27-Issue 6
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Item 29th EUROGRAPHICS General Assembly(The Eurographics Association and Blackwell Publishing Ltd, 2008)Item Computational Aesthetics 2008(The Eurographics Association and Blackwell Publishing Ltd, 2008)Item Computational Aesthetics 2009 Call for papers(The Eurographics Association and Blackwell Publishing Ltd, 2008)Item Computational Geometry Education for Computer Graphics Students(The Eurographics Association and Blackwell Publishing Ltd, 2008) Kolingerova, I.The paper surveys main features of computational geometry and presents the argument that a course oriented to applied computational geometry should be a part of the computer graphics curriculum, as it teaches effective algorithmic methods and helps to develop abstract thinking. Possible contents of the course and forms suitable and interesting for computer graphics students are discussed. The students feedback on such a course has been mostly positive.Item Displacement Mapping on the GPU - State of the Art(The Eurographics Association and Blackwell Publishing Ltd, 2008) Szirmay-Kalos, Laszlo; Umenhoffer, TamasThis paper reviews the latest developments of displacement mapping algorithms implemented on the vertex, geometry, and fragment shaders of graphics cards. Displacement mapping algorithms are classified as per-vertex and per-pixel methods. Per-pixel approaches are further categorized as safe algorithms that aim at correct solutions in all cases, to unsafe techniques that may fail in extreme cases but are usually much faster than safe algorithms, and to combined methods that exploit the robustness of safe and the speed of unsafe techniques. We discuss the possible roles of vertex, geometry and fragment shaders to implement these algorithms. Then the particular GPU-based bump, parallax, relief, sphere, horizon mapping, cone stepping, local ray tracing, pyramidal and view-dependent displacement mapping methods, as well as their numerous variations are reviewed providing also implementation details of the shader programs. We present these methods using uniform notations and also point out when different authors called similar concepts differently. In addition to basic displacement mapping, self-shadowing and silhouette processing are also reviewed. Based on our experiences gained having reimplemented these methods, their performance and quality are compared, and the advantages and disadvantages are fairly presented.Item Efficient CPU-based Volume Ray Tracing Techniques(The Eurographics Association and Blackwell Publishing Ltd, 2008) Marmitt, Gerd; Friedrich, Heiko; Slusallek, PhilippRecent research on high-performance ray tracing has achieved real-time performance even for highly complex surface models already on a single PC. In this report, we provide an overview of techniques for extending real-time ray tracing also to interactive volume rendering. We review fast rendering techniques for different volume representations and rendering modes in a variety of computing environments. The physically-based rendering approach of ray tracing enables high image quality and allows for easily mixing surface, volume and other primitives in a scene, while fully accounting for all of their optical interactions. We present optimized implementations and discuss the use of upcoming high-performance processors for volume ray tracing.Item Exaggerating Character Motions Using Sub-Joint Hierarchy(The Eurographics Association and Blackwell Publishing Ltd, 2008) Kwon, Ji-yong; Lee, In-KwonMotion capture cannot generate cartoon-style animation directly. We emulate the rubber-like exaggerations common in traditional character animation as a means of converting motion capture data into cartoon-like movement. We achieve this using trajectory-based motion exaggeration while allowing the violation of link-length constraints. We extend this technique to obtain smooth, rubber-like motion by dividing the original links into shorter sub-links and computing the positions of joints using Bezier curve interpolation and a mass-spring simulation. This method is fast enough to be used in real time.Item Image-Based Surface Compression(The Eurographics Association and Blackwell Publishing Ltd, 2008) Ochotta, Tilo; Saupe, DietmarWe present a generic framework for compression of densely sampled three-dimensional (3D) surfaces in order to satisfy the increasing demand for storing large amounts of 3D content. We decompose a given surface into patches that are parameterized as elevation maps over planar domains and resampled on regular grids. The resulting shaped images are encoded using a state-of-the-art wavelet image coder. We show that our method is not only applicable to mesh- and point-based geometry, but also outperforms current surface encoders for both primitives.Item Improving Multipath Radiosity with Bundles of Parallel Lines(The Eurographics Association and Blackwell Publishing Ltd, 2008) Martinez, Roel; Sbert, Mateu; Szirmay-Kalos, LaszloMonte Carlo approaches use random lines to distribute the light power in the scene but the cost of creating a set of random single lines is very costly. In this paper, we present several software and hardware techniques in order to reduce the computational cost of the generation of random single lines by using bundles of parallel lines. The bundle of parallel lines is