EG2014
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Item Pose Partitioning for Multi-resolution Segmentation of Arbitrary Mesh Animations(The Eurographics Association and John Wiley and Sons Ltd., 2014) Vasilakis, Andreas A.; Fudos, Ioannis; B. Levy and J. KautzWe present a complete approach to efficiently deriving a varying level-of-detail segmentation of arbitrary animated objects. An over-segmentation is built by combining sets of initial segments computed for each input pose, followed by a fast progressive simplification which aims at preserving rigid segments. The final segmentation result can be efficiently adjusted for cases where pose editing is performed or new poses are added at arbitrary positions in the mesh animation sequence. A smooth view of pose-to-pose segmentation transitions is offered by merging the partitioning of the current pose with that of the next pose. A perceptually friendly visualization scheme is also introduced for propagating segment colors between consecutive poses.We report on the efficiency and quality of our framework as compared to previous methods under a variety of skeletal and highly deformable mesh animations.Item Parameter Estimation and Comparative Evaluation of Crowd Simulations(The Eurographics Association and John Wiley and Sons Ltd., 2014) Wolinski, David; Guy, Stephen; Olivier, Anne-Helene; Lin, Ming; Manocha, Dinesh; Pettré, Julien; B. Levy and J. KautzWe present a novel framework to evaluate multi-agent crowd simulation algorithms based on real-world observations of crowd movements. A key aspect of our approach is to enable fair comparisons by automatically estimating the parameters that enable the simulation algorithms to best fit the given data. We formulate parameter estimation as an optimization problem, and propose a general framework to solve the combinatorial optimization problem for all parameterized crowd simulation algorithms. Our framework supports a variety of metrics to compare reference data and simulation outputs. The reference data may correspond to recorded trajectories, macroscopic parameters, or artist-driven sketches. We demonstrate the benefits of our framework for example-based simulation, modeling of cultural variations, artist-driven crowd animation, and relative comparison of some widely-used multi-agent simulation algorithms.Item Producing Creative Artistic Projects by Grouping Students' Computer Graphics Research Topics(The Eurographics Association, 2014) George-Molland, Anne-Laure; Plessiet, Cedric; Jean-Jacques Bourdin and Joaquim Jorge and Eike AndersonFor the last 2 years, our CG Art department experiments new pedagogical methods for our master's second year program in order to place the research right at the heart of the course syllabus. The main idea is to combine individual research and collective projects: on one side, each student focuses on a computer graphic research topic during the whole year, and on the other side, they produce an artistic group project during a 3-week intensive period, defined by the combination of each team members topic.Item Designing Large-Scale Interactive Traffic Animations for Urban Modeling(The Eurographics Association and John Wiley and Sons Ltd., 2014) Garcia-Dorado, Ignacio; Aliaga, Daniel G.; Ukkusuri, Satish V.; B. Levy and J. KautzDesigning and optimizing traffic behavior and animation is a challenging problem of interest to virtual environment content generation and to urban planning and design. While some traffic simulation methods have appeared in computer graphics, most related systems focus on the design of buildings, roads, or cities but without explicitly considering urban traffic. To our knowledge, our work provides the first interactive approach which enables a designer to specify a desired vehicular traffic behavior (e.g., road occupancy, travel time, emissions, etc.) and the system will automatically compute what realistic 3D urban model (e.g., an interconnected network of roads, parcels, and buildings) yields the specified behavior. Our system both altered and improved traffic behavior in novel procedurally-generated cities and in road networks of existing cities. Our urban models contain up to 360 km of roads, 300,000 vehicles, and typically cover four hours of simulated peak traffic time. The typical editing session time to "paint" a new traffic pattern and to compute the new/changed urban model is two to five minutes.Item 3D Video: from Capture to Diffusion(The Eurographics Association, 2014) Rémion, Yannick; Lucas, Laurent; Loscos, Céline; Nicolas Holzschuch and Karol MyszkowskiWhile 3D vision has existed for many years, the use of 3D cameras and video-based modeling by the film industry has induced an explosion of interest for 3D acquisition technology, 3D content and 3D displays. As