EG2002

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https://diglib.eg.org/handle/10.2312/228

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A Convolution-Based Algorithm for Animated Water Waves
(Eurographics Association, 2002) Loviscach, Jörn
A non-linear partial differential equation solver is too sophisticated for computer graphics applications if they are only used to render effects like circular waves and ship wakes. We present an approach which simulates waves through a convolution algorithm. It handles both gravity waves and capillary waves; the latter are often neglected even though they dominate small-scale behavior. The algorithm can be integrated into a complete solution architecture: First, standard commercial 3-D software is used to prepare an animated scene with objects traveling on a water surface. Based on the movements of these objects, waves are calculated and added as bump and displacement maps to the 3-D model.
Improved Integration for Cloth Simulation
(Eurographics Association, 2002) Parks, David L.; Forsyth, David A.
Most methods of cloth simulation produce animations that do not move very freely; the result often looks like the material is “swimming”. The primary sources of this phenomenon are the non-physical dissipation terms often added to the mechanics to ensure stability in the simulation, and the numerical damping that is implicit in the choice of ODE integration schemes. By disposing of the additional dissipation terms and choosing a new integrator, the generalized-a method, that was designed to safely integrate mechanical systems with extraneous high-frequency signals in their temporal component, we obtain more realistic results often with the about the same amount of computation.
The Voronoi-Quadtree: construction and visualization
(Eurographics Association, 2002) Coll, Narcís; Boada, Imma; Sellares, J.A.
We define a quadtree-based planar Voronoi diagram codification, the Voronoi-Quadtree, valid for generalized sites (points, line-segments, curve-arc segments, ...) and for different distance functions (Euclidean metrics, convex distance functions, ...).We present an algorithm for constructing, at a prefixed level of detail, the Voronoi-Quadtree associated to a Voronoi diagram determined by a set of sites and a given distance function. A second algorithm that, taking as input a Voronoi-Quadtree, visualizes a polygonal approximation of the boundary of the Voronoi diagram is also described.
Point Based Computer Graphics
(Eurographics Association, 2002) Gross, Markus; Pfister, Hanspeter; Zwicker, Matthias; Pauly, Mark; Stamminger, Marc; Alexa, Marc
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Global Illumination for Interactive Applications and High-Quality Animations
(Eurographics Association, 2002) Damez, Cyrille; Dmitriev, Kirill; Myszkowski, Karol
One of the main obstacles to the use of global illumination in image synthesis industry is the considerable amount of time needed to compute the lighting for a single image. Until now, this computational cost has prevented its widespread use in interactive design applications as well as in computer animations. Several algorithms have been proposed to address these issues. In this report, we present a much needed survey and classification of the most up-to-date of these methods. Roughly, two families of algorithms can be distinguished. The first one aims at providing interactive feedback for lighting design applications. The second one gives higher priority to the quality of results, and therefore relies on offline computations. Recently, impressive advances have been made in both categories. Indeed, with the steady progress of computing resources and graphics hardware, and the current trend of new algorithms for animated scenes, common use of global illumination seems closer than ever.
An Image-Based Radiosity Representation
(Eurographics Association, 2002) Mertens, Tom; Van Reeth, Frank
We present a geometry-independent radiosity representation which stems from image-based methodologies. Our image-based representation is inspired by the concept of layered depth images. To construct the radiosity function we render shaded depth images and warp them into the representation. This enables us to alter Keller’s instant radiosity algorithm to a view-independent variant, allowing interactive viewing of complex scenes without relighting every frame. Image warping is done on the host CPU, while graphics hardware is exploited for rendering the images. Our approach differs from the traditional finite element methods since no a priori meshing, nor an explicit form factor evaluation needs to be performed. The geometry independence ensures a reliable rendering time and memory usage, which are more dependent on image resolution rather than scene complexity. It also implies that lighting information is decoupled from scene representation, thereby avoiding the restriction to planar surfaces and issues such as discontinuity meshing.
Fast Volume Carving
(Eurographics Association, 2002) Pyo, Soon Hyoung; Shin, Yeong Gil
In recent years, the volumetric scene representation has been widely used in the fields of computer graphics and computer vision. In computer graphics, the representation is used to visualize and reconstruct 3D internal structures of 2D human-body medical data obtained from Magnetic Resonance Imaging (MRI) or Computed Tomography (CT). On the other hand, the volumetric representation is used to model 3D objects from a sequence of 2D images in computer vision. In both cases, eliminating some unnecessary part of the volumetric data is sometimes needed. For example, we need to remove skin or tissue which hides the target organ of human in volume rendering, or empty region of 3D objects being modeled in image-based modeling. In this paper, we propose a fast carving algorithm which can be applied in volume rendering and image-based modeling. The memory usage is minimized by using 1-bit field of a voxel to represent whether the voxel is carved or not. Our experiments show that we can carve out any part of the 5123 volume data in about a second. The carving speed is not affected by the complexity of objects.
