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Now showing 1 - 10 of 57
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    Building Morphological Representations for 2D and 3D Scalar Fields
    (The Eurographics Association, 2010) Comic, Lidija; Floriani, Leila De; Iuricich, Federico; Enrico Puppo and Andrea Brogni and Leila De Floriani
    Ascending and descending Morse complexes, defined by the critical points and integral lines of a scalar field f defined on a manifold domain D, induce a subdivision of D into regions of uniform gradient flow, and thus provide a compact description of the morphology of f on D. We propose a dimension-independent representation for the ascending and descending Morse complexes, and we describe a data structure which assumes a discrete representation of the field as a simplicial mesh, that we call the incidence-based data structure. We present algorithms for building such data structure for 2D and 3D scalar fields, which make use of a watershed approach to compute the cells of the Morse decompositions.
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    Sketch-Based Posing of 3D Faces for Facial Animation
    (The Eurographics Association, 2010) Gunnarsson, Orn; Maddock, Steve; John Collomosse and Ian Grimstead
    This paper presents a novel approach to creating 3D facial animation using a sketch-based interface where the animation is generated by interpolating a sequence of sketched key poses. The user does not need any knowledge of the underlying mechanism used to create different expressions or facial poses, and no animation controls or parameters are directly manipulated. Instead, the user sketches the desired shape of a facial feature and the system reconstructs a 3D feature which fits the sketched stroke. This is achieved using a maximum likelihood framework where a statistical model in conjunction with Hidden Markov Models handles sketch detection, and a hierarchical statistical mapping approach reconstructs a posed 3D mesh from a low-dimensional representation.
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    Towards a Voting Scheme for Calculating Light Source Positions from a given Target Illumination
    (The Eurographics Association, 2010) Zmugg, René; Havemann, Sven; Fellner, Dieter W.; Enrico Puppo and Andrea Brogni and Leila De Floriani
    Lighting conditions can make the difference between success or failure of an architectural space. The vision of space-light co-design is that architects can control the impression of an illuminated space already at an early design stage, instead of first designing spaces and then searching for a good lighting setup. As a first step towards this vision we propose a novel method to calculate potential light source positions from a given user defined target illumination. The method is independent of the tessellation of the scene and assumes a homogeneous diffuse Lambertian material. This allows using a voting system that determines potential positions for standard light sources with chosen size and brightness. Votes are cast from an illuminated surface point to all potential positions of a light source that would yield this illumination. Vote clusters consequently indicate a more probable light source position. With a slight extension the method can also identify mid-air light source positions.
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    A Thin-plate CAD Mesh Model Splitting Approach Based on Fitting Primitives
    (The Eurographics Association, 2010) Geng, Chun; Suzuki, Hiromasa; Yan, Dong-Ming; Michikawa, Takasi; Sato, Yuichi; Hashima, Masayoshi; Ohta, Eiji; John Collomosse and Ian Grimstead
    Extracting structural information from mesh models is crucial for Simulation Driven Design (SDD) in industrial applications. Focusing on thin-plate CAD mesh models (the most commonly used parts in electronic products such as PCs, mobile phones and so on), we present an algorithm based on primitive fitting for segmenting thin-plate CAD mesh models into parts of three different types, two of which are extruding surfaces and the other is a lateral surface. This method can be used for solid model reconstruction in the SDD process. Our approach involves two steps. First, a completely automatic method for accurate primitive fitting on CAD meshes is proposed based on the hierarchical primitive fitting framework. In the second step, a novel procedure is proposed for splitting thin-plate CAD mesh models by detecting parallel extruding surfaces and lateral surfaces. The method presented here has been proved to work smoothly in applications of real product design.
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    Monitor-Based tracking system for Wide Augmented Reality Environments
    (The Eurographics Association, 2010) Re, Guido Maria; Caruso, Giandomenico; Belluco, Paolo; Bordegoni, Monica; Enrico Puppo and Andrea Brogni and Leila De Floriani
    In Augmented Reality (AR) applications, the technological solutions used for tracking objects in the real environment are generally related to the conditions of the environment and to the application purposes. The selection of the most suitable tracking technology satisfies the best compromise among several issues including performance, accuracy and easiness of use. This paper describes an AR tracking approach based on a marker-based tracking and its development for wide environment by displaying itself on a monitor. This solution allows us to improve the visibility of the marker and the tracking, thanks to a dynamic control of marker s dimensions. The technical features and performances of our approach have been assessed by several testing sessions focused on comparative analyses.
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    Modeling Liquidus Hypersurfaces through Simplicial Complexes
    (The Eurographics Association, 2010) Natali, Mattia; Attene, Marco; Ottonello, Giulio; Enrico Puppo and Andrea Brogni and Leila De Floriani
    This paper describes an operational pipeline that exploits computational geometry to derive useful knowledge about the crystallization behaviour of materials composed of varying amounts of pure components. Starting from existing knowledge related to the pure components, we compute the Gibbs free energy of all their possible compositions in a given range of temperatures, both in liquid and solid phases. Then, we exploit the convex hull method to derive the coexistence of solid and liquid phases, and model the resulting liquidus hypersurface as a simplicial complex. On such a complex, we propose novel tools to robustly compute descent lines describing the crystallization path induced by heat loss for any initial composition in the system.
