28-Issue 6

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https://diglib.eg.org/handle/10.2312/148

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    Specular Effects on the GPU: State of the Art
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Szirmay-Kalos, Laszlo; Umenhoffer, Tamas; Patow, Gustavo; Szecsi, Laszlo; Sbert, Mateu
    This survey reviews algorithms that can render specular, i.e. mirror reflections, refractions, and caustics on the GPU. We establish a taxonomy of methods based on the three main different ways of representing the scene and computing ray intersections with the aid of the GPU, including ray tracing in the original geometry, ray tracing in the sampled geometry, and geometry transformation. Having discussed the possibilities of implementing ray tracing, we consider the generation of single reflections/refractions, interobject multiple reflections/refractions, and the general case which also includes self-reflections or refractions. Moving the focus from the eye to the light sources, caustic effect generation approaches are also examined.
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    State of the Art in Ray Tracing Animated Scenes
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Wald, Ingo; Mark, William R.; Guenther, Johannes; Boulos, Solomon; Ize, Thiago; Hunt, Warren; Parker, Steven G.; Shirley, Peter
    Ray 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 recently received much attention by researchers and 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 State of the Art Report (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.
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    Table of Contents and Cover
    (The Eurographics Association and Blackwell Publishing Ltd, 2009)
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    New EUROGRAPHICS Fellows
    (The Eurographics Association and Blackwell Publishing Ltd, 2009)
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    30th EUROGRAPHICS General Assembly
    (The Eurographics Association and Blackwell Publishing Ltd, 2009)
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    A Time Model for Time-Varying Visualization
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Wolter, M.; Assenmacher, I.; Hentschel, B.; Schirski, M.; Kuhlen, T.
    The analysis of unsteady phenomena is an important topic for scientific visualization. Several time-dependent visualization techniques exist, as well as solutions for dealing with the enormous size of time-varying data in interactive visualization. Many current visualization toolkits support displaying time-varying data sets. However, for the interactive exploration of time-varying data in scientific visualization, no common time model that describes the temporal properties which occur in the visualization process has been established. In this work, we propose a general time model which classifies the time frames of simulation phenomena and the connections between different time scales in the analysis process. This model is designed for intuitive interaction with time in visualization applications for the domain expert as well as for the developer of visualization tools. We demonstrate the benefits of our model by applying it to two use cases with different temporal properties.
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    Animating Quadrupeds: Methods and Applications
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Skrba, Ljiljana; Reveret, Lionel; Hetroy, Franck; Cani, Marie-Paule; O'Sullivan, Carol
    Films like Shrek, Madagascar, The Chronicles of Narnia and Charlotte s web all have something in common: realistic quadruped animations. While the animation of animals has been popular for a long time, the technical challenges associated with creating highly realistic, computer generated creatures have been receiving increasing attention recently. The entertainment, education and medical industries have increased the demand for simulation of realistic animals in the computer graphics area. In order to achieve this, several challenges need to be overcome: gathering and processing data that embodies the natural motion of an animal - which is made more difficult by the fact that most animals cannot be easily motion-captured; building accurate kinematic models for animals, with adapted animation skeletons in particular; and developing either kinematic or physically-based animation methods, either by embedding some a priori knowledge about the way that quadrupeds locomote and/or adopting examples of real motion. In this paper, we present an overview of the common techniques used to date for realistic quadruped animation. This includes an outline of the various ways that realistic quadruped motion can be achieved, through video-based acquisition, physics based models, inverse kinematics or some combination of the above.
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    2009 Eurographics Symposium on Parallel Graphics and Visualization
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Comba, Joao; Daniel, Weiskopf; Debattista, Kurt
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    Editing Object Behaviour in Video Sequences
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Scholz, Volker; El-Abed, Sascha; Seidel, Hans-Peter; Magnor, Marcus
    While there are various commercial-strength editing tools available today for still images, object-based manipulation of real-world video footage is still a challenging problem. In this system paper, we present a framework for interactive video editing. Our focus is on footage from a single, conventional video camera. By relying on spatio-temporal editing techniques operating on the video cube, we do not need to recover 3D scene geometry. Our framework is capable of removing and inserting objects, object motion editing, non-rigid object deformations, keyframe interpolation, as well as emulating camera motion. We demonstrate how movie shots with moderate complexity can be persuasively modified during post-processing.
