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Proceedings of the conference on Visualization '01

作者： Anna Vilanova Bartrolí Rainer Wegenkittl Andreas König Eduard Gröller Institute of Computer Graphics and Algorithms Vienna University of Technology Tiani Medgraph

ISBN: (纸本)9780780372009

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.

关键词： volume rendering virtual endoscopy

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DGCVis: an exploratory 3D visualization of graph pyramids

DGCVis: an exploratory 3D visualization of graph pyramids

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International Conference on Coordinated and Multiple Views in Exploratory Visualization

作者： A. Kerren F. Breier P. Kugler Institute of Computer Graphics and Algorithms University of Technology Vienna Vienna Austria

Hierarchies of plane graphs, called graph pyramids, are used for collecting, storing and analyzing geographical information based on satellite images or other input data. Important for the better understanding of the geographical data, like landscape properties or thematical maps, is the appropriate visualization of graph pyramids and related information. In this paper, we present an interactive visualization tool that supports several coordinated views on graph pyramids, subpyramids, thematical maps, etc. Furthermore, some implementation details and application results are discussed.

关键词： Image segmentation Image analysis Satellites Data visualization Shape computer graphics Information analysis Algorithm design and analysis Geography Environmental factors

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Seamless Texturing of Archaeological Data

Seamless Texturing of Archaeological Data

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International Congress on Digital Heritage

作者： Michael Birsak Przemyslaw Musialski Murat Arikan Michael Wimmer Institute of Computer Graphics and Algorithms Vienna University of Technology Vienna Austria

In this paper we propose a framework for out-of-core real-time rendering of high-quality textured archaeological data-sets. Our input is a triangle mesh and a set of calibrated and registered photographs. Our system performs the actual mapping of the photos to the mesh for high-quality reconstructions, which is a task referred to as the labeling problem. Another problem of such mappings are seams that arise on junctions between triangles that contain information from different photos. These are are approached with blending methods, referred to as leveling. We address both problems and introduce a novel labeling approach based on occlusion detection using depth maps that prevents texturing of parts of the model with images that do not contain the expected region. Moreover, we propose an improved approach for seam-leveling that penalizes too large values and helps to keep the resulting colors in a valid range. For high-performance visualization of the 3D models with a huge amount of textures, we make use of virtual texturing, and present an application that generates the needed texture atlas in significantly less time than existing scripts. Finally, we show how the mentioned components are integrated into a visualization application for digitized archaeological site.

关键词： Archaeological Data high-quality registered photographs

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Virtual colon flattening

Virtual colon flattening

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3rd Joint Eurographics - IEEE TCVG Symposium on Visualization, VisSym 2001

作者： Bartrolí, A. Vilanova Wegenkittl, R. König, A. Gröller, E. Sorantin, E. Institute of Computer Graphics and Algorithms Vienna University of Technology Tiani Medgraph Section of Digital Information and Image Processing Department of Radiology University Hospital Graz Austria

ISBN: (纸本)3211836748

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. © 2001 Eurographics Association. All rights reserved.

关键词： Image enhancement

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A branch-and-cut-and-price algorithm for a fingerprint-template compression application

A branch-and-cut-and-price algorithm for a fingerprint-templ...

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Federated Conference on computer Science and Information Systems (FedCSIS)

作者： Andreas M. Chwatal Corinna Thöni Karin Oberlechner Günther R. Raidl Institute of Computer Graphics and Algorithms Vienna University of Technology Vienna Austria

In this work we present a branch-and-cut-and-price algorithm for the compression of fingerprint minutiae templates, in order to embed them into passport images by watermarking techniques as an additional security feature. For this purpose the minutiae data, which is a set of characteristic points of the fingerprint, is encoded by a spanning tree whose edges are encoded efficiently by a reference to an element in a dictionary (template arc) and a small correction vector. Our proposed branch-and-cut-and-price algorithm creates meaningful template arcs from a huge set of possible ones on demand in the pricing-procedure. Cutting-planes are separated in order to obtain connected subgraphs from which spanning trees can then be easily deduced. Our computational experiments confirm the superior performance of the algorithm in comparison to previous approaches for the spanning tree based encoding scheme.

关键词： Vectors Pricing Upper bound Optimization Dictionaries Equations Encoding

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BRDF approximation and estimation for Augmented Reality

BRDF approximation and estimation for Augmented Reality

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International Conference on System Theory, Control, and Computing (ICSTCC)

作者： Patrick Kühtreiber Martin Knecht Christoph Traxler Austria Institute of Computer Graphics and Algorithms Vienna University of Technology Austria

In Augmented Reality applications it is important to have a good description of the surfaces of real objects if a consistent shading between real and virtual object is required. If such a description of a surface is not available it has to be estimated or approximated. In this paper several methods are presented that deal with the bi-directional reflectance distribution function (BRDF) approximation in Augmented Reality. Of course an important thing to discuss is whether the applications we present work in real-time and compute real looking results. Different methods can be used to achieve these goals. All of the methods presented work via image based lighting. Some require a 3D polygonal mesh representation of the object, for which the BRDF shall be approximated. Some methods estimate the BRDF parameters via error values and provide results at each iteration.

