[{"author":[{"last_name":"Ishida","id":"6F7C4B96-A8E9-11E9-A7CA-09ECE5697425","first_name":"Sadashige","full_name":"Ishida, Sadashige","orcid":"0000-0002-3121-3100"}],"doi":"10.15479/AT-ISTA-20551","file":[{"date_updated":"2025-11-01T18:26:14Z","relation":"source_file","date_created":"2025-11-01T18:26:14Z","content_type":"application/zip","file_name":"Thesis_tex.zip","file_size":72487812,"access_level":"open_access","checksum":"4eef80afcb67691cbb6549c4756fa534","creator":"sishida","file_id":"20583"},{"checksum":"1e5a557900bf2dce01966b211b15d0fe","creator":"sishida","file_id":"20623","access_level":"open_access","file_size":8945141,"content_type":"application/pdf","success":1,"file_name":"Thesis_Sadashige_Ishida_PDFA.pdf","date_created":"2025-11-10T08:45:05Z","date_updated":"2025-11-10T08:45:05Z","relation":"main_file"}],"acknowledgement":"Projects contained in this thesis were financially supported in part by the\r\nEuropean Research Council with grants 1. ERC Consolidator Grant 101045083 CoDiNA,\r\nand 2. the European Union’s Horizon 2020 research and innovation programme under grant\r\nagreement No. 638176.","publication_status":"published","type":"dissertation","month":"10","tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"degree_awarded":"PhD","supervisor":[{"first_name":"Christopher J","full_name":"Wojtan, Christopher J","orcid":"0000-0001-6646-5546","last_name":"Wojtan","id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87"},{"full_name":"Chern, Albert","first_name":"Albert","last_name":"Chern"}],"oa_version":"Published Version","alternative_title":["ISTA Thesis"],"OA_place":"publisher","related_material":{"record":[{"id":"12846","relation":"part_of_dissertation","status":"public"},{"status":"public","id":"12431","relation":"part_of_dissertation"},{"status":"public","id":"17361","relation":"part_of_dissertation"},{"relation":"part_of_dissertation","id":"20580","status":"public"}]},"oa":1,"_id":"20551","project":[{"_id":"2533E772-B435-11E9-9278-68D0E5697425","grant_number":"638176","name":"Big Splash: Efficient Simulation of Natural Phenomena at Extremely Large Scales","call_identifier":"H2020"},{"name":"Computational Discovery of Numerical Algorithms for Animation and Simulation of Natural Phenomena","grant_number":"101045083","_id":"34bc2376-11ca-11ed-8bc3-9a3b3961a088"}],"page":"141","date_published":"2025-10-31T00:00:00Z","ddc":["516"],"abstract":[{"text":"The space of codimension-2 shapes, such as curves in 3D and surfaces in 4D, is an infinite-dimensional manifold. This thesis explores geometric structures and dynamics on this space, with emphasis on their implications for physics, particularly hydrodynamics.\r\n\r\nOur investigation ranges from theoretical studies of infinite-dimensional symplectic and prequantum geometry to numerical computation of the time evolution of shapes. The thesis presents four main contributions.\r\n\r\nIn the first part, we introduce implicit representations of codimension-2 shapes using a class of complex-valued functions, and prove that the space of these implicit representations forms a prequantum bundle over the codimension-2 shape space. This reveals a new geometric interpretation of the canonical symplectic structure on the codimension-2 shape space.\r\n\r\nIn the second part, we use implicit representations to develop a simulation method for the dynamics of space curves. To handle chaotic systems such as vortex filaments in hydrodynamics, we exploit the infinite degrees of freedom, hidden in both the configuration and dynamics of implicit representations.\r\n\r\nIn the third part, we introduce new symplectic structures on the space of space curves, which generalize the only previously known symplectic structure on this space, allowing for new Hamiltonian dynamics of space curves.\r\n\r\nIn the fourth part, we apply a symplectic viewpoint to a differential geometric problem with practical applications. We derive a new area formula for spherical polygons via prequantization. ","lang":"eng"}],"date_created":"2025-10-27T10:28:52Z","department":[{"_id":"GradSch"},{"_id":"ChWo"}],"day":"31","acknowledged_ssus":[{"_id":"CampIT"}],"language":[{"iso":"eng"}],"ec_funded":1,"title":"Symplectic-prequantum structures and dynamics on the codimension-2 shape space","file_date_updated":"2025-11-10T08:45:05Z","date_updated":"2026-04-07T12:02:23Z","publication_identifier":{"issn":["2663-337X"],"isbn":["978-3-99078-070-1"]},"article_processing_charge":"No","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","has_accepted_license":"1","publisher":"Institute of Science and Technology Austria","citation":{"ieee":"S. Ishida, “Symplectic-prequantum structures and dynamics on the codimension-2 shape space,” Institute of Science and Technology Austria, 2025.","ama":"Ishida S. Symplectic-prequantum structures and dynamics on the codimension-2 shape space. 