EG2002

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3D Scanning Technology: Capabilities and Issues
(Eurographics Association, 2002) Scopigno, Roberto
The recent evolution of graphics technology makes it possible to manage very complex models on inexpensive platforms. These impressive rendering capabilities should be paired with detailed and accurate digital models. The construction of high quality 3D models is made easier by the increasing diffusion of automatic 3D measuring devices (often called 3D scanners). These allow to build highly accurate models of real 3D objects in a cost- and time-effective manner. The talk will present the capabilities of this technology focusing mainly on a particular application context: the acquisition of Cultural Heritage artifacts. The peculiar requirements of this domain (high accuracy in the acquisition of both shape and surface appearance, expected low cost and easiness of use of the tools) make it a perfect application example. This talk aims also at presenting and discussing the main issues in the acquisition of accurate 3D models, together with some limitations of current hardware and software tools. Some examples of the results of current projects will be shown.
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.
Interactive Visualization with Programmable Graphics Hardware
(Eurographics Association, 2002) Ertl, Thomas
One of the main scientific goals of visualization is the development of algorithms and appropriate data models which facilitate interactive visual analysis and direct manipulation of the increasingly large data sets which result from simulations running on massive parallel computer systems, from measurements employing fast highresolution sensors, or from large databases and hierarchical information spaces. This task can only be achieved with the optimization of all stages of the visualization pipeline: filtering, compression, and feature extraction of the raw data sets, adaptive visualization mappings which allow the users to choose between speed and accuracy, and exploiting new graphics hardware features for fast and high-quality rendering. The recent introduction of advanced programmability in widely available graphics hardware has already led to impressive progress in the area of volume visualization. However, besides the acceleration of the final rendering, flexible graphics hardware is increasingly being used also for the mapping and filtering stages of the visualization pipeline, thus giving rise to new levels of interactivity in visualization applications. The talk will present recent results of applying programmable graphics hardware in various visualization algorithms covering volume data, flow data, terrains, NPR rendering, and distributed and remote applications.
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.
Multi-dimensional and Multi-scale Visualizer of Large XML Documents
(Eurographics Association, 2002) Jacquemin, Christian; Jardino, Michele
3D-XV (3-Dimensional XML Visualizer) is an interactive graphical interface for accessing large structured documents. It relies on a geometrical model that combines a sequential organization and a hierarchical structure. In the overview mode, the user can access information through natural language queries. In the browsing mode, the content of the paragraphs is displayed in a moving walkway fashion. The model is compared with previous studies on document visualization for passage retrieval. The merits of interactive 3D manipulation through the intuitively oriented 3D-XV geometrical model are outlined.
Tutorial on Inhabited Virtual Heritage
(Eurographics Association, 2002) Magnenat-Thalmann, Nadia; Chalmers, Alan; Fua, Pascal; Thalmann, Daniel
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SAVANT: A new efficient approach to generating the visual hull
(Eurographics Association, 2002) Lyons, Alex; Kotcheff, Aaron
We present a new approach to generating a boundary representation (a polygonal mesh) of the visual hull from a set of silhouettes of an object taken from known camera positions. The approach uses spatial subdivision to compute the positions of vertices and then traverses the vertices around planar faces to produce a facetted representation of the visual hull. We show that, unlike standard approaches, the method is practical even for a large number of complex silhouettes. It is applicable to any 3D modeling system that uses the “shape-from-silhouette” approach to generating 3D models of objects. The approach can also be extended to efficiently compute polygonal mesh representations of the intersection of a set of arbitrary polyhedral models. This extends its applicability to CAD systems.
Interactive Polygonisation for Function-based Modelling
(Eurographics Association, 2002) Sourin, Alexei; Levinski, Konstantin
This paper addresses interactive function-based shape modelling. Interactive modification of the function model with concurrent visualization of the respective polygonal mesh lets us provide both the interactivity and any required level of detail leading to photo-realistic appearance of the resulting shapes. We have proposed an interactive visualisation method capable of handling local shape modifications with any desired precision. We illustrate the implementation of the proposed visualisation method on the example of the interactive function-based artistic shape modelling.
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.