Normal Enhancement for Interactive Non-photorealistic Rendering
(Eurographics Association, 2002) Cignoni, Paolo; Scopigno, Roberto; Tarini, Marco
We present a simple technique to improve the perception of shape of an object. Bump mapping is well-known in the computer graphics community for providing the impression of small-scale geometrical features (which actually are not there). Here, we propose a similar approach (variation of normals) for the purpose of enhancing perception of the given geometry. Our approach is based on a simple modification of the surface normals in order to enhance the geometric features of the object during the rendering. The enhanced normals produced by this approach can be used in any rendering technique. The technique presented is particularly well suited to improve the rendering of mechanical parts where common cheap shading techniques can often generate shading ambiguities.
Knowledge-Based Representation of Cinematic Expression and its Application to Animation
(Eurographics Association, 2002) Friedman, Doron; Feldman, Yishai
Camera control in virtual environments received growing attention recently, and some of the research turned to cinematography as a source for inspiration. Cinematic knowledge is a highly challenging domain for formalization. We have used a systematic knowledge-based approach for knowledge acquisition and formalized expert knowledge in the form of fine-grained rules. Given a screenplay, the rules interact to suggest a solution by symbolic constraint propagation and truth maintenance. We have implemented a prototype system that accepts screenplays in a formal language and generates editing decisions, based on a cinematic knowledge base. If the system is provided with 3D meshes and animations corresponding to the actions and objects mentioned in the screenplay, the system generates a 3D animation clip for the screenplay, based on its editing decisions. The system can be equipped with cinematic principles from various genres, and shows how complex cinematic phenomena can emerge from the interaction of simple rules.
Reverse Diffusion for Smooth Buildup of Progressivly Transmitted Geometry
(Eurographics Association, 2002) Buelow, Thomas
In this paper we consider 3D object surfaces which can be represented as scalar functions defined on the sphere. These objects can be modeled as series of spherical harmonic functions. A simple progressive transmission scheme could be implemented which transmits the expansion coefficients one by one and thus implements a coarse to fine reconstruction. The buildup of the object according to this scheme is not completely smooth: Wavy patterns appear which disappear in subsequent stages and are replaced by finer spurious patterns and so on. We propose a remedy for this behavior which is based on the simulation of a reversed diffusion process on the sphere.
View-Dependent Rendering for Polygonal Datasets
(Eurographics Association, 2002) El- Sana, Jihad; De Floriani, Leila; Puppo, Enrico; Shamir, Arik
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Visual Data Mining
(Eurographics Association, 2002) Keim, Daniel A.; Müller, Wolfgang; Schumann, Heidrun
Never before in history has data been generated at such high volumes as it is today. Exploring and analyzing the vast volumes of data has become increasingly difficult. Information visualization and visual data mining can help to deal with the flood of information. The advantage of visual data exploration is that the user is directly involved in the data mining process. There are a large number of information visualization techniques that have been developed over the last two decades to support the exploration of large data sets. In this star report, we provide an overview of information visualization and visual data mining techniques, and illustrate them using a few examples.
Real-Time Animated Grass
(Eurographics Association, 2002) Bakay, Brook; Lalonde, Paul; Heidrich, Wolfgang
We present a simple method to render fields of grass, animated in the wind, in real-time. The technique employs vertex shaders to render displacement maps with Russian-doll style transparent shells. Animation is achieved by translating the surface according to a local wind vector while preserving the length of the blades of grass. This technique achieves convincing results on current consumer graphics hardware and can be applied to other similar surfaces such as hair and fur.
Distance fields applied to character animation
(Eurographics Association, 2002) Rudomin, Isaac; Castillo, J.
A general hybrid geometric-physical method that is useful for animating characters with skin, clothing and a MPEG-4 compatible face is presented. This method uses an approximation to the underlying musculo-skeletal structure of the body and face to generate a distance field, used for collision detection purposes, and skin/clothing consisting of a particle-spring mesh. The results obtained deliver animation with plausible dynamics for fairly detailed models at around 60fps on a PIII computer with Nvidia Gforce2 graphics. The main contribution is to show that similar algorithms can be used for skin, clothing and facial animation, at interactive rates.