2025. doi:<a href=\"https://doi.org/10.15479/AT-ISTA-20551\">10.15479/AT-ISTA-20551</a>","ista":"Ishida S. 2025. Symplectic-prequantum structures and dynamics on the codimension-2 shape space. Institute of Science and Technology Austria.","apa":"Ishida, S. (2025). <i>Symplectic-prequantum structures and dynamics on the codimension-2 shape space</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT-ISTA-20551\">https://doi.org/10.15479/AT-ISTA-20551</a>","chicago":"Ishida, Sadashige. “Symplectic-Prequantum Structures and Dynamics on the Codimension-2 Shape Space.” Institute of Science and Technology Austria, 2025. <a href=\"https://doi.org/10.15479/AT-ISTA-20551\">https://doi.org/10.15479/AT-ISTA-20551</a>.","short":"S. Ishida, Symplectic-Prequantum Structures and Dynamics on the Codimension-2 Shape Space, Institute of Science and Technology Austria, 2025.","mla":"Ishida, Sadashige. <i>Symplectic-Prequantum Structures and Dynamics on the Codimension-2 Shape Space</i>. Institute of Science and Technology Austria, 2025, doi:<a href=\"https://doi.org/10.15479/AT-ISTA-20551\">10.15479/AT-ISTA-20551</a>."},"status":"public","year":"2025","corr_author":"1"},{"page":"106","project":[{"name":"Big Splash: Efficient Simulation of Natural Phenomena at Extremely Large Scales","grant_number":"638176","_id":"2533E772-B435-11E9-9278-68D0E5697425","call_identifier":"H2020"},{"_id":"34bc2376-11ca-11ed-8bc3-9a3b3961a088","name":"Computational Discovery of Numerical Algorithms for Animation and Simulation of Natural Phenomena","grant_number":"101045083"},{"name":"Alpha Shape Theory Extended","grant_number":"788183","_id":"266A2E9E-B435-11E9-9278-68D0E5697425","call_identifier":"H2020"},{"call_identifier":"H2020","grant_number":"638176","name":"Big Splash: Efficient Simulation of Natural Phenomena at Extremely Large Scales","_id":"2533E772-B435-11E9-9278-68D0E5697425"},{"call_identifier":"FWF","name":"Persistence and stability of geometric complexes","grant_number":"I02979-N35","_id":"2561EBF4-B435-11E9-9278-68D0E5697425"}],"oa":1,"_id":"19630","related_material":{"record":[{"id":"8135","relation":"part_of_dissertation","status":"public"},{"id":"17219","relation":"part_of_dissertation","status":"public"},{"status":"public","id":"8384","relation":"part_of_dissertation"}]},"OA_place":"publisher","alternative_title":["ISTA Thesis"],"oa_version":"Published Version","supervisor":[{"first_name":"Christopher J","full_name":"Wojtan, Christopher J","orcid":"0000-0001-6646-5546","last_name":"Wojtan","id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87"}],"degree_awarded":"PhD","month":"04","type":"dissertation","publication_status":"published","acknowledgement":"The project in Chapter 2 has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme under grant agreement No. 638176. The project in Chapter 3 was funded in part by the European Union (ERC-2021-COG 101045083 CoDiNA). The project in Chapter 4 has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreements No 78818 Alpha and No 638176). It was also partially supported by the DFG Collaborative Research Center TRR 109, 'Discretization in Geometry and Dynamics', through grant no. I02979-N35 of the Austrian Science Fund (FWF). Thank you for providing funds to support my work.","file":[{"date_updated":"2025-04-30T14:02:25Z","relation":"source_file","date_created":"2025-04-30T14:02:25Z","file_name":"Thesis_source_Heiss_Synak.zip","content_type":"application/x-zip-compressed","file_size":60670543,"access_level":"closed","creator":"cchlebak","checksum":"f00b519c27529daa0c3b2d4102b4fa7b","file_id":"19633"},{"date_created":"2025-04-30T14:02:42Z","relation":"main_file","date_updated":"2025-04-30T15:49:16Z","checksum":"6e40a2fd3b1b881af1385670854a682e","creator":"cchlebak","file_id":"19634","access_level":"open_access","file_size":21319043,"content_type":"application/pdf","file_name":"Thesis_PDFA_Heiss_Synak.pdf"}],"doi":"10.15479/AT-ISTA-19630","author":[{"first_name":"Peter","full_name":"Synak, Peter","id":"331776E2-F248-11E8-B48F-1D18A9856A87","last_name":"Synak"}],"corr_author":"1","year":"2025","status":"public","citation":{"mla":"Synak, Peter. <i>Methods for Fluid Simulation, Surface Tracking, and Statistics of Non-Manifold Structures</i>. Institute of Science and Technology Austria, 2025, doi:<a href=\"https://doi.org/10.15479/AT-ISTA-19630\">10.15479/AT-ISTA-19630</a>.","short":"P. Synak, Methods for Fluid Simulation, Surface Tracking, and Statistics of Non-Manifold Structures, Institute of Science and Technology Austria, 2025.","chicago":"Synak, Peter. “Methods for Fluid Simulation, Surface Tracking, and Statistics of Non-Manifold Structures.” Institute of Science and Technology Austria, 2025. <a href=\"https://doi.org/10.15479/AT-ISTA-19630\">https://doi.org/10.15479/AT-ISTA-19630</a>.","apa":"Synak, P. (2025). <i>Methods for fluid simulation, surface tracking, and statistics of non-manifold structures</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT-ISTA-19630\">https://doi.org/10.15479/AT-ISTA-19630</a>","ista":"Synak P. 2025. Methods for fluid simulation, surface tracking, and statistics of non-manifold structures. Institute of Science and Technology Austria.","ama":"Synak P. Methods for fluid simulation, surface tracking, and statistics of non-manifold structures. 