---
_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:
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degree_awarded: PhD
department:
- _id: ChWo
doi: 10.15479/AT:ISTA:th_640
file:
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publication_identifier:
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publisher: Institute of Science and Technology Austria
publist_id: '6238'
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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
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type: dissertation
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
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---
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abstract:
- lang: eng
text: PhD thesis LaTeX source code
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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:48
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:48
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:48.
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, 10.15479/AT:ISTA:48.
mla: Bojsen-Hansen, Morten. Tracking, Correcting and Absorbing Water Surface
Waves. Institute of Science and Technology Austria, 2016, doi:10.15479/AT:ISTA:48.
short: M. Bojsen-Hansen, (2016).
datarep_id: '48'
date_created: 2018-12-12T12:31:31Z
date_published: 2016-09-23T00:00:00Z
date_updated: 2024-02-21T13:50:48Z
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ddc:
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pubrep_id: '640'
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status: public
title: Tracking, Correcting and Absorbing Water Surface Waves
tmp:
image: /images/cc_by.png
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name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: research_data
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
year: '2016'
...
---
_id: '1363'
abstract:
- lang: eng
text: When aiming to seamlessly integrate a fluid simulation into a larger scenario
(like an open ocean), careful attention must be paid to boundary conditions. In
particular, one must implement special "non-reflecting" boundary conditions,
which dissipate out-going waves as they exit the simulation. Unfortunately, the
state of the art in non-reflecting boundary conditions (perfectly-matched layers,
or PMLs) only permits trivially simple inflow/outflow conditions, so there is
no reliable way to integrate a fluid simulation into a more complicated environment
like a stormy ocean or a turbulent river. This paper introduces the first method
for combining nonreflecting boundary conditions based on PMLs with inflow/outflow
boundary conditions that vary arbitrarily throughout space and time. Our algorithm
is a generalization of stateof- the-art mean-flow boundary conditions in the computational
fluid dynamics literature, and it allows for seamless integration of a fluid simulation
into much more complicated environments. Our method also opens the door for previously-unseen
postprocess effects like retroactively changing the location of solid obstacles,
and locally increasing the visual detail of a pre-existing simulation.
acknowledged_ssus:
- _id: ScienComp
acknowledgement: 'We thank the IST Austria Visual Computing group for helpful feedback
throughout the project. '
alternative_title:
- ACM Transactions on Graphics
article_number: '96'
author:
- first_name: Morten
full_name: Bojsen-Hansen, Morten
id: 439F0C8C-F248-11E8-B48F-1D18A9856A87
last_name: Bojsen-Hansen
orcid: 0000-0002-4417-3224
- 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: 'Bojsen-Hansen M, Wojtan C. Generalized non-reflecting boundaries for fluid
re-simulation. In: Vol 35. ACM; 2016. doi:10.1145/2897824.2925963'
apa: 'Bojsen-Hansen, M., & Wojtan, C. (2016). Generalized non-reflecting boundaries
for fluid re-simulation (Vol. 35). Presented at the ACM SIGGRAPH, Anaheim, CA,
USA: ACM. https://doi.org/10.1145/2897824.2925963'
chicago: Bojsen-Hansen, Morten, and Chris Wojtan. “Generalized Non-Reflecting Boundaries
for Fluid Re-Simulation,” Vol. 35. ACM, 2016. https://doi.org/10.1145/2897824.2925963.
ieee: M. Bojsen-Hansen and C. Wojtan, “Generalized non-reflecting boundaries for
fluid re-simulation,” presented at the ACM SIGGRAPH, Anaheim, CA, USA, 2016, vol.
35, no. 4.
ista: Bojsen-Hansen M, Wojtan C. 2016. Generalized non-reflecting boundaries for
fluid re-simulation. ACM SIGGRAPH, ACM Transactions on Graphics, vol. 35, 96.
mla: Bojsen-Hansen, Morten, and Chris Wojtan. Generalized Non-Reflecting Boundaries
for Fluid Re-Simulation. Vol. 35, no. 4, 96, ACM, 2016, doi:10.1145/2897824.2925963.
short: M. Bojsen-Hansen, 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: 2016-07-11T00:00:00Z
date_updated: 2023-02-21T10:36:12Z
day: '11'
ddc:
- '000'
department:
- _id: ChWo
doi: 10.1145/2897824.2925963
ec_funded: 1
file:
- access_level: open_access
checksum: 140b5532f0a2a006a0149cab7c73c17c
content_type: application/pdf
creator: system
date_created: 2018-12-12T10:13:00Z
date_updated: 2020-07-14T12:44:47Z
file_id: '4981'
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file_date_updated: 2020-07-14T12:44:47Z
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: '5879'
pubrep_id: '631'
quality_controlled: '1'
status: public
title: Generalized non-reflecting boundaries for fluid re-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: 4435EBFC-F248-11E8-B48F-1D18A9856A87
volume: 35
year: '2016'
...
---
_id: '2468'
abstract:
- lang: eng
text: Our work concerns the combination of an Eulerian liquid simulation with a
high-resolution surface tracker (e.g. the level set method or a Lagrangian triangle
mesh). The naive application of a high-resolution surface tracker to a low-resolution
velocity field can produce many visually disturbing physical and topological artifacts
that limit their use in practice. We address these problems by defining an error
function which compares the current state of the surface tracker to the set of
physically valid surface states. By reducing this error with a gradient descent
technique, we introduce a novel physics-based surface fairing method. Similarly,
by treating this error function as a potential energy, we derive a new surface
correction force that mimics the vortex sheet equations. We demonstrate our results
with both level set and mesh-based surface trackers.
article_number: '68'
author:
- first_name: Morten
full_name: Bojsen-Hansen, Morten
id: 439F0C8C-F248-11E8-B48F-1D18A9856A87
last_name: Bojsen-Hansen
orcid: 0000-0002-4417-3224
- 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: Bojsen-Hansen M, Wojtan C. Liquid surface tracking with error compensation.
