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Now showing 1 - 10 of 42
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    Real-time Inextensible Hair with Volume and Shape
    (The Eurographics Association, 2015) Sánchez-Banderas, Rosa María; Barreiro, Héctor; García-Fernández, Ignacio; Pérez, Mariano; Mateu Sbert and Jorge Lopez-Moreno
    Hair simulation is a common topic extensively studied in computer graphics. One of the many challenges in this field is simulating realistic hair in a real-time environment. In this paper, we propose a unified simulation scheme to consider three of the key features in hair simulation; inextensibility, shape preservation and hair-hair interaction. We use an extension to the Dynamic Follow the Leader (DFTL) method to include shape preservation. Our implementation is also coupled with a Lagrangian approach to address the hair-hair interaction dynamics. A GPU-friendly scheme is proposed that is able to exploit the massive parallelism these devices offer, being able to simulate thousands of strands in real-time. The method has been integrated in a game development platform with a shading model for rendering and several test applications have been developed using this implementation.
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    Object Completion using k-Sparse Optimization
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Mavridis, Pavlos; Sipiran, Ivan; Andreadis, Anthousis; Papaioannou, Georgios; Stam, Jos and Mitra, Niloy J. and Xu, Kun
    We present a new method for the completion of partial globally-symmetric 3D objects, based on the detection of partial and approximate symmetries in the incomplete input dataset. In our approach, symmetry detection is formulated as a constrained sparsity maximization problem, which is solved efficiently using a robust RANSACbased optimizer. The detected partial symmetries are then reused iteratively, in order to complete the missing parts of the object. A global error relaxation method minimizes the accumulated alignment errors and a nonrigid registration approach applies local deformations in order to properly handle approximate symmetry. Unlike previous approaches, our method does not rely on the computation of features, it uniformly handles translational, rotational and reflectional symmetries and can provide plausible object completion results, even on challenging cases, where more than half of the target object is missing. We demonstrate our algorithm in the completion of 3D scans with varying levels of partiality and we show the applicability of our approach in the repair and completion of heavily eroded or incomplete cultural heritage objects.
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    Hierarchical Multiview Rigid Registration
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Tang, Yizhi; Feng, Jieqing; Mirela Ben-Chen and Ligang Liu
    Registration is a key step in the 3D reconstruction of real-world objects. In this paper, we propose a hierarchical method for the rigid registration of multiple views. The multiview registration problem is solved via hierarchical optimization defined on an undirected graph. Each node or edge in this graph represents a single view or a connection between two overlapped views, respectively. The optimizations are performed hierarchically on the edges, the loops, and the entire graph. First, each overlapped pair of views is locally aligned. Then, a loop-based incremental registration algorithm is introduced to refine the initial pairwise alignments. After a loop is registered, the views in the loop are merged into a metaview in the graph. Finally, global error diffusion is applied to the entire graph to evenly distribute the accumulated errors to all views. In addition, a new objective function is defined to describe the loop closure problem; it improves the accuracy and robustness of registration by simultaneously considering transformation and registration errors. The experimental results show that the proposed hierarchical approach is accurate, efficient and robust for initial view states that are not well posed.
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    Incomplete 3D Shape Retrieval via Sparse Dictionary Learning
    (The Eurographics Association, 2015) Wan, Lili; Jiang, Jingyu; Zhang, Hao; Stam, Jos and Mitra, Niloy J. and Xu, Kun
    How to deal with missing data is one of the recurring questions in data analysis. The handling of significant missing data is a challenge. In this paper, we are interested in the problem of 3D shape retrieval where the query shape is incomplete with moderate to significant portions of the original shape missing. The key idea of our method is to grasp the basis local descriptors for each shape in the retrieved database by sparse dictionary learning and apply them in sparsely coding the local descriptors of an incomplete query. First, we present a method of computing heat kernel signatures for incomplete shapes. Next, for each shape in the database, a set of basis local descriptors, which is called a dictionary, is learned and taken as its representative. Finally, a query incomplete shape's heat kernel signatures are respectively reconstructed by each dictionary, and the shape similarities are therefore measured by the reconstruction errors. Experimental results show that the proposed method has achieved significant improvements over previous works on retrieving non-rigid incomplete shapes.
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    Isogeometric Analysis for Modelling and Design
    (The Eurographics Association, 2015) Riffnaller-Schiefer, Andreas; Augsdörfer, Ursula H.; Fellner, Dieter W.; B. Bickel and T. Ritschel
    We present an isogeometric design and analysis approach based on NURBS-compatible subdivision surfaces. The approach enables the description of watertight free-form surfaces of arbitrary degree, including conic sections and an accurate simulation and analysis based directly on the designed surface. To explore the seamless integration of design and analysis provided by the isogeometric approach, we built a prototype software which combines free-form modelling tools with thin shell simulation tools to offer the designer a wide range of design and analysis instruments.