2025. doi:<a href=\"https://doi.org/10.15479/AT-ISTA-19630\">10.15479/AT-ISTA-19630</a>","ieee":"P. Synak, “Methods for fluid simulation, surface tracking, and statistics of non-manifold structures,” Institute of Science and Technology Austria, 2025."},"publisher":"Institute of Science and Technology Austria","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","has_accepted_license":"1","article_processing_charge":"No","publication_identifier":{"issn":["2663-337X"]},"file_date_updated":"2025-04-30T15:49:16Z","date_updated":"2026-04-16T08:29:34Z","title":"Methods for fluid simulation, surface tracking, and statistics of non-manifold structures","ec_funded":1,"acknowledged_ssus":[{"_id":"ScienComp"}],"language":[{"iso":"eng"}],"day":"29","department":[{"_id":"ChWo"},{"_id":"GradSch"}],"date_created":"2025-04-29T09:39:34Z","abstract":[{"lang":"eng","text":"This thesis consists of three chapters, each corresponding to one publication. While each of these projects tackles a topic in a different area of research, they all share a common thread in the type of topological structure they handle - a partition of space into volumes separated by interfaces that meet in non-manifold junctions.\r\n\r\nIn Chapter 2, we study clusters of soap bubbles from a simulation perspective. In particular, we develop a surface-only algorithm that couples large scale motion and shape deformation of soap bubble clusters with the small scale evolution of the thin film's thickness, which is responsible for visual phenomena like surface vortices, Newton's interference patterns, capillary waves, and deformation-dependent rupturing of films in a foam. We model film thickness as a reduced degree of freedom in the Navier-Stokes equations and from them derive three sets of equations governing normal and tangential motion of the soap film surface, as well as the evolution of the thin film thickness. We discretize these equations on a non-manifold triangle mesh, extending and adapting operators to handle complex topology. We also present an incompressible fluid solver for 2.5D films and an advection algorithm for convecting fields across non-manifold surface junctions. Our simulations enhance bubble solvers with additional effects caused by convection, rippling, draining, and evaporation of the thin film.\r\n\r\nIn Chapter 3, we introduce a multi-material non-manifold mesh-based surface tracking algorithm that converts mesh defects, such as overlaps, self-intersections, and inversions into topological changes. Our algorithm generalizes prior work on manifold surface tracking with topological changes: it preserves surface features like mesh-based methods, and it robustly handles topological changes like level set methods. Our method also offers improved efficiency and robustness over the state of the art. We demonstrate the effectiveness of the approach on a range of examples, including complex soap film simulations, such as those presented in Chapter 2, but with an order of magnitude more interacting bubbles than what we could achieve before, and Boolean unions of non-manifold meshes consisting of millions of triangles.\r\n\r\nLastly, in Chapter 4, we utilize developments in the theory of random geometric complexes facilitated by observations from Discrete Morse theory. We survey the methods and results obtained with this new approach, and discuss some of its shortcomings. We use simulations to illustrate the results and to form conjectures, getting numerical estimates for combinatorial, topological, and geometric properties of weighted and unweighted Delaunay mosaics, their dual Voronoi tessellations, and the Alpha and Wrap complexes contained in the mosaics."}],"ddc":["519","006"],"date_published":"2025-04-29T00:00:00Z"},{"publisher":"Institute of Science and Technology Austria","citation":{"ama":"Etemadi A. Filling the holes of non-manifold self-intersecting meshes for implicit topology changes in surface tracking. 2024. doi:<a href=\"https://doi.org/10.15479/at:ista:18301\">10.15479/at:ista:18301</a>","ieee":"A. Etemadi, “Filling the holes of non-manifold self-intersecting meshes for implicit topology changes in surface tracking,” Institute of Science and Technology Austria, 2024.","ista":"Etemadi A. 2024. Filling the holes of non-manifold self-intersecting meshes for implicit topology changes in surface tracking. Institute of Science and Technology Austria.","apa":"Etemadi, A. (2024). <i>Filling the holes of non-manifold self-intersecting meshes for implicit topology changes in surface tracking</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/at:ista:18301\">https://doi.org/10.15479/at:ista:18301</a>","short":"A. Etemadi, Filling the Holes of Non-Manifold Self-Intersecting Meshes for Implicit Topology Changes in Surface Tracking, Institute of Science and Technology Austria, 2024.","chicago":"Etemadi, Arian. “Filling the Holes of Non-Manifold Self-Intersecting Meshes for Implicit Topology Changes in Surface Tracking.” Institute of Science and Technology Austria, 2024. <a href=\"https://doi.org/10.15479/at:ista:18301\">https://doi.org/10.15479/at:ista:18301</a>.","mla":"Etemadi, Arian. <i>Filling the Holes of Non-Manifold Self-Intersecting Meshes for Implicit Topology Changes in Surface Tracking</i>. Institute of Science and Technology Austria, 2024, doi:<a href=\"https://doi.org/10.15479/at:ista:18301\">10.15479/at:ista:18301</a>."