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Now showing 1 - 10 of 43
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    Managing Temporal Change of Cities with CityGML
    (The Eurographics Association, 2014) Morel, Maxime; Gesquière, Gilles; Gonzalo Besuievsky and Vincent Tourre
    An increasing number of cities are developing digital models. It becomes thus necessary to take into account changes over time. Interoperability and thus the use of standards is also recommended. In this paper, we propose a new method, based on CityGML to take into account changes in the objects which compose the city. This method is efficient for any kind of changes of the city objects (semantic, geometry, topology or appearance). We then propose an extension of our method in order to consider more frequent changes as it is the case with sensors data that can be linked with part of city objects.
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    Modelling of Clouds from a Hemispherical Image
    (The Eurographics Association, 2014) Alldieck, Thiemo; Lundtoft, Dennis H.; Montanari, Niels; Nikolov, Ivan; Vlaykov, Iskren G.; Madsen, Claus B.; Rita Borgo and Wen Tang
    This paper presents an image-based method for modelling clouds. Unlike previous image-based approaches, a hemispherical photograph is used as input, enabling to consider an entire sky instead of merely a portion. Our method computes the intensity and opacity of the clouds from the photograph. For this purpose, beforehand, the sun illumination is filtered, the pixels are classified between cloud and sky pixels, and the sky behind the clouds is reconstructed. After having been smoothed, the intensity of the clouds is used to create vertices on a hemisphere, and their radius coordinate is modulated by the intensity value of the corresponding pixel. Finally, the mesh is generated by triangulation of the vertices. Additionally, the use of the opacity of the clouds to simulate their transparency and render them is proposed. The results show that our method can be used to produce a realistic full sky populated with clouds in a very straightforward way for the user.
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    MVE - A Multi-View Reconstruction Environment
    (The Eurographics Association, 2014) Fuhrmann, Simon; Langguth, Fabian; Goesele, Michael; Reinhard Klein and Pedro Santos
    We present MVE, the Multi-View Environment. MVE is an end-to-end multi-view geometry reconstruction software which takes photos of a scene as input and produces a surface triangle mesh as result. The system covers a structure-from-motion algorithm, multi-view stereo reconstruction, generation of extremely dense point clouds, and reconstruction of surfaces from point clouds. In contrast to most image-based geometry reconstruction approaches, our system is focused on reconstruction of multi-scale scenes, an important aspect in many areas such as cultural heritage. It allows to reconstruct large datasets containing some detailed regions with much higher resolution than the rest of the scene. Our system provides a graphical user interface for structure-from-motion reconstruction, visual inspection of images, depth maps, and rendering of scenes and meshes.
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    Coupling Hair with Smoothed Particle Hydrodynamics Fluids
    (The Eurographics Association, 2014) Lin, Wei-Chin; Jan Bender and Christian Duriez and Fabrice Jaillet and Gabriel Zachmann
    We present a two-way coupling technique for simulating the complex interaction between hair and fluids. In our approach, the motion of hair and fluids is simulated by evaluating the hydrodynamic forces among them based on boundary handling techniques used in SPH (Smoothed Particle Hydrodynamics) fluids. When hair makes contact with fluids, water absorption inside the hair volume can be simulated with a diffusion process by treating the hair volume as porous media with anisotropic permeability. The saturation of each hair strand is then used to derive the adhesive force between wet hair strands. This enables us to simulate the formation of hair clumps dynamically without the need to employ post clumping processes. The proposed method can be easily applied to any SPH fluid solvers as well as various hair models.
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    Evaluating the Curvature Analysis as a Key Feature for the Semantic Description of Architectural Elements
    (The Eurographics Association, 2014) Adrian, Julie; Buglio, David Lo; Luca, Livio De; Reinhard Klein and Pedro Santos
    The recent developments in the fields of photogrammetry and laser scanning, have made possible mass acquisitions of heritage artifacts with a particularly high level of geometric accuracy. A processing of the digital model will be necessary to isolate some characteristics in order to carry on an analysis of the architectural object. In this poster, the potentialities of the curvature maps, extracted from digital acquisitions, are defined to conduct the study on the morphology of architectural elements. The current work focuses on the technical and theoretical issues that will ultimately result in an average surface signature. This will allow to identify the degree of remoteness of each attribute.