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    Two Examples of GPGPU Acceleration of Memory-intensive Algorithms
    (The Eurographics Association, 2010) Marras, Stefano; Mura, Claudio; Gobbetti, Enrico; Scateni, Riccardo; Scopigno, Roberto; Enrico Puppo and Andrea Brogni and Leila De Floriani
    The advent of GPGPU technologies has allowed for sensible speed-ups in many high-dimension, memory-intensive computational problems. In this paper we demonstrate the e ectiveness of such techniques by describing two applications of GPGPU computing to two di erent subfields of computer graphics, namely computer vision and mesh processing. In the first case, CUDA technology is employed to accelerate the computation of approximation of motion between two images, known also as optical flow. As for mesh processing, we exploit the massivelyparallel architecture of CUDA devices to accelerate the face clustering procedure that is employed in many recent mesh segmentation algorithms. In both cases, the results obtained so far are presented and thoroughly discussed, along with the expected future development of the work.
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    A Framework for Virtual Restoration of Ancient Documents by Combination of Multispectral and 3D Imaging
    (The Eurographics Association, 2010) Bianco, Gianfranco; Bruno, Fabio; Tonazzini, A.; Salerno, E.; Savino, P.; Zitova, B.; Sroubek, F.; Console, E.; Enrico Puppo and Andrea Brogni and Leila De Floriani
    Historical documents often undergo various changes over time, that alter their original state and reduce their legibility. Digital techniques are widely applied for document preservation, archiving, analysis and dissemination over the Internet. The goal of restoration is to improve the document legibility for both human and automatic operators, to extract patterns and enhance colour reproduction. Our paper presents a framework for virtual restoration of ancient documents based on a combination of multispectral acquisition, 3D imaging and digital image analysis. The proposed framework consists of several steps. First, digital representations of the documents are acquired as multispectral images and 3D surface maps, the latter reconstructed by a structured light technique. A multispectral camera and a digital projector are used in triangular configuration for 2D and 3D data acquisition. Then the multispectral images are registered against possible misalignments, and the 3D surface representation is used to correct geometrical distortions. Document flattening is then performed by 3D surface parameterization and texture mapping. Statistical techniques of decorrelation are applied to extract individual context parts of the document patterns (stamp, text, etc.) and to attenuate interferences. The processed data are then binarized by the proper segmentation technique. The entire digital object history - all the acquisition and processing steps, with the corresponding parameters - is stored in metadata files. These data can be exploited in a future evaluation of the restoration process and can be used for either the creation of an expert knowledge database or the extraction of cross-document observations and conclusions.
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    Composition of Texture Atlases for 3D Mesh Multi-texturing
    (The Eurographics Association, 2010) Pagés, Rafael; Arnaldo, Sergio; Morán, Francisco; Berjón, Daniel; Enrico Puppo and Andrea Brogni and Leila De Floriani
    We introduce an automatic technique for mapping onto a 3D triangle mesh, approximating the shape of a real 3D object, a high resolution texture synthesized from several pictures taken simultaneously by real cameras surrounding the object. We create a texture atlas by first unwrapping the 3D mesh to form a set of 2D patches with no distortion (i.e., the angles and relative sizes of the 3D triangles are preserved in the atlas), and then mixing the color information from the input images, through another three steps: step no. 2 packs the 2D patches so that the bounding canvas of the set is as small as possible; step no. 3 assigns at most one triangle to each canvas pixel; finally, in step no. 4, the color of each pixel is calculated as a smoothly varying weighted average of the corresponding pixels from several input photographs. Our method is especially good for the creation of realistic 3D models without the need of having graphic artists retouch the texture.
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    An Improved Discrete Level of Detail Model Through an Incremental Representation
    (The Eurographics Association, 2010) Ribelles, Jose; López, Angeles; Belmonte, Oscar; John Collomosse and Ian Grimstead
    Real-time applications such as computer and video games, virtual reality and scientific simulation require rendering of complex models for realism. Graphics rendering engines include multiresolution modelling techniques to accelerate the visualization process. The Discrete Level of Detail framework (DLoD) is usually the most popular while the Continuous Level of Detail framework (CLoD) is still not as widely used by software developers. In this paper, we first discuss the benefits and drawbacks of both frameworks. Then, we present a model based on coding a discrete number of levels of detail (LoDs), with more LoDs coded than is usual in DLoD, and with an incremental representation, which is often used in CLoD. This model obtains a performance similar to DLoD by providing optimized LoDs for efficient visualization, while the popping effect is imperceptible. We present specific proposals for each of the three main stages involved in multiresolution processing: geometry simplification, construction of the incremental representation and retrieval of either uniform or view-dependent LoDs.