such, 3D video has become one of the new technology trends of this century. This tutorial aims at introducing theoretical, technological and practical concepts associated to multiview systems. It covers acquisition, manipulation, and rendering. Stepping away from traditional 3D vision, the authors, all currently involved in these areas, provide the necessary elements for understanding the underlying computer-based science of these technologies.Item Pathline Glyphs(The Eurographics Association and John Wiley and Sons Ltd., 2014) Hlawatsch, Marcel; Sadlo, Filip; Jang, Hajun; Weiskopf, Daniel; B. Levy and J. KautzVisualization of pathlines is common and highly relevant for the analysis of unsteady flow. However, pathlines can intersect, leading to visual clutter and perceptual issues. This makes it intrinsically difficult to provide expressive visualizations of the entire domain by an arrangement of multiple pathlines, in contrast to well-established streamline placement techniques. We present an approach to reduce these problems. It is inspired by glyph-based visualization and small multiples: we partition the domain into cells, each corresponding to a downscaled version of the entire domain. Inside these cells, a single downscaled pathline is drawn. On the overview scale, our pathline glyphs lead to emergent visual patterns that provide insight into time-dependent flow behavior. Zooming-in allows us to analyze individual pathlines in detail and compare neighboring lines. The overall approach is complemented with a context-preserving zoom lens and interactive pathline-based exploration. While we primarily target the visualization of 2D flow, we also address the extension to 3D. Our evaluation includes several examples, comparison to other flow visualization techniques, and a user study with domain experts.Item SAFE: Structure-aware Facade Editing(The Eurographics Association and John Wiley and Sons Ltd., 2014) Dang, Minh; Ceylan, Duygu; Neubert, Boris; Pauly, Mark; B. Levy and J. KautzMany man-made objects, in particular building facades, exhibit dominant structural relations such as symmetry and regularity. When editing these shapes, a common objective is to preserve these relations. However, often there are numerous plausible editing results that all preserve the desired structural relations of the input, creating ambiguity. We propose an interactive facade editing framework that explores this structural ambiguity. We first analyze the input in a semi-automatic manner to detect different groupings of the facade elements and the relations among them. We then provide an incremental editing process where a set of variations that preserve the detected relations in a particular grouping are generated at each step. Starting from one input example, our system can quickly generate various facade configurationsItem Hexahedral Mesh Adaptation to Imprint Geometric Details: Application to CAD Models(The Eurographics Association, 2014) Goff, Nicolas Le; Ledoux, Franck; Weill, Jean-Christophe; Mathias Paulin and Carsten DachsbacherA novel algorithm is proposed to modify any unstructured hexahedral mesh in order to diminish the global time of numerical simulation processes, like optimization process and parametric studies. It consists in an imprinting algorithm that allows us to automatically add geometric details into an existing mesh. This addition is done using geometric projections, sheets (layers of hexahedral elements) insertions and combinatorial algorithms while preserving the hexahedral mesh structure as best as possible.Item Two Exceptional Projects from a Multidisciplinary Game Development Curriculum(The Eurographics Association, 2014) Pledger, Jon; Chen, Minsi; Jean-Jacques Bourdin and Joaquim Jorge and Eike AndersonThe purpose of this paper is to present two exceptional projects, SS Eternity and Bloom, from a module that is part of an undergraduate Computer Games focused degree. Here teams have developed innovative solutions to the themes they have been set. Both artists and programmers have applied their knowledge gained from previous modules to produce work that has pushed their artistic skills and knowledge to new boundaries of outstanding achievement.Item Reconstructing Complex Indoor Environments with Arbitrary Wall Orientations(The Eurographics Association, 2014) Mura, Claudio; Villanueva, Alberto Jaspe; Mattausch, Oliver; Gobbetti, Enrico; Pajarola, Renato; Mathias Paulin and Carsten DachsbacherReconstructing the architectural shape of interiors is a problem that is gaining increasing attention in the field of computer graphics. Some solutions have been proposed in recent years, but cluttered environments with multiple rooms and non-vertical walls still represent a challenge for state-of-the-art methods. We propose an occlusionsaware pipeline that extends current solutions to work with complex environments with arbitrary wall orientations.Item Quantifying 3D Shape Similarity Using Maps: Recent Trends, Applications and Perspectives(The Eurographics Association, 2014) Biasotti, S.; Cerri, A.; Bronstein, A.; Bronstein, M.; Sylvain Lefebvre and Michela SpagnuoloShape similarity is an acute issue in Computer Vision and Computer Graphics that involves many aspects of human perception of the real world, including judged and perceived similarity concepts, deterministic and probabilistic decisions and their formalization. 