STARs 2007
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Item Preface and Table of Contents(The Eurographics Association, 2007) -; Dieter Schmalstieg and Jiri BittnerPreface and Table of ContentsItem Shape Representations Based on Simplicial and Cell Complexes(The Eurographics Association, 2007) Floriani, L. De; Hui, A.; Dieter Schmalstieg and Jiri BittnerSimplicial and cell complexes are the most common way to discretize 3D shapes and two-, three and higherdimensional scalar fields. In this state-of-the-art report, we review, analyze and compare data structures for simplicial and cell complexes. We first classify such representations, based on the dimension of the complexes they can encode, into dimension-independent, and dimension-specific ones. We further classify the data structures in each group according to the basic types of topological entities they represent. We present a description of each data structure in terms of the entities and topological relations it encodes, and we evaluate it based on its expressive power, on its storage cost, on the efficiency in supporting navigation inside the complex (i.e., in retrieving topological relations not explicitly encoded in the data structure). We also discuss a decomposition approach to modeling non-manifold shapes, which has led to powerful and scalable representations.Item Spectral Methods for Mesh Processing and Analysis(The Eurographics Association, 2007) Zhang, Hao; Kaick, Oliver van; Dyer, Ramsay; Dieter Schmalstieg and Jiri BittnerSpectral methods for mesh processing and analysis rely on the eigenvalues, eigenvectors, or eigenspace projections derived from appropriately defined mesh operators to carry out desired tasks. Early works in this area can be traced back to the seminal paper by Taubin in 1995, where spectral analysis of mesh geometry based on a combinatorial Laplacian aids our understanding of the low-pass filtering approach to mesh smoothing. Over the past ten years or so, the list of applications in the area of geometry processing which utilize the eigenstructures of a variety of mesh operators in different manners have been growing steadily. Many works presented so far draw parallels from developments in fields such as graph theory, computer vision, machine learning, graph drawing, numerical linear algebra, and high-performance computing. This state-of-the-art report aims to provide a comprehensive survey on the spectral approach, focusing on its power and versatility in solving geometry processing problems and attempting to bridge the gap between relevant research in computer graphics and other fields. Necessary theoretical background will be provided and existing works will be classified according to different criteria - the operators or eigenstructures employed, application domains, or the dimensionality of the spectral embeddings used - and described in adequate length. Finally, despite much empirical success, there still remain many open questions pertaining to the spectral approach, which we will discuss in the report as well.Item State of the Art in Ray Tracing Animated Scenes(The Eurographics Association, 2007) Wald, Ingo; Mark, William R.; Günther, Johannes; Boulos, Solomon; Ize, Thiago; Hunt, Warren; Parker, Steven G.; Shirley, Peter; Dieter Schmalstieg and Jiri BittnerRay tracing has long been a method of choice for off-line rendering, but traditionally was too slow for interactive use. With faster hardware and algorithmic improvements this has recently changed, and real-time ray tracing is finally within reach. However, real-time capability also opens up new problems that do not exist in an off-line environment. In particular real-time ray tracing offers the opportunity to interactively ray trace moving/animated scene content. This presents a challenge to the data structures that have been developed for ray tracing over the past few decades. Spatial data structures crucial for fast ray tracing must be rebuilt or updated as the scene changes, and this can become a bottleneck for the speed of ray tracing. This bottleneck has received much recent attention by researchers that has resulted in a multitude of different algorithms, data structures, and strategies for handling animated scenes. The effectiveness of techniques for ray tracing dynamic scenes vary dramatically depending on details such as scene complexity, model structure, type of motion, and the coherency of the rays. Consequently, there is so far no approach that is best in all cases, and determining the best technique for a particular problem can be a challenge. In this STAR, we aim to survey the different approaches to ray tracing animated scenes, discussing their strengths and weaknesses, and their relationship to other approaches. The overall goal is to help the reader choose the best approach depending on the situation, and to expose promising areas where there is potential for algorithmic improvements.Item Towards Automatic Character Skeletonization and Interactive Skin Deformation(The Eurographics Association, 2007) Giacomo, T. Di; Moccozet, L.; Magnenat-Thalmann, N.; Boulic, R.; Thalmann, D.; Dieter Schmalstieg and Jiri BittnerCharacters are of paramount importance in computer graphics since they enrich 3D worlds with immersion and life, and extend the range of possible applications. They are also very complex objects to manage due to their articulated structure, to their motion-dependent deformations, and to the familiarity we have with them. With the wide variety of issues to be considered when modeling, rendering, and animating characters, lots of work has focused on character representation and animation. In this STAR we present core and recent techniques to automatically generate a skeleton from a character representation, in order to animate it with bone-based animation techniques. We then present core and recent methods for computing the deformation of the skin according to body movements.Item The Visual Computing of Projector-Camera Systems(The Eurographics Association, 2007) Bimber, Oliver; Iwai, Daisuke; Wetzstein, Gordon; Grundhöfer, Anselm; Dieter Schmalstieg and Jiri BittnerThis state-of-the-art report focuses on real-time image correction techniques that enable projector-camera systems to display images onto screens that are not optimized for projections, such as geometrically complex, colored and textured surfaces. It reviews hardware accelerated methods like pixel-precise geometric warping, radiometric compensation, multi-focal projection, and the correction of general light modulation effects. Online and offline calibration as well as invisible coding methods are explained. Novel attempts in super-resolution, high dynamic range and high-speed projection are discussed. These techniques open a variety of new applications for projection displays. Some of them will also be presented in this report.Item Visualization of Multi-variate Scientific Data(The Eurographics Association, 2007) Bürger, Raphael; Hauser, Helwig; Dieter Schmalstieg and Jiri BittnerIn this state-of-the-art report we discuss relevant research works related to the visualization of complex, multivariate data. We focus on non-classical approaches, i.e. approaches which haven t been discussed in previous related reports, and we highlight techniques which potentially lead towards new directions in visualization research. We discuss how different techniques take effect at specific stages of the visualization pipeline and how they apply to multi-variate data sets being composed of scalars, vectors, and tensors. We also provide a categorization of these techniques in the aim for a better overview of related approaches. In the second part of this paper we take a look at recent techniques that are useful for the visualization of complex data sets either because they are general purpose or because they can be adapted to specific problems.