24-Issue 4
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Item Practical CFD Simulations on Programmable Graphics Hardware using SMAC(The Eurographics Association and Blackwell Publishing Ltd., 2005) Scheidegger, Carlos E.; Comba, Joao L. D.; Da Cunha, Rudnei D.The explosive growth in integration technology and the parallel nature of rasterization-based graphics APIs (Application Programming Interface) changed the panorama of consumer-level graphics: today, GPUs (Graphics Processing Units) are cheap, fast and ubiquitous. We show how to harness the computational power of GPUs and solve the incompressible Navier-Stokes fluid equations significantly faster (more than one order of magnitude in average) than on CPU solvers of comparable cost. While past approaches typically used Stam s implicit solver, we use a variation of SMAC (Simplified Marker and Cell). SMAC is widely used in engineering applications, where experimental reproducibility is essential. Thus, we show that the GPU is a viable and affordable processor for scientific applications. Our solver works with general rectangular domains (possibly with obstacles), implements a variety of boundary conditions and incorporates energy transport through the traditional Boussinesq approximation. Finally, we discuss the implications of our solver in light of future GPU features, and possible extensions such as three-dimensional domains and free-boundary problems.Item Editorial(The Eurographics Association and Blackwell Publishing Ltd., 2005) Duke, David; Scopigno, RobertoItem 26th EUROGRAPHICS General Assembly(The Eurographics Association and Blackwell Publishing Ltd., 2005)Item 3D Posture Reconstruction and Human Animation from 2D Feature Points(The Eurographics Association and Blackwell Publishing Ltd., 2005) Zhao, Jianhui; Li, Ling; Chee Keong, KwohAn optimal approach is proposed in this paper for posture reconstruction and human animation from 2D feature points extracted from the monocular images containing human motions. Biomechanical constraints are encoded in every joint of the adopted 3D skeletal human model to make sure that each state of the joints represents a physically valid posture. Size of the human model is adjusted to be consistent with the human figure represented by feature points. Energy Function is defined to represent the residuals between the extracted 2D feature points and the corresponding features resulted from projection of the 3D human model. Local Adjustment and Global Adjustment procedures are proposed to place the joints and body segments into proper locations and orientations in 3D space to create the posture with the minimum value of Energy Function. To find the optimal solution of the ill-posed recovery problem from 2D to 3D, Genetic Algorithm is employed in the high-dimensional parameter space by considering all the parameters simultaneously. Smooth and continuous changes between consecutive frames are considered in development of the human animation procedure. The proposed approach produces optimal reconstruction results of any possible human postures and movements. It is different from classical kinematics and dynamics formulations, and is an attempt to bridge the gap between computer vision and computer animation in human motion study.Item Algorithms for Interactive Editing of Level Set Models(The Eurographics Association and Blackwell Publishing Ltd., 2005) Museth, Ken; Breen, David E.; Whitaker, Ross T.; Mauch, Sean; Johnson, DavidLevel set models combine a low-level volumetric representation, the mathematics of deformable implicit surfaces and powerful, robust numerical techniques to produce a novel approach to shape design. While these models offer many benefits, their large-scale representation and numerical requirements create significant challenges when developing an interactive system. This paper describes the collection of techniques and algorithms (some new, some pre-existing) needed to overcome these challenges and to create an interactive editing system for this new type of geometric model. We summarize the algorithms for producing level set input models and, more importantly, for localizing/minimizing computation during the editing process. These algorithms include distance calculations, scan conversion, closest point determination, fast marching methods, bounding box creation, fast and incremental mesh extraction, numerical integration and narrow band techniques. Together these algorithms provide the capabilities required for interactive editing of level set models.Item Parametric Generation of Facial Expressions Based on FACS(The Eurographics Association and Blackwell Publishing Ltd., 2005) Wojdel, A.; Rothkrantz, L. J. M.This paper presents a parametric performance-based model for facial animation that was inspired by Facial Action Coding System (FACS) developed by P. Ekman and F. W. Friesen. The FACS consists of 44 Action Units (AUs) corresponding to visual changes on the face. Additionally, predefined co-occurrence rules describe how different AUs influence