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    Retrieval of Objects Captured with Kinect One Camera
    (The Eurographics Association, 2015) Pascoal, Pedro B.; Proença, Pedro; Gaspar, Filipe; Dias, Miguel Sales; Teixeira, Filipe; Ferreira, Alfredo; Seib, Viktor; Link, Norman; Paulus, Dietrich; Tatsuma, Atsushi; Aono, Masaki; I. Pratikakis and M. Spagnuolo and T. Theoharis and L. Van Gool and R. Veltkamp
    Low-cost RGB-D sensing technology, such as the Microsoft Kinect, is gaining acceptance in the scientific community and even entering into our homes. This technology enables ordinary users to capture everyday object into digital 3D representations. Considering the image retrieval context, whereas the ability to digitalize photos led to a rapid increase of large collections of images, which in turn raised the need of efficient search and retrieval techniques. We believe the same is happening now for the 3D domain. Therefore, it is essential to identify which 3D shape descriptors, provide better matching and retrieval of such digitalized objects. In this paper, we start by presenting a collection of 3D objects acquired using the latest version of Microsoft Kinect, namely, Kinect One. This dataset, comprising 175 common household objects classified into 18 different classes, was then used for the SHape REtrieval Contest (SHREC). Two groups have submitted their 3D matching techniques, providing the rank list with top 10 results, using the complete set of 175 objects as queries.
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    Projective Feature Learning for 3D Shapes with Multi-View Depth Images
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Xie, Zhige; Xu, Kai; Shan, Wen; Liu, Ligang; Xiong, Yueshan; Huang, Hui; Stam, Jos and Mitra, Niloy J. and Xu, Kun
    Feature learning for 3D shapes is challenging due to the lack of natural paramterization for 3D surface models. We adopt the multi-view depth image representation and propose Multi-View Deep Extreme Learning Machine (MVD-ELM) to achieve fast and quality projective feature learning for 3D shapes. In contrast to existing multiview learning approaches, our method ensures the feature maps learned for different views are mutually dependent via shared weights and in each layer, their unprojections together form a valid 3D reconstruction of the input 3D shape through using normalized convolution kernels. These lead to a more accurate 3D feature learning as shown by the encouraging results in several applications. Moreover, the 3D reconstruction property enables clear visualization of the learned features, which further demonstrates the meaningfulness of our feature learning.
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    Light-Guided Tree Modeling of Diverse Biomorphs
    (The Eurographics Association, 2015) Yi, Lei; Li, Hongjun; Guo, Jianwei; Deussen, Oliver; Zhang, Xiaopeng; Stam, Jos and Mitra, Niloy J. and Xu, Kun
    Creation of tree models faithful to light environment is an important task in computer graphics as well as in botanical research, such as horticulture and forestry. In this paper, we propose an approach to model virtual trees with constraints of light resources and tree morphological properties. By the allocation of received light resources, tree model parameters are estimated, including branching directions and branching sizes. The light energy is calculated by sampling the environmental space, so that the final architecture of trees could be modeled corresponding to its growth environments. Experimental results show that the proposed method create trees with architectures guided by light resources.
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    Fast Edge-based Geodesic Poisson Disk Remeshing
    (The Eurographics Association, 2015) Uhlmann, Tom; Váša, Libor; Brunnett, Guido; B. Bickel and T. Ritschel
    Triangular meshes of high complexity are common when created by a 3D scanner device and must be reduced for further processing. The geodesic Poisson disk remeshing [FZ08] is a method that generates a simplified mesh with highly regular triangles at the cost of exorbitant computation time. In this paper we will outline a new approach to this technique that makes it applicable for highly complex models. Our approach operates directly on the surface of the mesh, therefore works for meshes of arbitrary topology. Meshes consisting of millions of triangles can be reduced to an arbitrary complexity in just a few minutes while the original approach processes meshes with thousands of triangles in the same time. Our easy to implement remeshing technique also provides several options to preserve features.
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    Layer-Based Procedural Design of Façades
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Ilcík, Martin; Musialski, Przemyslaw; Auzinger, Thomas; Wimmer, Michael; Olga Sorkine-Hornung and Michael Wimmer
    We present a novel procedural framework for interactively modeling building façades. Common procedural approaches, such as shape grammars, assume that building façades are organized in a tree structure, while in practice this is often not the case. Consequently, the complexity of their layout description becomes unmanageable for interactive editing. In contrast, we obtain a façade by composing multiple overlapping layers, where each layer contains a single rectilinear grid of façade elements described by two simple generator patterns. This way, the design process becomes more intuitive and the editing effort for complex layouts is significantly reduced. To achieve this, we present a method for the automated merging of different layers in the form of a mixed discrete and continuous optimization problem. Finally, we provide several modeling examples and a comparison to shape grammars in order to highlight the advantages of our method when designing realistic building façades.