关键词： Lighting Light sources Cameras Estimation Materials Mathematical model Approximation methods

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Uncertainty-aware exploration of continuous parameter spaces using multivariate prediction

Uncertainty-aware exploration of continuous parameter spaces...

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13th Eurographics / IEEE Symposium on Visualization, EuroVis 2011

作者： Berger, W. Piringer, H. Filzmoser, P. Gröller, E. VRVis Research Center Austria Department of Statistics and Probability Theory Vienna University of Technology Austria Institute of Computer Graphics and Algorithms Vienna University of Technology Austria

Systems projecting a continuous n-dimensional parameter space to a continuous m-dimensional target space play an important role in science and engineering. If evaluating the system is expensive, however, an analysis is often limited to a small number of sample points. The main contribution of this paper is an interactive approach to enable a continuous analysis of a sampled parameter space with respect to multiple target values. We employ methods from statistical learning to predict results in real-time at any user-defined point and its neighborhood. In particular, we describe techniques to guide the user to potentially interesting parameter regions, and we visualize the inherent uncertainty of predictions in 2D scatterplots and parallel coordinates. An evaluation describes a real-world scenario in the application context of car engine design and reports feedback of domain experts. The results indicate that our approach is suitable to accelerate a local sensitivity analysis of multiple target dimensions, and to determine a sufficient local sampling density for interesting parameter regions. © 2011 The Author(s) Journal compilation © 2011 The Eurographics Association and Blackwell Publishing Ltd. Published by Blackwell Publishing.

关键词： Forecasting

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Letting ants labeling point features [sic.: for 'labeling' read 'label']

Letting ants labeling point features [sic.: for 'labeling' r...

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Congress on Evolutionary Computation

作者： M. Schreyer G.R. Raidl Institute of Computer Graphics and Algorithms University of Technology Vienna Vienna Austria

This paper describes an ant colony system (ACS) for labeling point features. A pre-processing step reduces the search space in a safe way. The ACS applies local improvement and masking, a technique that focuses the optimization on critical regions. Empirical results indicate that the ACS reliably identifies high-quality solutions which are in many cases better than those of a state-of-the-art genetic algorithm for point-feature labeling.

关键词： Labeling Space technology computer graphics Ant colony optimization Genetic algorithms Visualization Tagging Cities and towns NP-hard problem Knowledge based systems

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Profile flags: A novel metaphor for probing of T2 maps

Profile flags: A novel metaphor for probing of T2 maps

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VIS 05: IEEE Visualization 2005, Proceedings

作者： Mlejnek, Matej Ermes, Pierre Vilanova, Anna Van Rijt, Rob Der Van Bosch, Harrie Den Gerritsen, Frans Gröller, Meister Eduard Institute of Computer Graphics and Algorithms Vienna University of Technology Austria Philips Medical Systems Best Netherlands Department of Biomedical Engineering Technische Universiteit Eindhoven Netherlands Catharina Hospital Eindhoven Netherlands

ISBN: (纸本)0780394623

This paper describes a tool for the visualization of T2 maps of knee cartilage. Given the anatomical scan and the T2 map of the cartilage, we combine the information on the shape and the quality of the cartilage in a single image. The Profile Flag is an intuitive 3D glyph for probing and annotating of the underlying data. It comprises a bulletin board pin-like shape with a small flag on top of it. While moving the glyph along the reconstructed surface of an object, the curve data measured along the pin's needle and in its neighborhood are shown on the flag. The application area of the Profile Flag is manifold, enabling the visualization of profile data of dense but inhomogeneous objects. Furthermore, it extracts the essential part of the data without removing or even reducing the context information. By sticking Profile Flags into the investigated structure, one or more significant locations can be annotated by showing the local characteristics of the data at that locations. In this paper we are demonstrating the properties of the tool by visualizing T2 maps of knee cartilage. © 2005 IEEE.

关键词： Cartilage

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Hierarchical interactive image segmentation using irregular pyramids

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Lecture Notes in computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 2011年 6658 LNCS卷 245-254页

作者： Gerstmayer, Michael Haxhimusa, Yll Kropatsch, Walter G. Pattern Recognition and Image Processing Group Institute of Computer Graphics and Algorithms Vienna University of Technology Austria

ISBN: (纸本)9783642208430

In this paper we describe modifications of irregular image segmentation pyramids based on user-interaction. We first build a hierarchy of segmentations by the minimum spanning tree based method, then regions from different (granularity) levels are combined to a final (better) segmentation with user-specified operations guiding the segmentation process. Based on these operations the users can produce a final image segmentation that best suits their applications. This work can be used for applications where we need accuracy in image segmentation, in annotating images or creating ground truth among others. © 2011 Springer-Verlag Berlin Heidelberg.

关键词： Image segmentation

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