| 1. |
- Bock, Alexander, 1985-
(författare)
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Tailoring visualization applications for tasks and users
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Exponential increases in available computational resources over the recent decades have fueled an information explosion in almost every scientific field. This has led to a societal change shifting from an information-poor research environment to an over-abundance of information. As many of these cases involve too much information to directly comprehend, visualization proves to be an effective tool to gain insight into these large datasets. While visualization has been used since the beginning of mankind, its importance is only increasing as the exponential information growth widens the difference between the amount of gathered data and the relatively constant human ability to ingest information. Visualization, as a methodology and tool of transforming complex data into an intuitive visual representation can leverage the combined computational resources and the human cognitive capabilities in order to mitigate this growing discrepancy.A large portion of visualization research is, directly or indirectly, targets users in an application domain, such as medicine, biology, physics, or others. Applied research is aimed at the creation of visualization applications or systems that solve a specific problem within the domain. Combining prior research and applying it to a concrete problem enables the possibility to compare and determine the usability and usefulness of existing visualization techniques. These applications can only be effective when the domain experts are closely involved in the design process, leading to an iterative workflow that informs its form and function. These visualization solutions can be separated into three categories: Exploration, in which users perform an initial study of data, Analysis, in which an established technique is repeatedly applied to a large number of datasets, and Communication in which findings are published to a wider public audience.This thesis presents five examples of application development in finite element modeling, medicine, urban search & rescue, and astronomy and astrophysics. For the finite element modeling, an exploration tool for simulations of stress tensors in a human heart uses a compression method to achieve interactive frame rates. In the medical domain, an analysis system aimed at guiding surgeons during Deep Brain Stimulation interventions fuses multiple modalities in order to improve their outcome. A second analysis application is targeted at the Urban Search & Rescue community supporting the extraction of injured victims and enabling a more sophisticated decision making strategy. For the astronomical domain, first, an exploration application enables the analysis of time-varying volumetric plasma simulations to improving these simulations and thus better predict space weather. A final system focusses on combining all three categories into a single application that enables the same tools to be used for Exploration, Analysis, and Communication, thus requiring the handling of large coordinate systems, and high-fidelity rendering of planetary surfaces and spacecraft operations.
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| 2. |
- Bruckner, Stefan, et al.
(författare)
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A Model of Spatial Directness in Interactive Visualization
- 2018
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Ingår i: IEEE Transactions on Visualization and Computer Graphics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-2626 .- 1941-0506.
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the concept of directness in the context of spatial interaction with visualization. In particular, we propose a model that allows practitioners to analyze and describe the spatial directness of interaction techniques, ultimately to be able to better understand interaction issues that may affect usability. To reach these goals, we distinguish between different types of directness. Each type of directness depends on a particular mapping between different spaces, for which we consider the data space, the visualization space, the output space, the user space, the manipulation space, and the interaction space. In addition to the introduction of the model itself, we also show how to apply it to several real-world interaction scenarios in visualization, and thus discuss the resulting types of spatial directness, without recommending either more direct or more indirect interaction techniques. In particular, we will demonstrate descriptive and evaluative usage of the proposed model, and also briefly discuss its generative usage.
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| 3. |
- Duran Rosich, David, et al.
(författare)
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Visualization of Large Molecular Trajectories
- 2018
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Ingår i: IEEE Transactions on Visualization and Computer Graphics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-2626 .- 1941-0506.
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Tidskriftsartikel (refereegranskat)abstract
- The analysis of protein-ligand interactions is a time-intensive task. Researchers have to analyze multiple physico-chemical properties of the protein at once and combine them to derive conclusions about the protein-ligand interplay. Typically, several charts are inspected, and 3D animations can be played side-by-side to obtain a deeper understanding of the data. With the advances in simulation techniques, larger and larger datasets are available, with up to hundreds of thousands of steps. Unfortunately, such large trajectories are very difficult to investigate with traditional approaches. Therefore, the need for special tools that facilitate inspection of these large trajectories becomes substantial. In this paper, we present a novel system for visual exploration of very large trajectories in an interactive and user-friendly way. Several visualization motifs are automatically derived from the data to give the user the information about interactions between protein and ligand. Our system offers specialized widgets to ease and accelerate data inspection and navigation to interesting parts of the simulation. The system is suitable also for simulations where multiple ligands are involved. We have tested the usefulness of our tool on a set of datasets obtained from protein engineers, and we describe the expert feedback.
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| 4. |
- Henzler, Philipp, et al.
