Vilanova-2000-VCF/", } @techreport{Tsoi-2000-Ada, title = "Adaptive Visualization over the Internet", author = "Kei Nam Tsoi and Eduard Gr\"{o}ller", year = "2000", abstract = "This report gives an account to our work in adaptive visualization over the Internet ressearch. In this report we present our prototypes of adaptive visualization systems and an agent-based visualization model for network applications. We proposed a intelligent agent system for adaptively dispatch of visualization processes between a cluster of computers based on the changing network transmission bandwidth and processing prower. We also discuss the scientific contributions of our work to the current research in Interne-based visualization system design.", month = nov, number = "TR-186-2-00-21", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "code mobility, adaptive visualization, Internet, visualizaion, agents", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Tsoi-2000-Ada/", } @techreport{Hladuvka-2000-ExpX, title = "Exploiting Eigenvalues of the Hessian Matrix for Volume Decimation", author = "Ji\v{r}\'{i} Hlad\r{u}vka and Eduard Gr\"{o}ller", year = "2000", abstract = "In recent years the Hessian matrix and its eigenvalues became important in pattern recognition. Several algorithms based on the information they provide have been introduced. We recall the relationship between the eigenvalues of Hessian matrix and the 2nd order edge detection filter, show the usefulness of treating them separately and exploit these facts to design a combined threshold operation to generate sparse data sets.", month = oct, number = "TR-186-2-00-19", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Laplacian filter, Eigenvalues, Hessian matrix, Sparse data, Volume Rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Hladuvka-2000-ExpX/", } @techreport{Hauser-2000-Tho, title = "Thorough Insights by Enhanced Visualization of Flow Topology", author = "Helwig Hauser and Eduard Gr\"{o}ller", year = "2000", abstract = "The investigation of flow data can be eased by the visualization of topological information about the flow. Especially, when empirical models or numerical results from flow simulation are investigated, often the first step of analysis is to search structural elements, like fixed points, separatrices, etc. The work presented in this paper focuses on the visualization of 3D dynamical systems (comparable to flow data) on the basis of results which are obtained by automatic analysis of the flow topology. Fixed points are determined and the Jacobian matrix of the flow is investigated at these points of phase space to obtain the associated stable and/or unstable invariant sets. Furthermore, this paper presents how Poincare maps are used to visualize structural information about cyclic flow data together with direct visualization cues like stream lines or stream surfaces.", month = aug, number = "TR-186-2-00-17", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Hauser-2000-Tho/", } @techreport{Hauser-2000-TwoX, title = "Two-level volume rendering - fusing MIP and DVR", author = "Helwig Hauser and Lukas Mroz and Gian-Italo Bischi and Eduard Gr\"{o}ller", year = "2000", abstract = "In this paper we present a two-level approach for fusing direct volume rendering (DVR) and maximum-intensity projection (MIP) within a joint rendering method. Different structures within the data-set are rendered locally by either MIP or DVR on an object-by-object basis. Globally all the results of subsequent object renderings are combined in a merging step (usually compositing in our case). This allows to selectively choose the most suitable technique for depicting each object within the data, while keeping the amount of information contained in the image at a reasonable level. This is especially useful when inner structures should be visualized together with semi-transparent outer parts, similar to the focus-and-context approach known from information visualization. We also present an implementation of our approach, which allows to explore volumetric data using two-level rendering at interactive frame rates. ", month = apr, number = "TR-186-2-00-11", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "dynamical systems, interactive visualization, maximum intensity projection, direct volume rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Hauser-2000-TwoX/", } @techreport{Mroz-2000-MasX, title = "Mastering Interactive Surface Rendering for Java-Based Diagnostic Applications", author = "Lukas Mroz and Rainer Wegenkittl and Eduard Gr\"{o}ller", year = "2000", abstract = "The display of iso-surfaces in medical data sets is an important visualization technique used by radiologists for the diagnosis of volumetric density data sets. The demands put by radiologists on such a display technique are interactivity, multiple stacked transparent surfaces and cutting planes that allow an interactive clipping of the surfaces. This paper presents a Java based, platform independent implementation of a very fast surface rendering algorithm which combines the advantages of explicit surface representation, splatting, and shear-warp projection to fulfill all these requirements. The algorithm is implemented within the context of J-Vision, an application for viewing and diagnosing medical images which is currently in use at various hospitals. ", month = apr, number = "TR-186-2-00-10", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "medical applications, surface rendering, volume visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Mroz-2000-MasX/", } @techreport{Theussl-2000-MWI, title = "Mastering Windows: Improving Reconstruction", author = "Thomas Theu{\ss}l and Helwig Hauser and Eduard Gr\"{o}ller", year = "2000", abstract = "Ideal reconstruction filters, for function or arbitrary derivative reconstruction, have to be bounded in order to be practicable since they are infinite in their spatial extent. This can be accomplished by multiplying them with windowing functions. In this paper we discuss and assess the quality of commonly used windows and show that most of them are unsatisfactory in terms of numerical accuracy. The best performing windows are Blackman, Kaiser and Gaussian windows. The latter two are particularly useful since both have a parameter to control their shape, which, on the other hand, requires to find appropriate values for these parameters. We show how to derive optimal parameter values for Kaiser and Gaussian windows using a Taylor series expansion of the convolution sum. Optimal values for function and first derivative reconstruction for window widths of two, three, four and five are presented explicitly.", month = apr, number = "TR-186-2-00-08", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Taylor series expansion, frequency response, windowing, ideal reconstruction", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Theussl-2000-MWI/", } @techreport{Wegenkitt-2000-MIV, title = "Mastering Interactive Virtual Bronchioscopy on a Low--End PC", author = "Rainer Wegenkittl and Anna Vilanova i Bartroli and Balint Heged\"{u}s and Daniel Wagner and Martin C. Freund and Eduard Gr\"{o}ller", year = "2000", abstract = "Virtual endoscopy presents the cross-sectional acquired 3D-data of a computer tomograph as an endoluminal view. The common approach for the visualization of a virtual endoscopy is surface rendering, yielding images close to a real endoscopy. If external structures are of interest, volume rendering techniques have to be used. These methods do not display the exact shape of the inner lumen very well. For certain applications, e.g. operation planning of a trans-bronchial biopsy, both, the shape of the inner lumen as well as outer structures like blood vessels and the tumor have to be delineated. In this paper a method is described, that allows a quick and easy hybrid visualization using overlays of different visualization methods like different surfaces or volume renderings with different transfer functions in real time on a low-end PC. To achieve real time frame rates, image based rendering techniques have been used.", month = mar, number = "TR-186-2-00-13", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization system, virtual endoscopy, medical visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Wegenkitt-2000-MIV/", } @techreport{Koenig-2000-ATFS, title = "Mastering Transfer Function Specification by using VolumePro Technology", author = "Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "2000", abstract = "A new user-interface paradigm for the specification of transfer functions is presented. The specification is usually a difficult task as mapping information for a number of different domains (data range, color, opacity, etc.) has to be defined. In the presented approach, the definition of the mapping information can be realized independently for each property domain. A set of specification tools is provided for each domain, enabling users with different levels of experience or demanding time restrictions to choose an appropriate approach for their needs. Real-time feedback during the manipulation of parameters has been proven to be crucial to the specification. An interactive direct-volume-rendering display is realized by utilizing dedicated hardware acceleration. ", month = mar, number = "TR-186-2-00-07", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "VolumePro ray-casting system, Transfer Function Specification, Volume Visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Koenig-2000-ATFS/", } @techreport{Vilanova-2000-CAT, title = "Cylindrical Approximation of Tubular Organs for Virtual Endoscopy", author = "Anna Vilanova i Bartroli and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "2000", abstract = "Virtual endoscopy is a promising medical application of volume visualization techniques. A virtual endoscopy system requires high quality and perspective projection rendering, as well as real-time navigation. In this paper the generation of a cylindrical structure for tubular shaped organs (i.e. colon, aorta) is presented. This structure represents an approximation of the real organ. The cylindrical structure will be used to accelerate high quality volume rendering.", month = feb, number = "TR-186-2-00-02", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Vilanova-2000-CAT/", } @techreport{Csebfalvi-2000-GELR, title = "Gradient Estimation in Volume Data using 4D Linear Regression", author = "L\'{a}szl\'{o} Neumann and Bal\'{a}zs Cs\'{e}bfalvi and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "2000", abstract = "In this paper a new gradient estimation method is presented which is based on linear regression. Previous contextual shading techniques try to fit an approximate function to a set of surface points in the neighborhood of a given voxel. Therefore, a system of linear equations has to be solved using the computationally expensive Gaussian elimination. In contrast, our method approximates the density function itself in a local neighborhood with a 3D regression hyperplane. This approach also leads to a system of linear equations but we will show that it can be solved with an efficient convolution. Our method provides at each voxel location the normal vector and the translation of the regression hyperplane which are considered as a gradient and a filtered density value respectively. Therefore, this technique can be used for surface smoothing and gradient estimation at the same time. ", month = feb, number = "TR-186-2-00-03", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Linear Regression., Gradient Estimation, Volume Rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/2000/Csebfalvi-2000-GELR/", } @techreport{koenig-1999-AlV, title = "AlVis - An Aluminium-Foam Visualization and Investigation Tool", author = "Andreas K\"{o}nig and Helmut Doleisch and Andreas Kottar and Brigitte Kriszt and Eduard Gr\"{o}ller", year = "1999", abstract = "In recent years there has been an increased interest in metal foams in the field of material science. The stress absorbing potential is one of the most interesting properties for the application of aluminium foam (e.g. car manufacturing). Material scientists need to investigate the structure of metal foams in order to optimize their deformation behavior. An interactive tool for the investigation is presented in this work. Real-time surface rendering, automatic parameter determination, and display of local and global foam properties enable the user to understand the complex structure of the metal foam.", month = dec, number = "TR-186-2-99-23", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "surface extraction, aluminum foam investigation", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/koenig-1999-AlV/", } @techreport{Mroz-1999-IHQ, title = "Interactive High-Quality Maximum Intensity Projection", author = "Lukas Mroz and Helwig Hauser and Eduard Gr\"{o}ller", year = "1999", abstract = "Maximum Intensity Projection (MIP) is a volume rendering technique which is used to visualize high-intensity structures within volumetric data. At each pixel the highest data value, which is encountered along a corresponding viewing ray is depicted. MIP is, for example, commonly used to extract vascular structures from medical data sets (angiography). Due to lack of depth information in MIP images, animation or interactive variation of viewing parameters is frequently used for investigation. Up to now no MIP algorithms exist which are of both interactive speed and high quality. In this paper we present a high-quality MIP algorithm (trilinear interpolation within cells), which is up to 50 times faster than brute-force MIP and at least 20 times faster than comparable optimized techniques. This speed-up is accomplished by using an alternative storage scheme for volume cells (sorted by value) and by removing cells which do not contribute to any MIP projection (regardless of the viewing direction) in a preprocessing step. Also, a fast maximum estimation within cells is used to further speed up the algorithm. ", month = dec, number = "TR-186-2-99-25", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "trilinear interpolation, angiography, maximum intensity projection, volume visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Mroz-1999-IHQ/", } @techreport{Mroz-1999-MIP, title = "Maximum Intensity Projection at Warp Speed", author = "Lukas Mroz and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "1999", abstract = "Maximum Intensity Projection (MIP) is a volume rendering technique which is used to extract high-intensity structures from volumetric scalar 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, i.e., 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 a MIP is usually non-interactive, this is done by calculating multiple images offline and playing them back as an animation. In this paper a novel algorithm is proposed which is capable of interactively generating Maximum Intensity Projection images even on low-end hardware using parallel projection. Two methods for preprocessing data and removing voxels which will due to their neighborhood never contribute to a MIP are discussed. 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 the 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).", month = dec, number = "TR-186-2-99-24", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "real-time rendering, maximum intensity projection, volume visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Mroz-1999-MIP/", } @techreport{Hauser-1999-SSI, title = "Smart surface interrogation for advanced visualization techniques", author = "Helwig Hauser and Thomas Theu{\ss}l and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "1999", abstract = "Highly elaborated visualization techniques that are based on surfaces often are independent from the origin of the surface data. Nevertheless, most of the recently presented advanced visualizatio methods were developed for a specific type of surface although principally applicable to generic surfaces. In this paper we discuss a unified surface interrogation model which provides generic access to surface properties up to degree two, i.e., surface-point locations, normals, and curvature properties, regardless of the origin of the surface. Surface types and interrogation algorithms are compared and summarized. At the end of this paper we present an object-oriented implementation of this model, called {\sc{}Smurf", month = nov, number = "TR-186-2-99-19", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "surface properties, surfaces, visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Hauser-1999-SSI/", } @techreport{Theussl-1999-MDH, title = "The Multi-Dimensional Hartley Transform as a Basis for Volume Rendering", author = "Thomas Theu{\ss}l and Robert F. Tobler and Eduard Gr\"{o}ller", year = "1999", abstract = "The Fast Hartley Transform (FHT), a discrete version of the Hartley Transform (HT), has been studied in various papers and shown to be faster and more convenient to implement and handle than the corresponding Fast Fourier Transform (FFT). As the HT is not as nicely separable as the FT, a multidimensional version of the HT needs to perform a final correction step to convert the result of separate HTs for each dimension into the final multi-dimensional transform. Although there exist algorithms for two and three dimensions, no generalization to arbitrary dimensions can be found in the literature. We demonstrate an easily comprehensible and efficient implementation of the fast HT and its multi-dimensional extension. By adapting this algorithm to volume rendering by the projection-slice theorem and by the use for filter analysis in frequency domain we further demonstrate the importance of the HT in this application area.", month = oct, number = "TR-186-2-99-21", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "volume rendering, Fourier transform, Hartley transform", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Theussl-1999-MDH/", } @techreport{Fuhr-1999-Multi, title = "Fast Surface Rendering of Volumetric Data", author = "Bal\'{a}zs Cs\'{e}bfalvi and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "1999", abstract = "In this paper a new direct volume-rendering method is presented for fast display of iso-surfaces. In order to reduce the data to be processed, the algorithm eliminates those voxels which are invisible from a specific domain of viewing directions. The remaining surface points are stored in an appropriate data structure optimized for fast shear-warp projection. The proposed data structure also supports the application of cutting planes in order to visualize the internal part of the volume as well. Unlike many other surface-oriented techniques, the presented method does not trade image quality for speed. It does not require any specialized hardware either to achieve interactive frame rates, thus it can be widely used in medical imaging applications even on low end hardware.", month = may, number = "TR-186-2-99-13", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Medical