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End date: 2009 × Subject: Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Line and Curve Generation ×

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Now showing 1 - 10 of 22
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    3D Scene Comparison using Topological Graphs
    (The Eurographics Association, 2007) Paraboschi, L.; Biasotti, S.; Falcidieno, B.; Raffaele De Amicis and Giuseppe Conti
    New technologies for shape acquisition and rendering of digital shapes have simplified the process of creating virtual scenes; nonetheless, shape annotation, recognition and manipulation of both the complete virtual scenes and even of subparts of them are still open problems. In this paper we deal with the problem of comparing two (or more) object sets, where each model is represented by an attributed graph. We will define a new distance to estimate the possible similarities among the sets of graphs and will validate our work using the shape graph [BGSF06].
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    Normal Estimation for Point Clouds: A Comparison Study for a Voronoi Based Method
    (The Eurographics Association, 2005) Dey, Tamal K.; Li, Gang; Sun, Jian; Marc Alexa and Szymon Rusinkiewicz and Mark Pauly and Matthias Zwicker
    Many applications that process a point cloud data benefit from a reliable normal estimation step. Given a point cloud presumably sampled from an unknown surface, the problem is to estimate the normals of the surface at the data points. Two approaches, one based on numerical optimizations and another based on Voronoi diagrams are known for the problem. Variations of numerical approaches work well even when point clouds are contaminated with noise. Recently a variation of the Voronoi based method is proposed for noisy point clouds. The centrality of the normal estimation step in point cloud processing begs a thorough study of the two approaches so that one knows which approach is appropriate for what circumstances. This paper presents such results.
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    Magnetic Curves: Curvature-Controlled Aesthetic Curves Using Magnetic Fields
    (The Eurographics Association, 2009) Xu, Ling; Mould, David; Oliver Deussen and Peter Hall
    We describe 'magnetic curves', a particle-tracing method that creates curves with constantly changing curvature. It is well known that charged particles in a constant magnetic field trace out circular or helical trajectories. Motivated by John Ruskin's advice to use variation in curvature to achieve aesthetic curves, we propose to continuously change the charge on a simulated particle so that it can trace out a complex curve with continuously varying curvature. We show some examples of abstract figures created by this method and also show how some stylized representational forms, including fire, hair, and trees, can be drawn with magnetic curves.
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    Volume Deformation via Scattered Data Interpolation
    (The Eurographics Association, 2007) Correa, Carlos D.; Silver, Deborah; Chen, Min; H.-C. Hege and R. Machiraju and T. Moeller and M. Sramek
    With the advent of contemporary GPUs, it has been possible to perform volume deformation at interactive rates. In particular, it has been shown that deformation can be important for the purposes of illustration. In such cases, rather than being the result of a physically-based simulation, volume deformation is often goal-oriented and user-guided. For this purpose, it is important to provide the user with tools for directly specifying a deformation interactively and refine it based on constraints or user intention. In many cases, deformation is obtained based on a reference object or image. In this paper, we present a method for deforming volumetric objects based on user guided scattered data interpolation. A GPU-based implementation enables real-time manipulation of 2D images and volumes. We show how this approach can have applications in scientific illustration, volume exploration and visualization, generation of animations and special effects, among others.
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    Sketch and Paint-based Interface for Highlight Modeling
    (The Eurographics Association, 2008) Pacanowski, Romain; Granier, Xavier; Schlick, Christophe; Poulin, Pierre; Christine Alvarado and Marie-Paule Cani
    In computer graphics, highlights capture much of the appearance of light reflection off a surface. They are generally limited to pre-defined models (e.g., Phong, Blinn) or to measured data. In this paper, we introduce new tools and a corresponding highlight model to provide computer graphics artists a more expressive approach to design highlights. For each defined light key-direction, the artist simply sketches and paints the main highlight features (shape, intensity, and color) on a plane oriented perpendicularly to the reflected direction. For other light-and- view configurations, our system smoothly blends the different user-defined highlights. Based on GPU cabilities, our solution allows real-time editing and feedback. We illustrate our approach with a wide range of highlights, with complex shapes and varying colors. This solution also demonstrates the simplicity of introduced tools.
