Issue 3

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https://diglib.eg.org/handle/10.2312/101

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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.
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.
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.
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.
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.
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.
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.
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.
The Synthesis of Rock Textures in Chinese Landscape Painting
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Way, Der-Lor; Shih, Zen-Chung
In Chinese landscape painting, rock textures portray the orientation of mountains and contribute to the atmosphere. Many landscape-painting skills are required according to the type of rock. Landscape painting is the major theme of Chinese painting. Over the centuries, masters of Chinese landscape painting developed various texture strokes. Hemp-fiber and axe-cut are two major types of texture strokes. A slightly sinuous and seemingly broken line, the hemp-fiber stroke is used for describing the gentle slopes of rock formations whereas the axe-cut stroke best depicts hard, rocky surfaces. This paper presents a novel method of synthesizing rock textures in Chinese landscape painting, useful not only to artists who want to paint interactively, but also in automated rendering of natural scenes. The method proposed underwrites the complete painting process after users have specified only the contour and parameters.
Integrating Behavioural Animation Techniques
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Monzani, Jean-Sebastien; Caicedo, Angela; Thalmann, Daniel
Our research focuses on animating autonomous virtual humans which are able to take decisions by themselves. We especially address in this paper the technical problem of integrating altogether the physical simulation of agents (represented as virtual humans in a 3D environment) and their behaviours and motivations, driven by a Beliefs, Desires and Intentions architecture. We also explain how goals drive plans, and how an agent can coherently handle concurrent tasks.
Reflective Interaction in Virtual Environments
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Lane, JRT; Lalioti, V.
The proliferation of projection-based systems in recent years resulted in a variety of specialised interaction techniques that make Virtual Environments a better man machine interface. However, the success of these techniques and metaphors is directly linked to the interaction and tracking devices used in their implementation. Users find that devices such as the data glove, stylus or joystick can be expensive and cumbersome especially for the inexperienced. A variety of approaches exist that make use of computer vision for tracking gestures or for achieving wireless interaction. Typically these approaches involve the use of a two- camera pair, or a stereoscopic camera.Our approach uses only one camera and one or more reflective surfaces, to effectively and accurately calculate 3D information. The calibration time is minimal and it allows for a very flexible positioning of the camera and reflecting surfaces. Wireless interaction and natural interaction metaphors in the user's physical space can be created using our method. The method can be combined easily and effectively with projection-based systems as well as with standard and stereoscopic monitors, or extended for the use in augmented spaces. It is an inexpensive method that uses commonly available hardware and therefore its application areas as an interaction and tracking device, include games and use of virtual environments in education. In this paper, we describe the method and its use as an interaction device in two applications, and conclude with a discussion on its advantages and limitations.
Accurate and Fast Proximity Queries Between Polyhedra Using Convex Surface Decomposition
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Ehmann, Stephen A.; Lin, Ming C.
The need to perform fast and accurate proximity queries arises frequently in physically-based modeling, simulation, animation, real-time interaction within a virtual environment, and game dynamics. The set of proximity queries include intersection detection, tolerance verification, exact and approximate minimum distance computation, and (disjoint) contact determination. Specialized data structures and algorithms have often been designed to perform each type of query separately. We present a unified approach to perform any of these queries seamlessly for general, rigid polyhedral objects with boundary representations which are orientable 2-manifolds. The proposed method involves a hierarchical data structure built upon a surface decomposition of the models. Furthermore, the incremental query algorithm takes advantage of coherence between successive frames. It has been applied to complex benchmarks and compares very favorably with earlier algorithms and systems.
Texture Mapping with Hard Constraints
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Eckstein, Ilya; Surazhsky, Vitaly; Gotsman, Craig
We show how to continuously map a texture onto a 3D triangle mesh when some of the mesh vertices are constrained to have given (u, v) coordinates. This problem arises frequently in interactive texture mapping applications and, to the best of our knowledge, a complete and efficient solution is not available. Our techniques always guarantee a solution by introducing extra (Steiner) vertices in the triangulation if needed. We show how to apply our methods to texture mapping in multi-resolution scenarios and image warping and morphing.
Are Points the Better Graphics Primitives?
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Gross, Markus
Since the early days of graphics the computer based representation of three-dimensional geometry has been one of the core research fields. Today, various sophisticated geometric modelling techniques including NURBS or implicit surfaces allow the creation of 3D graphics models with increasingly complex shape. In spite of these methods the triangle has survived over decades as the king of graphics primitives meeting the right balance between descriptive power and computational burden. As a consequence, today's consumer graphics hardware is heavily tailored for high performance triangle processing. In addition, a new generation of geometry processing methods including hierarchical representations, geometric filtering, or feature detection fosters the concept of triangle meshes for graphics modelling.Unlike triangles, points have amazingly been neglected as a graphics primitive. Although being included in APIs since many years, it is only recently that point samples experience a renaissance in computer graphics. Conceptually, points provide a mere discretization of geometry without explicit storage of topology. Thus, point samples reduce the representation to the essentials needed for rendering and enable us to generate highly optimized object representations. Although the loss of topology poses great challenges for graphics processing, the latest generation of algorithms features high performance rendering, point/pixel shading, anisotropic texture mapping, and advanced signal processing of point sampled geometry.This talk will give an overview of how recent research results in the processing of triangles and points are changing our traditional way of thinking of surface representations in computer graphics - and will discuss the question: Are Points the Better Graphics Primitives?
Feature Sensitive Remeshing
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Vorsatz, J.; Rossl, C.; Kobbelt, L. P.; Seidel, H.-P.
Remeshing artifacts are a fundamental problem when converting a given geometry into a triangle mesh. We propose a new remeshing technique that is sensitive to features. First, the resolution of the mesh is iteratively adapted by a global restructuring process which additionally optimizes the connectivity. Then a particle system approach evenly distributes the vertices across the original geometry. To exactly find the features we extend this relaxation procedure by an effective mechanism to attract the vertices to feature edges. The attracting force is imposed by means of a hierarchical curvature field and does not require any thresholding parameters to classify the features.
Drawing for Illustration and Annotation in 3D
(Blackwell Publishers Ltd and the Eurographics Association, 2001) Bourguignon, David; Cani, Marie-Paule; Drettakis, George
We present a system for sketching in 3D, which strives to preserve the degree of expression, imagination, and simplicity of use achieved by 2D drawing. Our system directly uses user-drawn strokes to infer the sketches representing the same scene from different viewpoints, rather than attempting to reconstruct a 3D model. This is achieved by interpreting strokes as indications of a local surface silhouette or contour. Strokes thus deform and disappear progressively as we move away from the original viewpoint. They may be occluded by objects indicated by other strokes, or, in contrast, be drawn above such objects. The user draws on a plane which can be positioned explicitly or relative to other objects or strokes in the sketch. Our system is interactive, since we use fast algorithms and graphics hardware for rendering. We present applications to education, design, architecture and fashion, where 3D sketches can be used alone or as an annotation of an existing 3D model.

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