Imaging., Volume Rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Fuhr-1999-Multi/", } @techreport{Mroz-1999-ReaX, title = "Real-Time Maximum Intensity Projection", author = "Lukas Mroz and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "1999", abstract = "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).", month = apr, number = "TR-186-2-99-09", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "angiography, Maximum Intensity Projection, Volume Visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Mroz-1999-ReaX/", } @techreport{Mroz-1999-Adv, title = "Advanced High-Quality Maximum Intensity Projection for Volume Visualization", author = "Lukas Mroz and Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1999", abstract = "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). Due to lack of depth information in MIP images, animation of the viewpoint is frequently used for viewing. Although interactive MIP algorithms exist, the quality of the results is moderate. The generation of high-quality MIP animation loops is computationally expensive with rendering times of several seconds per frame. In this paper we present a fast algorithm for high-quality MIP. Cells of the data set which will never contribute to a MIP due to their neighborhood are removed during a preprocessing step. The remaining cells are stored in a way which improves cache coherency independent of the viewing direction and minimizes the number of required maximum evaluations.", month = apr, number = "TR-186-2-99-10", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "angiography, Maximum Intensity Projection, Volume Visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Mroz-1999-Adv/", } @techreport{Vilanova-1999-VirX, title = "VirEn: A Virtual Endoscopy System", author = "Anna Vilanova i Bartroli and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "1999", abstract = "Virtual endoscopy systems are promising tools for the simplification of daily clinical procedures. In this paper, a conceptual framework for a virtual endoscopy system (VirEn) is proposed, which is intended to be a highly interactive system. Research efforts have concentrated on the generation of an optimal path for the automated navigation of the data set. Extensions to existing thinning algorithms used to generate the optimal path are presented and discussed. First results produced with VirEn are shown.", month = mar, number = "TR-186-2-99-06", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Thinning, Navigation, Virtual Endoscopy, Volume Visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Vilanova-1999-VirX/", } @techreport{Koenig-1999-MVA, title = "Multiple Views and Magic Mirrors - fMRI Visualization of the Human Brain", author = "Andreas K\"{o}nig and Helmut Doleisch and Eduard Gr\"{o}ller", year = "1999", abstract = "Multimodal visualization of functional and anatomical data of the human brain is an important field in medical volume visualization. The aim of this application is to provide the user with information on the location of functional activations in the different regions of the brain. When the approach of direct volume rendering is chosen, the visual impression of details usually suffers from accumulating the image from colors and opacities derived from the data set. We present extensions to overcome this problem: \emph{Transfer function volumes} are used for the highlighting of activated regions. \emph{Multiple views", month = feb, number = "TR-186-2-99-08", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "fMRI, Multimodality, Volume Visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Koenig-1999-MVA/", } @techreport{Csebfalvi-1999-MIP, title = "Fast Maximum Intensity Projection using Binary Shear-Warp Factorization", author = "Bal\'{a}zs Cs\'{e}bfalvi and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "1999", abstract = "This paper presents a fast maximum intensity projection technique based on binary shear-warp factorization. The proposed method divides the density domain into a small number of intervals, and to each interval a binary code representation is assigned. In a preprocessing step, an additional volume is created which contains for each voxel the code of the interval enclosing the given voxel density. We present an appropriate data structure for storing this volume and an efficient lookup table technique which can be used to rapidly access a voxel of a certain density code. The volume is efficiently resampled along viewing rays only in voxels where the densities reside in the interval which contains the appropriate maximum value.", month = jan, number = "TR-186-2-99-02", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Shear-Warp Factorization., Volume Rendering, Maximum Intensity Projection", URL = "https://www.cg.tuwien.ac.at/research/publications/1999/Csebfalvi-1999-MIP/", } @techreport{Loeffelmann-1998-SMURF, title = "Smurf -- a Smart surface model for advanced visualization techniques", author = "Helwig L\"{o}ffelmann and Thomas Theu{\ss}l and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "1998", abstract = "Highly elaborated visualization techniques that are based on surfaces often are independent from the origin of the surface data. For re-using advanced visualization methods for surfaces of various kind, we developed an abstract surface interrogation layer called Smurf. In this paper we discuss the steps necessary to unify multiple types of surfaces under a shared general purpose interface.", month = oct, number = "TR-186-2-98-26", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "surfaces, visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Loeffelmann-1998-SMURF/", } @techreport{Berger-1998-Col, title = "Color-Table Animation of Fast Oriented Line Integral Convolution for Vector Field Visualization", author = "Siegrun Berger and Eduard Gr\"{o}ller", year = "1998", abstract = "Fast Oriented Line Integral Convolution (FROLIC), which is a variant of LIC, illustrates 2D vector fields by approximating a streamlet by a set of disks with varying intensity. FROLIC does not only show the direction of the flow but also its orientation. This paper presents color-table animation of FROLIC images. Various color-table compositions are discussed in detail. When animating FROLIC images visual artifacts (pulsation, synchronization) must be avoided. Several strategies in this respect are dealt with. Color-table animation of FROLIC has been implemented as Visual C++ application for Windows NT, whereby the calculation of the dynamical system is performed with Mathematica. This allows researchers from various disciplines to conveniently explore and investigate analytically defined 2D and 3D vector fields.", month = jul, number = "TR-186-2-98-22", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "color-table animation, Line Integral Convolution, FROLIC", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Berger-1998-Col/", } @techreport{fuhrmann-1998-reaX, title = "Real-TimeTechniques for 3D Flow Visualization", author = "Anton Fuhrmann and Eduard Gr\"{o}ller", year = "1998", abstract = "Visualization of three dimensional flow has to overcome a lot of problems to be effective. Among them are occlusion of distant details, lack of directional and depth hints and cluttering. In this paper we present methods which address these problems for realtime graphic representations applicable in virtual environments. We use animated, opacity-mapped streamlines as visualization icon for 3D flow visualization. We present a texture mapping technique to keep the level of texture detail along a streamline nearly constant even when the velocity of the flow varies considerably. An algorithm is described which distributes the dashtubes evenly in space. We apply magic lenses and magic boxes as interaction techniques for investigating densly filled areas without overwhelming the observer with visual detail. Implementation details of these methods and their integration in our virtual environment conclude the paper.", month = may, number = "TR-186-2-98-16", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "focussing, virtual reality, texture techniques, flow visualization, realtime", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/fuhrmann-1998-reaX/", } @techreport{Mroz-1998-SelX, title = "Selected Trends in Scientific Visualization", author = "Lukas Mroz and Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1998", abstract = "Visualization became an important branch of scientific research during the past decade. Some topics of visualization, e.g., flow visualization and volume visualization, already provide lots of high-quality solutions to the most important problems. Others such as information visualization, are rather young disciplines which continuously provide lots of new advances. One such topic is the visualization over the Internet. Quite a number of approaches emerged during the last two years which facilitate this idea and embed the World Wide Web into the visualization process. Another trend in visualization is collaborative visualization within an augmented reality setup. Users exploit real 3D interaction and augmented reality to combine communication and investigation during research or education. Thirdly, the visualization of multi-dimensional and multi-modal data is a rather hot challenge to current scientific research. Coping with the restriction of just a few dimensions for representing visualization results is a big open problem in visualization and currently