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    Effect of the Size of the Field of View on the Perceived Amplitude of Rotations of the Visual Scene
    (The Eurographics Association, 2008) Ogier, Maelle; Bülthoff, Heinrich H.; Bresciani, Jean-Pierre; Robert van Liere and Betty Mohler
    Efficient navigation requires a good representation of body position/orientation in the environment and an accurate updating of this representation when the body-environment relationship changes. We tested here whether the visual flow alone - i.e., no landmark - can be used to update this representation when the visual scene is rotated, and whether having a limited horizontal field of view (30 or 60 degrees), as it is the case in most virtual reality applications, degrades the performance as compared to a full field of view. Our results show that (i) the visual flow alone does not allow for accurately estimating the amplitude of rotations of the visual scene, notably giving rise to a systematic underestimation of rotations larger than 30 degrees, and (ii) having more than 30 degrees of horizontal field of view does not really improve the performance. Taken together, these results suggest that a 30 degree field of view is enough to (under)estimate the amplitude of visual rotations when only visual flow information is available, and that landmarks should probably be provided if the amplitude of the rotations has to be accurately perceived.
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    Stippling and Silhouettes Rendering in Geometry-Image Space
    (The Eurographics Association, 2005) Yuan, Xiaoru; Nguyen, Minh X.; Zhang, Nan; Chen, Baoquan; Kavita Bala and Philip Dutre
    We present a novel non-photorealistic rendering method that performs all operations in a geometry-image domain. We first apply global conformal parameterization to the input geometry model and generate corresponding geometry images. Strokes and silhouettes are then computed in the geometry-image domain. The geometry-image space provides combined benefits of the existing image space and object space approaches. It allows us to take advantage of the regularity of 2D images and yet still have full access to the object geometry information. A wide range of image processing tools can be leveraged to assist various operations involved in achieving non-photorealistic rendering with coherence.
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    Multiple Uses of 3D Scanning for the Valorization of an Artistic Site: the Case of Luni
    (The Eurographics Association, 2008) Dellepiane, Matteo; Callieri, Marco; Paribeni, Emanuela; Sorge, Elena; Sulfaro, Nino; Marianelli, Veronica; Scopigno, Roberto; Vittorio Scarano and Rosario De Chiara and Ugo Erra
    The heritage site of Luni is a very interesting location, which tells the story of an ancient roman colony, and of an area where different cultures left their heritage. In particular, the remains of the pediments of an ancient temple represent a very interesting case and an open field of study for art historians. The scanning of a group of statue belonging to the pediments showed that the produced 3D models could be used in several ways, not only for archival and presentation purposes but also to provide interactive support for the work of the restorers and the scholars. In particular, the use of 3D models to propose and validate hypothesis about the original position of the fragments in the context of the fronton could be an alternative solution to the direct manipulation of them. Moreover, the analysis of the original color of the statues, and the representation different hypothesis about the ancient appearance can be produced through the interactive editing of the 3D models of the statues. In this paper we present the scanning campaign which resulted in the acquisition of five statues,the preliminary results of some of the uses of the models produced with acquired data, and a brief description of other possible future applications of them. This shows how 3D scanning can be considered by now a mature technology for the support of restoration and preservation of Cultural Heritage.
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    Realistic Soft Shadows by Penumbra-Wedges Blending
    (The Eurographics Association, 2006) Forest, Vincent; Barthe, Loïc; Paulin, Mathias; Marc Olano and Philipp Slusallek
    Recent real-time shadow generation techniques try to provide shadows with realistic penumbrae. However, most techniques are whether non-physically based or too simplified to produce convicing results. The penumbra-wedges algorithm is a physical approach based on the assumption that penumbrae are non-overlapping. In this paper, we propose an algorithm that takes the advantages of the penumbra-wedges method but solves the "non-overlapping" limitation. We first compute the light occlusion regions per fragment. Then we use this information to detect the areas where penumbrae are overlapping and we perform a realistic penumbra blending.
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    Defining and Computing Curve-skeletons with Medial Geodesic Function
    (The Eurographics Association, 2006) Dey, Tamal K.; Sun, Jian; Alla Sheffer and Konrad Polthier
    Many applications in geometric modeling, computer graphics, visualization and computer vision benefit from a reduced representation called curve-skeletons of a shape. These are curves possibly with branches which compactly represent the shape geometry and topology. The lack of a proper mathematical definition has been a bottleneck in developing and applying the the curve-skeletons. A set of desirable properties of these skeletons has been identified and the existing algorithms try to satisfy these properties mainly through a procedural definition. We define a function called medial geodesic on the medial axis which leads to a methematical definition and an approximation algorithm for curve-skeletons. Empirical study shows that the algorithm is robust against noise, operates well with a single user parameter, and produces curve-skeletons with the desirable properties. Moreover, the curveskeletons can be associated with additional attributes that follow naturally from the definition. These attributes capture shape eccentricity, a local measure of how far a shape is away from a tubular one.