@phdthesis{Prohaska2007, author = {Prohaska, Steffen}, title = {Skeleton-based visualization of massive voxel objects with network-like architecture}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14888}, year = {2007}, abstract = {This work introduces novel internal and external memory algorithms for computing voxel skeletons of massive voxel objects with complex network-like architecture and for converting these voxel skeletons to piecewise linear geometry, that is triangle meshes and piecewise straight lines. The presented techniques help to tackle the challenge of visualizing and analyzing 3d images of increasing size and complexity, which are becoming more and more important in, for example, biological and medical research. Section 2.3.1 contributes to the theoretical foundations of thinning algorithms with a discussion of homotopic thinning in the grid cell model. The grid cell model explicitly represents a cell complex built of faces, edges, and vertices shared between voxels. A characterization of pairs of cells to be deleted is much simpler than characterizations of simple voxels were before. The grid cell model resolves topologically unclear voxel configurations at junctions and locked voxel configurations causing, for example, interior voxels in sets of non-simple voxels. A general conclusion is that the grid cell model is superior to indecomposable voxels for algorithms that need detailed control of topology. Section 2.3.2 introduces a noise-insensitive measure based on the geodesic distance along the boundary to compute two-dimensional skeletons. The measure is able to retain thin object structures if they are geometrically important while ignoring noise on the object's boundary. This combination of properties is not known of other measures. The measure is also used to guide erosion in a thinning process from the boundary towards lines centered within plate-like structures. Geodesic distance based quantities seem to be well suited to robustly identify one- and two-dimensional skeletons. Chapter 6 applies the method to visualization of bone micro-architecture. Chapter 3 describes a novel geometry generation scheme for representing voxel skeletons, which retracts voxel skeletons to piecewise linear geometry per dual cube. The generated triangle meshes and graphs provide a link to geometry processing and efficient rendering of voxel skeletons. The scheme creates non-closed surfaces with boundaries, which contain fewer triangles than a representation of voxel skeletons using closed surfaces like small cubes or iso-surfaces. A conclusion is that thinking specifically about voxel skeleton configurations instead of generic voxel configurations helps to deal with the topological implications. The geometry generation is one foundation of the applications presented in Chapter 6. Chapter 5 presents a novel external memory algorithm for distance ordered homotopic thinning. The presented method extends known algorithms for computing chamfer distance transformations and thinning to execute I/O-efficiently when input is larger than the available main memory. The applied block-wise decomposition schemes are quite simple. Yet it was necessary to carefully analyze effects of block boundaries to devise globally correct external memory variants of known algorithms. In general, doing so is superior to naive block-wise processing ignoring boundary effects. Chapter 6 applies the algorithms in a novel method based on confocal microscopy for quantitative study of micro-vascular networks in the field of microcirculation.}, language = {en} } @misc{RosanwoPetzProhaskaetal.2008, author = {Rosanwo, Olufemi and Petz, Christoph and Prohaska, Steffen and Hotz, Ingrid and Hege, Hans-Christian}, title = {Dual Streamline Seeding - Method and Implementation}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-11032}, number = {08-49}, year = {2008}, abstract = {This work introduces a novel streamline seeding technique based on dual streamlines that are orthogonal to the vector field, instead of tangential. The greedy algorithm presented here produces a net of orthogonal streamlines that is iteratively refined resulting in good domain coverage and a high degree of continuity and uniformity. The algorithm is easy to implement and efficient, and it naturally extends to curved surfaces.}, language = {en} } @misc{ClasenPaarProhaska2011, author = {Clasen, Malte and Paar, Philip and Prohaska, Steffen}, title = {Level of Detail for Trees Using Clustered Ellipsoids}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-14251}, number = {11-41}, year = {2011}, abstract = {We present a level of detail method for trees based on ellipsoids and lines. We leverage the Expectation Maximization algorithm with a Gaussian Mixture Model to create a hierarchy of high-quality leaf clusterings, while the branches are simplified using agglomerative bottom-up clustering to preserve the connectivity. The simplification runs in a preprocessing step and requires no human interaction. For a fly by over and through a scene of 10k trees, our method renders on average at 40 ms/frame, up to 6 times faster than billboard clouds with comparable artifacts.