simulated with a general purpose polygon filling algorithm, like the painter s algorithm. We also present two graphics hardware implementations. The first approach uses two depth buffers in order to represent stochastically a bundle of parallel global lines. The second one uses multiple depth buffers and the aim is to exploit coherence between projection planes for each iteration. All algorithms were implemented with the multipath method.Item Interference Shaders of Thin Films(The Eurographics Association and Blackwell Publishing Ltd, 2008) Sun, Yinlong; Wang, QiqiThis paper presents a systematic study of light interferences at single thin films. Based on Fresnel s law, we have derived generic expressions of reflectance and transmittance for film interference, as well as specific expressions for free thin films and films coated on transparent or opaque objects. By combining film interference and volume absorption, we have obtained the reflectances and transmittances of film-coated thin objects such as ribbons. Illumination models for all interference cases of single thin films are presented, and they have been implemented and tested for various structures and materials.Item New EUROGRAPHICS Fellows(The Eurographics Association and Blackwell Publishing Ltd, 2008)Item Practical HDR Texture Compression(The Eurographics Association and Blackwell Publishing Ltd, 2008) Munkberg, J.; Clarberg, P.; Hasselgren, J.; Akenine-Moeller, T.The use of high dynamic range (HDR) textures in real-time graphics applications can increase realism and provide a more vivid experience. However, the increased bandwidth and storage requirements for uncompressed HDR data can become a major bottleneck. Hence, several recent algorithms for HDR texture compression have been proposed. In this paper, we discuss several practical issues one has to confront in order to develop and implement HDR texture compression schemes. These include improved texture filtering and efficient offline compression. For compression, we describe how Procrustes analysis can be used to quickly match a predefined template shape against chrominance data. To reduce the cost of HDR texture filtering, we perform filtering prior to the colour transformation, and use a simple trick to reduce the incurred errors. We also introduce a number of novel compression modes, which can be combined with existing compression schemes, or used on their own.Item Statistical optimization of octree searches(The Eurographics Association and Blackwell Publishing Ltd, 2008) Castro, Rener; Lewiner, Thomas; Lopes, Helio; Tavares, Geovan; Bordignon, AlexThis work emerged from the following observation: usual search procedures for octrees start from the root to retrieve the data stored at the leaves. But as the leaves are the farthest nodes to the root, why start from the root? With usual octree representations, there is no other way to access a leaf. However, hashed octrees allow direct access to any node, given its position in space and its depth in the octree. Search procedures take the position as an input, but the depth remains unknown. This work proposes to estimate the depth of an arbitrary node through a statistical optimization of the average cost of search procedures. As the highest costs of these algorithms are obtained when starting from the root, this method improves on both the memory footprint by the use of hashed octrees, and execution time through the proposed optimization.Item Surface Reconstruction from Unorganized Point Data with Quadrics(The Eurographics Association and Blackwell Publishing Ltd, 2008) Vanco, Marek; Hamann, Bernd; Brunnett, GuidoWe present a reverse engineering method for constructing a surface approximation scheme whose input is a set of unorganized noisy points in space and whose output is a set of quadric patches. The local surface properties, necessary for the subsequent segmentation, are estimated directly from the data using a simple and efficient data structure-the neighborhood graph. Our segmentation scheme, based on principal curvatures, constructs initial point subsets, which may be enlarged or further subdivided based on associated approximation error estimates obtained through approximation of the initial segments by quadric surfaces. Our method is highly efficient and produces a high-quality piecewise quadric surface approximation of engineering objects, which we demonstrate for several simple and complex example data sets.Item A survey on Mesh Segmentation Techniques(The Eurographics Association and Blackwell Publishing Ltd, 2008) Shamir, ArielWe present a review of the state of the art of segmentation and partitioning techniques of boundary meshes. Recently, these have become a part of many mesh and object manipulation algorithms in computer graphics, geometric modelling and computer aided design. We formulate the segmentation problem as an optimization problem and identify two primarily distinct types of mesh segmentation, namely part segmentation and surface-patch segmentation. We classify previous segmentation solutions according to the different segmentation goals, the optimization criteria and features used, and the various algorithmic techniques employed. We also present some generic algorithms for the major segmentation techniques.Item Table of Contents and Cover(The Eurographics Association and Blackwell Publishing Ltd, 2008)