@misc{SakuraiOnoCarretal.2019, author = {Sakurai, Daisuke and Ono, Kenji and Carr, Hamish and Nonaka, Jorji and Kawanabe, Tomohiro}, title = {Flexible Fiber Surfaces: A Reeb-Free Approach}, journal = {Topological Methods in Data Analysis and Visualization V}, editor = {Carr, Hamish and Fujishiro, Issei and Sadlo, Filip and Takahashi, Shigeo}, publisher = {Springer}, pages = {14}, year = {2019}, abstract = {The fiber surface generalizes the popular isosurface to multi-fields, so that pre-images can be visualized as surfaces. As with the isosurface, however, the fiber surface suffers from visual occlusion. We propose to avoid such occlusion by restricting the components to only the relevant ones with a new component-wise flexing algorithm. The approach, flexible fiber surface, generalizes the manipulation idea found in the flexible isosurface for the fiber surface. The flexible isosurface in the original form, however, relies on the contour tree. For the fiber surface, this corresponds to the Reeb space, which is challenging for both the computation and user interaction. We thus take a Reeb-free approach, in which one does not compute the Reeb space. Under this constraint, we generalize a few selected interactions in the flexible isosurface and discuss the implication of the restriction.}, language = {en} } @misc{SakuraiOnoCarretal.2019, author = {Sakurai, Daisuke and Ono, Kenji and Carr, Hamish and Nonaka, Jorji and Kawanabe, Tomohiro}, title = {Flexible Fiber Surfaces: A Reeb-Free Approach}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-72599}, year = {2019}, abstract = {The fiber surface generalizes the popular isosurface to multi-fields, so that pre-images can be visualized as surfaces. As with the isosurface, however, the fiber surface suffers from visual occlusion. We propose to avoid such occlusion by restricting the components to only the relevant ones with a new component-wise flexing algorithm. The approach, flexible fiber surface, generalizes the manipulation idea found in the flexible isosurface for the fiber surface. The flexible isosurface in the original form, however, relies on the contour tree. For the fiber surface, this corresponds to the Reeb space, which is challenging for both the computation and user interaction. We thus take a Reeb-free approach, in which one does not compute the Reeb space. Under this constraint, we generalize a few selected interactions in the flexible isosurface and discuss the implication of the restriction.}, language = {en} } @misc{SakuraiHegeKuhnetal.2017, author = {Sakurai, Daisuke and Hege, Hans-Christian and Kuhn, Alexander and Rust, Henning and Kern, Bastian and Breitkopf, Tom-Lukas}, title = {An Application-Oriented Framework for Feature Tracking in Atmospheric Sciences}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-72617}, year = {2017}, abstract = {In atmospheric sciences, sizes of data sets grow continuously due to increasing resolutions. A central task is the comparison of spatiotemporal fields, to assess different simulations and to compare simulations with observations. A significant information reduction is possible by focusing on geometric-topological features of the fields or on derived meteorological objects. Due to the huge size of the data sets, spatial features have to be extracted in time slices and traced over time. Fields with chaotic component, i.e. without 1:1 spatiotemporal correspondences, can be compared by looking upon statistics of feature properties. Feature extraction, however, requires a clear mathematical definition of the features - which many meteorological objects still lack. Traditionally, object extractions are often heuristic, defined only by implemented algorithms, and thus are not comparable. This work surveys our framework designed for efficient development of feature tracking methods and for testing new feature definitions. The framework supports well-established visualization practices and is being used by atmospheric researchers to diagnose and compare data.}, language = {en} } @article{KuhnEngelkeRoessletal.2014, author = {Kuhn, Alexander and Engelke, Wito and R{\"o}ssl, Christian and Hadwiger, Markus and Theisel, Holger}, title = {Time Line Cell Tracking for the Approximation of Lagrangian Coherent Structures with Subgrid Accuracy}, volume = {33}, journal = {Computer Graphics Forum}, publisher = {Wiley Blackwell}, issn = {0934-5892}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-43990}, pages = {222 -- 234}, year = {2014}, language = {en} } @misc{GuentherKuhnHegeetal.2016, author = {G{\"u}nther, Tobias and Kuhn, Alexander and Hege, Hans-Christian and Theisel, Holger}, title = {MCFTLE: Monte Carlo Rendering of Finite-Time Lyapunov Exponent Fields}, issn = {1438-0064}, doi = {10.1111/cgf.12914}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-59054}, year = {2016}, abstract = {Traditionally, Lagrangian fields such as finite-time Lyapunov exponents (FTLE) are precomputed on a discrete grid and are ray casted afterwards. This, however, introduces both grid discretization errors and sampling errors during ray marching. In this work, we apply a progressive, view-dependent Monte Carlo-based approach for the visualization