}, language = {en} } @misc{KlindtBaumProhaskaetal.2013, author = {Klindt, Marco and Baum, Daniel and Prohaska, Steffen and Hege, Hans-Christian}, title = {iCon.text - a customizable iPad app for kiosk applications in museum exhibitions}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-17731}, year = {2013}, abstract = {We present iCon.text, a kiosk platform for the iPad centered around artefacts, whose content and layout can be tailored without programming skills for specific museum exhibitions. The central metaphor to access information is a virtual postcard with one front and a customizable number of back sides that provide details about exhibits to museum visitors in textual and image form. Back sides can link to others cards. Access to these postcards is possible through one or more navigation views that can be navigated to from a navigation bar. The entry point to the application is designed as a multitouch interactive pile of cards in a playful manner that allows visitors of any age an easy approach to the presentation and interaction metaphor. To directly access a certain postcard, a mosaic view can be uitilized to provide an overview about all available exhibits. A category view groups postcards into themes. Locating artefacts on a zoomable map or exhibition floor plan allows for conveying information about spatial contexts between different objects and their location. Furthermore, contexts can be illustrated with a two stage view comprising an overview and corresponding detail views to provide further insights into the spatial, temporal, and thematic contexts of artefacts. The application scaffolding allows the design of bilingual presentations to support exhibitions with an international audience. The logo of the presenting institution or exhibition can be incorporated to display the the kiosk's corporate design branding and to access an imprint or further informations. Usage is logged into files to provide a basis for extracting statistical information about the usage. The details about the exhibits are presented as images and as such impose no limit to the design choices made by the content provider or exhibition designer. The application (enhanced with a panoramic view) has been integrated successfully into a large special exhibition about the ancient city of Pergamon 2011/2012 at the Pergamon Museum Berlin within the interdisciplinary project "Berlin Sculpture Network".}, language = {en} } @inproceedings{ProhaskaHegeGiehletal.2003, author = {Prohaska, Steffen and Hege, Hans-Christian and Giehl, Michael and Gowin, Wolfgang}, title = {A Virtual Laboratory for Assessment of Bone Biopsies}, booktitle = {14th IAA Humans in Space Symposium}, address = {Banff, Alberta, Canada}, pages = {7}, year = {2003}, language = {en} } @inproceedings{SaparinGowinZaikinetal.2003, author = {Saparin, Peter and Gowin, Wolfgang and Zaikin, Alexei and Thomsen, Jesper and Prohaska, Steffen and Hege, Hans-Christian and Kurths, J{\"u}rgen}, title = {Quantification of Changes in Spatial Structure of Human Bone Biopsies Using 3D Measures of Complexity}, booktitle = {14th IAA Humans in Space Symposium}, address = {Banff, Alberta, Canada}, year = {2003}, language = {en} } @inproceedings{ProhaskaHegeGiehletal.2003, author = {Prohaska, Steffen and Hege, Hans-Christian and Giehl, Michael and Gowin, Wolfgang}, title = {Interactive Visualization to Support Quantification of Bone Biopsies}, booktitle = {2nd European Congress 'Achievements in Space Medicine into Health Care Practice and Industry'}, address = {Berlin-Adlershof}, year = {2003}, language = {en} } @inproceedings{SaparinGowinZaikinetal.2003, author = {Saparin, Peter and Gowin, Wolfgang and Zaikin, Alexei and Prohaska, Steffen}, title = {Quantification of changes in human bone structure at different skeletal locations using measures of complexity}, booktitle = {2nd European Congress 'Achievements in Space Medicine into Health Care Practice and Industry'}, address = {Berlin-Adlershof}, year = {2003}, language = {en} } @inproceedings{GowinSaparinProhaskaetal.2003, author = {Gowin, Wolfgang and Saparin, Peter and Prohaska, Steffen and Hege, Hans-Christian and Belle, Stefan and Felsenberg, Dieter}, title = {Architectural Reasons for the Femoral Neck Fracture Location}, booktitle = {2nd European Congress 'Achievements in Space Medicine into Health Care Practice and Industry'}, address = {Berlin-Adlershof}, year = {2003}, language = {en} } @inproceedings{ZaikinSaparinProhaskaetal.2003, author = {Zaikin, Alexei and Saparin, Peter and Prohaska, Steffen and Kurths, J{\"u}rgen and Gowin, Wolfgang}, title = {2D and 3D bone modelling for analysis of changes in the bone architecture and for evaluation of structural measures.