each other. In our model, each facial animation parameter corresponds to one of the AUs as defined in FACS. Implementation of the model is completed with methods for accumulating displacement from separate AUs together, and fuzzy-logical adaptation of co-occurrence rules from the FACS. We also describe the method for adapting our model to a specific person.Item New EUROGRAPHICS Fellows(The Eurographics Association and Blackwell Publishing Ltd., 2005)Item Approximation of a Variable Density Cloud of Points by Shrinking a Discrete Membrane(The Eurographics Association and Blackwell Publishing Ltd., 2005) Esteve, Jordi; Brunet, Pere; Vinacua, AlvarThis paper describes a method to obtain a closed surface that approximates a general 3D data point set with nonuniform density. Aside from the positions of the initial data points, no other information is used. Particularly, neither the topological relations between the points nor the normal to the surface at the data points are needed. The reconstructed surface does not exactly interpolate the initial data points, but approximates them with a bounded maximum distance. The method allows one to reconstruct closed surfaces with arbitrary genus and closed surfaces with disconnected shells.Item A Survey of Inverse Surface Design From Light Transport Behavior Specification(The Eurographics Association and Blackwell Publishing Ltd., 2005) Patow, Gustavo; Pueyo, XavierInverse surface design problems from light transport behavior specification usually represent extremely complex and costly processes, but their importance is well known. In particular, they are very interesting for lighting and luminaire design, in which it is usually difficult to test design decisions on a physical model in order to avoid costly mistakes. In this survey, we present the main ideas behind these kinds of problems, characterize them, and summarize existing work in the area, revealing problems that remain open and possible areas of further research.Item A Family of Inexpensive Sampling Schemes(The Eurographics Association and Blackwell Publishing Ltd., 2005) Hasselgren, Jon; Akenine-Moeller, Tomas; Laine, SamuliTo improve image quality in computer graphics, antialiazing techniques such as supersampling and multisampling are used. We explore a family of inexpensive sampling schemes that cost as little as 1.25 samples per pixel and up to 2.0 samples per pixel. By placing sample points in the corners or on the edges of the pixels, sharing can occur between pixels, and this makes it possible to create inexpensive sampling schemes. Using an evaluation and optimization framework, we present optimized sampling patterns costing 1.25, 1.5, 1.75 and 2.0 samples per pixel.Item Author Index Volume 24 (2005)(The Eurographics Association and Blackwell Publishing Ltd., 2005)Item REPORT OF THE STATUTORY AUDITORS TO THE GENERAL MEETING OF THE MEMBERS OF EUROGRAPHICS ASSOCIATION GENEVA(The Eurographics Association and Blackwell Publishing Ltd., 2005)Item Adaptive Deformable Models for Graphics and Vision(The Eurographics Association and Blackwell Publishing Ltd., 2005) Goldenstein, Siome; Vogler, Christian; Velho, LuizDeformable models are a powerful tool in both computer graphics and computer vision. The description and implementation of the deformations have to be simultaneously flexible and powerful, otherwise the technique may not satisfy the requirements of all the distinct applications. In this paper, we introduce a new method for the deformable model specification: deformable fields. Deformable fields are conceptually simple, lead to an easy implementation, and are suitable for adaptive models. We apply our new technique to describe an adaptive deformable face, and compare three different adaptation strategies. We show how our technique is suitable to describe different individuals, how to construct a model based on information from a single image, and how it allows the tracking of the deformation parameters over a video sequence.Item Constrained Visualization Using the Shepard Interpolation Family(The Eurographics Association and Blackwell Publishing Ltd., 2005) Brodlie, K. W.; Asim, M. R.; Unsworth, K.This paper discusses the problem of visualizing data where there are underlying constraints that must be preserved. For example, we may know that the data are inherently positive. We show how the Modified Quadratic Shepard method, which interpolates scattered data of any dimensionality, can be constrained to preserve positivity. We do this by forcing the quadratic basis functions to be positive. The method can be extended to handle other types of constraints, including lower bound of 0 and upper bound of 1-as occurs with fractional data. A further extension allows general range restrictions, creating an interpolant that lies between any two specified functions as the lower and upper bounds.Item Siggraph 2005 Los Angeles, California, 31st July-4th August 2005(The Eurographics Association and Blackwell Publishing Ltd., 2005) Laycock, S.D.; Laycock, R.G.; Day, A.M.