3D models carry multiple information with them (e.g., geometry, topology, texture, time evolution, appearance), which can be thought as the filter that drives the recognition process. Assessing and quantifying the similarity between 3D shapes is necessary to explore large dataset of shapes, and tune the analysis framework to the user's needs. Many efforts have been done in this sense, including several attempts to formalize suitable notions of similarity and distance among 3D objects and their shapes. In the last years, 3D shape analysis knew a rapidly growing interest in a number of challenging issues, ranging from deformable shape similarity to partial matching and view-point selection. In this panorama, we focus on methods which quantify shape similarity (between two objects and sets of models) and compare these shapes in terms of their properties (i.e., global and local, geometric, differential and topological) conveyed by (sets of) maps. After presenting in detail the theoretical foundations underlying these methods, we review their usage in a number of 3D shape application domains, ranging from matching and retrieval to annotation and segmentation. Particular emphasis will be given to analyse the suitability of the different methods for specific classes of shapes (e.g. rigid or isometric shapes), as well as the flexibility of the various methods at the different stages of the shape comparison process. Finally, the most promising directions for future research developments are discussed.Item A Randomized Algorithm for Natural Object Colorization(The Eurographics Association and John Wiley and Sons Ltd., 2014) Jin, Sou-Young; Choi, Ho Jin; Tai, Yu-Wing; B. Levy and J. KautzNatural objects often contain vivid color distribution with wide variety of colors. Conventional colorization techniques, on the other hand, produce colors that are relatively flat with little color variation. In this paper, we introduce a randomized algorithm which considers not only the value of target color but also the distribution of target color. In essence, our algorithm paints a color distribution to a region which synthesizes color distribution of a natural object. Our approach models the correlation between intensity and color in HSV color space in terms of H - S, H - V and S - V joint histogram. During the colorization process, we randomly swap and reassign color of a pixel to minimize a cost function that measures color consistency to its neighborhood and intensity-to-color correlation captured in the joint histogram. We tested our algorithm extensively on many natural objects and our user study confirms that our results are more vivid and natural compared to results from previous techniques.Item Regional Time Stepping for SPH(The Eurographics Association, 2014) Goswami, Prashant; Batty, Christopher; Eric Galin and Michael WandThis paper presents novel and efficient strategies to spatially adapt the amount of computational effort applied based on the local dynamics of a free surface flow, for classic weakly compressible SPH (WCSPH). Using a convenient and readily parallelizable block-based approach, different regions of the fluid are assigned differing time steps and solved at different rates to minimize computational cost. We demonstrate that our approach can achieve about two times speed-up over the standard method even in highly dynamic scenes.Item Analogy-Driven 3D Style Transfer(The Eurographics Association and John Wiley and Sons Ltd., 2014) Ma, Chongyang; Huang, Haibin; Sheffer, Alla; Kalogerakis, Evangelos; Wang, Rui; B. Levy and J. KautzStyle transfer aims to apply the style of an exemplar model to a target one, while retaining the target s structure. The main challenge in this process is to algorithmically distinguish style from structure, a high-level, potentially ill-posed cognitive task. Inspired by cognitive science research we recast style transfer in terms of shape analogies. In IQ testing, shape analogy queries present the subject with three shapes: source, target and exemplar, and ask them to select an output such that the transformation, or analogy, from the exemplar to the output is similar to that from the source to