}, booktitle = {2nd European Congress 'Achievements in Space Medicine into Health Care Practice and Industry'}, address = {Berlin-Adlershof}, year = {2003}, language = {en} } @inproceedings{ThomsenKollerLaibetal.2003, author = {Thomsen, Jesper and Koller, Bruno and Laib, Andreas and Prohaska, Steffen and Giehl, Michael and Gowin, Wolfgang}, title = {Comparison between Static Histomorphometric Measures Conducted by Traditionally 2D Histomorphometry and 3D μ-CT in Human Tibial Biopsies}, booktitle = {2nd European Congress 'Achievements in Space Medicine into Health Care Practice and Industry'}, address = {Berlin-Adlershof}, year = {2003}, language = {en} } @inproceedings{HegeWeinkaufProhaskaetal.2004, author = {Hege, Hans-Christian and Weinkauf, Tino and Prohaska, Steffen and Hutanu, Andrei}, title = {Distributed visualization and analysis of fluid dynamics data}, booktitle = {Proc. Fourth International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration}, address = {Sendai, Japan}, pages = {145 -- 150}, year = {2004}, language = {en} } @inproceedings{HegeSchirmacherWesterhoffetal.2002, author = {Hege, Hans-Christian and Schirmacher, Hartmut and Westerhoff, Malte and Lamecker, Hans and Prohaska, Steffen and Zachow, Stefan}, title = {From Image Data to Three-Dimensional Models - Case Studies on the Impact of 3D Patient Models}, booktitle = {Proceedings of the Japan Korea Computer Graphics Conference 2002}, publisher = {Kanazawa University}, address = {Kanazawa City, Ishikawa, Japan}, year = {2002}, language = {en} } @article{ProhaskaHegeGiehletal.2002, author = {Prohaska, Steffen and Hege, Hans-Christian and Giehl, Michael and Gowin, Wolfgang}, title = {Visual Analysis of Trabecular Bone Structure}, volume = {9 (1)}, journal = {Journal of Gravitational Physiology}, pages = {171 -- 172}, year = {2002}, language = {en} } @misc{GowinSaparinFelsenbergetal.2002, author = {Gowin, Wolfgang and Saparin, Peter and Felsenberg, Dieter and Kurths, J{\"u}rgen and Zaikin, Alexei and Prohaska, Steffen and Hege, Hans-Christian}, title = {Regional Structural Skeletal Discordance Assessed by Measures of Complexity}, year = {2002}, language = {en} } @article{ZaikinSaparinProhaskaetal.2002, author = {Zaikin, Alexei and Saparin, Peter and Prohaska, Steffen and Kurths, J{\"u}rgen and Gowin, Wolfgang}, title = {Bone Modeling and Structural Measures of Complexity}, volume = {9}, journal = {Journal of Gravitational Physiology}, doi = {10.1016/j.actaastro.2005.01.007}, pages = {175 -- 176}, year = {2002}, language = {en} } @article{GowinSaparinProhaskaetal.2002, author = {Gowin, Wolfgang and Saparin, Peter and Prohaska, Steffen and Hege, Hans-Christian and Felsenberg, Dieter}, title = {Femoral Neck Fractures: Reasons for the Most Common Location of Fractures}, volume = {73}, journal = {Acta Orthop. Scand. (Suppl. 304)}, pages = {26}, year = {2002}, language = {en} } @article{CassotLauwersFouardetal.2006, author = {Cassot, Francis and Lauwers, Frederic and Fouard, C{\´e}line and Prohaska, Steffen and Lauwer-Cances, Valerie}, title = {A novel three-dimensional computer assisted method for a quantitative study of microvascular networks of the human cerebral cortex}, volume = {13}, journal = {Microcirculation}, pages = {15 -- 32}, year = {2006}, language = {en} } @inproceedings{ProhaskaHege2002, author = {Prohaska, Steffen and Hege, Hans-Christian}, title = {Fast Visualization of Plane-Like Structures in Voxel Data}, booktitle = {Proceedings of IEEE Visualization 2002}, editor = {J. Moorhead, Robert and Gross, Markus and I. Joy, Kenneth}, publisher = {IEEE Computer Society Press}, address = {Boston MA, USA}, doi = {10.1109/VISUAL.2002.1183753}, pages = {29 -- 36}, year = {2002}, language = {en} } @misc{HombergBaumWiebeletal.2013, author = {Homberg, Ulrike and Baum, Daniel and Wiebel, Alexander and Prohaska, Steffen and Hege, Hans-Christian}, title = {Definition, Extraction, and Validation of Pore Structures in Porous Materials}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-42510}, year = {2013}, abstract = {An intuitive and sparse representation of the void space of porous materials supports the efficient analysis and visualization of interesting qualitative and quantitative parameters of such materials. We introduce definitions of the elements of this void space, here called pore space, based on its distance function, and present methods to extract these elements using the extremal structures of the distance function. The presented methods are implemented by an image processing pipeline that determines pore centers, pore paths and pore constrictions. These pore space elements build a graph that represents the topology of the pore space in a compact way. The representations we derive from μCT image data of realistic soil specimens enable the computation of many statistical parameters and, thus, provide a basis for further visual analysis and application-specific developments. We introduced parts of our pipeline in previous work. In this chapter, we present additional details and compare our results with the analytic computation of the pore space elements for a sphere packing in order to show the correctness of our graph computation.}, language = {en} }