ACM Transactions on Graphics. 2013;32(4). doi:10.1145/2461912.2461991
apa: Bojsen-Hansen, M., & Wojtan, C. (2013). Liquid surface tracking with error
compensation. ACM Transactions on Graphics. ACM. https://doi.org/10.1145/2461912.2461991
chicago: Bojsen-Hansen, Morten, and Chris Wojtan. “Liquid Surface Tracking with
Error Compensation.” ACM Transactions on Graphics. ACM, 2013. https://doi.org/10.1145/2461912.2461991.
ieee: M. Bojsen-Hansen and C. Wojtan, “Liquid surface tracking with error compensation,”
ACM Transactions on Graphics, vol. 32, no. 4. ACM, 2013.
ista: Bojsen-Hansen M, Wojtan C. 2013. Liquid surface tracking with error compensation.
ACM Transactions on Graphics. 32(4), 68.
mla: Bojsen-Hansen, Morten, and Chris Wojtan. “Liquid Surface Tracking with Error
Compensation.” ACM Transactions on Graphics, vol. 32, no. 4, 68, ACM, 2013,
doi:10.1145/2461912.2461991.
short: M. Bojsen-Hansen, C. Wojtan, ACM Transactions on Graphics 32 (2013).
date_created: 2018-12-11T11:57:50Z
date_published: 2013-07-01T00:00:00Z
date_updated: 2023-02-23T10:44:18Z
day: '01'
ddc:
- '000'
department:
- _id: ChWo
doi: 10.1145/2461912.2461991
file:
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checksum: 53d905e0180e23ef3e813b969ffed4e1
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oa: 1
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publist_id: '4434'
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status: public
title: Liquid surface tracking with error compensation
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 32
year: '2013'
...
---
_id: '3118'
abstract:
- lang: eng
text: We present a method for recovering a temporally coherent, deforming triangle
mesh with arbitrarily changing topology from an incoherent sequence of static
closed surfaces. We solve this problem using the surface geometry alone, without
any prior information like surface templates or velocity fields. Our system combines
a proven strategy for triangle mesh improvement, a robust multi-resolution non-rigid
registration routine, and a reliable technique for changing surface mesh topology.
We also introduce a novel topological constraint enforcement algorithm to ensure
that the output and input always have similar topology. We apply our technique
to a series of diverse input data from video reconstructions, physics simulations,
and artistic morphs. The structured output of our algorithm allows us to efficiently
track information like colors and displacement maps, recover velocity information,
and solve PDEs on the mesh as a post process.
acknowledgement: "This work is supported by the SNF fellowship PBEZP2-134464.\r\nWe
would like to thank Xiaochen Hu for implementing mesh con- version tools, Duygu
Ceylan for helping with the rendering, and Art Tevs for the human performance data
comparison. We also thank Nils Thuerey and Christopher Batty for helpful discussions. "
alternative_title:
- SIGGRAPH
article_number: '53'
article_processing_charge: No
article_type: original
author:
- first_name: Morten
full_name: Bojsen-Hansen, Morten
id: 439F0C8C-F248-11E8-B48F-1D18A9856A87
last_name: Bojsen-Hansen
orcid: 0000-0002-4417-3224
- first_name: Hao
full_name: Li, Hao
last_name: Li
- 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: Bojsen-Hansen M, Li H, Wojtan C. Tracking surfaces with evolving topology.
ACM Transactions on Graphics. 2012;31(4). doi:10.1145/2185520.2185549
apa: Bojsen-Hansen, M., Li, H., & Wojtan, C. (2012). Tracking surfaces with
evolving topology. ACM Transactions on Graphics. ACM. https://doi.org/10.1145/2185520.2185549
chicago: Bojsen-Hansen, Morten, Hao Li, and Chris Wojtan. “Tracking Surfaces with
Evolving Topology.” ACM Transactions on Graphics. ACM, 2012. https://doi.org/10.1145/2185520.2185549.
ieee: M. Bojsen-Hansen, H. Li, and C. Wojtan, “Tracking surfaces with evolving topology,”
ACM Transactions on Graphics, vol. 31, no. 4. ACM, 2012.
ista: Bojsen-Hansen M, Li H, Wojtan C. 2012. Tracking surfaces with evolving topology.
ACM Transactions on Graphics. 31(4), 53.
mla: Bojsen-Hansen, Morten, et al. “Tracking Surfaces with Evolving Topology.” ACM
Transactions on Graphics, vol. 31, no. 4, 53, ACM, 2012, doi:10.1145/2185520.2185549.
short: M. Bojsen-Hansen, H. Li, C. Wojtan, ACM Transactions on Graphics 31 (2012).
date_created: 2018-12-11T12:01:29Z
date_published: 2012-07-01T00:00:00Z
date_updated: 2022-05-24T08:21:11Z
day: '01'
ddc:
- '000'
department:
- _id: ChWo
doi: 10.1145/2185520.2185549
file:
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checksum: 1e219c5bf4e5552c1290c62eefa5cd60
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creator: system
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publication: ACM Transactions on Graphics
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title: Tracking surfaces with evolving topology
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 31
year: '2012'
...