Interactive High-Quality Volume Rendering with Flexible Consumer Graphics Hardware
(Eurographics Association, 2002) Engel, Klaus; Ertl, Thomas
Recently, the classic rendering pipeline in 3D graphics hardware has become flexible by means of programmable geometry engines and rasterization units. This development is primarily driven by the mass market of computer games and entertainment software, whose demand for new special effects and more realistic 3D environments induced a reconsideration of the once static rendering pipeline. Besides the impact on visual scene complexity in computer games, these advances in flexibility provide an enormous potential for new volume rendering algorithms. Thereby, they make yet unseen quality as well as improved performance for scientific visualization possible and allow to visualize hidden features contained within volumetric data. The goal of this report is to deliver insight into the new possibilities that programmable state-of-the-art graphics hardware offers to the field of interactive, high-quality volume rendering. We cover different slicing approaches for texture-based volume rendering, non-polygonal iso-surfaces, dot-product shading, environment-map shading, shadows, pre- and post-classification, multi-dimensional classification, high-quality filtering, pre-integrated classification and pre-integrated volume rendering, large volume visualization and volumetric effects.
3D Data Acquisition
(Eurographics Association, 2002) Scopigno,Roberto; Andujar, Carlos; Goesele,Michael; Lensch, Hendrik P. A.
3D scanners and image acquisition systems are rapidly becoming more affordable and allow to build highly accurate models of real 3D objects in a cost- and time-effective manner. This tutorial will present the potential of this technology, review the state of the art in model acquisition methods, and will discuss the 3D acquisition pipeline from physical acquisition until the final digital model. First, different scanning techniques such as time-of-flight or structured light approaches will briefly be presented. Other acquisition related issues including the design of the scanning studio will be discussed and evaluated. In the area of registration, we will consider both the problems of initially aligning individual scans, and of refining this alignment with variations of the Iterative Closest Point method. For scan integration and mesh reconstruction, we will compare various methods for computing interpolating and approximating surfaces. We will then look at various ways in which surface properties such as color and reflectance can be extracted from acquired imagery. Finally, we will examine techniques for the efficient management and rendering of very large, attribute-rich meshes, including methods for the construction of simplified triangle-based representation and sample-based rendering approaches.
Artificial Animals and Humans: From Physics to Intelligence
(Eurographics Association, 2002) Terzopoulos, Demetri
The confluence of virtual reality and artificial life, an emerging discipline that spans the computational and biological sciences, has yielded synthetic worlds inhabited by realistic, artificial flora and fauna. Artificial animals are complex synthetic organisms that possess functional biomechanical bodies, sensors, and brains with locomotion, perception, behavior, learning, and cognition centers. Artificial humans and other animals are of interest in computer graphics because they are self-animating characters that dramatically advance the state of the art of production animation and interactive game technologies. More broadly, these biomimetic autonomous agents in their realistic virtual worlds also foster deeper, computationally oriented insights into natural living systems.
Feature interference in free form template matching
(Eurographics Association, 2002) Song, Y.; Vergeest, J. S. M.; Horvath, I.
Template matching is a useful method in the reconstruction of free form surfaces. In this paper, matching of free form surfaces with parameterized templates is studied with the emphasis on feature interference. By their definitions in 3- Dimensional space, free form features are introduced, analyzed and parameterized first. An optimization function based on a Hausdorff-like shape distance measuring method is proposed and applied as measuring method between the digitalized model surface and the parameterized feature template. The proposed method not only can fit isolated free form features, but also works when a feature is interfered by other free form features in some specified conditions. A series of numerical experiments have been conducted to demonstrate the proposed methods based on ACIS and Open Inventor. Fitting strategies are proposed as well.
Flexible bump map capture from video
(Eurographics Association, 2002) Paterson, James Alexander; Fitzgibbon, Andrew W.
We extend recent techniques for the automated capture of surface normal maps or bump maps from real-world material samples. In contrast to recent systems, which have required cumbersome laboratory setups with careful calibration, we propose a moving-camera system which requires only one light source, rigidly attached to the camera. We describe a simple but accurate image-based calibration technique which allows the construction of an approximation to the standard photometric stereo setup. We show how to optimally estimate the system geometry during capture, and demonstrate that the accuracy of the new system is sufficient to allow normals to be computed.
Concise Tour to the Virtual Old Prague
(Eurographics Association, 2002) Zara, Jiri
This paper describes a structure and a user interface of the Internet based 3D presentation of existing historical part of city Prague. The application offers a smooth tour to selected regions of the real city, utilizing number of standard and modern technologies including VRML, Java, and PHP. The architecture of the whole virtual model is presented together with several advanced and specific features like dynamic loading und unloading objects or newly proposed LOD for urban scenes. This running web application seems to be currently unique in terms of complexity, functionality, and scaleability for further growth. The paper introduces methodology suitable for immediate creation of arbitrary virtual city according to a real one.

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