VMV2020

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https://diglib.eg.org/handle/10.2312/2632934

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Partial Matching of Trajectories with Particle Orientation for Exploratory Trajectory Visualization
(The Eurographics Association, 2020) Kahlert, Franziska; Gumhold, Stefan; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Trajectories of moving objects are of interest in multiple research fields ranging from geographic information science to behavioral science. Movement patterns of the studied object are often analyzed. Therefore, similar trajectories are retrieved which introduces the need for a similarity measure of trajectories. Similarity measures taken the shape of the trajectory into account are widely researched. Though, there are more attributes that can be relevant to distinguish different movements. One of them is the object orientation along the trajectory. The orientation is of interest in research fields where it influences the movement behavior like the impact of external forces in particles simulations. Trajectory retrieval taking particle orientation into account is still an open research question. Therefore, this work presents a similarity measure for trajectory retrieval considering the complex interaction of linear and rotational movement of particles. Furthermore, the similarity measure applies partial matching allowing for exploration of trajectory parts such as events that may occur along a trajectory tracked over a long time. The proposed algorithm is incorporated into an application for exploratory trajectory visualization.
Visualization Aided Interface Reconstruction
(The Eurographics Association, 2020) Penk, Dominik; Müller, Jonas; Felfer, Peter; Grosso, Roberto; Stamminger, Marc; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Modern atom probe tomography measurements generate large point clouds of atomic locations in solids. A common analysis task in these datasets is to put the location of specific atom types in relation to crystallographic features such as the interface between two crystals (grain boundaries). In cases where these features represent surfaces, their extraction is carried out manually in most cases. In this paper we propose a method for semi automatic extraction of such two dimensional manifold and non-manifold surfaces from a given dataset. We first aid the user to filter the atom data by providing an interactive visualization of the dataset tailored towards enhancing these interfaces. Once a desired set of points representing the interface is found, we provide an automatic surface extraction method to compute an explicit parametric representation of the visualized surface. In case of non-manifold interface structures, this parametric representation is then used to calculate the intersections of the individual manifold parts of the interfaces.
Visual Exploration of Cultural Heritage Collections with Linked Spatiotemporal, Shape and Metadata Views
(The Eurographics Association, 2020) Lengauer, Stefan; Komar, Alexander; Karl, Stephan; Trinkl, Elisabeth; Preiner, Reinhold; Schreck, Tobias; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
The analysis of Cultural Heritage (CH) artefacts is an important task in the Digital Humanities. Increasingly, rich CH artefact data comprising metadata of different modalities becomes available in digital libraries and research data repositories. How- ever, the large amounts and heterogeneity of artefacts in these repositories compromise their accessibility for common domain analysis tasks, as domain researchers lack a structural overview of the spatial, temporal, and categorical traits of the artefacts in these collections. Still, researchers need to compare artefacts along different modalities, put them into context, and deal with possible uncertainties, subjectivities, or missing data. To date, many works support domain research via interactive visuali- sation. The majority relies primarily on visualisation of text and metadata including spatiotemporal, image and shape data. However, fewer consider these types of data in a tightly coupled way. We present an approach for tightly integrated multimodal visual exploration of large CH data collections along space, time and shape traits. Based on requirements obtained in collab- oration with domain researchers, we introduce a set of interlinked views for exploration of said modalities. An appropriately defined approach automatically computes most significant correlations across different modalities, guiding the user towards de- tecting interesting artefact relationships. We apply our approach to pertinent archaeological data collections, and demonstrate that characteristic explorative tasks are effectively supported and domain-relevant artefact relations can be discovered.
