--- _id: '1412' abstract: - lang: eng text: Combining high-resolution level set surface tracking with lower resolution physics is an inexpensive method for achieving highly detailed liquid animations. Unfortunately, the inherent resolution mismatch introduces several types of disturbing visual artifacts. We identify the primary sources of these artifacts and present simple, efficient, and practical solutions to address them. First, we propose an unconditionally stable filtering method that selectively removes sub-grid surface artifacts not seen by the fluid physics, while preserving fine detail in dynamic splashing regions. It provides comparable results to recent error-correction techniques at lower cost, without substepping, and with better scaling behavior. Second, we show how a modified narrow-band scheme can ensure accurate free surface boundary conditions in the presence of large resolution mismatches. Our scheme preserves the efficiency of the narrow-band methodology, while eliminating objectionable stairstep artifacts observed in prior work. Third, we demonstrate that the use of linear interpolation of velocity during advection of the high-resolution level set surface is responsible for visible grid-aligned kinks; we therefore advocate higher-order velocity interpolation, and show that it dramatically reduces this artifact. While these three contributions are orthogonal, our results demonstrate that taken together they efficiently address the dominant sources of visual artifacts arising with high-resolution embedded liquid surfaces; the proposed approach offers improved visual quality, a straightforward implementation, and substantially greater scalability than competing methods. acknowledgement: 'This research was supported by NSERC (RGPIN-04360-2014) and IST Austria. ' author: - first_name: Ryan full_name: Goldade, Ryan last_name: Goldade - first_name: Christopher full_name: Batty, Christopher last_name: Batty - first_name: Christopher J full_name: Wojtan, Christopher J id: 3C61F1D2-F248-11E8-B48F-1D18A9856A87 last_name: Wojtan orcid: 0000-0001-6646-5546 citation: ama: Goldade R, Batty C, Wojtan C. A practical method for high-resolution embedded liquid surfaces. Computer Graphics Forum. 2016;35(2):233-242. doi:10.1111/cgf.12826 apa: Goldade, R., Batty, C., & Wojtan, C. (2016). A practical method for high-resolution embedded liquid surfaces. Computer Graphics Forum. Wiley-Blackwell. https://doi.org/10.1111/cgf.12826 chicago: Goldade, Ryan, Christopher Batty, and Chris Wojtan. “A Practical Method for High-Resolution Embedded Liquid Surfaces.” Computer Graphics Forum. Wiley-Blackwell, 2016. https://doi.org/10.1111/cgf.12826. ieee: R. Goldade, C. Batty, and C. Wojtan, “A practical method for high-resolution embedded liquid surfaces,” Computer Graphics Forum, vol. 35, no. 2. Wiley-Blackwell, pp. 233–242, 2016. ista: Goldade R, Batty C, Wojtan C. 2016. A practical method for high-resolution embedded liquid surfaces. Computer Graphics Forum. 35(2), 233–242. mla: Goldade, Ryan, et al. “A Practical Method for High-Resolution Embedded Liquid Surfaces.” Computer Graphics Forum, vol. 35, no. 2, Wiley-Blackwell, 2016, pp. 233–42, doi:10.1111/cgf.12826. short: R. Goldade, C. Batty, C. Wojtan, Computer Graphics Forum 35 (2016) 233–242. date_created: 2018-12-11T11:51:52Z date_published: 2016-05-27T00:00:00Z date_updated: 2023-02-21T10:38:30Z day: '27' ddc: - '000' department: - _id: ChWo doi: 10.1111/cgf.12826 ec_funded: 1 file: - access_level: open_access checksum: 8e61387ee2e3bd0e776fbe301629bfd9 content_type: application/pdf creator: system date_created: 2018-12-12T10:13:18Z date_updated: 2020-07-14T12:44:53Z file_id: '5000' file_name: IST-2016-612-v1+2_Wojtan_APracticalMethod_PostPrint_2016.pdf file_size: 15873858 relation: main_file file_date_updated: 2020-07-14T12:44:53Z has_accepted_license: '1' intvolume: ' 35' issue: '2' language: - iso: eng month: '05' oa: 1 oa_version: Submitted Version page: 233 - 242 project: - _id: 2533E772-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '638176' name: Efficient Simulation of Natural Phenomena at Extremely Large Scales publication: Computer Graphics Forum publication_status: published publisher: Wiley-Blackwell publist_id: '5795' pubrep_id: '612' quality_controlled: '1' scopus_import: 1 status: public title: A practical method for high-resolution embedded liquid surfaces type: journal_article