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Now showing 1 - 10 of 120
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    Pairwise Matching of Stone Tools Based on Flake-Surface Contour Points and Normals
    (The Eurographics Association, 2017) Xi, Yang; Matsuyama, Katsutsugu; Konno, Kouichi; Tobias Schreck and Tim Weyrich and Robert Sablatnig and Benjamin Stular
    Stone tools constitute the main artifacts facilitating archaeological research of the Paleolithic era. The reassembly of stone tools is the most important research work for analyzing human activities of that period. In recent decades, large numbers of methods have been presented to solve various registration or matching problems for point clouds; however, few methods have been successfully applied to the matching of flakes, a type of stone tool. Therefore, we propose a new matching method for studying stone tools to improve archaeological research. Our method processes pairwise matching of stone tools based on contour points and mean normals of regions on all flake surfaces, according to the characteristics of the flake models. The sample experiments conducted in this study indicate that our new method achieves superior matching results for flakes, compared with the existing methods.
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    Line Integration for Rendering Heterogeneous Emissive Volumes
    (The Eurographics Association and John Wiley & Sons Ltd., 2017) Simon, Florian; Hanika, Johannes; Zirr, Tobias; Dachsbacher, Carsten; Zwicker, Matthias and Sander, Pedro
    Emissive media are often challenging to render: in thin regions where only few scattering events occur the emission is poorly sampled, while sampling events for emission can be disadvantageous due to absorption in dense regions. We extend the standard path space measurement contribution to also collect emission along path segments, not only at vertices. We apply this extension to two estimators: extending paths via scattering and distance sampling, and next event estimation. In order to do so, we unify the two approaches and derive the corresponding Monte Carlo estimators to interpret next event estimation as a solid angle sampling technique. We avoid connecting paths to vertices hidden behind dense absorbing layers of smoke by also including transmittance sampling into next event estimation. We demonstrate the advantages of our line integration approach which generates estimators with lower variance since entire segments are accounted for. Also, our novel forward next event estimation technique yields faster run times compared to previous next event estimation as it penetrates less deeply into dense volumes.
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    Appearance Bending: A Perceptual Editing Paradigm for Data-Driven Material Models
    (The Eurographics Association, 2017) Mylo, Marlon; Giesel, Martin; Zaidi, Qasim; Hullin, Matthias; Klein, Reinhard; Matthias Hullin and Reinhard Klein and Thomas Schultz and Angela Yao
    Data-driven representations of material appearance play an important role in a wide range of applications. Unlike with analytical models, however, the intuitive and efficient editing of tabulated reflectance data is still an open problem. In this work, we introduce appearance bending, a set of image-based manipulation operators, such as thicken, inflate, and roughen, that implement recent insights from perceptual studies. In particular, we exploit a link between certain perceived visual properties of a material, and specific bands in its spectrum of spatial frequencies or octaves of a wavelet decomposition. The result is an editing interface that produces plausible results at interactive rates, even for drastic manipulations. We present the effectiveness of our method on a database of bidirectional texture functions (BTFs) for a variety of material samples.
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    3D Ground Reaction Force Visualization onto Training Video for Sprint Training Support System
    (The Eurographics Association, 2017) Taketomi, Takafumi; Yoshitake, Yasuhide; Yamamoto, Goshiro; Sandor, Christian; Kato, Hirokazu; Tony Huang and Arindam Dey
    We propose a method for visualizing 3D ground reaction forces for sprint training. Currently, sprinters can check their 3D ground force data using a 2D graph representation. In order to check the relationship between 3D ground force and their sprint form, they must check the 2D graph and a training video repeatedly. To allow simultaneous observation of the 2D graph and the training video, we use a mixed reality technology to overlay 3D ground reaction force onto the training video. In this study, we focus on 2D-3D registration between the image sequence and 3D ground reaction data. We achieved 2D-3D registration by using a constrained bundle adjustment approach. In the experiment, we apply our method to the training videos. The results confirm that our method can correctly overly 3D ground reaction force onto the videos.
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    Depth-aware Neural Style Transfer
    (Association for Computing Machinery, Inc (ACM), 2017) Liu, Xiao-Chang; Cheng, Ming-Ming; Lai, Yu-Kun; Rosin, Paul L.; Holger Winnemoeller and Lyn Bartram
    Neural style transfer has recently received signi cant a ention and demonstrated amazing results. An e cient solution proposed by Johnson et al. trains feed-forward convolutional neural networks by de ning and optimizing perceptual loss functions. Such methods are typically based on high-level features extracted from pre-trained neural networks, where the loss functions contain two components: style loss and content loss. However, such pre-trained networks are originally designed for object recognition, and hence the high-level features o en focus on the primary target and neglect other details. As a result, when input images contain multiple objects potentially at di erent depths, the resulting images are o en unsatisfactory because image layout is destroyed and the boundary between the foreground and background as well as di erent objects becomes obscured. We observe that the depth map e ectively re ects the spatial distribution in an image and preserving the depth map of the content image a er stylization helps produce an image that preserves its semantic content. In this paper, we introduce a novel approach for neural style transfer that integrates depth preservation as additional loss, preserving overall image layout while performing style transfer.
