137 research outputs found
Modeling the response of Greenland outlet glaciers to global warming using a coupled flow line-plume model
In recent decades, the Greenland Ice Sheet has experienced an accelerated mass loss, contributing to approximately 25 % of contemporary sea level rise (SLR). This mass loss is caused by increased surface melt over a large area of the ice sheet and by the thinning, retreat and acceleration of numerous Greenland outlet glaciers. The latter is likely connected to enhanced submarine melting that, in turn, can be explained by ocean warming and enhanced subglacial discharge. The mechanisms involved in submarine melting are not yet fully understood and are only simplistically incorporated in some models of the Greenland Ice Sheet. Here, we investigate the response of 12 representative Greenland outlet glaciers to atmospheric and oceanic warming using a coupled line–plume glacier–flow line model resolving one horizontal dimension. The model parameters have been tuned for individual outlet glaciers using present-day observational constraints. We then run the model from present to the year 2100, forcing the model with changes in surface mass balance and surface runoff from simulations with a regional climate model for the RCP8.5 scenario, and applying a linear ocean temperature warming with different rates of changes representing uncertainties in the CMIP5 model experiments for the same climate change scenario. We also use different initial temperature–salinity profiles obtained from direct measurements and from ocean reanalysis data. Using different combinations of submarine melting and calving parameters that reproduce the present-day state of the glaciers, we estimate uncertainties in the contribution to global SLR for individual glaciers. We also perform a sensitivity analysis of the three forcing factors (changes in surface mass balance, ocean temperature and subglacial discharge), which shows that the roles of the different forcing factors are diverse for individual glaciers. We find that changes in ocean temperature and subglacial discharge are of comparable importance for the cumulative contribution of all 12 glaciers to global SLR in the 21st century. The median range of the cumulative contribution to the global SLR for all 12 glaciers is about 18 mm (the glaciers' dynamic response to changes of all three forcing factors). Neglecting changes in ocean temperature and subglacial discharge (which control submarine melt) and investigating the response to changes in surface mass balance only leads to a cumulative contribution of 5 mm SLR. Thus, from the 18 mm we associate roughly 70 % with the glaciers' dynamic response to increased subglacial discharge and ocean temperature and the remaining 30 % (5 mm) to the response to increased surface mass loss. We also find a strong correlation (correlation coefficient 0.74) between present-day grounding line discharge and their future contribution to SLR in 2100. If the contribution of the 12 glaciers is scaled up to the total present-day discharge of Greenland, we estimate the midrange contribution of all Greenland glaciers to 21st-century SLR to be approximately 50 mm. This number adds to SLR derived from a stand-alone ice sheet model (880 mm) that does not resolve outlet glaciers and thus increases SLR by over 50 %. This result confirms earlier studies showing that the response of the outlet glaciers to global warming has to be taken into account to correctly assess the total contribution of Greenland to sea level change
RL-LABEL: A Deep Reinforcement Learning Approach Intended for AR Label Placement in Dynamic Scenarios
Labels are widely used in augmented reality (AR) to display digital
information. Ensuring the readability of AR labels requires placing them
occlusion-free while keeping visual linkings legible, especially when multiple
labels exist in the scene. Although existing optimization-based methods, such
as force-based methods, are effective in managing AR labels in static
scenarios, they often struggle in dynamic scenarios with constantly moving
objects. This is due to their focus on generating layouts optimal for the
current moment, neglecting future moments and leading to sub-optimal or
unstable layouts over time. In this work, we present RL-LABEL, a deep
reinforcement learning-based method for managing the placement of AR labels in
scenarios involving moving objects. RL-LABEL considers the current and
predicted future states of objects and labels, such as positions and
velocities, as well as the user's viewpoint, to make informed decisions about
label placement. It balances the trade-offs between immediate and long-term
objectives. Our experiments on two real-world datasets show that RL-LABEL
effectively learns the decision-making process for long-term optimization,
outperforming two baselines (i.e., no view management and a force-based method)
by minimizing label occlusions, line intersections, and label movement
distance. Additionally, a user study involving 18 participants indicates that
RL-LABEL excels over the baselines in aiding users to identify, compare, and
summarize data on AR labels within dynamic scenes
VIRD: Immersive Match Video Analysis for High-Performance Badminton Coaching
Badminton is a fast-paced sport that requires a strategic combination of
spatial, temporal, and technical tactics. To gain a competitive edge at
high-level competitions, badminton professionals frequently analyze match
videos to gain insights and develop game strategies. However, the current
process for analyzing matches is time-consuming and relies heavily on manual
note-taking, due to the lack of automatic data collection and appropriate
visualization tools. As a result, there is a gap in effectively analyzing
matches and communicating insights among badminton coaches and players. This
work proposes an end-to-end immersive match analysis pipeline designed in close
collaboration with badminton professionals, including Olympic and national
coaches and players. We present VIRD, a VR Bird (i.e., shuttle) immersive
analysis tool, that supports interactive badminton game analysis in an
immersive environment based on 3D reconstructed game views of the match video.