user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87 volume: 35 year: '2016' ... --- _id: '1413' abstract: - lang: eng text: This paper generalizes the well-known Diffusion Curves Images (DCI), which are composed of a set of Bezier curves with colors specified on either side. These colors are diffused as Laplace functions over the image domain, which results in smooth color gradients interrupted by the Bezier curves. Our new formulation allows for more color control away from the boundary, providing a similar expressive power as recent Bilaplace image models without introducing associated issues and computational costs. The new model is based on a special Laplace function blending and a new edge blur formulation. We demonstrate that given some user-defined boundary curves over an input raster image, fitting colors and edge blur from the image to the new model and subsequent editing and animation is equally convenient as with DCIs. Numerous examples and comparisons to DCIs are presented. author: - first_name: Stefan full_name: Jeschke, Stefan id: 44D6411A-F248-11E8-B48F-1D18A9856A87 last_name: Jeschke citation: ama: 'Jeschke S. Generalized diffusion curves: An improved vector representation for smooth-shaded images. Computer Graphics Forum. 2016;35(2):71-79. doi:10.1111/cgf.12812' apa: 'Jeschke, S. (2016). Generalized diffusion curves: An improved vector representation for smooth-shaded images. Computer Graphics Forum. Wiley-Blackwell. https://doi.org/10.1111/cgf.12812' chicago: 'Jeschke, Stefan. “Generalized Diffusion Curves: An Improved Vector Representation for Smooth-Shaded Images.” Computer Graphics Forum. Wiley-Blackwell, 2016. https://doi.org/10.1111/cgf.12812.' ieee: 'S. Jeschke, “Generalized diffusion curves: An improved vector representation for smooth-shaded images,” Computer Graphics Forum, vol. 35, no. 2. Wiley-Blackwell, pp. 71–79, 2016.' ista: 'Jeschke S. 2016. Generalized diffusion curves: An improved vector representation for smooth-shaded images. Computer Graphics Forum. 35(2), 71–79.' mla: 'Jeschke, Stefan. “Generalized Diffusion Curves: An Improved Vector Representation for Smooth-Shaded Images.” Computer Graphics Forum, vol. 35, no. 2, Wiley-Blackwell, 2016, pp. 71–79, doi:10.1111/cgf.12812.' short: S. Jeschke, Computer Graphics Forum 35 (2016) 71–79. date_created: 2018-12-11T11:51:53Z date_published: 2016-05-01T00:00:00Z date_updated: 2021-01-12T06:50:34Z day: '01' department: - _id: ChWo doi: 10.1111/cgf.12812 intvolume: ' 35' issue: '2' language: - iso: eng month: '05' oa_version: None page: 71 - 79 project: - _id: 25357BD2-B435-11E9-9278-68D0E5697425 call_identifier: FWF grant_number: P 24352-N23 name: 'Deep Pictures: Creating Visual and Haptic Vector Images' publication: Computer Graphics Forum publication_status: published publisher: Wiley-Blackwell publist_id: '5794' quality_controlled: '1' scopus_import: 1 status: public title: 'Generalized diffusion curves: An improved vector representation for smooth-shaded images' type: journal_article user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87 volume: 35 year: '2016' ... --- _id: '1415' abstract: - lang: eng text: The Fluid Implicit Particle method (FLIP) for liquid simulations uses particles to reduce numerical dissipation and provide important visual cues for events like complex splashes and small-scale features near the liquid surface. Unfortunately, FLIP simulations can be computationally expensive, because they require a dense sampling of particles to fill the entire liquid volume. Furthermore, the vast majority of these FLIP particles contribute nothing to the fluid's visual appearance, especially for larger volumes of liquid. We present a method that only uses FLIP particles within a narrow band of the liquid surface, while efficiently representing the remaining inner volume on a regular grid. We show that a naïve realization of this idea introduces unstable and uncontrollable energy fluctuations, and we propose a novel coupling scheme between FLIP particles and regular grid which overcomes this problem. Our method drastically reduces the particle count and simulation times while yielding results that are nearly indistinguishable from regular FLIP simulations. Our approach is easy to integrate into any existing FLIP implementation. author: - first_name: Florian full_name: Ferstl, Florian last_name: Ferstl - first_name: Ryoichi full_name: Ando, Ryoichi last_name: Ando - first_name: Christopher J full_name: Wojtan, Christopher J id: 3C61F1D2-F248-11E8-B48F-1D18A9856A87 last_name: Wojtan orcid: 0000-0001-6646-5546 - first_name: Rüdiger full_name: Westermann, Rüdiger last_name: Westermann - first_name: Nils full_name: Thuerey, Nils last_name: Thuerey citation: ama: Ferstl F, Ando R, Wojtan C, Westermann R, Thuerey N. Narrow band FLIP for liquid simulations. Computer Graphics Forum. 