the target. The logical process involved in identifying the source-to-target analogies implicitly detects the structural differences between the source and target and can be used effectively to facilitate style transfer. Since the exemplar has a similar structure to the source, applying the analogy to the exemplar will provide the output we seek. The main technical challenge we address is to compute the source to target analogies, consistent with human logic. We observe that the typical analogies we look for consist of a small set of simple transformations, which when applied to the exemplar generate a continuous, seamless output model. To assemble a shape analogy, we compute an optimal set of source-to-target transformations, such that the assembled analogy best fits these criteria. The assembled analogy is then applied to the exemplar shape to produce the desired output model. We use the proposed framework to seamlessly transfer a variety of style properties between 2D and 3D objects and demonstrate significant improvements over the state of the art in style transfer. We further show that our framework can be used to successfully complete partial scans with the help of a user provided structural template, coherently propagating scan style across the completed surfaces.Item Feedback Control for Rotational Movements in Feature Space(The Eurographics Association and John Wiley and Sons Ltd., 2014) Borno, Mazen Al; Fiume, Eugene; Hertzmann, A.; Lasa, M. de; B. Levy and J. KautzSynthesizing controllers for rotational movements in feature space is an open research problem and is particularly challenging because of the need to precisely regulate the character s global orientation, angular momentum and inertia. This paper presents feature-based controllers for a wide variety of rotational movements, including cartwheels, dives and flips. We show that the controllers can be made robust to large external disturbances by using a time-invariant control scheme. The generality of the control laws is demonstrated by providing examples of the flip controller with different apexes, the diving controller with different heights and styles, the cartwheel controller with different speeds and straddle widths, etc. The controllers do not rely on any input motion or offline optimization.Item Self-similarity for Accurate Compression of Point Sampled Surfaces(The Eurographics Association and John Wiley and Sons Ltd., 2014) Digne, Julie; Chaine, Raphaëlle; Valette, Sébastien; B. Levy and J. KautzMost surfaces, be it from a fine-art artifact or a mechanical object, are characterized by a strong self-similarity. This property finds its source in the natural structures of objects but also in the fabrication processes: regularity of the sculpting technique, or machine tool. In this paper, we propose to exploit the self-similarity of the underlying shapes for compressing point cloud surfaces which can contain millions of points at a very high precision. Our approach locally resamples the point cloud in order to highlight the self-similarity of the shape, while remaining consistent with the original shape and the scanner precision. It then uses this self-similarity to create an ad hoc dictionary on which the local neighborhoods will be sparsely represented, thus allowing for a light-weight representation of the total surface. We demonstrate the validity of our approach on several point clouds from finearts and mechanical objects, as well as a urban scene. In addition, we show that our approach also achieves a filtering of noise whose magnitude is smaller than the scanner precision.Item Look me in the Eyes: A Survey of Eye and Gaze Animation for Virtual Agents and Artificial Systems(The Eurographics Association, 2014) Ruhland, K.; Andrist, S.; Badler, J. B.; Peters, C. E.; Badler, N. I.; Gleicher, M.; Mutlu, B.; McDonnell, R.; Sylvain Lefebvre and Michela SpagnuoloA person's emotions and state of mind are apparent in their face and eyes. As a Latin proverb states: ''The face is the portrait of the mind; the eyes, its informers.''. This presents a huge challenge for computer graphics researchers in the generation of artificial entities that aim to replicate the movement and appearance of the human eye, which is so important in human-human interactions. This State of the Art Report provides an overview of the efforts made on tackling this challenging task. As with many topics in Computer Graphics, a cross-disciplinary approach is required to fully understand the workings of the eye in the transmission of information to the user. We discuss the movement of the eyeballs, eyelids, and the head from a physiological perspective and how these movements can be modelled, rendered and animated in computer graphics applications. Further, we present recent research from