Volume 20 (2001)

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On-the-Fly Processing of Generalized Lumigraphs
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Schirmacher, Hartmut; Ming, Li; Seidel, Hans-Peter
We introduce a flexible and powerful concept for reconstructing arbitrary views from multiple source images on the fly. Our approach is based on a Lumigraph structure with per-pixel depth values, and generalizes the classical two-plane parameterized light fields and Lumigraphs. With our technique, it is possible to render arbitrary views of time-varying, non-diffuse scenes at interactive frame rates, and it allows using any kind of sensor that yields images with dense depth information. We demonstrate the flexibility and efficiency of our approach through various examples.
Adaptive Representation of Specular Light
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Briere, Normand; Poulin, Pierre
Caustics produce beautiful and intriguing illumination patterns. However, their complex behavior makes them difficult to simulate accurately in all but the simplest configurations. To capture their appearance, we present an adaptive approach based upon light beams. Exploiting the coherence between the light rays forming a beam greatly reduces the number of samples required for precise illumination reconstruction. The beams characterize the light distribution due to interactions with specular surfaces in 3D space. They thus allow for the treatment of illumination within single-scattering participating media. A hierarchical structure enclosing the light beams possesses inherent properties to detect efficiently all beams reaching any 3D point, to adapt itself according to illumination effects in the final image, and to reduce memory consumption via caching.
Mesh Optimization for Polygonized Isosurfaces
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Ohtake, Yutaka; Belyaev, Alexander G.
In this paper, we propose a method for improvement of isosurface polygonizations. Given an initial polygonization of an isosurface, we introduce a mesh evolution process initialized by the polygonization. The evolving mesh converges quickly to its limit mesh which provides with a high quality approximation of the isosurface even if the isosurface has sharp features, boundary, complex topology. To analyze how close the evolving mesh approaches its destined isosurface, we introduce error estimators measuring the deviations of the mesh vertices from the isosurface and mesh normals from the isosurface normals. A new technique for mesh editing with isosurfaces is also proposed. In particular, it can be used for creating carving effects.
Eurographics
(Blackwell Publishers Ltd and the Eurographics Association., 2001)
Global Illumination as a Combination of Continuous Random Walk and Finite-Element Based Iteration
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Szirmay-Kalos, Laszlo; Csonka, Ferenc; Antal, Gyorgy
The paper introduces a global illumination method that combines continuous and finite-element approaches, pre-serving the speed of finite-element based iteration and the accuracy of continuous random walks. The basic idea is to decompose the radiance function to a finite-element component that is only a rough estimate and to a difference component that is obtained by Monte-Carlo techniques. Iteration and random walk are handled uniformly in the framework of stochastic iteration. This uniform treatment allows the finite-element component to be built up adap-tively aiming at minimizing the Monte-Carlo component. The method is also suited for interactive walkthrough animation in glossy scenes since when the viewpoint changes, only the small Monte-Carlo component needs to be recomputed.
Why Games Will Be the Preeminent Art Form of the 21stCentury
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Hecker, Chris
Computer games share many artistic and technical characteristics with films of the early 1900s. Games' artistic evolution is hampered by the lack of artistic respect from society at large, and the lack of technical standards that would allow artistic innovation. The same problems affected cinema during its birth. During the early 20th century, film managed to find its way from popular diversion to highly respected art form. Will games follow the same course, or will they be stuck forever in the ghetto of pop culture? What technological and artistic changes need to occur in the medium for games to evolve beyond merely shooting aliens and into an art form worthy of association with painting, music, writing, and film? This talk will pose some of those questions, if not attempt to answer them.
Visibility Driven Rasterization
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Meissner, M.; Bartz, D.; Gunther, R.; Strasser, W.
We present a new visibility driven rasterization scheme that significantly increases the rendering performance of modern graphic subsystems. Instead of rasterizing, texturing, lighting, and depth-testing each individual pixel, we introduce a two-level visibility mask within the rasterization stage which facilitates the removal of groups of pixels and triangles from rasterization and subsequent pipeline stages.Local visibility information is stored within the visibility mask that is updated several times during the generation of a frame. The update can easily be accomplished by extending already available (in hardware) occlusion culling mechanisms (i.e. those of HP and SGI), where it is possible to integrate the additional functionality without any additional delay cycles. In addition to these existing hardware based occlusion culling approaches-which cull only geometry contained in bounding volumes determined as occluded-we are able to significantly accelerate the rendering of the geometry determined as visible. However, our approach does not specifically rely on such occlusion culling hardware.The proposed new rasterization scheme is well suited for hardware implementation, can easily be integrated into low-cost rasterizers, and its scalability can vary upon available chip real estate. Only incremental modifications of modern graphics subsystems are required to achieve a significant improvement in rendering performance.