},"status":"public","year":"2024","corr_author":"1","date_updated":"2026-04-07T13:02:36Z","file_date_updated":"2024-10-24T14:34:54Z","publication_identifier":{"issn":["2791-4585"]},"article_processing_charge":"No","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","has_accepted_license":"1","language":[{"iso":"eng"}],"title":"Filling the holes of non-manifold self-intersecting meshes for implicit topology changes in surface tracking","date_published":"2024-10-15T00:00:00Z","ddc":["000"],"abstract":[{"lang":"eng","text":"Physics simulation in computer graphics can bring triangle meshes into topologically invalid states. The method in this thesis contributed to Heiss-Synak* and Kalinov* et al. [2024] who devised a non-manifold hybrid surface tracker—a surface tracker that repairs explicit non-manifold triangle meshes with the help of the implicit domain. Specifically, this thesis provides an algorithm for filling the holes that are left after removing problematic parts of the mesh."}],"date_created":"2024-10-11T19:52:20Z","department":[{"_id":"GradSch"},{"_id":"ChWo"}],"day":"15","license":"https://creativecommons.org/licenses/by-sa/4.0/","page":"39","OA_place":"publisher","related_material":{"record":[{"relation":"part_of_dissertation","id":"17219","status":"public"}]},"oa":1,"_id":"18301","keyword":["surface tracking","non-manifold","hole-filling","topology change","multi-material","solid-modeling"],"tmp":{"short":"CC BY-SA (4.0)","legal_code_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","name":"Creative Commons Attribution-ShareAlike 4.0 International Public License (CC BY-SA 4.0)","image":"/images/cc_by_sa.png"},"degree_awarded":"MS","supervisor":[{"id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87","last_name":"Wojtan","orcid":"0000-0001-6646-5546","full_name":"Wojtan, Christopher J","first_name":"Christopher J"}],"oa_version":"Published Version","alternative_title":["ISTA Master's Thesis"],"author":[{"last_name":"Etemadihaghighi","id":"36cea3aa-f38e-11ec-8ae0-c65ae6f6098f","full_name":"Etemadihaghighi, Arian","first_name":"Arian"}],"doi":"10.15479/at:ista:18301","file":[{"date_updated":"2024-10-24T14:34:42Z","relation":"main_file","date_created":"2024-10-24T14:34:42Z","file_name":"thesis-arian-etemadi.pdf","content_type":"application/pdf","success":1,"file_size":8914218,"access_level":"open_access","file_id":"18469","checksum":"80fb7923e229ad9d39253d7c8a8083d0","creator":"aetemadi"},{"date_updated":"2024-10-24T14:34:54Z","relation":"source_file","date_created":"2024-10-24T14:34:54Z","content_type":"application/x-zip-compressed","file_name":"thesis-arian-etemadi-latex-source.zip","file_size":9802650,"access_level":"closed","file_id":"18470","checksum":"1c02586ed7d441d5ec441867650568d1","creator":"aetemadi"}],"publication_status":"published","type":"dissertation","month":"10"},{"file_date_updated":"2023-02-02T09:39:25Z","date_updated":"2026-04-16T08:31:54Z","publication_identifier":{"issn":["2663-337X"],"isbn":["978-3-99078-020-6"]},"article_processing_charge":"No","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","has_accepted_license":"1","publisher":"Institute of Science and Technology Austria","citation":{"chicago":"Sperl, Georg. “Homogenizing Yarn Simulations: Large-Scale Mechanics, Small-Scale Detail, and Quantitative Fitting.” Institute of Science and Technology Austria, 2022. <a href=\"https://doi.org/10.15479/at:ista:12103\">https://doi.org/10.15479/at:ista:12103</a>.","short":"G. Sperl, Homogenizing Yarn Simulations: Large-Scale Mechanics, Small-Scale Detail, and Quantitative Fitting, Institute of Science and Technology Austria, 2022.","mla":"Sperl, Georg. <i>Homogenizing Yarn Simulations: Large-Scale Mechanics, Small-Scale Detail, and Quantitative Fitting</i>. Institute of Science and Technology Austria, 2022, doi:<a href=\"https://doi.org/10.15479/at:ista:12103\">10.15479/at:ista:12103</a>.","ama":"Sperl G. Homogenizing yarn simulations: Large-scale mechanics, small-scale detail, and quantitative fitting. 2022. doi:<a href=\"https://doi.org/10.15479/at:ista:12103\">10.15479/at:ista:12103</a>","ieee":"G. Sperl, “Homogenizing yarn simulations: Large-scale mechanics, small-scale detail, and quantitative fitting,” Institute of Science and Technology Austria, 2022.","apa":"Sperl, G. (2022). <i>Homogenizing yarn simulations: Large-scale mechanics, small-scale detail, and quantitative fitting</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/at:ista:12103\">https://doi.org/10.15479/at:ista:12103</a>","ista":"Sperl G. 2022. Homogenizing yarn simulations: Large-scale mechanics, small-scale detail, and quantitative fitting. Institute of Science and Technology Austria."