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Item Join Now!(Blackwell Publishers, Inc and the Eurographics Association, 2003)Item Creation and Control of Real-time Continuous Level of Detail on Programmable Graphics Hardware(Blackwell Publishers, Inc and the Eurographics Association, 2003) Southern, Richard; Gain, JamesContinuity in level of detail sequences is essential in hiding visual artefacts that occur when switching between discrete levels of detail. However, construction and implementation of these sequences is prohibitively complex. We present a new structure, the g-mesh, which greatly simplifies the implementation of continuous level of detail in large scenes. We also introduce a novel greedy predictive level of detail control system suited to the g-mesh. Finally we achieve a dramatic improvement in the rendering of morphing sequences by exploiting current graphics hardware.ACM CSS: I.3.5 Computational Geometry and Object Modeling-Geometric Transformations, Object Hierarchies, I.3.6 Methodology and Techniques-Graphics Data StructuresItem State of the Art in Global Illumination for Interactive Applications and High-quality Animations(Blackwell Publishers, Inc and the Eurographics Association, 2003) Damez, Cyrille; Dmitriev, Kirill; Myszkowski, KarolGlobal illumination algorithms are regarded as computationally intensive. This cost is a practical problem when producing animations or when interactions with complex models are required. Several algorithms have been proposed to address this issue. Roughly, two families of methods can be distinguished. The first one aims at providing interactive feedback for lighting design applications. The second one gives higher priority to the quality of results, and therefore relies on offline computations. Recently, impressive advances have been made in both categories. In this report, we present a survey and classification of the most up-to-date of these methods.ACM CSS: I.3.7 Computer Graphics-Three-Dimensional Graphics and RealismItem Quad/Triangle Subdivision(Blackwell Publishers, Inc and the Eurographics Association, 2003) Stam, Jos; Loop, CharlesIn this paper we introduce a new subdivision operator that unifies triangular and quadrilateral subdivision schemes. Designers often want the added flexibility of having both quads and triangles in their models. It is also well known that triangle meshes generate poor limit surfaces when using a quad scheme, while quad-only meshes behave poorly with triangular schemes. Our new scheme is a generalization of the well known Catmull-Clark and Loop subdivision algorithms. We show that our surfaces areC1everywhere and provide a proof that it is impossible to construct such aC2scheme at the quad/triangle boundary. However, we provide rules that produce surfaces with bounded curvature at the regular quad/triangle boundary and provide optimal masks that minimize the curvature divergence elsewhere. We demonstrate the visual quality of our surfaces with several examples.ACM CSS: I.3.5 Computer Graphics-Curve, surface, solid, and object representationsItem Interpolating an Unlimited Number of Curves Meeting at Extraordinary Points on Subdivision Surfaces*(Blackwell Publishers, Inc and the Eurographics Association, 2003) Nasri, Ahmed H.Interpolating curves by subdivision surfaces is one of the major constraints that is partially addressed in the literature. So far, no more than two intersecting curves can be interpolated by a subdivision surface such as Doo-Sabin or Catmull-Clark surfaces. One approach that has been used in both of theses surfaces is the polygonal complex approach where a curve can be defined by a control mesh rather than a control polygon. Such a definition allows a curve to carry with it cross derivative information which can be naturally embodied in the mesh of a subdivision surface. This paper extends the use of this approach to interpolate an unlimited number of curves meeting at an extraordinary point on a subdivision surface. At that point, the curves can all meet with eitherC0orC1continuity, yet still have common tangent plane. A straight forward application is the generation of subdivision surfaces through 3-regular meshes of curves for which an easy interface can be used.Item Editorial(Blackwell Publishers, Inc and the Eurographics Association, 2003) Duke, David; Scopigno, RobertoItem The Perspective Silhouette of a Canal Surface(Blackwell Publishers, Inc and the Eurographics Association, 2003) Kim, Ku-Jin; Lee, In-KwonWe present an efficient and robust algorithm for parameterizing the perspective silhouette of a canal surface and detecting each connected component of the silhouette. A canal surface is the envelope of a moving sphere with varying radius, defined by the trajectoryC(t)of