Hoops: 3D Curves as Conservative Occluders for Cell-Visibility
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Brunet, Pere; Navazo, Isabel; Rossignac, Jarek; Saona-Vazquez, Carlos
Most visibility culling algorithms require convexity of occluders. Occluder synthesis algorithms attempt to construct large convex occluders inside bulky non-convex sets. Occluder fusion algorithms generate convex occluders that are contained in the umbra cast by a group of objects given an area light. In this paper we prove that convexity requirements can be shifted from the occluders to their umbra with no loss of efficiency, and use this property to show how some special non-planar, non-convex closed polylines that we call "hoops" can be used to compute occlusion efficiently for objects that have no large interior convex sets and were thus rejected by previous approaches.
Rapid High Quality Compression of Volume Data for Visualization
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Nguyen, Ky Giang; Saupe, Dietmar
Volume data sets resulting from, e.g., computerized tomography (CT) or magnetic resonance (MR) imaging modalities require enormous storage capacity even at moderate resolution levels. Such large files may require compression for processing in CPU memory which, however, comes at the cost of decoding times and some loss in reconstruction quality with respect to the original data. For many typical volume visualization applications (rendering of volume slices, subvolumes of interest, or isosurfaces) only a part of the volume data needs to be decoded. Thus, efficient compression techniques are needed that provide random access and rapid decompression of arbitrary parts the volume data. We propose a technique which is block based and operates in the wavelet transformed domain. We report performance results which compare favorably with previously published methods yielding large reconstruction quality gains from about 6 to 12 dB in PSNR for a5123 -volume extracted from the Visible Human data set. In terms of compression our algorithm compressed the data 6 times as much as the previous state-of-the-art block based coder for a given PSNR quality.
Haptic Device Control - Will it Fit Standardized Input Models?
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Arnold, D. B.; Day, A. M.; Jennings, V.; Courtenay, A.; Duce, D. A.
Over recent years a wide variety of interaction devices involving haptic feedback have been brought to the market, but they vary widely in terms of input measures recorded. These range from one dimensional input on a haptic feedback steering wheel to a six degree of freedom position and orientation device and further, to assemblies of such devices. On the surface most of the variations can be accommodated logically with standardized input models combining existing logical input devices and haptic feedback processes as acknowledgement/echos. However it is very uncertain whether such a model can adequately model the system requirements for effective haptic feedback.In this paper we review the input models that have developed over the past 20 years and ask "Is it the end of the road for the conceptual model of input incorporated into the early graphics standards and elaborated over the years?" In addition, to highlight the problems of implementation with haptic interaction, we describe a typical application, the simulation of a collision with a virtual wall.
Walk-Through Illustrations: Frame-Coherent Pen-and-Ink Style in a Game Engine
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Freudenberg, Bert; Masuch, Maic; Strothotte, Thomas
In this paper we show how a game engine designed to generate photorealistic images can be extended to produce non-photorealistic and hybrid renditions. We introduce new hardware-based methods to accomplish pen-and-ink illustrations. The combination of the highly optimized processing of a game engine and the use of hardware for NPR algorithms yields real-time animation of pen-and-ink illustrations.The particular advance of this method is that it yields the first real-time, frame-coherent pen-and-ink animations which maintain both tone and texture.
A Dynamic Motion Control Technique for Human-like Articulated Figures
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Oshita, Masaki; Makinouchi, Akifumi
This paper presents a dynamic motion control technique for human-like articulated figures in a physically based character animation system. This method controls a figure such that the figure tracks input motion specified by a user. When environmental physical input such as an external force or a collision impulse are applied to the figure, this method generates dynamically changing motion in response to the physical input. We have introduced comfort and balance control to compute the angular acceleration of the figure's joints. Our algorithm controls the several parts of a human-like articulated figure separetely through the minimum number of degrees-of-freedom. Using this approach, our algorithm simulates realistic human motions at efficient computational cost. Unlike existing dynamic simulation systems, our method assumes that input motion is already realistic, and is aimed at dynamically changing the input motion in real-time only when unexpected physical input is applied to the figure. As such, our method works efficiently in the framework of current computer games.