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    Visual Navigation Support for Liver Applicator Placement using Interactive Map Displays
    (The Eurographics Association, 2017) Hettig, Julian; Mistelbauer, Gabriel; Rieder, Christian; Lawonn, Kai; Hansen, Christian; Stefan Bruckner and Anja Hennemuth and Bernhard Kainz and Ingrid Hotz and Dorit Merhof and Christian Rieder
    Navigated placement of an ablation applicator in liver surgery would benefit from an effective intraoperative visualization of delicate 3D anatomical structures. In this paper, we propose an approach that facilitates surgery with an interactive as well as an animated map display to support navigated applicator placement in the liver. By reducing the visual complexity of 3D anatomical structures, we provide only the most important information on and around a planned applicator path. By employing different illustrative visualization techniques, the applicator path and its surrounding critical structures, such as blood vessels, are clearly conveyed in an unobstructed way. To retain contextual information around the applicator path and its tip, we desaturate these structures with increasing distance. To alleviate time-consuming and tedious interaction during surgery, our visualization is controlled solely by the position and orientation of a tracked applicator. This enables a direct interaction with the map display without interruption of the intervention. Based on our requirement analysis, we conducted a pilot study with eleven participants and an interactive user study with six domain experts to assess the task completion time, error rate, visual parameters and the usefulness of the animation. The outcome of our pilot study shows that our map display facilitates significantly faster decision making (11.8 s vs. 40.9 s) and significantly fewer false assessments of structures at risk (7.4 % vs. 10.3 %) compared to a currently employed 3D visualization. Furthermore, the animation supports timely perception of the course and depth of upcoming blood vessels, and helps to detect possible areas at risk along the path in advance. Hence, the obtained results demonstrate that our proposed interactive map displays exhibit potential to improve the outcome of navigated liver interventions.
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    Fast and Accurate Simulation of Gravitational Field of Irregular-shaped Bodies using Polydisperse Sphere Packings
    (The Eurographics Association, 2017) Srinivas, Abhishek; Weller, Rene; Zachmann, Gabriel; Robert W. Lindeman and Gerd Bruder and Daisuke Iwai
    Currently, interest in space missions to small bodies (e.g., asteroids) is increasing, both scientifically and commercially. One of the important aspects of these missions is to test the navigation, guidance, and control algorithms. The most cost and time efficient way to do this is to simulate the missions in virtual testbeds. To do so, a physically-based simulation of the small bodies' physical properties is essential. One of the most important physical properties, especially for landing operations, is the gravitational field, which can be quite irregular, depending on the shape and mass distribution of the body. In this paper, we present a novel algorithm to simulate gravitational fields for small bodies like asteroids. The main idea is to represent the small body's mass by a polydisperse sphere packing. This allows for an easy and efficient parallelization. Our GPU-based implementation outperforms traditional methods by more than two orders of magnitude while achieving a similar accuracy.
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    Automated Regression Tests for Character Animation Systems
    (ACM, 2017) Mohr-Daurat, Hubert; Bernhard Thomaszewski and KangKang Yin and Rahul Narain
    We present a process to verify code changes in an animation system by using regression tests which guarantee to cover every combination of animation features used in production. For this, we need to identify the untested combinations of animation features, create an immutable set of animation data which is representative of it, and when performing the tests, automatically compare the difference in the generated poses at each revision of the code.
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    User-study Based Optimization of Fast and Accurate Mahalanobis Brushing in Scatterplots
    (The Eurographics Association, 2017) Fan, Chaoran; Hauser, Helwig; Matthias Hullin and Reinhard Klein and Thomas Schultz and Angela Yao
    Brushing is at the heart of most modern visual analytics solutions with coordinated, multiple views and effective brushing is crucial for swift and efficient processes in data exploration and analysis. Given a certain data subset that the user wishes to brush in a data visualization, traditional brushes are usually either accurate (like the lasso) or fast (e.g., a simple geometry like a rectangle or circle). In this paper, we now present a new, fast and accurate brushing technique for scatterplots, based on the Mahalanobis brush, which we have extended and then optimized using data from a user study. We explain the principal, sketchbased model of our new brushing technique (based on a simple click-and-drag interaction), the details of the user study and the related parameter optimization, as well as a quantitative evaluation, considering efficiency, accuracy, and also a comparison with the original Mahalanobis brush.
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    Evaporation and Condensation of SPH-based Fluids
    (ACM, 2017) Hochstetter, Hendrik; Kolb, Andreas; Bernhard Thomaszewski and KangKang Yin and Rahul Narain
    In this paper we present a method to simulate evaporation and condensation of liquids. Therefore, both the air and liquid phases have to be simulated. We use, as a carrier of vapor, a coarse grid for the air phase and mass-preservingly couple it to an SPH-based liquid and rigid body simulation. Since condensation only takes place on rigid surfaces, it is captured using textures that carry water to achieve high surface detail. The textures can exchange water with the air phase and are used to generate new particles due to condensation effects yielding a full two-way coupling of air phase and liquid. In order to allow gradual evaporation and condensation processes, liquid particles can take on variable sizes. Our proposed improved implicit surface definition is able to render dynamic contact angles for moving droplets yielding highly detailed fluid rendering.