25-Issue 2

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https://diglib.eg.org/handle/10.2312/125

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    Anti-aliasing with Stratified B-spline Filters of Arbitrary Degree
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Gamito, Manuel N.; Maddock, Steve C.
    A simple and elegant method is presented to perform anti-aliasing in raytraced images. The method uses stratified sampling to reduce the occurrence of artefacts in an image and features a B-spline filter to compute the final luminous intensity at each pixel. The method is scalable through the specification of the filter degree. A B-spline filter of degree one amounts to a simple anti-aliasing scheme with box filtering. Increasing the degree of the B-spline generates progressively smoother filters. Computation of the filter values is done in a recursive way, as part of a sequence of Newton-Raphson iterations, to obtain the optimal sample positions in screen space. The proposed method can perform both anti-aliasing in space and in time, the latter being more commonly known as motion blur. We show an application of the method to the ray casting of implicit procedural surfaces.
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    A Comparative Evaluation of Metrics for Fast Mesh Simplification
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Matias van Kaick, Oliver; Pedrini, Helio
    Triangle mesh simplification is of great interest in a variety of knowledge domains, since it allows manipulation and visualization of large models, and it is the starting point for the design of many multiresolution representations. A crucial point in the structure of a simplification method is the definition of an appropriate metric for guiding the decimation process, with the purpose of generating low error approximations at different levels of resolution. This paper proposes two new alternative metrics for mesh simplification, with the aim of producing high-quality results with reduced execution time and memory usage, and being simple to implement. A set of different established metrics is also described and a comparative evaluation of these metrics against the two new metrics is performed. A single implementation is used in the experiments, in order to enable the evaluation of these metrics independently from other simplification aspects. Results obtained from the simplification of a number of models, using the different metrics, are compared.
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    Editorial
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Duke, David; Scopigno, Roberto
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    Errata
    (The Eurographics Association and Blackwell Publishing Ltd, 2006)
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    A Hierarchical Topology-Based Model for Handling Complex Indoor Scenes
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Fradin, D.; Meneveaux, D.; Lienhardt, P.
    This paper presents a topology-based representation dedicated to complex indoor scenes. It accounts for memory management and performances during modelling, visualization and lighting simulation. We propose to enlarge a topological model (called generalized maps) with multipartition and hierarchy. Multipartition allows the user to group objects together according to semantics. Hierarchy provides a coarse-to-fine description of the environment. The topological model we propose has been used for devising a modeller prototype and generating efficient data structure in the context of visualization, global illumination and 1 GHz wave propagation simulation. We presently handle buildings composed of up to one billion triangles.
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    Interactive Multiresolution Editing and Display of Large Terrains
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Atlan, Samuel; Garland, Michael
    In recent years, many systems have been developed for the real-time display of very large terrains. While many of these techniques combine high-quality rendering with impressive performance, most make the fundamental assumption that the terrain is represented by a fixed height map that cannot be altered at run time. Such systems frequently rely on extensive preprocessing of the raw terrain data. They are mostly designed for maximum performance. Consequently, these techniques are ill-suited for the many applications such as geological simulations and games in which terrain surfaces must be altered interactively.We present a two-component system that can achieve real-time view-dependent rendering while allowing on-line multiresolution alterations of a large terrain. Our fundamental height map representation is a wavelet quadtree hierarchy, allowing one to easily apply arbitrary multiresolution edits to the terrain. Our display algorithm extracts a view-dependent approximation of the terrain from the wavelet quadtree in real time. The algorithm dynamically alters this approximation based on any ongoing edits. To allow for flexibility and to limit performance loss, the two components of this system have been designed to be as independent as possible.
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    Memory-Conserving Bounding Volume Hierarchies with Coherent Raytracing
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Mahovsky, J.; Wyvill, B.
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    SVG.Open 2005 Conference
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Neumann, Andreas
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    Third Eurographics Symposium on Geometry Processing (in cooperation with ACM SIGGRAPH)
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Desbrun, Mathieu
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    Transformation and Normal Vector Calculation of Parametrically Defined Surfaces Based on Dual Vectors and Screw Theory: Application to Phong s Shading Model
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Papageorgiou, Stavros G.; Aspragathos, Nikos A.
    This paper presents a new approach for the transformation and normal vector calculation algorithms of parametrically defined surfaces via dual vectors and line transformations. The surface is defined via dual points, the transformation is performed by rotations and translations based on screw theory while normal vector calculation is utilized for shading based on Phong s illumination model. The main benefit of this approach lies into the compactness of the surface s representation since geometrical characteristics, such as tangent vectors, that are necessary for shading algorithms, are included within its definition. An extensive comparison is performed between the proposed approach and the traditional homogeneous model, presenting the merits of our approach. Analytical and experimental determination of the computational cost via computer implementation of 3D surface transformation and shading is presented. Point-based methods for the representation, transformation and shading of parametrically defined surfaces are compared to the introduced line-based methods (dual quaternions and dual orthogonal matrices). It is shown that the simplified rendering procedure of 3D objects, is considerably faster using screw theory over the traditional point-based structures.
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    Undersampled Light Field Rendering by a Plane Sweep
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Liu, Yang; Chen, George; Max, Nelson; Hofsetz, Christian; McGuinness, Peter
    Images synthesized by light field rendering exhibit aliasing artifacts when the light field is undersampled; adding new light field samples improves the image quality and reduces aliasing but new samples are expensive to acquire. Light field rays are traditionally gathered directly from the source images, but new rays can also be inferred through geometry estimation. This paper describes a light field rendering approach based on this principle that estimates geometry from the set of source images using multi-baseline stereo reconstruction to supplement the existing light field rays to meet the minimum sampling requirement. The rendering and reconstruction steps are computed over a set of planes in the scene volume, and output images are synthesized by compositing results from these planes together. The planes are each processed independently and the number of planes can be adjusted to scale the amount of computation to achieve the desired frame rate. The reconstruction fidelity (and by extension image quality) is improved by a library of matching templates to support matches along discontinuities in the image or geometry (e.g. object profiles and concavities). Given a set of silhouette images, the visual hull can be constructed and applied to further improve reconstruction by removing outlier matches. The algorithm is efficiently implemented by a set of image filter operations on commodity graphics hardware and achieves image synthesis at interactive rates.
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    Verification of Physically Based Rendering Algorithms
    (The Eurographics Association and Blackwell Publishing Ltd, 2006) Ulbricht, Christiane; Wilkie, Alexander; Purgathofer, Werner
    Within computer graphics, the field of predictive rendering is concerned with those methods of image synthesis that yield results that do not only look real, but are also radiometrically correct renditions of nature, i.e. which are accurate predictions of what a real scene would look like under given lighting conditions.In order to guarantee the correctness of the results obtained by such techniques, three stages of such a rendering system have to be verified with particular care: the light reflection models, the light transport simulation and the perceptually based calculations used at display time.In this report, we will concentrate on the state of the art with respect to the second step in this chain. Various approaches for experimental verification of the implementation of a physically based rendering system have been proposed so far. However, the problem of proving that the results are correct is not fully solved yet, and no standardized methodology is available. We give an overview of existing literature, discuss the strengths and weaknesses of the described methods and illustrate the unsolved problems. We also briefly discuss the related issue of image quality metrics.