Horizon Map Capture
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Rushmeier, Holly; Balmelli, Laurent; Bernardini, Fausto
We present a method for computing horizon maps from captured images of a bumpy surface. 1Horizon maps encode surface self-shadowing effects, and can be used with bump or normals maps to realistically render surfaces with small height perturbations. The method does not rely on complete surface reconstruction, and requires only eight captured images as input. In this paper we discuss how shadow information is extrapolated from the eight captured images to compute the horizon map. Our implementation accounts for the noise and uncertainties in physically acquired data.
Antialiasing of Environment Maps
(Blackwell Publishers Ltd and the Eurographics Association., 2001) Schilling, Andreas
Environment maps, like texture maps or any other maps consisting of discretely stored data have to be properly filtered, if they are being resampled in the process of rendering an image. For environment maps, this is especially important, as the sampling rate is subject to extreme changes due to the curvature of the reflecting surfaces. However, for the same reason, the antialiasing is especially difficult to perform, as the sampling rate has to be determined for each pixel. We introduce a method to perform this calculation and determine the parameters for anisotropic filtering of the environment map. Instead of the BRDF, we employ roughness pyramids to account for the properties of the reflecting surface. The principles that are used to perform this antialiasing can be applied for antialiasing reflected textures in general e.g. in ray tracing.
Modeling Stochastic Dynamical Systems for Interactive Simulation
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Reissell, L.-M.; Pai, Dinesh K.
We present techniques for constructing approximate stochastic models of complicated dynamical systems for applications in interactive computer graphics. The models are designed to produce realistic interaction at low cost.We describe two kinds of stochastic models: continuous state (ARX) models and discrete state (Markov chains) models. System identi cation techniques are used for learning the input-output dynamics automatically, from either measurements of a real system or from an accurate simulation. The synthesis of behavior in this manner is several orders of magnitude faster than physical simulation.We demonstrate the techniques with two examples: (1) the dynamics of candle ame in the wind, modeled using data from a real candle and (2) the motion of a falling leaf, modeled using data from a complex simulation. We have implemented an interactive Java program which demonstrates real-time interaction with a realistically behaving simulation of a cartoon candle ame. The user makes the ame animation icker by blowing into a microphone.
Eurographics
(Blackwell Publishers Ltd and the Eurographics Association, 2001)
A High Performance Solver for the Animation of Deformable Objects using Advanced Numerical Methods
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Hauth, Michael; Etzmuss, Olaf
Physically based modelling of deformable objects has become the most popular technique to model textiles, skin or human tissue. The crucial problem in the animation of deformable objects is the solution of the resulting differential equations. Recently fast solutions have been presented. In this work we will first give a theoretical analysis and then exploit special properties of the system and advanced numerical techniques to achieve further speed-ups of the simulations. Also, higher accuracy, leading to higher quality animations, will be achieved and an error bound is enforced.
Triangle Strip Compression
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Isenburg, Martin
In this paper we introduce a simple and efficient scheme for encoding the connectivity and the stripification of a triangle mesh. Since generating a good set of triangle strips is a hard problem, it is desirable to do this just once and store the computed strips with the triangle mesh. However, no previously reported mesh encoding scheme is designed to include triangle strip information into the compressed representation. Our algorithm encodes the stripification and the connectivity in an interwoven fashion, that exploits the correlation existing between the two.
An Adaptive Method for Indirect Illumination Using Light Vectors
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Serpaggi, Xavier; Peroche, Bernard
In computer graphics, several phenomema need to be taken into account when it comes to the field of photo-realism. One of the most relevant is obviously the notion of global, and more precisely indirect, illumination. In "classical" ray-tracing if you are not under the light, then you are in a shadow. A great amount of work has been carried out which proposes ray-tracing based solutions to take into account the fact that "there is a certain amount of light in shadows". All of these methods carry the same weaknesses: high computation time and a lot of parameters you need to manage to get something out of the method. This paper proposes a generic computation method of indirect illumination based on Monte Carlo sampling and on the sequential analysis theory, which is faster and more automatic than classical methods.
Editorial
(Blackwell Publishers Ltd and the Eurographics Association., 2001)

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