2016;35(2):225-232. doi:10.1111/cgf.12825 apa: Ferstl, F., Ando, R., Wojtan, C., Westermann, R., & Thuerey, N. (2016). Narrow band FLIP for liquid simulations. Computer Graphics Forum. Wiley-Blackwell. https://doi.org/10.1111/cgf.12825 chicago: Ferstl, Florian, Ryoichi Ando, Chris Wojtan, Rüdiger Westermann, and Nils Thuerey. “Narrow Band FLIP for Liquid Simulations.” Computer Graphics Forum. Wiley-Blackwell, 2016. https://doi.org/10.1111/cgf.12825. ieee: F. Ferstl, R. Ando, C. Wojtan, R. Westermann, and N. Thuerey, “Narrow band FLIP for liquid simulations,” Computer Graphics Forum, vol. 35, no. 2. Wiley-Blackwell, pp. 225–232, 2016. ista: Ferstl F, Ando R, Wojtan C, Westermann R, Thuerey N. 2016. Narrow band FLIP for liquid simulations. Computer Graphics Forum. 35(2), 225–232. mla: Ferstl, Florian, et al. “Narrow Band FLIP for Liquid Simulations.” Computer Graphics Forum, vol. 35, no. 2, Wiley-Blackwell, 2016, pp. 225–32, doi:10.1111/cgf.12825. short: F. Ferstl, R. Ando, C. Wojtan, R. Westermann, N. Thuerey, Computer Graphics Forum 35 (2016) 225–232. date_created: 2018-12-11T11:51:53Z date_published: 2016-05-01T00:00:00Z date_updated: 2023-02-21T10:38:38Z day: '01' ddc: - '000' department: - _id: ChWo doi: 10.1111/cgf.12825 file: - access_level: open_access checksum: 984afbe510ed48019025dff1dcc7baad content_type: application/pdf creator: system date_created: 2018-12-12T10:12:22Z date_updated: 2020-07-14T12:44:53Z file_id: '4940' file_name: IST-2016-611-v1+3_CW_nbflip_postprint_2016.pdf file_size: 5938324 relation: main_file file_date_updated: 2020-07-14T12:44:53Z has_accepted_license: '1' intvolume: ' 35' issue: '2' language: - iso: eng month: '05' oa: 1 oa_version: Submitted Version page: 225 - 232 publication: Computer Graphics Forum publication_status: published publisher: Wiley-Blackwell publist_id: '5793' pubrep_id: '611' quality_controlled: '1' scopus_import: 1 status: public title: Narrow band FLIP for liquid simulations type: journal_article user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87 volume: 35 year: '2016' ... --- _id: '1362' abstract: - lang: eng text: We present a boundary element based method for fast simulation of brittle fracture. By introducing simplifying assumptions that allow us to quickly estimate stress intensities and opening displacements during crack propagation, we build a fracture algorithm where the cost of each time step scales linearly with the length of the crackfront. The transition from a full boundary element method to our faster variant is possible at the beginning of any time step. This allows us to build a hybrid method, which uses the expensive but more accurate BEM while the number of degrees of freedom is low, and uses the fast method once that number exceeds a given threshold as the crack geometry becomes more complicated. Furthermore, we integrate this fracture simulation with a standard rigid-body solver. Our rigid-body coupling solves a Neumann boundary value problem by carefully separating translational, rotational and deformational components of the collision forces and then applying a Tikhonov regularizer to the resulting linear system. We show that our method produces physically reasonable results in standard test cases and is capable of dealing with complex scenes faster than previous finite- or boundary element approaches. alternative_title: - ACM Transactions on Graphics article_number: '104' author: - first_name: David full_name: Hahn, David id: 357A6A66-F248-11E8-B48F-1D18A9856A87 last_name: Hahn - first_name: Christopher J full_name: Wojtan, Christopher J id: 3C61F1D2-F248-11E8-B48F-1D18A9856A87 last_name: Wojtan orcid: 0000-0001-6646-5546 citation: ama: 'Hahn D, Wojtan C. Fast approximations for boundary element based brittle fracture simulation. In: Vol 35. ACM; 2016. doi:10.1145/2897824.2925902' apa: 'Hahn, D., & Wojtan, C. (2016). Fast approximations for boundary element based brittle fracture simulation (Vol. 35). Presented