subject to eager research.", month = apr, number = "TR-186-2-98-15", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "augmented reality,information visualizat, web technologies, Visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Mroz-1998-SelX/", } @techreport{Mroz-1998-Bri, title = "Bringing Your Visualization Application to the Internet", author = "Lukas Mroz and Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1998", abstract = "The Internet has a growing importance as a medium for presenting visualization and offering visualization tools. Due to strong variations in the quality of avaliable resources it is extremely difficult to design visualization systems including the Internet, which are capable of interactively visualizing user data. In this paper we identify requirements for a distributed visualization system to interactively visualize user data. As a possible solution to the identified problems we present a model for a visualization pipeline capable of fulfilling these requirements. Finally a proof-of-concept implementation of our ideas into Net Phase Plane, a visualization tool for dynamical systems, is discussed.", month = apr, number = "TR-186-2-98-14", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "interactivity, visualization over the internet", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Mroz-1998-Bri/", } @techreport{Loeffelmann-1998-VDS, title = "Visualizing Dynamical Systems near Critical Points", author = "Helwig L\"{o}ffelmann and Helmut Doleisch and Eduard Gr\"{o}ller", year = "1998", abstract = "In this paper we present two visualization techniques. One uses the topological structure of the dynamical system near critical points to build an abstract description of the flow. The other places bunches of streamlets around the critical points to visualize the flow characteristics locally. Combining both methods a powerful visualization technique is present, since both the topological information as well as intuitive visual cues are provided.", month = mar, number = "TR-186-2-98-09", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, dynamical systems, critical points, vector field topology", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Loeffelmann-1998-VDS/", } @techreport{Castro-1998-TFS, title = "Transfer Function Specification for the Visualization of Medical Data", author = "Silvia Castro and Andreas K\"{o}nig and Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1998", abstract = "The application of transfer functions to map data values to visual properties as, e.g., color and opacity, is a crucial step in direct volume rendering. Due to the complex relationship between the transfer function and the resulting image it is usually extremely difficult to model an appropriate mapping. In this paper we present an advanced transfer function specification scheme for the visualization of medical data. The concept of metadata is used to make the modeling of transfer functions more intuitive. A small number of parameters is sufficient to completely describe a transfer function, thus this specification scheme is suitable for (semi-)automated search techniques.", month = mar, number = "TR-186-2-98-12", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "volume rendering, multi-modal and multi-dimensional data v, visualization systems, visualization of medical data", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Castro-1998-TFS/", } @techreport{Groeller-1998-TunVis, title = "TunVis: Visualizing specific geologic features for tunnel planning and construction", author = "Horst Otto Meinhart and Rainer Wegenkittl and Eduard Gr\"{o}ller", year = "1998", abstract = "This paper describes a method and a system for visualizing a virtual tunnel through an existing geologic formation and a method for the generation of a camera animation along the tunnel axis. The tunnel is built from geologic data coming from vertical sample drills from the mountain top along the selected tunnel axis. Its wire frame model is then edited by a geologist and image information of the rock appearance is textured onto the tunnel wall, resulting in a photorealistic representation of the expected geologic rock formations. Finally a camera animation and video options are defined to render a video sequence of the camera movement.", month = feb, number = "TR-186-2-98-08", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, geologic features, tunnel planning", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Groeller-1998-TunVis/", } @techreport{Groeller-1998-VDS, title = "Visualization of Dynamical Systems", author = "Eduard Gr\"{o}ller and Helwig L\"{o}ffelmann and Rainer Wegenkittl", year = "1998", abstract = "The visualization of analytically defined dynamical systems is important for a thorough understanding of the underlying system behavior. An introduction to analytically defined dynamical systems is given. Various visualization techniques for dynamical systems are discussed. Several current research directions concerning the visualization of dynamical systems are treated in more detail. These are: texture based techniques, visualization of high-dimensional dynamical systems, advanced streamsurface representations, local analysis - Poincare' sections, visualizing econometric models.", month = feb, number = "TR-186-2-98-07", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, dynamical systems", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Groeller-1998-VDS/", } @techreport{Groeller-1998-VAD, title = "Visualization of Analytically Defined Dynamical Systems", author = "Eduard Gr\"{o}ller and Helwig L\"{o}ffelmann and Rainer Wegenkittl", year = "1998", abstract = "The visualization of analytically defined dynamical systems is important for a thorough understanding of the underlying system behavior. An overview of theoretical concepts concerning analytically defined dynamical systems is given. Various visualization techniques for dynamical systems are discussed. Three current research directions concerning the visualization of dynamical systems are treated in more detail. These are: texture based techniques, visualization of high-dimensional dynamical systems, and advanced streamsurface representations. ", month = feb, number = "TR-186-2-98-06", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, dynamical systems", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Groeller-1998-VAD/", } @techreport{Loeffelmann-1998-EVC, title = "Enhancing the Visualization of Characteristic Structures in Dynamical Systems", author = "Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1998", abstract = "We present a thread of streamlets as a new technique to visualize dynamical systems in three-space. A trade-off is made between solely visualizing a mathematical abstraction through lower-dimensional manifolds, i.e., characteristic structures such as fixed point, separatrices, etc., and directly encoding the flow through stream lines or stream surfaces. Bundlers 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.", month = jan, number = "TR-186-2-98-05", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, dynamical systems", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Loeffelmann-1998-EVC/", } @techreport{Koenig-1998-NC, title = "Real Time Simulation and Visualization of NC Milling Processes for Inhomogeneous Materials on Low-End Graphics Hardware", author = "Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "1998", abstract = "Simulation and visualization of NC milling processes has become an important step in computer aided manufacturing. The usage of stock materials with specific locally varying properties (like density, accuracy, color, ...) becomes more and more important with new technologies emerging in the material industry. Our new approach, using volumetric representation, has been adapted to this needs and copes with inhomogeneous material properties. Taking color as one possible material property, our approach enables the visualization of milled wood or compound materials. Furthermore, our approach has been developed with the usage of low-end graphics hardware in mind. The algorithms have been optimized to ensure interactive update rates even on standard personal computers without hardware graphics acceleration.", month = jan, number = "TR-186-2-98-04", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, NC milling", URL = "https://www.cg.tuwien.ac.at/research/publications/1998/Koenig-1998-NC/", } @techreport{Fischel-1997-CSVVP, title = "Case study: Visualizing Various Properties of Dynamical Systems", author = "Georg Fischel and Helmut Doleisch and Lukas Mroz and Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1997", abstract = "There is a wide range of visualization techniques for dynamical systems. These methods are used to visualize certain properties as, e.g., stability of fixed points, characteristic changes of velocity, and bifurcations. This paper gives a short introduction to dynamical systems and describes several visualization techniques. Some of those are applied to three different dynamical systems. The application of different visualization methods to dynamical systems shows, how scientific visualization can be used for analyzing the behavior of dynamical systems, and how visualization can make analysis of a dynamical system fast and efficient.", month = sep, number = "TR-186-2-97-16", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", URL = "https://www.cg.tuwien.ac.at/research/publications/1997/Fischel-1997-CSVVP/", } @techreport{Milik-1997-GMMO, title = "Geometry of Mixed-mode Oscillations in the 3-d Autocatalator", author = "Alexandra Milik and Peter Szmolyan and Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1997", abstract = "We present a geometric explanation of a basic mechanism generating mixed-mode oscillations in a prototypical simple model of a chemical oscillator. Our approach is based on geometric singular perturbation theory and canard solutions. We explain how the small oscillations are generated near a special point, which is classified as a folded saddle-node for the reduced problem. The canard solution passing through this point separates small oscillations from large relaxation type oscillations. This allows to define a one-dimensional return map in a natural way. This bimodal map is capable of explaining the observed bifurcation sequence convincingly.", month = aug, number = "TR-186-2-97-14", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", URL = "https://www.cg.tuwien.ac.at/research/publications/1997/Milik-1997-GMMO/", } @techreport{Glaeser-1997-EVG, title = "Efficient Volume-Generation During the Simulation of NC-Milling", author = "Georg Glaeser and Eduard Gr\"{o}ller", year = "1997", abstract = "This paper presents an efficient and robust algorithm for the geometric determination of swept volumes during the simulation of NC-milling (three-axis machining and five-axis machining). The boundary Y of the volume swept by a cutter F is represented polygonally by using instantaneous helical motions to exactly determine the line of contact between F and Y. Applying concepts of differential geometry allows a better and more efficient approximation of tool paths. Tool paths are explicitly calculated when a design surface G is to be milled along prescribed curves. We also describe how to quickly determine a polygonized representation of the truncated material during the milling process by means of 'G-buffering'. This polygon-oriented algorithm is perfectly suitable for Boolean subtractions and error assessment.", month = apr, number = "TR-186-2-97-10", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "G-Buffer, sweeps, solid modeling, NC-verification, NC-milling, computer aided manufacturing", URL = "https://www.cg.tuwien.ac.at/research/publications/1997/Glaeser-1997-EVG/", } @techreport{Loeffelmann-1997-FV2, title = "Fast Visualization of 2D Dynamical Systems by the use of Virtual Ink Droplets", author = "Helwig L\"{o}ffelmann and Andreas K\"{o}nig and Eduard Gr\"{o}ller", year = "1997", abstract = "This paper presents a new visualization technique for flow fields in 2D. It utilizes a physical model of smearing ink over a sheet of paper as an intuitive metaphor for the representation of a dynamical system. This technique is capable of producing images that are comparable to those generated with line integral convolution (LIC), which is a well-known and established visualization technique for planar vector fields. Similar to oriented line integral convolution (OLIC), an extension to LIC, the virtual ink droplet method is capable of visualizing not only direction and velocity of flow (as LIC does), but also the orientation of vectors. The main advantage of the new method is, that animation sequences, which intuitively represent the dynamics induced by the underlying dynamical system, can be computed much more efficiently than by the use of LIC or OLIC. A speed-up of about 200 is usually achieved when virtual ink droplets are used instead.", month = apr, number = "TR-186-2-97-13", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, dynamical systems, flow visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1997/Loeffelmann-1997-FV2/", } @techreport{Wegenkittl-97-FOL, title = "Fast Oriented Line Integral Convolution for Vector Field Visualization via the Internet", author = "Rainer Wegenkittl and Eduard Gr\"{o}ller", year = "1997", abstract = "Oriented Line Integral Convolution (OLIC) illustrates flow fields by convolving a sparse texture with an anisotropic convolution kernel. The kernel is aligned to the underlying flow of the vector field. OLIC does not only show the direction of the flow but also its orientation. This paper presents Fast Rendering of Oriented Line Integral Convolution (FROLIC), which is approximately two orders of magnitude faster than OLIC. Costly convolution operations as done in OLIC are replaced in FROLIC by approximating a streamlet through a set of disks with varying intensity. The issue of overlapping streamlets is discussed. Two efficient animation techniques for animating FROLIC images are described. FROLIC has been implemented as a Java applet. This allows researchers from various disciplines (typically with inhomogenous hardware environments) to conveniently explore and investigate analytically defined 2D vector fields.", month = mar, number = "TR-186-2-97-07", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "vector field visualization, Line Integral Convolution", URL = "https://www.cg.tuwien.ac.at/research/publications/1997/Wegenkittl-97-FOL/", } @techreport{Wegenkittl-97-VBH, title = "Visualizing the Behavior of Higher Dimensional Dynamical Systems", author = "Rainer Wegenkittl and Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1997", abstract = "In recent years scientific visualization has been driven by the need to visualize high-dimensional data sets within high-dimensional spaces. However most visualization methods are designed for showing some statistical features of the data set. This paper deals with the visualization of trajectories of high-dimensional dynamical systems which form a L^n_n data set of a smooth n-dimensional flow. Three methods that are based on the idea of parallel coordinates are presented and discussed. Visualizations done with these new methods are shown and an interactive visualization tool for the exploration of high-dimensional dynamical systems is proposed.", month = mar, number = "TR-186-2-97-08", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "dynamical system, multi-dimension visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1997/Wegenkittl-97-VBH/", } @techreport{Loeffelmann-1997-VPM, title = "Visualizing Poincare Maps together with the underlying flow", author = "Helwig L\"{o}ffelmann and Thomas Kucera and Eduard Gr\"{o}ller", year = "1997", abstract = "We present a set of advanced techniques for the visualization of 2D Poincare maps. Since 2D Poincare maps are a mathematical abstraction of periodic or quasiperiodic 3D flows, we propose to embed the 2D visualization with standard 3D techniques to improve the understanding of the Poincare maps. Methods to enhance the representation of the relation $x\leftrightarrow{}P(x)$, e.g., the use of spot noise, are presented as well as techniques to visualize the repeated application of $P$, e.g., the approximation of $P$ as a warp function. It is shown that animation can be very useful to further improve the visualization. For example, the animation of the construction of Poincare map $P$ is inherently a proper visualization. During the paper we present a set of examples which demonstrate the usefulness of our techniques.", month = mar, number = "TR-186-2-97-06", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Poincare maps, dynamical systems, visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1997/Loeffelmann-1997-VPM/", } @techreport{Loeffelmann-1997-HSV, title = "Hierarchical Streamarrows for the Visualization of Dynamical Systems", author = "Helwig L\"{o}ffelmann and Lukas Mroz and Eduard Gr\"{o}ller", year = "1997", 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.", month = jan, number = "TR-186-2-97-02", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "streamsurfaces, visualization, dynamical systems", URL = "https://www.cg.tuwien.ac.at/research/publications/1997/Loeffelmann-1997-HSV/", } @techreport{Wegenkittl-1996-AFR, title = "Animating Flowfields: Rendering of Oriented Line Integral Convolution", author = "Rainer Wegenkittl and Eduard Gr\"{o}ller and Werner Purgathofer", year = "1996", abstract = "Line Integral Convolution (LIC) is a common approach for the visualization of vector fields. It is well suited for visualizing the direction of a flow field, but it gives no information about the orientation of the underlying vectors. We introduce Oriented Line Integral Convolution (OLIC), where direction as well as orientation are encoded within the resulting image. This is achieved by using a low frequency input texture and a ramp like (unisotropic) convolution kernel. This method can be animated, whereby the computation of so called pixel traces fastens the calculation process. In the result section various OLICs using simple and real-world vector fields are shown.", month = dec, number = "TR-186-2-96-23", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "flowfield visualization, line integral convolution", URL = "https://www.cg.tuwien.ac.at/research/publications/1996/Wegenkittl-1996-AFR/", } @techreport{Wegenkittl-1996-SDI, title = "Simulation of Differential Interferometry and Comparison with Experimental Results", author = "Rainer Wegenkittl and Eduard Gr\"{o}ller and Andreas Goldsteiner", year = "1996", 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 very 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 finallysome results allowing a comparison between experimental and simulated interferograms are shown.", month = nov, number = "TR-186-2-96-22", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "interferometry, simulation", URL = "https://www.cg.tuwien.ac.at/research/publications/1996/Wegenkittl-1996-SDI/", } @techreport{Loeffelmann-1996-DS3, title = "DynSys3D: A workbench for developing advanced visualization techniques in the field of three-dimensional dynamical systems", author = "Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1996", abstract = "This work describes DynSys3D, a framework for testing and implementing visualization techniques in the area of three-dimensional dynamical systems. DynSys3D has been designed to meet requirements which allow a fast and modular investigation of dynamical systems. Such requirements are, e.g., extendability, interactivity, and symmetry. Some visualization examples realized with DynSys3D illustrate the flexibility of the system.", month = nov, number = "TR-186-2-96-21", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, dynamical systems", URL = "https://www.cg.tuwien.ac.at/research/publications/1996/Loeffelmann-1996-DS3/", } @techreport{wegenkittl-1996-GTW, title = "A Guided Tour to Wonderland: Visualizing the Slow-Fast Dynamics of an Analytical Dynamical System", author = "Rainer Wegenkittl and Eduard Gr\"{o}ller and Werner Purgathofer", year = "1996", abstract = "The analysis of complex dynamical systems produces large amounts of data that have to be interpreted efficiently. Visualizing the phase space of such systems illustrates geometrically the behavior of the underlying dynamics. This work investigates the visualization of Wonderland, a four dimensional econometric model, which describes interactions between population growth, economic activity and environmental implications. Wonderland belongs to a class of interesting dynamical systems with a pronounced slow-fast dynamics, i.e., some variables are changing much faster than others. Furthermore the behavior of the Wonderland model is characterized by manifolds which are not streamsurfaces, i.e., the flow does not stay within these surfaces. This paper discusses the application and adaptation of various visualization techniques to analytical dynamical systems with special properties as mentioned above.", month = apr, number = "TR-186-2-96-11", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "vector field visualization, complex dynamical systems", URL = "https://www.cg.tuwien.ac.at/research/publications/1996/wegenkittl-1996-GTW/", } @techreport{loeffelmann-1996-CVA, title = "Classifying the Visualization of Analytically Specified Dynamical Systems", author = "Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller and Rainer Wegenkittl and Werner Purgathofer", year = "1996", abstract = "In this paper we suggest a classification of visualization techniques for analytically specified dynamical systems into four different approaches. We distinguish between local properties, the topology of behavior, global properties, and classes of dynamical systems with respect to various topics of visualization. By presenting advanced visualization techniques that we applied during three recent projects, we discuss their embedding within the classification scheme The dynamical systems visualized are the ``Dynastic Cycle'', which is a model for rise and fall of dynasties in ancient China, the ``Wonderland'' model, that simulates the interactions of population growth, economic activities, and environmental pollution, and a model for mixed-mode oscillations, which occurs in chemistry. ", month = apr, number = "TR-186-2-96-15", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, dynamical systems", URL = "https://www.cg.tuwien.ac.at/research/publications/1996/loeffelmann-1996-CVA/", } @techreport{loeffelmann-1996-SVM, title = "Streamarrows: Visualizing Multiple Layers of Streamsurfaces", author = "Helwig L\"{o}ffelmann and Lukas Mroz and Eduard Gr\"{o}ller and Werner Purgathofer", year = "1996", abstract = "Occlusion is a crucial spatial cue for the human visual system. Painters as well as researchers in the field of computer graphics have been dealing with this aspect for a long time. In the field of visualization occlusion can be especially problematic. We present a new approach to dealing with streamsurfaces that occlude major parts of the system representation. Analyzing mixed-mode oscillations, which are a special class of analytically defined dynamical systems, we came across geometrically complex streamsurfaces with curly shape. Certain regions of these surfaces, that are necessary to describe the behavior of the system, occlude major parts of the model. We combined and adopted several visualization techniques to deal with this problem. Streamarrows, which are semi-transparent portions of the streamsurface, allow the viewer to see through and diminish the problem of occlusion. Cross-sections and the removal of certain portions of the model reduce occlusion as well and thus improve visual perception. Choosing the shape of an arrow for segmentation allows to visualize even more information at the streamsurface, e.g., the direction of the flow. An anisotropic spot noise texture is further used to emphasize flow within a streamsurface. Finally animation techniques were applied to facilitate the interpretation of dynamical systems with complex shaped streamsurfaces.", month = apr, number = "TR-186-2-96-12", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "flow visualization, streamsurfaces, complex dynamical systems, mixed-mode oscillations", URL = "https://www.cg.tuwien.ac.at/research/publications/1996/loeffelmann-1996-SVM/", } @techreport{groeller-1996-ACE, title = "Autostereograms - Classification and Experimental Investigations", author = "Thomas Tonnhofer and Eduard Gr\"{o}ller", year = "1996", abstract = "One important branch in computer graphics is the research for representing three-dimensional objects. Many different techniques have been developed to convey to a user of a two-dimensional medium that he sees a three-dimensional scene. Apart from realistic image synthesis, e.g., ray tracing and radiostiy, there are techniques which try to generate a real three-dimensional impression for the viewer. In the last years a new technique to produce such pictures has gained popularity. The generated images are called autostereograms. An interesting feature with this technique is, that only single pictures have to be produced and that no additional equipment is needed to produce a three dimensional impression. Therefore autostereograms are also called 'single image stereograms' (SIS). This work gives an overview on the technique of autostereograms. After a short description of the algorithms to generate autostereograms a detailed classification is introduced. After that the perceptability of autostereograms and software related to the topic is discussed. Moreover, experiments with animated autostereograms will be presented. Finally some experiments concerning the usage and change of colors in autostereograms and the combination of two depth-scenes within one image will be discussed.", month = mar, number = "TR-186-2-96-09", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Autostereograms", URL = "https://www.cg.tuwien.ac.at/research/publications/1996/groeller-1996-ACE/", } @techreport{groeller-1996-avn, title = "Analysis and Visualization of Nonlinear Time Sequences", author = "Anton M. Kirchsteiger and Eduard Gr\"{o}ller", year = "1996", abstract = "During the last years there has been a considerable increase in the interest in nonlinear dynamical systems. More and more scientists apply nonlinear techniques to analyze their data sets which are often given as discrete time sequences. This paper gives a short overview on nonlinear systems and time sequences resulting from such nonlinear systems. The concept of attractors is explained and Poincare maps are described. The analysis of time sequences is discussed with respect to applying visualization techniques as steering tools in the investigation process. Because discrete time sequences resulting from measurements are typically affected by noise a signal - noise separation has to be done. The method of time delays is then subsequently used for phase-space reconstruction. Important numbers to characterize dynamical systems are fractal dimension and Lyapunov exponents. These concepts are therefore treated as well. A low cost visualization system (AVTS) was implemented which is designed to specifically support a researcher in his investigation of nonlinear time sequences. Emphasis has been put on handling of large data sets, as well as fast interactive manipulation and visual representation of time sequences. The visual inspection with AVTS allows the research to quickly focus his investigation on interesting portions of the data.", month = jan, number = "TR-186-2-96-05", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Visualization, Time Sequences, Nonlinearity, Fractal Dimension", URL = "https://www.cg.tuwien.ac.at/research/publications/1996/groeller-1996-avn/", } @techreport{Groeller-1995-GOW, title = "The Geometry of Wonderland", author = "Eduard Gr\"{o}ller and Rainer Wegenkittl and Alexandra Milik and Alexia Prskawetz and Gustav Feichtinger and Warren C. Sanderson", year = "1995", abstract = "We analyze Wonderland - a model of demographic,economic and environmental interactions - by combining numerical simulations with basic ideas of geometric singular perturbation theory. This theory dealing with slow-fast dynamical systems helps us to gain new insights into the system's behaviour. We give conditions for the occurrence of rapid environmental changes