A Design and Application Space for Visualizing User Sessions of Virtual and Mixed Reality Environments
(The Eurographics Association, 2020) Agarwal, Shivam; Auda, Jonas; Schneegaß, Stefan; Beck, Fabian; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Virtual and mixed reality environments gain complexity due to the inclusion of multiple users and physical objects. A core challenge for developers and researchers while analyzing sessions from such environments lies in understanding the interaction between entities. Additionally, the raw data recorded from such sessions is difficult to analyze due to the simultaneous temporal and spatial changes of multiple entities. However, similar data has already been visualized in other areas of application. We analyze which aspects of these related visualizations can be leveraged for analyzing user sessions in virtual and mixed reality environments and describe a design and application space for such visualizations. First, we examine what information is typically generated in interactive virtual and mixed reality applications and how it can be analyzed through such visualizations. Next, we study visualizations from related research fields and derive seven visualization categories. These categories act as building blocks of the design space, which can be combined into specific visualization systems. We also discuss the application space for these visualizations in debugging and evaluation scenarios. We present two application examples that showcase how one can visualize virtual and mixed reality user sessions and derive useful insights from them.
Interactive Generation of 1D Embeddings from 2D Multi-dimensional Data Projections
(The Eurographics Association, 2020) Ngo, Quynh Quang; Linsen, Lars; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Visual analysis of multi-dimensional data is commonly supported by mapping the data to a 2D embedding. When analyzing a sequence of multi-dimensional data, e.g., in case of temporal data, the usage of 1D embeddings allows for plotting the entire sequence in a 2D layout. Despite the good performance in generating 2D embeddings, 1D embeddings often exhibit a much lower quality for pattern recognition tasks. We propose to overcome the issue by involving the user to generate 1D embeddings of multi-dimensional data in a two-step procedure: We first generate a 2D embedding and then leave the task of reducing the 2D to a 1D embedding to the user. We demonstrate that an interactive generation of 1D embeddings from 2D projected views can be performed efficiently, effectively, and targeted towards an analysis task. We compare the performance of our approach against automatically generated 1D and 2D embeddings involving a user study for our interactive approach. We test the 1D approaches when being applied to time-varying multi-dimensional data.
A Compact Patch-Based Representation for Technical Mesh Models
(The Eurographics Association, 2020) Kammann, Lars; Menzel, Stefan; Botsch, Mario; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
We present a compact and intuitive geometry representation for technical models initially given as triangle meshes. For CADlike models the defining features often coincide with the intersection between smooth surface patches. Our algorithm therefore first segments the input model into patches of constant curvature. The intersections between these patches are encoded through Bézier curves of adaptive degree, the patches enclosed by them are encoded by their (constant) mean and Gaussian curvatures. This sparse geometry representation enables intuitive understanding and editing by manipulating either the patches' curvature values and/or the feature curves. During decoding/reconstruction we exploit remeshing and hence are independent of the underlying triangulation, such that besides the feature curve topology no additional connectivity information has to be stored. We also enforce discrete developability for patches with vanishing Gaussian curvature in order to obtain straight ruling lines.
WLD: A Wavelet and Learning based Line Descriptor for Line Feature Matching
(The Eurographics Association, 2020) Lange, Manuel; Raisch, Claudio; Schilling, Andreas; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
We present a machine learning based and wavelet enhanced line feature descriptor for line feature matching. Therefor we trained a neural network to compute a descriptor for a line, given preprocessed information from the image area around the line. In the preprocessing step we utilize wavelets to extract meaningful information from the image for the descriptor. This process is inspired by the human vision system. We used the Unreal Engine 4 and multiple different freely available scenes to create our training data. We conducted the evaluation on ground truth labeled images of our own and from the Middlebury Stereo Dataset. To show the advancement of our method in terms of matching quality, we compare it to the Line Band Descriptor (LBD), to the Deep Learning Based Line Descriptor (DLD), which we used as a starting point for this work, and to the Learnable Line Segment Descriptor for Visual SLAM (LLD). We publish the project on github to support the community: https://github.com/manuellange/WLD
Multi-Layer Alpha Tracing
(The Eurographics Association, 2020) Brüll, Felix; Grosch, Thorsten; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Rendering many transparent surfaces in real-time is still an open problem. We introduce two techniques for fast transparency rendering with ray tracing hardware, one being exact and the other being approximate but of high quality. Our approximate technique is called Multi-Layer Alpha Tracing, operates in bounded memory and is up to 60% faster than naive ray traversal. It outperforms existing rasterization techniques in terms of image quality and performance while maintaining a small memory footprint. It can also be used to accelerate ray tracing of transparent objects for the reflected rays.