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    3D Volume Matching for Mesh Animation of Moving Actors
    (The Eurographics Association, 2014) Blache, Ludovic; Loscos, Celine; Nocent, Olivier; Lucas, Laurent; Benjamin Bustos and Hedi Tabia and Jean-Philippe Vandeborre and Remco Veltkamp
    4D multiview reconstruction of moving actors has many applications in the entertainment industry and although studios providing such services become more accessible, efforts have to be done in order to improve the underlying technology to produce high-quality 4D contents. In this paper, we enable surface matching for an animated mesh sequence in order to introduce coherence in the data. The context is provided by an indoor multi-camera system which performs synchronized video captures from multiple viewpoints in a chroma key studio. Our input is given by a volumetric silhouette-based reconstruction algorithm that generates a visual hull at each frame of the video sequence. These 3D volumetric models differ from one frame to another, in terms of structure and topology, which makes them very difficult to use in post-production and 3D animation software solutions. Our goal is to transform this input sequence of independent 3D volumes into a single dynamic volumetric structure, directly usable in post-production. These volumes are then transformed into an animated mesh. Our approach is based on a motion estimation procedure. An unsigned distance function on the volumes is used as the main shape descriptor and a 3D surface matching algorithm minimizes the interference between unrelated surface regions. Experimental results, tested on our multiview datasets, show that our method outperforms approaches based on optical flow when considering robustness over several frames.
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    Evaluation of Visualizations for Interface Analysis of SPH
    (The Eurographics Association, 2014) Krone, Michael; Huber, Markus; Scharnowski, Katrin; Hirschler, Manuel; Kauker, Daniel; Reina, Guido; Nieken, Ulrich; Weiskopf, Daniel; Ertl, Thomas; N. Elmqvist and M. Hlawitschka and J. Kennedy
    We present a GPU-accelerated visualization application that employs methods from computer graphics and visualizationto analyze SPH simulations from the field of material science. To this end, we extract the isosurfacethat separates the stable phases in a fluid mixture via the kernel function that was used by the simulation. Ourapplication enables the analysis of the separation process using interactive 3D renderings of the data and an additionalline chart that shows the computed surface area over time. This also allows us to validate the correctnessof the simulation method, since the surface area can be compared to the power law that describes the change inarea over time. Furthermore, we compare the isosurface that is based on the simulation kernel with an establishedmethod to extract smooth high-quality SPH surfaces. The comparison focuses on demonstrating the applicabilityfor data analysis in the context of material science, which is based on the resulting surface area and how wellthe two phases are separated with respect to the original particles. The evaluation was carried out together withexperts in material science.
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    Comparative Evaluation of Feature Line Techniques for Shape Depiction
    (The Eurographics Association, 2014) Lawonn, Kai; Baer, Alexandra; Saalfeld, Patrick; Preim, Bernhard; Jan Bender and Arjan Kuijper and Tatiana von Landesberger and Holger Theisel and Philipp Urban
    This paper presents a qualitative evaluation of feature line techniques on various surfaces. We introduce the most commonly used feature lines and compare them. The techniques were analyzed with respect to the degree of realism in comparison with a shaded image with respect to the aesthetic impression they create. First, a pilot study with 20 participants was conducted to make an inquiry about their behavior and the duration. Based on the result of the pilot study, the final evaluation was carried out with 129 participants. We evaluate and interpret the trial results by using the Schulze method and give recommendations for which kind of surface, which feature line technique is most appropriate.
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    Massively Parallel Batch Neural Gas for Bounding Volume Hierarchy Construction
    (The Eurographics Association, 2014) Weller, René; Mainzer, David; Srinivas, Abhishek; Teschner, Matthias; Zachmann, Gabriel; Jan Bender and Christian Duriez and Fabrice Jaillet and Gabriel Zachmann
    Ordinary bounding volume hierarchy (BVH) construction algorithms create BVHs that approximate the boundary of the objects. In this paper, we present a BVH construction that instead approximates the volume of the objects with successively finer levels. It is based on Batch Neural Gas (BNG), a clustering algorithm that is known from machine learning. Additionally, we present a novel massively parallel version of this BNG-based hierarchy construction that runs completely on the GPU. It reduces the theoretical complexity of the sequential algorithm from O(nlogn) to O(log2 n) and also our CUDA implementation outperforms the CPU version significantly in practice.
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    Topological Reconstruction of Complex 3D Buildings and Automatic Extraction of Levels of Detail
    (The Eurographics Association, 2014) Diakité, Abdoulaye A.; Damiand, Guillaume; Maercke, Dirk Van; Gonzalo Besuievsky and Vincent Tourre
    This paper describes a new method allowing to retrieve the indoor and outdoor topology of a detailed 3D building model from its geometry and to extract different levels of detail (LoD) from the resulting topological description. No prior information about the initial model, except its geometric information is needed as input, and using the combinatorial maps data structure, the method recovers the topological information of the identified parts of the building. The topology is needed for most of the applications using 3D building models after the architects design it. While classical models available are mainly furnished in a Boundary Representation (B-Rep) format, we discuss how to recover the components that allow to distinguish the several parts of the building (defined as volumes) then the spatial relationships linking them.