in Wonderland. Since the chosen approach is inherently geometric we also focus on the visualization of our results.", month = dec, number = "TR-186-2-95-17", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "dynamical system, visualization", URL = "https://www.cg.tuwien.ac.at/research/publications/1995/Groeller-1995-GOW/", } @techreport{Groeller-1995-SDC, title = "Simulation und Darstellung computergenerierter Strickware", author = "Eduard Gr\"{o}ller and R. T. Rau and Wolfgang Stra{\ss}er", year = "1995", abstract = "In Computer Graphics a boundary representation of objects is often used to generate realistic synthetic images. For certain objects it is more suitable to use a volume representation. In this paper we investigate the visualization of knitting patterns where the details of the yarn were modeled by voxel data. The visualization and the modeling of textiles has already been investigated in depth in the computer graphics literature. However most of the publications consider woven fabrics. In the case of knitwear the topological specification of the knitting pattern allows a subdivision into basic elements. The thread course and the microstructure of the yarn are then approximated by voxel data. The periodic structure of knitting patterns allows for a compact representation and an efficient rendering. The generated images demonstrate the possible realistic simulations. ", month = nov, number = "TR-186-2-95-15", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "knitwear, volume visualization, textile modeling", URL = "https://www.cg.tuwien.ac.at/research/publications/1995/Groeller-1995-SDC/", } @techreport{Groeller-1995-CCG, title = "Coherence in Computer Graphics", author = "Eduard Gr\"{o}ller and Werner Purgathofer", year = "1995", abstract = "Coherence denotes similarities between items or entities. It describes the extent to which these items or entities are locally constant. An introduction to coherence and a survey of various types of coherence, that are used in computer graphics, are given. Techniques and data structures for exploiting coherence in computer graphics are described. Incremental techniques, bounding volume schemes, subdivision techniques and several geometric data structures are discussed in more detail. Applications of coherence principles to computer graphics are treated and a survey of previous research is done.", month = mar, number = "TR-186-2-95-04", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "coherence, computer graphics, incremental techniques, bounding volumes, subdivision", URL = "https://www.cg.tuwien.ac.at/research/publications/1995/Groeller-1995-CCG/", } @techreport{Acquisto-1995-DCR, title = "A Distortion Camera for Ray Tracing", author = "Pietro Acquisto and Eduard Gr\"{o}ller", year = "1995", abstract = "Ray tracing is a powerful technique for realistic image generation. Typically a simple camera definition is used, whereby a 3D environment is mapped onto an image plane either by an orthographic or perspective projection. The concept of the usual simple camera definition is extended in several ways to achieve distorted views or projections of the object scene. The origins of primary rays are not required to lie on a plane anymore. Thus projections onto curved image surfaces are possible. The directions of primary rays may be chosen according to various nonlinear functions that allow nonstandard projections of the environment. The concept of centers of interest (coins) is introduced that enables to concentrate on especially interesting portions of object space. A center of interest is a 3D position that either distorts (attracts) a portion of the image surface or locally influences the directions of primary rays. The results of a test implementation are presented to show the feasibility of the methods presented. Several applications of distorted images are: creating elemental holographic images and raster omnimax images, virtual reality and arts.", month = mar, number = "TR-186-2-95-05", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "ray tracing, distortion camera, projection, image generation", URL = "https://www.cg.tuwien.ac.at/research/publications/1995/Acquisto-1995-DCR/", } @techreport{Loeffelmann-1995-RTE, title = "Ray Tracing with Extended Cameras", author = "Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1995", abstract = "This paper presents an extension of the camera module for ray tracers. As an alternative to the standard pinhole camera an Abstract Camera Machine is introduced, which represents a generalization of the camera module at an abstract level. The Abstract Camera Machine itself is based on simple transformations and mappings, which are chosen from a large set of representatives. They are integrated as sub-modules to complete the camera mapping procedure, which generates rays out of image locations (pixels). Depending on what type of transformations are used, many different extended cameras can be built. The structure of the Abstract Camera Machine and an overview of the transformations and mappings are given. Some results, which were rendered by using a public domain ray tracer in combination with the extended cameras, are presented as well. They show the feasibility of this approach and give an impression of the areas of application for this extension to the camera module. Using extended cameras it is easily possible to produce special and artistic effects, e.g., a local zoom of especially interesting regions. Overviews of given scenes can be modelled and several views of the same object can be integrated into one picture, e.g., a building could be shown from the inside and the outside simultaneously.", month = mar, number = "TR-186-2-95-06", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Ray Tracing, Camera Model, Projections, Image Distortions", URL = "https://www.cg.tuwien.ac.at/research/publications/1995/Loeffelmann-1995-RTE/", } @techreport{Groeller-1995-IED, title = "Interactive Exploration of Dynamical Systems", author = "Eduard Gr\"{o}ller", year = "1995", abstract = "Nonlinear deterministic dynamical systems often exhibit complex and chaotic behavior which is difficult to comprehend. Visualizing the characteristics of such systems is therefore essential for an understanding of the underlying dynamics. In this paper concepts for the interactive graphical exploration of analytically defined dynamical systems are discussed. Emphasis is put on interactivity which shall facilitate the investigation and exploration of such systems. The following topics on dynamical systems are treated in more detail: interactive specification, simple and fast graphical representation, and interactive modification. The paper concentrates on 2D and 3D orthographic projections of higher-dimensional phase spaces and on the display of bifurcation diagrams. A prototype software system which incorporates the previously presented ideas is shortly discussed. The software system is intended to offer a quick insight into the dynamics of a dynamical system and to enable fast investigation of variations of a dynamical system.", month = jan, number = "TR-186-2-95-1", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "dynamical system, interactive analysis, phase space, bifurcation, chaos theory", URL = "https://www.cg.tuwien.ac.at/research/publications/1995/Groeller-1995-IED/", } @techreport{Fischel-1995-VLS, title = "Visualization of Local Stability of Dynamical Systems", author = "Georg Fischel and Eduard Gr\"{o}ller", year = "1995", abstract = "Several methods for visualizing local stability properties of dynamical systems are presented. The calculation of characteristic values of local stability for linear and nonlinear systems is discussed. Two principles of visualizing local stability are introduced. The first 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.", month = jan, number = "TR-186-2-95-2", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", URL = "https://www.cg.tuwien.ac.at/research/publications/1995/Fischel-1995-VLS/", } @techreport{Groeller-1994-HIS, title = "Hyperrealistic Image Synthesis and Manipulation", author = "Eduard Gr\"{o}ller", year = "1994", abstract = "Computer graphics techniques allow the generation of realistic and hyperrealistic images. Some of these techniques are discussed in this paper. Ray tracing and radiosity produce 2D images out of a 3D synthetic object description. Two extensions of the ray tracing technique (nonlinear ray tracing, extended camera specification) are described. Finally image warping and image morphing which manipulate 2D images to produce modified 2D images is dealt with.", month = nov, number = "TR-186-2-94-11", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "(nonlinear) ray tracing, radiosity, extended camera specification, morphing", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Groeller-1994-HIS/", } @techreport{Loeffelmann-1994-PSQ, title = "Parameterizing Superquadrics", author = "Helwig L\"{o}ffelmann and Eduard Gr\"{o}ller", year = "1994", abstract = "Superquadrics are well known and often used 3D surface objects in computer graphics. They are used for modelling parts of scenes that are then rendered using photorealistic image synthesis algorithms (e.g., ray tracing). For some techniques, like texturing, which are part of these rendering methods, the type of the parameterization of such a surface has to be chosen carefully and is not intuitively obvious at first sight. There are cases, where the straight forward extension of quadric