Portal-Based Path Perturbation for Metropolis Light Transport
(The Eurographics Association, 2020) Otsu, Hisanari; Hanika, Johannes; Dachsbacher, Carsten; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Light transport simulation in scenes with difficult visibility still remains a challenging problem. Markov chain Monte Carlo (MCMC) rendering is often employed for such configurations. It generates a sequence of correlated light transport paths by iteratively mutating the current state, a path, to another. Since the proposed path is correlated to the current path, MCMC can explore regions of the path space, also with difficult visibility, once they have been found. To improve the efficiency of the exploration, we propose a path mutation strategy making use of the concept of portals. Portals are user-defined objects in the scene to guide the sampling of the difficult visibility, which have been employed in the context of non-MCMC rendering. Our mutation strategy perturbs a path edge around the intersection point of the edge and the portal, instead of perturbing the edge by moving a path vertex as in the ordinary path mutation strategies. This reduces the probability for the proposed path being rejected due to changes in visibility.
Segmenting Computer-Tomographic Scans of Ancient Clay Artefacts for Visual Analysis of Cuneiform Inscriptions
(The Eurographics Association, 2020) Rolff, Tim; Rautenhaus, Marc; Olbrich, Stephan; Frintrop, Simone; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
We address the automatic segmentation of computer tomographic scans of ancient clay tablets with cuneiform inscriptions enclosed inside a clay envelope. Such separation of parts of similar material properties in the scan enables domain scientists to virtually investigate the historically valuable artefacts by means of 3D visualization without physical destruction.We investigate two segmentation methods, the Priority-Flood algorithm and the Compact Watershed algorithm, the latter being modified by employing a distance metric that takes the ellipsoidal shape of the artefacts into account. Additionally, we propose a novel presegmentation method that suppresses the intensity values of the distance transform at contact points between clay envelope and tablet. We apply all methods to volumetric scans of a replicated clay tablet and analyze their performance under varying noise distributions. Evaluation by comparison to a manually segmented ground truth shows best results for the novel suppressionbased approach.
Static Visualization of Unsteady Flows by Flow Steadification
(The Eurographics Association, 2020) Wolligandt, Steve; Wilde, Thomas; Rössl, Christian; Theisel, Holger; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Finding static visual representations of time-varying phenomena is a standard problem in visualization. We are interested in unsteady flow data, i.e., we want to find a static visualization - one single still image - that shows as much of the global behavior of particle trajectories (path lines) as possible. We propose a new approach, which we call steadification: given a time-dependent flow field v, we construct a new steady vector field w such that the stream lines of w correspond to the path lines of v. With this, the temporal behavior of v can be visualized by using standard methods for steady vector field visualization. We present a formal description as a constraint optimization that can be mapped to finding a set cover, a NP-hard problem that is solved approximately and fairly efficiently by a greedy algorithm. As an application, we introduce the first 2D image-based flow visualization technique that shows the behavior of path lines in a static visualization, even if the path lines have a significantly different behavior than stream lines.
Real-time High-resolution Visualisation
(The Eurographics Association, 2020) Frieß, Florian; Müller, Christoph; Ertl, Thomas; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
While visualisation often strives for abstraction, the interactive exploration of large scientific data sets like densely sampled 3D fields or massive particle data sets still benefits from rendering their graphical representation in large detail on high-resolution displays such as Powerwalls or tiled display walls driven by multiple GPUs or even GPU clusters. Such visualisation systems are typically rather unique in their setup of hardware and software which makes transferring a visualisation application from one high-resolution system to another one a complicated task. As more and more such visualisation systems get installed, collaboration becomes desirable in the sense of sharing such a visualisation running on one site in real time with another highresolution display on a remote site while at the same time communicating via video and audio. Since typical video conference solutions or web-based collaboration tools often cannot deal with resolutions exceeding 4K, with stereo displays or with multi- GPU setups, we designed and implemented a new system based on state-of-the-art hardware and software technologies to transmit high-resolution visualisations including video and audio streams via the internet to remote large displays and back. Our system architecture is built on efficient capturing, encoding and transmission of pixel streams and thus supports a multitude of configurations combining audio and video streams in a generic approach.