psychology and sociology that seeks to understand higher level behaviours, such as attention and eye-gaze, during the expression of emotion or during conversation, and how they are synthesised in Computer Graphics and Robotics.Item Skeleton-based Joints Position Detection(The Eurographics Association, 2014) Madaras, Martin; Piovarci, Michal; Kovacovský, Tomás; Mathias Paulin and Carsten DachsbacherWe present a system for detection of joint positions in scans of articulated models. Our method is based purely on skeletons extracted from scanned point clouds of input models. First, skeletons are extracted from scans and then an estimation of possible matches between skeletons is performed. The matches are evaluated and sorted out. The whole matching process is fully automatic, but some user-driven suggestions can be included. Finally, we pick the best matching of skeletons and create a union-skeleton containing all the nodes from all the skeletons. We find nodes in the union-skeleton with rotation changes higher than the predefined threshold. We take these nodes as joints and visualize them in original scans.Item Clean Color: Improving Multi-filament 3D Prints(The Eurographics Association and John Wiley and Sons Ltd., 2014) Hergel, Jean; Lefebvre, Sylvain; B. Levy and J. KautzFused Filament Fabrication is an additive manufacturing process by which a 3D object is created from plastic filament. The filament is pushed through a hot nozzle where it melts. The nozzle deposits plastic layer after layer to create the final object. This process has been popularized by the RepRap community. Several printers feature multiple extruders, allowing objects to be formed from multiple materials or colors. The extruders are mounted side by side on the printer carriage. However, the print quality suffers when objects with color patterns are printed a disappointment for designers interested in 3D printing their colored digital models. The most severe issue is the oozing of plastic from the idle extruders: Plastics of different colors bleed onto each other giving the surface a smudged aspect, excess strings oozing from the extruder deposit on the surface, and holes appear due to this missing plastic. Fixing this issue is difficult: increasing the printing speed reduces oozing but also degrades surface quality on large prints the required speed level become impractical. Adding a physical mechanism increases cost and print time as extruders travel to a cleaning station. Instead, we rely on software and exploit degrees of freedom of the printing process. We introduce three techniques that complement each other in improving the print quality significantly. We first reduce the impact of oozing plastic by choosing a better azimuth angle for the printed part. We build a disposable rampart in close proximity of the part, giving the extruders the opportunity to wipe oozing strings and refill with hot plastic. We finally introduce a toolpath planner avoiding and hiding most of the defects due to oozing, and seamlessly integrating the rampart. We demonstrate our technique on several challenging multiple color prints, and show that our tool path planner improves the surface finish of single color prints as well.Item Manipulating Refractive and Reflective Binocular Disparity(The Eurographics Association and John Wiley and Sons Ltd., 2014) Dabala, Lukasz; Kellnhofer, Petr; Ritschel, Tobias; Didyk, Piotr; Templin, Krzysztof; Myszkowski, Karol; Rokita, P.; Seidel, Hans-Peter; B. Levy and J. KautzPresenting stereoscopic content on 3D displays is a challenging task, usually requiring manual adjustments. A number of techniques have been developed to aid this process, but they account for binocular disparity of surfaces that are diffuse and opaque only. However, combinations of transparent as well as specular materials are common in the real and virtual worlds, and pose a significant problem. For example, excessive disparities can be created which cannot be fused by the observer. Also, multiple stereo interpretations become possible, e. g., for glass, that both reflects and refracts, which may confuse the observer and result in poor 3D experience. In this work, we propose an efficient method for analyzing and controlling disparities in computer-generated images of such scenes where surface positions and a layer decomposition are available. Instead of assuming a single per-pixel disparity value, we estimate all possibly perceived disparities at each image location. Based on this representation, we define an optimization to find the best per-pixel camera parameters, assuring that all disparities can be easily fused by a human. A preliminary perceptual study indicates, that our approach combines comfortable viewing with realistic depiction of typical specular scenes.