parameterizations to superquadrics do not produce satisfying results. We therefore investigate a number of different parameterizations in combination with the corresponding formulas, and point out some significant differences between them.", month = nov, number = "TR-186-2-94-5", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "parameterization, quadrics, superquadrics", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Loeffelmann-1994-PSQ/", } @techreport{Groeller-1994-AIV, title = "Attract - Interactive Visualization of Dynamical Systems", author = "Eduard Gr\"{o}ller and Herbert Oppolzer", year = "1994", abstract = "An interactive program for visualizing the long term behavior of dynamical systems, e.g., attractors and bifurcation diagrams, is presented. The program allows an easy specification of a set of formulas and constants which describe a dynamical system. This set of equations is then used for displaying the geometrical structure of the long term development of the dynamical system. The user defines the assignment of variables of the dynamical system to at most three spatial axes and one color axis. Viewing parameters, e.g., point of view, zoom, rotation angle, can again be changed interactively. The program is intended to provide researchers working on dynamical systems with a fast visual analysis and experimentation tool.", month = nov, number = "TR-186-2-94-14", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, interactive, dynamical system, chaos, strange attractor, bifurcation diagram", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Groeller-1994-AIV/", } @techreport{Groeller-1994-MRN, title = "Modeling and Rendering of Nonlinear Iterated Function Systems", author = "Eduard Gr\"{o}ller", year = "1994", abstract = "Iterated Function Systems are typically defined through sets of contractive linear transformations. The theory of Iterated Function Systems is based on the contractivity but not on the linearity of the defining functions. Piecewise bilinear distortions of grids are used in this work to specify nonlinear Iterated Function Systems. Nonlinear Iterated Functions Systems are characterized by a higher degree of flexibility and greater modeling capability than their linear counterparts. Modeling and rendering aspects are discussed. Limit sets of 2D nonlinear Iterated Function Systems are represented by approximating point sets. Limit sets of 3D nonlinear Iterated Function Systems are either rendered by displaying approximating point sets (z-buffer approach) or through ray tracing an approximate set of 3D solids. Example images of a test implementation are presented.", month = nov, number = "TR-186-2-94-12", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "Fractals, Iterated Functions Systems, nonlinear, Modeling, Rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Groeller-1994-MRN/", } @techreport{Purgathofer-1994-CPI, title = "A Collection of Papers of the Institute of Computer Graphics", author = "Werner Purgathofer and Martin Feda and Michael Gervautz and Robert Devide and Werner Petricek and Eduard Gr\"{o}ller and Helwig L\"{o}ffelmann and Michael Zeiller and A. Vesel", year = "1994", abstract = "This is the first technical report of the Institute of Computer Graphics at the Technical University of Vienna. It contains papers published by our research group between 1992 and 1993 providing an overview of our work during that time.", month = aug, number = "TR-186-2-94-1", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "computer graphics, visualization, animation, radiosity, monte carlo, multi media, nonlinear ray tracing, coherence, collision detection", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Purgathofer-1994-CPI/", } @techreport{Groeller-1994-IDN, title = "Interactive Design of Nonlinear Functions for Iterated Function Systems", author = "Eduard Gr\"{o}ller and Rainer Wegenkittl", year = "1994", abstract = "The basic requirement for the functions of an Iterated Function System (IFS for short) is contractivity. Nevertheless the majority of recent scientific investigations is concentrating on IFSs defined through a set of contractive linear functions. Simpler handling of this kind of functions and a more predictable result is the main reason for this approach. In this work we use distorted grids (representing nonlinear functions) to specify an IFS with a higher degree of flexibility and a higher modelling capability. A program for modeling these grids with so-called high-level operations is presented. Attention is directed to the interactivity of designing the IFS and rendering its limit set. Therefore a z-Buffer for displaying the result of a stochastic algorithm is included. Example images designed with the implemented software system are presented.", month = aug, number = "TR-186-2-94-3", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "iterated function system (IFS), nonlinear, interactive design, fractals, rendering", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Groeller-1994-IDN/", } @techreport{Groeller-1994-AVT, title = "Application of Visualization Techniques to Complex and Chaotic Dynamical Systems", author = "Eduard Gr\"{o}ller", year = "1994", abstract = "Visualization provides powerful tools for the investigation of dynamical systems. The application of various visualization techniques to complex and chaotic dynamical systems is discussed. The interactive specification and modification of strange attractors allow an easier understanding of the underlying dynamics. Graphical time series analysis visualizes time series and phase space reconstruction techniques. Visualization of Nonlinear Iterated Function systems is described as well. Finally advanced visualization techniques are employed to illustrate shape and chaotic properties of strange attractors.", month = jun, number = "TR-186-2-94-13", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visualization, dynamical systems, chaos, fractals, interactive, strange attractors, graphical time series analysis, iterated function systems", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Groeller-1994-AVT/", } @techreport{Groeller-1994-ITV, title = "Interactive Transformation of 2D Vector Data", author = "Eduard Gr\"{o}ller", year = "1994", abstract = "A program for the interactive transformation of 2D vector data is presented. The program allows the definition of local and global transformations to establish a matching between two data sets. Zoologists deduce relationships between life forms by investigating their geometric shape. The presented program enables the investigation of 2D cross-sections of, e.g., insect bodies. The amount of the distortion required to map one cross-section onto another illustrates evolutionary links among different species. The program is intended to facilitate the above mentioned research activities.", month = jun, number = "TR-186-2-94-8", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "interactive morphing, 2D vector data, grid distortions, point based morphing, attracting (repelling) points", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Groeller-1994-ITV/", } @techreport{Jankovic-1994-PBM, title = "Physically Based Matching of Multimodal Medical Information", author = "Vojtech Jankovic and Eduard Gr\"{o}ller", year = "1994", abstract = "The paper presents a general non-rigid body representation suitable for physically-based modeling of deformations of inhomogenious objects. The reliability of the obtained results is demonstrated on real medical data sets - CT an MR scans of human brain.", month = jun, number = "TR-186-2-94-9", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "physically-based modeling, medical imaging, morphing, multimodal matching, morphing of inhomogeneous material", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Jankovic-1994-PBM/", } @techreport{Groeller-1994-CSA, title = "Coherence in scan-line algorithms for CSG", author = "Eduard Gr\"{o}ller and Peter Brunner", year = "1994", abstract = "Scan-line algorithms for visibility calculation exploit various types of coherence properties. Several scan-line algorithms for Constructive Solid Geometry (CSG) are discussed. In one approach CSG primitives are represented by polygonal approximations. Another technique processes CSG primitives as general quadric surfaces. We investigate the handling of frequently occurring quadric surfaces (cube, cone, sphere, cylinder) as distinct cases. Thus the differing properties of such objects can be used more efficiently than a uniform approach would allow. A so called eBRep (extended Boundary Representation) is defined for the frequently occurring quadric surfaces. An eBRep is an exact representation of a quadric object and contains curved edges and faces. For each of the above mentioned quadric surfaces a different, geometry dependent eBRep is specified. A comparison between the polygon-based scan-line algorithm for CSG and our eBRep based approach is done. eBRep is a storage efficient exact representation of quadric surfaces, well suited for scan-line visibility determination.", month = jan, number = "TR-186-2-94-10", address = "Favoritenstrasse 9-11/E193-02, A-1040 Vienna, Austria", institution = "Institute of Computer Graphics and Algorithms, Vienna University of Technology ", note = "human contact: technical-report@cg.tuwien.ac.at", keywords = "visibility, scan-line algorithm, Constructive Solid Geometry (CSG), quadrics, coherence", URL = "https://www.cg.tuwien.ac.at/research/publications/1994/Groeller-1994-CSA/", }