of such Lagrangian fields in time-dependent flows. Our ap- proach avoids grid discretization and ray marching errors completely, is consistent, and has a low memory consumption. The system provides noisy previews that con- verge over time to an accurate high-quality visualization. Compared to traditional approaches, the proposed system avoids explicitly predefined fieldline seeding structures, and uses a Monte Carlo sampling strategy named Woodcock tracking to distribute samples along the view ray. An acceleration of this sampling strategy requires local upper bounds for the FTLE values, which we progressively acquire during the rendering. Our approach is tailored for high-quality visualizations of complex FTLE fields and is guaranteed to faithfully represent detailed ridge surface structures as indicators for Lagrangian coherent structures (LCS). We demonstrate the effectiveness of our approach by using a set of analytic test cases and real-world numerical simulations.}, language = {en} } @inproceedings{SakuraiHegeKuhnetal.2017, author = {Sakurai, Daisuke and Hege, Hans-Christian and Kuhn, Alexander and Rust, Henning and Kern, Bastian and Breitkopf, Tom-Lukas}, title = {An Application-Oriented Framework for Feature Tracking in Atmospheric Sciences}, booktitle = {Proceedings of 2017 IEEE 7th Symposium on Large Data Analysis and Visualization (LDAV)}, doi = {10.1109/LDAV.2017.8231857}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-66685}, pages = {96 -- 97}, year = {2017}, abstract = {In atmospheric sciences, sizes of data sets grow continuously due to increasing resolutions. A central task is the comparison of spatiotemporal fields, to assess different simulations and to compare simulations with observations. A significant information reduction is possible by focusing on geometric-topological features of the fields or on derived meteorological objects. Due to the huge size of the data sets, spatial features have to be extracted in time slices and traced over time. Fields with chaotic component, i.e. without 1:1 spatiotemporal correspondences, can be compared by looking upon statistics of feature properties. Feature extraction, however, requires a clear mathematical definition of the features - which many meteorological objects still lack. Traditionally, object extractions are often heuristic, defined only by implemented algorithms, and thus are not comparable. This work surveys our framework designed for efficient development of feature tracking methods and for testing new feature definitions. The framework supports well-established visualization practices and is being used by atmospheric researchers to diagnose and compare data.}, language = {en} } @article{GuentherKuhnHegeetal.2017, author = {G{\"u}nther, Tobias and Kuhn, Alexander and Hege, Hans-Christian and Gross, Markus and Theisel, Holger}, title = {Progressive Monte Carlo rendering of atmospheric flow features across scales}, volume = {2}, journal = {Physical Review Fluids}, doi = {10.1103/PhysRevFluids.2.090502}, pages = {09050-1 -- 09050-3}, year = {2017}, abstract = {To improve existing weather prediction and reanalysis capabilities, high-resolution and multi-modal climate data becomes an increasingly important topic. The advent of increasingly dense numerical simulation of atmospheric phenomena, provides new means to better understand dynamic processes and to visualize structural flow patterns that remain hidden otherwise. In the presented illustrations we demonstrate an advanced technique to visualize multiple scales of dense flow fields and Lagrangian patterns therein, simulated by state-of-the-art simulation models for each scale. They provide a deeper insight into the structural differences and patterns that occur on each scale and highlight the complexity of flow phenomena in our atmosphere. This paper is associated with a poster winner of a 2016 APS/DFD Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. The original poster is available from the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2016.GFM.P0030}, language = {en} } @inproceedings{KuhnLindowGuentheretal.2013, author = {Kuhn, Alexander and Lindow, Norbert and G{\"u}nther, Tobias and Wiebel, Alexander and Theisel, Holger and Hege, Hans-Christian}, title = {Trajectory Density Projection for Vector Field Visualization}, booktitle = {EuroVis 2013, short papers. M. Hlawitschka, Tino Weinkauf (eds.)}, doi = {10.2312/PE.EuroVisShort.EuroVisShort2013.031-035}, pages = {31 -- 35}, year = {2013}, language = {en} } @article{GuentherKuhnKutzetal.2013, author = {G{\"u}nther, Tobias and Kuhn, Alexander and Kutz, Benjamin and Theisel, Holger}, title = {Mass-Dependent Integral Curves in Unsteady Vector Fields}, volume = {32}, journal = {Computer Graphics Forum}, doi = {10.1111/cgf.12108}, pages = {211 -- 220}, year = {2013}, language = {en} } @article{GuentherKuhnHegeetal.2016, author = {G{\"u}nther, Tobias and Kuhn, Alexander and Hege, Hans-Christian and Theisel, Holger}, title = {MCFTLE: Monte Carlo Rendering of Finite-Time Lyapunov Exponent Fields}, volume = {35}, journal = {Computer Graphics Forum}, number = {3}, doi = {10.1111/cgf.12914}, pages = {381 -- 390}, year = {2016}, language = {en} }