},"status":"public","year":"2022","corr_author":"1","date_published":"2022-09-22T00:00:00Z","ddc":["000","620"],"abstract":[{"text":"The complex yarn structure of knitted and woven fabrics gives rise to both a mechanical and\r\nvisual complexity. The small-scale interactions of yarns colliding with and pulling on each\r\nother result in drastically different large-scale stretching and bending behavior, introducing\r\nanisotropy, curling, and more. While simulating cloth as individual yarns can reproduce this\r\ncomplexity and match the quality of real fabric, it may be too computationally expensive for\r\nlarge fabrics. On the other hand, continuum-based approaches do not need to discretize the\r\ncloth at a stitch-level, but it is non-trivial to find a material model that would replicate the\r\nlarge-scale behavior of yarn fabrics, and they discard the intricate visual detail. In this thesis,\r\nwe discuss three methods to try and bridge the gap between small-scale and large-scale yarn\r\nmechanics using numerical homogenization: fitting a continuum model to periodic yarn simulations, adding mechanics-aware yarn detail onto thin-shell simulations, and quantitatively\r\nfitting yarn parameters to physical measurements of real fabric.\r\nTo start, we present a method for animating yarn-level cloth effects using a thin-shell solver.\r\nWe first use a large number of periodic yarn-level simulations to build a model of the potential\r\nenergy density of the cloth, and then use it to compute forces in a thin-shell simulator. The\r\nresulting simulations faithfully reproduce expected effects like the stiffening of woven fabrics\r\nand the highly deformable nature and anisotropy of knitted fabrics at a fraction of the cost of\r\nfull yarn-level simulation.\r\nWhile our thin-shell simulations are able to capture large-scale yarn mechanics, they lack\r\nthe rich visual detail of yarn-level simulations. Therefore, we propose a method to animate\r\nyarn-level cloth geometry on top of an underlying deforming mesh in a mechanics-aware\r\nfashion in real time. Using triangle strains to interpolate precomputed yarn geometry, we are\r\nable to reproduce effects such as knit loops tightening under stretching at negligible cost.\r\nFinally, we introduce a methodology for inverse-modeling of yarn-level mechanics of cloth,\r\nbased on the mechanical response of fabrics in the real world. We compile a database from\r\nphysical tests of several knitted fabrics used in the textile industry spanning diverse physical\r\nproperties like stiffness, nonlinearity, and anisotropy. We then develop a system for approximating these mechanical responses with yarn-level cloth simulation, using homogenized\r\nshell models to speed up computation and adding some small-but-necessary extensions to\r\nyarn-level models used in computer graphics.\r\n","lang":"eng"}],"date_created":"2023-01-24T10:49:46Z","department":[{"_id":"GradSch"},{"_id":"ChWo"}],"day":"22","language":[{"iso":"eng"}],"acknowledged_ssus":[{"_id":"SSU"}],"ec_funded":1,"title":"Homogenizing yarn simulations: Large-scale mechanics, small-scale detail, and quantitative fitting","OA_place":"publisher","related_material":{"record":[{"relation":"part_of_dissertation","id":"11736","status":"public"},{"status":"public","id":"9818","relation":"part_of_dissertation"},{"relation":"part_of_dissertation","id":"8385","status":"public"}]},"_id":"12358","oa":1,"project":[{"call_identifier":"H2020","_id":"2533E772-B435-11E9-9278-68D0E5697425","name":"Big Splash: Efficient Simulation of Natural Phenomena at Extremely Large Scales","grant_number":"638176"}],"page":"138","author":[{"first_name":"Georg","full_name":"Sperl, Georg","last_name":"Sperl","id":"4DD40360-F248-11E8-B48F-1D18A9856A87"}],"doi":"10.15479/at:ista:12103","file":[{"content_type":"application/pdf","file_name":"thesis_gsperl.pdf","file_size":104497530,"access_level":"open_access","checksum":"083722acbb8115e52e3b0fdec6226769","creator":"cchlebak","title":"Thesis","file_id":"12371","relation":"main_file","date_updated":"2023-02-02T09:29:57Z","description":"This is the main PDF file of the thesis. File size: 105 MB","date_created":"2023-01-25T12:04:41Z"},{"file_size":23183710,"file_name":"thesis_gsperl_compressed.pdf","content_type":"application/pdf","checksum":"511f82025e5fcb70bff4731d6896ca07","creator":"cchlebak","title":"Thesis (compressed 23MB)","file_id":"12483","access_level":"open_access","description":"This version of the thesis uses stronger image compression for a smaller file size of 23MB.","date_created":"2023-02-02T09:33:37Z","date_updated":"2023-02-02T09:33:37Z","relation":"main_file"},{"content_type":"application/x-zip-compressed","file_name":"thesis-source.zip","file_size":98382247,"access_level":"open_access","creator":"cchlebak","checksum":"ed4cb85225eedff761c25bddfc37a2ed","file_id":"12484","date_updated":"2023-02-02T09:39:25Z","relation":"source_file","date_created":"2023-02-02T09:39:25Z"}],"publication_status":"published","type":"dissertation","month":"09","supervisor":[{"id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87","last_name":"Wojtan","orcid":"0000-0001-6646-5546","full_name":"Wojtan, Christopher J","first_name":"Christopher J"}],"degree_awarded":"PhD","oa_version":"Published Version","alternative_title":["ISTA Thesis"]},{"project":[{"grant_number":"638176","name":"Big Splash: Efficient