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    Biorthogonal Wavelets Based on Interpolatory Subdivision
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Wang, H.; Ma, W.
    This article presents an efficient construction of biorthogonal wavelets built upon an interpolatory subdivision for quadrilateral meshes. The interpolatory subdivision scheme is first turned into a scheme for reversible primitive wavelet synthesis. Some desired properties are then incorporated in the primitive wavelet using the lifting scheme. The analysis and synthesis algorithms of the resulting new wavelet are finally obtained as local and in-place lifting operations. The wavelet inherits the advantage of refinement with added levels of resolution. Numerical experiments show that the lifted wavelet built upon interpolatory, subdivision has sufficient stability and better performance in dealing with closed or open semi-regular quadrilateral meshes compared with other existing wavelets for quadrilateral manifold meshes.
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    Material Space Texturing
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Ray, N.; Levy, B.; Wang, H.; Turk, G.; Vallet, B.
    Many objects have patterns that vary in appearance at different surface locations. We say that these are differences in materials, and we present a material-space approach for interactively designing such textures. At the heart of our approach is a new method to pre-calculate and use a 3D texture tile that is periodic in the spatial dimensions (s, t) and that also has a material axis along which the materials change smoothly. Given two textures and their feature masks, our algorithm produces such a tile in two steps. The first step resolves the features morphing by a level set advection approach, improved to ensure convergence. The second step performs the texture synthesis at each slice in material-space, constrained by the morphed feature masks. With such tiles, our system lets a user interactively place and edit textures on a surface, and in particular, allows the user to specify which material appears at given positions on the object. Additional operations include changing the scale and orientation of the texture. We support these operations by using a global surface parameterization that is closely related to quad re-meshing. Re-parameterization is performed on-the-fly whenever the user s constraints are modified.
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    Filling N-Sided Regions by Quad Meshes for Subdivision Surfaces
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Nasri, A.; Sabin, M.; Yasseen, Z.
    Given an n-sided region bounded by a loop of n polylines, we present a general algorithm to fill such a region by a quad mesh suitable for a subdivision scheme. Typically, the approach consists of two phases: the topological phase and the geometrical phase. In the first part, the connectivity of the mesh is based on determining a partitioning of the region into rectangular subregions across which regular grid could be constructed. The geometrical phase generalizes discrete Coon s patches to position the vertices in the 3D space. The generated mesh could be taken as input to any quad-based subdivision scheme, such as that of Catmull-Clark or Doo-Sabin to generate the corresponding limit surface. The goal of the algorithm is to generate smooth meshes with minimum number and less valence of extraordinary vertices deemed undesirable in such subdivision schemes.
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    COBRA: Compression of the Basis for PCA Represented Animations
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Vasa, L.; Skala, V.
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    Evenly Spaced Streamlines for Surfaces: An Image-Based Approach
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Spencer, Benjamin; Laramee, Robert S.; Chen, Guoning; Zhang, Eugene
    We introduce a novel, automatic streamline seeding algorithm for vector fields defined on surfaces in 3D space. The algorithm generates evenly spaced streamlines fast, simply and efficiently for any general surface-based vector field. It is general because it handles large, complex, unstructured, adaptive resolution grids with holes and discontinuities, does not require a parametrization, and can generate both sparse and dense representations of the flow. It is efficient because streamlines are only integrated for visible portions of the surface. It is simple because the image-based approach removes the need to perform streamline tracing on a triangular mesh, a process which is complicated at best. And it is fast because it makes effective, balanced use of both the CPU and the GPU. The key to the algorithm s speed, simplicity and efficiency is its image-based seeding strategy. We demonstrate our algorithm on complex, real-world simulation data sets from computational fluid dynamics and compare it with object-space streamline visualizations.
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    Education Programme at Eurographics 2009
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Domik, G.; Scateni, R.
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    Visualization of Multi-Variate Scientific Data
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Fuchs, R.; Hauser, H.
    In this state-of-the-art report we discuss relevant research works related to the visualization of complex, multi-variate data. 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 with the aim for a better overview of related approaches. Based on this classification we highlight combinable and hybrid approaches and focus on techniques that potentially lead towards new directions in visualization research. 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.