We propose a top-down analytic workflow that allows users to seamlessly move
from a high-level match overview to a detailed game view of individual rallies
and shots, using situated 3D visualizations and video. We collect 3D spatial
and dynamic shot data and player poses with computer vision models and
visualize them in VR. Through immersive visualizations, coaches can
interactively analyze situated spatial data (player positions, poses, and shot
trajectories) with flexible viewpoints while navigating between shots and
rallies effectively with embodied interaction. We evaluated the usefulness of
VIRD with Olympic and national-level coaches and players in real matches.
Results show that immersive analytics supports effective badminton match
analysis with reduced context-switching costs and enhances spatial
understanding with a high sense of presence.Comment: To Appear in IEEE Transactions on Visualization and Computer Graphics
(IEEE VIS), 202
Residency Octree: A Hybrid Approach for Scalable Web-Based Multi-Volume Rendering
We present a hybrid multi-volume rendering approach based on a novel
Residency Octree that combines the advantages of out-of-core volume rendering
using page tables with those of standard octrees. Octree approaches work by
performing hierarchical tree traversal. However, in octree volume rendering,
tree traversal and the selection of data resolution are intrinsically coupled.
This makes fine-grained empty-space skipping costly. Page tables, on the other
hand, allow access to any cached brick from any resolution. However, they do
not offer a clear and efficient strategy for substituting missing
high-resolution data with lower-resolution data. We enable flexible
mixed-resolution out-of-core multi-volume rendering by decoupling the cache
residency of multi-resolution data from a resolution-independent spatial
subdivision determined by the tree. Instead of one-to-one node-to-brick
correspondences, each residency octree node is mapped to a set of bricks from
different resolution levels. This makes it possible to efficiently and
adaptively choose and mix resolutions, adapt sampling rates, and compensate for
cache misses. At the same time, residency octrees support fine-grained
empty-space skipping, independent of the data subdivision used for caching.
Finally, to facilitate collaboration and outreach, and to eliminate local data
storage, our implementation is a web-based, pure client-side renderer using
WebGPU and WebAssembly. Our method is faster than prior approaches and
efficient for many data channels with a flexible and adaptive choice of data
resolution.Comment: VIS 2023 - full pape
Sporthesia: Augmenting Sports Videos Using Natural Language
Augmented sports videos, which combine visualizations and video effects to
present data in actual scenes, can communicate insights engagingly and thus
have been increasingly popular for sports enthusiasts around the world. Yet,
creating augmented sports videos remains a challenging task, requiring
considerable time and video editing skills. On the other hand, sports insights
are often communicated using natural language, such as in commentaries, oral
presentations, and articles, but usually lack visual cues. Thus, this work aims
to facilitate the creation of augmented sports videos by enabling analysts to
directly create visualizations embedded in videos using insights expressed in
natural language. To achieve this goal, we propose a three-step approach - 1)
detecting visualizable entities in the text, 2) mapping these entities into
visualizations, and 3) scheduling these visualizations to play with the video -
and analyzed 155 sports video clips and the accompanying commentaries for
accomplishing these steps. Informed by our analysis, we have designed and
implemented Sporthesia, a proof-of-concept system that takes racket-based
sports videos and textual commentaries as the input and outputs augmented
videos. We demonstrate Sporthesia's applicability in two exemplar scenarios,
i.e., authoring augmented sports videos using text and augmenting historical
sports videos based on auditory comments. A technical evaluation shows that
Sporthesia achieves high accuracy (F1-score of 0.9) in detecting visualizable
entities in the text. An expert evaluation with eight sports analysts suggests
high utility, effectiveness, and satisfaction with our language-driven
authoring method and provides insights for future improvement and
opportunities.Comment: 10 pages, IEEE VIS conferenc
iBall: Augmenting Basketball Videos with Gaze-moderated Embedded Visualizations
We present iBall, a basketball video-watching system that leverages
gaze-moderated embedded visualizations to facilitate game understanding and
engagement of casual fans. Video broadcasting and online video platforms make
watching basketball games increasingly accessible. Yet, for new or casual fans,
watching basketball videos is often confusing due to their limited basketball
knowledge and the lack of accessible, on-demand information to resolve their
confusion. To assist casual fans in watching basketball videos, we compared the
game-watching behaviors of casual and die-hard fans in a formative study and
developed iBall based on the fndings. iBall embeds visualizations into
basketball videos using a computer vision pipeline, and automatically adapts
the visualizations based on the game context and users' gaze, helping casual
fans appreciate basketball games without being overwhelmed. We confrmed the
usefulness, usability, and engagement of iBall in a study with 16 casual fans,
and further collected feedback from 8 die-hard fans.Comment: ACM CHI2
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