at the ACM SIGGRAPH, Anaheim, CA, USA: ACM. https://doi.org/10.1145/2897824.2925902' chicago: Hahn, David, and Chris Wojtan. “Fast Approximations for Boundary Element Based Brittle Fracture Simulation,” Vol. 35. ACM, 2016. https://doi.org/10.1145/2897824.2925902. ieee: D. Hahn and C. Wojtan, “Fast approximations for boundary element based brittle fracture simulation,” presented at the ACM SIGGRAPH, Anaheim, CA, USA, 2016, vol. 35, no. 4. ista: Hahn D, Wojtan C. 2016. Fast approximations for boundary element based brittle fracture simulation. ACM SIGGRAPH, ACM Transactions on Graphics, vol. 35, 104. mla: Hahn, David, and Chris Wojtan. Fast Approximations for Boundary Element Based Brittle Fracture Simulation. Vol. 35, no. 4, 104, ACM, 2016, doi:10.1145/2897824.2925902. short: D. Hahn, C. Wojtan, in:, ACM, 2016. conference: end_date: 2016-07-28 location: Anaheim, CA, USA name: ACM SIGGRAPH start_date: 2016-07-24 date_created: 2018-12-11T11:51:35Z date_published: 2016-07-01T00:00:00Z date_updated: 2023-09-07T12:02:56Z day: '01' ddc: - '000' department: - _id: ChWo doi: 10.1145/2897824.2925902 ec_funded: 1 file: - access_level: open_access checksum: 943712d9c9dc8bb5048d4adc561d7d38 content_type: application/pdf creator: system date_created: 2018-12-12T10:15:04Z date_updated: 2020-07-14T12:44:46Z file_id: '5121' file_name: IST-2016-632-v1+2_a104-hahn.pdf file_size: 12453704 relation: main_file file_date_updated: 2020-07-14T12:44:46Z has_accepted_license: '1' intvolume: ' 35' issue: '4' language: - iso: eng month: '07' oa: 1 oa_version: Published Version project: - _id: 2533E772-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '638176' name: Efficient Simulation of Natural Phenomena at Extremely Large Scales publication_status: published publisher: ACM publist_id: '5880' pubrep_id: '632' quality_controlled: '1' related_material: record: - id: '839' relation: dissertation_contains status: public status: public title: Fast approximations for boundary element based brittle fracture simulation tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: conference user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87 volume: 35 year: '2016' ... --- _id: '1122' abstract: - lang: eng 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." 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. " alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Morten full_name: Bojsen-Hansen, Morten id: 439F0C8C-F248-11E8-B48F-1D18A9856A87 last_name: Bojsen-Hansen orcid: 0000-0002-4417-3224 citation: ama: Bojsen-Hansen M. Tracking, correcting and absorbing water surface waves. 2016. doi:10.15479/AT:ISTA:th_640 apa: Bojsen-Hansen, M. (2016). Tracking, correcting and absorbing water surface waves. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:th_640 chicago: Bojsen-Hansen, Morten. “Tracking, Correcting and Absorbing Water Surface Waves.” Institute of Science and Technology Austria, 2016. https://doi.org/10.15479/AT:ISTA:th_640. 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. mla: Bojsen-Hansen, Morten. Tracking, Correcting and Absorbing Water Surface Waves. Institute of Science and Technology Austria, 2016, doi:10.15479/AT:ISTA:th_640. short: M. Bojsen-Hansen, Tracking, Correcting and Absorbing Water Surface Waves, Institute of Science and Technology Austria, 2016. date_created: 2018-12-11T11:50:16Z date_published: 2016-07-15T00:00:00Z date_updated: 2024-02-21T13:50:48Z day: '15' ddc: - '004' - '005' - '006' - '532' - '621' degree_awarded: PhD department: - _id: ChWo doi: 10.15479/AT:ISTA:th_640 file: - access_level: open_access content_type: application/pdf creator: system date_created: 2018-12-12T10:13:02Z date_updated: 2018-12-12T10:13:02Z file_id: '4982' file_name: IST-2016-640-v1+1_2016_Bojsen-Hansen_TCaAWSW.pdf file_size: 13869345 relation: main_file file_date_updated: 2018-12-12T10:13:02Z has_accepted_license: '1' language: - iso: eng month: '07' oa: 1 oa_version: Published Version page: '114' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria publist_id: '6238' related_material: record: - id: '5558' relation: other status: public status: public supervisor: - first_name: Christopher J full_name: Wojtan, Christopher J id: 3C61F1D2-F248-11E8-B48F-1D18A9856A87 last_name: Wojtan orcid: 0000-0001-6646-5546 title: Tracking, correcting and absorbing water surface waves tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2016' ...