(författare)
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Single-image Tomography : 3D Volumes from 2D Cranial X-Rays
- 2018
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Ingår i: Computer Graphics Forum (Proceedings of Eurographics 2018). - : Wiley-Blackwell Publishing Inc.. - 0167-7055. ; 37:2, s. 377-388
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Tidskriftsartikel (refereegranskat)abstract
- As many different 3D volumes could produce the same 2D x‐ray image, inverting this process is challenging. We show that recent deep learning‐based convolutional neural networks can solve this task. As the main challenge in learning is the sheer amount of data created when extending the 2D image into a 3D volume, we suggest firstly to learn a coarse, fixed‐resolution volume which is then fused in a second step with the input x‐ray into a high‐resolution volume. To train and validate our approach we introduce a new dataset that comprises of close to half a million computer‐simulated 2D x‐ray images of 3D volumes scanned from 175 mammalian species. Future applications of our approach include stereoscopic rendering of legacy x‐ray images, re‐rendering of x‐rays including changes of illumination, view pose or geometry. Our evaluation includes comparison to previous tomography work, previous learning methods using our data, a user study and application to a set of real x‐rays.
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| 5. |
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| 6. |
- Hermosilla, Pedro, et al.
(författare)
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A General Illumination Model for Molecular Visualization
- 2018
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Ingår i: Computer Graphics Forum (Proceedings of EuroVis 2018). - : Wiley-Blackwell Publishing Inc.. - 0167-7055. ; 37:3, s. 367-378
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Tidskriftsartikel (refereegranskat)abstract
- Several visual representations have been developed over the years to visualize molecular structures, and to enable a better understanding of their underlying chemical processes. Today, the most frequently used atom‐based representations are the Space‐filling, the Solvent Excluded Surface, the Balls‐and‐Sticks, and the Licorice models. While each of these representations has its individual benefits, when applied to large‐scale models spatial arrangements can be difficult to interpret when employing current visualization techniques. In the past it has been shown that global illumination techniques improve the perception of molecular visualizations; unfortunately existing approaches are tailored towards a single visual representation. We propose a general illumination model for molecular visualization that is valid for different representations. With our illumination model, it becomes possible, for the first time, to achieve consistent illumination among all atom‐based molecular representations. The proposed model can be further evaluated in real‐time, as it employs an analytical solution to simulate diffuse light interactions between objects. To be able to derive such a solution for the rather complicated and diverse visual representations, we propose the use of regression analysis together with adapted parameter sampling strategies as well as shape parametrization guided sampling, which are applied to the geometric building blocks of the targeted visual representations. We will discuss the proposed sampling strategies, the derived illumination model, and demonstrate its capabilities when visualizing several dynamic molecules.
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| 7. |
- Hermosilla, Pedro, et al.
(författare)
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Monte Carlo Convolution for Learning on Non-Uniformly Sampled Point Clouds
- 2018
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Ingår i: ACM Transactions on Graphics. - : Association for Computing Machinery (ACM). - 0730-0301 .- 1557-7368. ; 37:6
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Tidskriftsartikel (refereegranskat)abstract
- Deep learning systems extensively use convolution operations to process input data. Though convolution is clearly defined for structured data such as 2D images or 3D volumes, this is not true for other data types such as sparse point clouds. Previous techniques have developed approximations to convolutions for restricted conditions. Unfortunately, their applicability is limited and cannot be used for general point clouds. We propose an efficient and effective method to learn convolutions for non-uniformly sampled point clouds, as they are obtained with modern acquisition techniques. Learning is enabled by four key novelties: first, representing the convolution kernel itself as a multilayer perceptron; second, phrasing convolution as a Monte Carlo integration problem, third, using this notion to combine information from multiple samplings at different levels; and fourth using Poisson disk sampling as a scalable means of hierarchical point cloud learning. The key idea across all these contributions is to guarantee adequate consideration of the underlying non-uniform sample distribution function from a Monte Carlo perspective. To make the proposed concepts applicable to real-world tasks, we furthermore propose an efficient implementation which significantly reduces the GPU memory required during the training process. By employing our method in hierarchical network architectures we can outperform most of the state-of-the-art networks on established point cloud segmentation, classification and normal estimation benchmarks. Furthermore, in contrast to most existing approaches, we also demonstrate the robustness of our method with respect to sampling variations, even when training with uniformly sampled data only. To support the direct application of these concepts, we provide a ready-to-use TensorFlow implementation of these layers at https://github.com/viscom-ulm/MCCNN.
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| 8. |
- Jönsson, Daniel, 1984-, et al.