Data Reconstruction from Colored Slice-and-Dice Treemaps
(The Eurographics Association, 2020) Henkel, Markus; Knauthe, Volker; Landesberger, Tatiana von; Guthe, Stefan; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Treemaps illustrate hierarchical data, such as file systems or budget structures. Colors are often used to encode additional information or to emphasize the tree structure. Given a treemap, one may want to retrieve the underlying data. However, treemap reconstruction is challenging, as the inner tree structure needs to be derived almost exclusively from leaf node rectangles. Furthermore, treemaps are well known to suffer from ambiguities, i.e., different input data may produce the same drawing. We present a novel reconstruction approach for slice-and-dice treemaps. Moreover, we evaluate the influence of five color schemes to resolve ambiguities. Our work can be used for the reproducibility of published data and for assessing ambiguities in slice-and-dice treemaps.
VMV 2020: Frontmatter
(The Eurographics Association, 2020) Krüger, Jens; Niessner, Matthias; Stückler, Jörg; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Visualizing Sets and Changes in Membership Using Layered Set Intersection Graphs
(The Eurographics Association, 2020) Agarwal, Shivam; Tkachev, Gleb; Wermelinger, Michel; Beck, Fabian; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Challenges in set visualization include representing overlaps among sets, changes in their membership, and details of constituent elements. We present a visualization technique that addresses these challenges. The approach uses set intersection graphs that explicitly visualize each set intersection as a rectangular node and elements as circles inside them. We represent the graph as a layered node-link diagram using colors to indicate the sets. The layers reflect different levels of intersections, from the base sets in the lowest layer to potentially the intersection of all sets in the highest layer. We provide different perspectives to show temporal changes in set membership. Graphs for individual, two, and all timesteps are visualized in static, diff, and aggregated views. Together with linked views and filters, the technique supports the detailed exploration of dynamic set data. We demonstrate the effectiveness of the proposed approach by discussing two application examples. The submitted supplemental material contains a video showing proposed interactions in the implementation and the prototype itself.
Visualization Framework for Assisting Interface Optimization of Hybrid Component Design
(The Eurographics Association, 2020) Kretzschmar, Vanessa; Gillmann, Christina; Günther, Fabian; Stommel, Markus; Scheuermann, Gerik; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
Reliable component design is one of structural mechanics' main objectives. Especially for lightweight constructions, hybrid parts made of a multi-material combination are used. The design process for these parts often becomes very challenging. The critical section of such hybrid parts is usually the interface layer that often builds the weakest zone. In this paper, we study a hybrid part made of metal and carbon fiber-reinforced composite, where the metal insert is coated by a thermoplastic to decrease the jump in stiffness between the two primary structural materials. To prevent stress peaks in small volumes of the part , mechanical engineers aim to design functional elements at the thermoplastic interface, to homogenize the stress distribution. The placement of such load transmitting functional elements at the thermoplastics interface has a crucial impact on the overall stability and mechanical performance of the design. Resulting from this, mechanical engineers acquire large amounts of simulations outputting multi-field datasets, to examine the impact of differently designed load transmitting elements, their number, and positioning in the interface between metal and composite. In order to assist mechanical engineers in deeper exploration of the often numerous set of simulations, a framework based on visual analytics techniques was developed in close collaboration with engineers. To match their needs, a requirement analysis was performed, and visualizations were discussed steadily. We show how the presented framework helps engineers gaining novel insights to optimize the hybrid component based on the selected load transmitting elements.

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