Simulation of Natural Phenomena at Extremely Large Scales","_id":"2533E772-B435-11E9-9278-68D0E5697425","call_identifier":"H2020"}],"page":"124","publist_id":"6809","pubrep_id":"855","OA_place":"publisher","related_material":{"record":[{"relation":"popular_science","id":"5568","status":"public"},{"status":"public","relation":"part_of_dissertation","id":"1362"},{"relation":"part_of_dissertation","id":"1633","status":"public"}]},"oa":1,"_id":"839","tmp":{"short":"CC BY-SA (4.0)","legal_code_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","name":"Creative Commons Attribution-ShareAlike 4.0 International Public License (CC BY-SA 4.0)","image":"/images/cc_by_sa.png"},"degree_awarded":"PhD","supervisor":[{"first_name":"Christopher J","full_name":"Wojtan, Christopher J","orcid":"0000-0001-6646-5546","last_name":"Wojtan","id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87"}],"alternative_title":["ISTA Thesis"],"oa_version":"Published Version","author":[{"last_name":"Hahn","id":"357A6A66-F248-11E8-B48F-1D18A9856A87","full_name":"Hahn, David","first_name":"David"}],"file":[{"file_id":"5100","checksum":"6c1ae8c90bfaba5e089417fefbc4a272","creator":"system","access_level":"open_access","file_size":14596191,"content_type":"application/pdf","file_name":"IST-2017-855-v1+1_thesis_online_pdfA.pdf","date_created":"2018-12-12T10:14:46Z","relation":"main_file","date_updated":"2020-07-14T12:48:13Z"},{"date_created":"2019-04-05T08:40:30Z","date_updated":"2020-07-14T12:48:13Z","relation":"source_file","file_id":"6207","checksum":"421672f68d563b029869c5cf1713f919","creator":"dernst","access_level":"closed","file_size":15060566,"file_name":"2017_thesis_Hahn_source.zip","content_type":"application/zip"}],"doi":"10.15479/AT:ISTA:th_855","publication_status":"published","acknowledgement":"ERC H2020 programme (grant agreement no. 638176)\r\nFirst of all, let me thank my committee members, especially my supervisor, Chris\r\nWojtan, for supporting me throughout my PhD. Obviously, none of this work would\r\nhave been possible without you.\r\nFurthermore, Thank You to all the people who have contributed to this work in various\r\nways, in particular Martin Schanz and his group for providing and supporting the\r\nHyENA boundary element library, as well as Eder Miguel and Morten Bojsen-Hansen\r\nfor (repeatedly) proof reading and providing valuable suggestions during the writing\r\nof this thesis.\r\nI would also like to thank Bernd Bickel, and all the members – past and present – of his\r\nand Chris’ research groups at IST Austria for always providing honest and insightful\r\nfeedback throughout many joint group meetings, as well as Christopher Batty, Eitan\r\nGrinspun, and Fang Da for many insights into boundary element methods during our\r\ncollaboration.\r\nAs only virtual objects have been harmed in the process of creating this work, I would\r\nlike to acknowledge the Stanford scanning repository for providing the “Bunny” and\r\n“Armadillo” models, the AIM@SHAPE repository for “Pierre’s hand, watertight”, and\r\nS. Gainsbourg for the “Column” via Archive3D.net. Sorry for breaking these models\r\nin many different ways.\r\n","month":"08","type":"dissertation","publisher":"Institute of Science and Technology Austria","citation":{"mla":"Hahn, David. <i>Brittle Fracture Simulation with Boundary Elements for Computer Graphics</i>. Institute of Science and Technology Austria, 2017, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_855\">10.15479/AT:ISTA:th_855</a>.","chicago":"Hahn, David. “Brittle Fracture Simulation with Boundary Elements for Computer Graphics.” Institute of Science and Technology Austria, 2017. <a href=\"https://doi.org/10.15479/AT:ISTA:th_855\">https://doi.org/10.15479/AT:ISTA:th_855</a>.","short":"D. Hahn, Brittle Fracture Simulation with Boundary Elements for Computer Graphics, Institute of Science and Technology Austria, 2017.","apa":"Hahn, D. (2017). <i>Brittle fracture simulation with boundary elements for computer graphics</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:th_855\">https://doi.org/10.15479/AT:ISTA:th_855</a>","ista":"Hahn D. 2017. Brittle fracture simulation with boundary elements for computer graphics. Institute of Science and Technology Austria.","ieee":"D. Hahn, “Brittle fracture simulation with boundary elements for computer graphics,” Institute of Science and Technology Austria, 2017.","ama":"Hahn D. Brittle fracture simulation with boundary elements for computer graphics. 2017. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_855\">10.15479/AT:ISTA:th_855</a>"},"status":"public","year":"2017","corr_author":"1","publication_identifier":{"issn":["2663-337X"]},"date_updated":"2026-04-08T14:20:16Z","file_date_updated":"2020-07-14T12:48:13Z","article_processing_charge":"No","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","has_accepted_license":"1","language":[{"iso":"eng"}],"ec_funded":1,"title":"Brittle fracture simulation with boundary elements for computer graphics","ddc":["004","005","006","531","621"],"date_published":"2017-08-14T00:00:00Z","date_created":"2018-12-11T11:48:47Z","abstract":[{"lang":"eng","text":"This thesis describes a brittle fracture simulation method for visual effects applications. Building upon a symmetric Galerkin boundary element method, we first compute stress intensity factors following the theory of linear elastic fracture mechanics. We then use these stress intensities to simulate the motion of a propagating crack front at a significantly higher resolution than the overall deformation of the breaking object. Allowing for spatial variations of the material's toughness during crack propagation produces visually realistic, highly-detailed fracture surfaces. Furthermore, we introduce approximations for stress intensities and crack opening displacements, resulting in both practical speed-up and theoretically superior runtime complexity compared to previous methods. While we choose a quasi-static approach to fracture mechanics, ignoring dynamic deformations, we also couple our fracture simulation framework to a standard rigid-body dynamics solver, enabling visual effects artists to simulate both large scale motion, as well as fracturing due to collision forces in a combined system. As fractures inside of an object grow, their geometry must be represented both in the coarse boundary element mesh, as well as at the desired fine output resolution. Using a boundary element method, we avoid complicated volumetric meshing operations. Instead we describe a simple set of surface meshing operations that allow us to progressively add cracks to the mesh of an object and still re-use all previously computed entries of the linear boundary element system matrix. On the high resolution level, we opt for an implicit surface representation. We then describe how to capture fracture surfaces during crack propagation, as well as separate the individual fragments resulting from the fracture process, based on this implicit representation. We show results obtained with our method, either solving the full boundary element system in every time step, or alternatively using our fast approximations. These results demonstrate that both of these methods perform well in basic test cases and produce realistic fracture surfaces. Furthermore we show that our fast approximations substantially out-perform the standard approach in more demanding scenarios. Finally, these two methods naturally combine, using the full solution while the problem size is manageably small and switching to the fast approximations later on. The resulting hybrid method gives the user a direct way to choose between speed and accuracy of the simulation. "}],"day":"14","department":[{"_id":"ChWo"}]},{"corr_author":"1","year":"2016","status":"public","citation":{"ama":"Bojsen-Hansen M. Tracking, correcting and absorbing water surface waves. 2016. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_640\">10.15479/AT:ISTA:th_640</a>","ieee":"M. Bojsen-Hansen, “Tracking, correcting and absorbing water surface waves,” Institute of Science and Technology Austria, 2016.","ista":"Bojsen-Hansen M. 2016. Tracking, correcting and absorbing water surface waves. Institute of Science and Technology Austria.","apa":"Bojsen-Hansen, M. (2016). <i>Tracking, correcting and absorbing water surface waves</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:th_640\">https://doi.org/10.15479/AT:ISTA:th_640</a>","chicago":"Bojsen-Hansen, Morten. “Tracking, Correcting and Absorbing Water Surface Waves.” Institute of Science and Technology Austria, 2016. <a href=\"https://doi.org/10.15479/AT:ISTA:th_640\">https://doi.org/10.15479/AT:ISTA:th_640</a>.","short":"M. Bojsen-Hansen, Tracking, Correcting and Absorbing Water Surface Waves, Institute of Science and Technology Austria, 2016.","mla":"Bojsen-Hansen, Morten. <i>Tracking, Correcting and Absorbing Water Surface Waves</i>. Institute of Science and Technology Austria, 2016, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_640\">10.15479/AT:ISTA:th_640</a>."},"publisher":"Institute of Science and Technology Austria","has_accepted_license":"1","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","article_processing_charge":"No","publication_identifier":{"issn":["2663-337X"]},"file_date_updated":"2018-12-12T10:13:02Z","date_updated":"2026-04-08T14:24:06Z","title":"Tracking, correcting and absorbing water surface waves","language":[{"iso":"eng"}],"day":"15","department":[{"_id":"ChWo"}],"date_created":"2018-12-11T11:50:16Z","abstract":[{"text":"Computer graphics is an extremely exciting field for two reasons. On the one hand,\r\nthere is a healthy injection of pragmatism coming from the visual effects industry\r\nthat want robust algorithms that work so they can produce results at an increasingly\r\nfrantic pace. On the other hand, they must always try to push the envelope and\r\nachieve the impossible to wow their audiences in the next blockbuster, which means\r\nthat the industry has not succumb to conservatism, and there is plenty of room to\r\ntry out new and crazy ideas if there is a chance that it will pan into something\r\nuseful.\r\nWater simulation has been in visual effects for decades, however it still remains\r\nextremely challenging because of its high computational cost and difficult artdirectability.