(författare)
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Inviwo - A Visualization System with Usage Abstraction Levels
- 2020
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Ingår i: IEEE Transactions on Visualization and Computer Graphics. - : IEEE. - 1077-2626 .- 1941-0506. ; 26:11, s. 3241-3254
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Tidskriftsartikel (refereegranskat)abstract
- The complexity of todays visualization applications demands specific visualization systems tailored for the development of these applications. Frequently, such systems utilize levels of abstraction to improve the application development process, for insta
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| 9. |
- Kreiser, Julian, et al.
(författare)
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A Survey of Flattening-Based Medical Visualization Techniques
- 2018
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Ingår i: Computer Graphics Forum (Proceedings of EuroVis 2018). - : Wiley-Blackwell Publishing Inc.. - 0167-7055. ; 37:3, s. 597-624
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Tidskriftsartikel (refereegranskat)abstract
- In many areas of medicine, visualization research can help with task simplification, abstraction or complexity reduction. A common visualization approach is to facilitate parameterization techniques which flatten a usually 3D object into a 2D plane. Within this state of the art report (STAR), we review such techniques used in medical visualization and investigate how they can be classified with respect to the handled data and the underlying tasks. Many of these techniques are inspired by mesh parameterization algorithms which help to project a triangulation in ℝ3 to a simpler domain in ℝ2. It is often claimed that this makes complex structures easier to understand and compare by humans and machines. Within this STAR we review such flattening techniques which have been developed for the analysis of the following medical entities: the circulation system, the colon, the brain, tumors, and bones. For each of these five application scenarios, we have analyzed the tasks and requirements, and classified the reviewed techniques with respect to a developed coding system. Furthermore, we present guidelines for the future development of flattening techniques in these areas.
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| 10. |
- Kreiser, Julian, et al.
(författare)
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Decision Graph Embedding for High-Resolution Manometry Diagnosis
- 2018
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Ingår i: IEEE Transactions on Visualization and Computer Graphics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1077-2626 .- 1941-0506. ; 24:1, s. 873-882
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution manometry is an imaging modality which enables the categorization of esophageal motility disorders. Spatio-temporal pressure data along the esophagus is acquired using a tubular device and multiple test swallows are performed by the patient. Current approaches visualize these swallows as individual instances, despite the fact that aggregated metrics are relevant in the diagnostic process. Based on the current Chicago Classification, which serves as the gold standard in this area, we introduce a visualization supporting an efficient and correct diagnosis. To reach this goal, we propose a novel decision graph representing the Chicago Classification with workflow optimization in mind. Based on this graph, we are further able to prioritize the different metrics used during diagnosis and can exploit this prioritization in the actual data visualization. Thus, different disorders and their related parameters are directly represented and intuitively influence the appearance of our visualization. Within this paper, we introduce our novel visualization, justify the design decisions, and provide the results of a user study we performed with medical students as well as a domain expert. On top of the presented visualization, we further discuss how to derive a visual signature for individual patients that allows us for the first time to perform an intuitive comparison between subjects, in the form of small multiples.
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| 11. |
- Kreiser, Julian, et al.
(författare)
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Visually Supporting Multiple Needle Placement in Irreversible Electroporation Interventions
- 2018
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Ingår i: Computer Graphics Forum. - : Wiley-Blackwell Publishing Inc.. - 0167-7055. ; 37:6, s. 59-71
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Tidskriftsartikel (refereegranskat)abstract
- Irreversible electroporation (IRE) is a minimally invasive technique for small tumour ablation. Multiple needles are inserted around the planned treatment zone and, depending on the size, inside as well. An applied electric field triggers instant cell death around this zone. To ensure the correct application of IRE, certain criteria need to be fulfilled. The needles' placement in the tissue has to be parallel, at the same depth, and in a pattern which allows the electric field to effectively destroy the targeted lesions. As multiple needles need to synchronously fulfill these criteria, it is challenging for the surgeon to perform a successful IRE. Therefore, we propose a visualization which exploits intuitive visual coding to support the surgeon when conducting IREs. We consider two scenarios: first, to monitor IRE parameters while inserting needles during laparoscopic surgery; second, to validate IRE parameters in post‐placement scenarios using computed tomography. With the help of an easy to comprehend and lightweight visualization, surgeons are enabled to quickly visually detect what needs to be adjusted. We have evaluated our visualization together with surgeons to investigate the practical use for IRE liver ablations. A quantitative study shows the effectiveness compared to a single 3D view placement method.
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