its center and a radius functionr(t). This moving sphere,S(t), touches the canal surface at a characteristic circleK(t). We decompose the canal surface into a set of characteristic circles, compute the silhouette points on each characteristic circle, and then parameterize the silhouette curve. The perspective silhouette of the sphereS(t)from a given viewpoint consists of a circleQ(t); by identifying the values oftat whichK(t)andQ(t)touch, we can find all the connected components of the silhouette curve of the canal surface.ACM CSS: I.3.7 Computer Graphics-Three Dimensional Graphics and RealismItem Automatic Hybrid Hierarchy Creation: a Cost-model Based Approach(Blackwell Publishers, Inc and the Eurographics Association, 2003) Masso, J. P. Molina; Lopez, P. GonzalezWhile using hierarchical search structures has been proved as one of the most efficient acceleration techniques when rendering complex scenes, automatic creation of appropriate hierarchies is not solved yet. Well-known algorithms for automatic creation of bounding volume hierarchies are not enough. Higher performance is achieved by introducing spatial uniform subdivision, although algorithms proposed up to now are not truly automatic, as they need some parameters to be adjusted. In this paper we present a full-automatic hierarchy creation scheme that structures the scene in a hybrid way, combining bounding volumes and voxel grids in the same tree, selecting the search structure that best fits to each scene region. It uses no parameters at all. This efficient proposal relies on a new cost model that estimates the goodness of a hybrid hierarchy if used for rendering the scene.ACM CSS: I.3.7 Computer Graphics-Three-Dimensional Graphics and RealismItem Two-dimensional Potential Fields for Advanced Implicit Modeling Operators(Blackwell Publishers, Inc and the Eurographics Association, 2003) Barthe, L.; Dodgson, N. A.; Sabin, M. A.; Wyvill, B.; Gaildrat, V.Current methods for building models using implicit volume techniques present problems defining accurate and controllable blend shapes between implicit primitives. We present new methods to extend the freedom and controllability of implicit volume modeling. The main idea is to use a free-form curve to define the profile of the blend region between implicit primitives.The use of a free-form implicit curve, controlled point-by-point in the Euclidean user space, allows us to group boolean composition operators with sharp transitions or smooth free-form transitions in a single modeling metaphor. This idea is generalized for the creation, sculpting and manipulation of volume objects, while providing the user with simplicity, controllability and freedom in implicit modeling.ACM CSS: I.3.5 Computational Gemoetry and Object Modeling-Curve, surface, solid, and object representationsItem Emotion Disc and Emotion Squares: Tools to Explore the Facial Expression Space(Blackwell Publishers, Inc and the Eurographics Association, 2003) Ruttkay, Zsofia; Noot, Han; Ten Hagen, PaulIn the paper we present two novel interactive tools, Emotion Disc and Emotion Squares, to explore the facial expression space. They map navigation in a two-dimensional circle, by the first tool, or in two two-dimensional squares, by the second tool, to the high-dimensional parameter space of facial expressions, by using a small number of predefined reference expressions. They can be used as exploration tools by researchers, or as control devices by end-users to put expressions on the face of embodied agents or avatars in applications like games, telepresence and education.Item EG Network Service Computer Graphics forum(Blackwell Publishers, Inc and the Eurographics Association, 2003)Eurographics and Computer Graphics forum offer a variety of services on the international networks. You can find details of our latest events, how to prepare a paper for the conference or for the journal and much more besides. This information can be accessed mainly through the EG website but we also offer some support for ftp and mail server access.Item On the Optimality of Valence-based Connectivity Coding(Blackwell Publishers, Inc and the Eurographics Association, 2003) Gotsman, CraigWe show that the average entropy of the distribution of valences in valence sequences for the class of manifold 3D triangle meshes and the class of manifold 3D polygon meshes is strictly less than the entropy of these classes themselves. This implies that, apart from a valence sequence, another essential piece of information is needed for valence-based connectivity coding of manifold 3D meshes. Since there is no upper bound on the size of this extra piece of information, the result implies that the question of optimality of valence-based connectivity coding is still open.