\r\nThe work in this thesis tries to address some of these difficulties.\r\nSpecifically, we make the following three novel contributions to the state-of-the-art\r\nin water simulation for visual effects.\r\nFirst, we develop the first algorithm that can convert any sequence of closed\r\nsurfaces in time into a moving triangle mesh. State-of-the-art methods at the time\r\ncould only handle surfaces with fixed connectivity, but we are the first to be able to\r\nhandle surfaces that merge and split apart. This is important for water simulation\r\npractitioners, because it allows them to convert splashy water surfaces extracted\r\nfrom particles or simulated using grid-based level sets into triangle meshes that can\r\nbe either textured and enhanced with extra surface dynamics as a post-process.\r\nWe also apply our algorithm to other phenomena that merge and split apart, such\r\nas morphs and noisy reconstructions of human performances.\r\nSecond, we formulate a surface-based energy that measures the deviation of a\r\nwater surface froma physically valid state. Such discrepancies arise when there is a\r\nmismatch in the degrees of freedom between the water surface and the underlying\r\nphysics solver. This commonly happens when practitioners use a moving triangle\r\nmesh with a grid-based physics solver, or when high-resolution grid-based surfaces\r\nare combined with low-resolution physics. Following the direction of steepest\r\ndescent on our surface-based energy, we can either smooth these artifacts or turn\r\nthem into high-resolution waves by interpreting the energy as a physical potential.\r\nThird, we extend state-of-the-art techniques in non-reflecting boundaries to handle spatially and time-varying background flows. This allows a novel new\r\nworkflow where practitioners can re-simulate part of an existing simulation, such\r\nas removing a solid obstacle, adding a new splash or locally changing the resolution.\r\nSuch changes can easily lead to new waves in the re-simulated region that would\r\nreflect off of the new simulation boundary, effectively ruining the illusion of a\r\nseamless simulation boundary between the existing and new simulations. Our\r\nnon-reflecting boundaries makes sure that such waves are absorbed.","lang":"eng"}],"ddc":["004","005","006","532","621"],"date_published":"2016-07-15T00:00:00Z","publist_id":"6238","page":"114","oa":1,"_id":"1122","related_material":{"record":[{"status":"public","id":"5558","relation":"other"}]},"OA_place":"publisher","alternative_title":["ISTA Thesis"],"oa_version":"Published Version","supervisor":[{"last_name":"Wojtan","id":"3C61F1D2-F248-11E8-B48F-1D18A9856A87","full_name":"Wojtan, Christopher J","orcid":"0000-0001-6646-5546","first_name":"Christopher J"}],"degree_awarded":"PhD","tmp":{"legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","short":"CC BY (4.0)","image":"/images/cc_by.png","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)"},"month":"07","type":"dissertation","publication_status":"published","acknowledgement":"First and foremost I would like to thank Chris. I have been incredibly lucky to have\r\nyou as my advisor. Your integrity and aspiration to do the right thing in all walks of\r\nlife is something I admire and aspire to. I also really appreciate the fact that when\r\nworking with you it felt like we were equals. I think we had a very synergetic work\r\nrelationship: I learned immensely from you, but I dare say that you learned a few\r\nthings from me as well. ;)\r\nNext, I would like to thank my amazing committee. Hao, it was a fantastic\r\nexperience working with you. You showed me how to persevere and keep morale\r\nhigh when things were looking the most bleak before the deadline. You are an\r\nincredible motivator and super fun to be around! Vladimir, thanks for the shared\r\nlunches and the poker games. Sorry for not bringing them back when I got busy.\r\nAlso, sorry for embarrassing you by asking about your guitar playing that one\r\ntime. You really are quite awesome! Nils, one of the friendliest and most humble\r\npeople you will meet and a top notch researcher to boot! Thank you for joining\r\nmy committee late!\r\nI would also like to acknowledge the Visual Computing group at IST Austria\r\nfrom whom I have learned so much. The excellent discussions we had in reading\r\ngroups and research meetings really helped me become a better researcher!\r\nNext, I would like to thank all the amazing people that I met during my PhD\r\nstudies, both at IST Austria, in Vienna and elsewhere. ","file":[{"content_type":"application/pdf","file_name":"IST-2016-640-v1+1_2016_Bojsen-Hansen_TCaAWSW.pdf","file_size":13869345,"access_level":"open_access","file_id":"4982","creator":"system","date_updated":"2018-12-12T10:13:02Z","relation":"main_file","date_created":"2018-12-12T10:13:02Z"}],"doi":"10.15479/AT:ISTA:th_640","author":[{"last_name":"Bojsen-Hansen","id":"439F0C8C-F248-11E8-B48F-1D18A9856A87","first_name":"Morten","full_name":"Bojsen-Hansen, Morten","orcid":"0000-0002-4417-3224"}]}]