Mesh Decimation for Displacement Mapping
(Eurographics Association, 2002) Collins, Gordon; Hilton, Adrian
We present a mesh decimation algorithm for triangular meshes. Unlike other decimation algorithms we are not concerned with geometric error but with the existence of a displacement mapping which can map between the original and decimated meshes. We use the implicit function theorem to derive a condition which ensures the existence of a displacement map. The algorithm is applied to some standard scanned models and reduction rates around 99% are seen.
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.
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.
Frame-Coherent Stippling
(Eurographics Association, 2002) Meruvia Pastor, Oscar E.; Strothotte, Thomas
Stippling is an artistic rendering technique where shading and texture is given by placing points or stipples on the canvas until the desired darkness is achieved. Computer-generated stippling has focused on producing high quality 2D renditions for print media, while stippling of 3D models in animation has received little attention. In this paper we present a technique to produce frame-coherent animations of 3D models using stippling as a rendering style. The problem for which we provide a solution is how to obtain an even distribution of stipples and at the same time ensure frame-to-frame coherence while shading changes over time. In our approach, particles are placed on the surface of the 3D model and adaptively rendered as stipples using OpenGL point primitives and the input model as a canvas. At each frame, the density of particles can be increased if necessary. Selection of particles during rendering takes into account the screen space projection of the edges of a polygon fan that surrounds the particles and the desired tone at the position of the particles. The rendering technique presented here can be applied to arbitrary polygonal meshes and can be extended to include grey scale textures, bump mapping and custom illumination models.
View Interpolation for Dynamic Scenes
(Eurographics Association, 2002) Xiao, Jiangjian; Rao, Cen; Shah, Mubarak
This paper describes a novel technique for synthesizing a dynamic scene from two images without the use of a 3D model. A scene containing rigid or non-rigid objects, in which each object can move in any orientation or direction, is considered. It is shown that such a scene can be converted into several equivalent static scenes, where each scene only includes one rigid object. Our method can generate a series of continuous and realistic intermediate views from only two reference images without 3D knowledge. The procedure consists of three main steps: segmentation, morphing and postwarping. The key frames are first segmented into several layers. Each layer can be realistically morphed after determining its fundamental matrix. Based on the decomposition of 3D rotation matrix, an optimized and unique postwarping path is automatically determined by the least distortion method and boundary connection constraint. Finally, four experiments, which include morphing of a rotating rigid object in presence of occlusion and morphing of non-rigid objects (human), are demonstrated.
Texturing Calibrated Head Model from Images
(Eurographics Association, 2002) Lempitsky, Victor; Ivanov, Denis; Kuzmin, Yevgeniy
In this paper we address a well-known problem of producing an animated model of a human head from a pair of orthogonal photographs and present a new technique of generating consistent high-quality texture for a polygonal 3D mesh which represents a personalized 3D head. The described technique is based on a combination of two different approaches to this problem and significantly extends them in order to produce optimal image in terms of minimizing visual artifacts and keeping level of details as high as possible. After a brief introduction to the complete calibration pipeline that we have used, we describe the stages of texture generation procedure, which consists of indexing available photographs with texture coordinates, finding optimal merging lines and balancing visual differences to allow for seamless merging while preserving high-frequency details. The presented technique has been evaluated within head animation software and demonstrated its ability of yielding high-quality textured model from photographs.
Eurographics 2002 - Presentation of European Groups doing Computer Graphics Research
(Eurographics Association, 2002)
This brochure contains a concentrated description of many European Computer Graphics research labs. It was produced to accompany a track of lab presentations at the annual conference Eurographics’2002 in Saarbrücken in September 2002. European CG researchers were invited through the call for participation to present their research unit to a broader audience, including the readers of this booklet. In addition we have invited the leaders of the most active labs personally to send their contributions. We believe that only relatively few important CG institutes and research organisations are missing, and that this brochure therefore gives a nice overview of what is going on in Europe in Computer Graphics. Most of the labs collected in this brochure presented themselves with a short talk during the conference, often given by their heads in person, and participants had the oportunity to ask a few rather organisational questions.
Real-time 3D Deformations by Means of Compactly Supported Radial Basis Functions
(Eurographics Association, 2002) Kojekine, Nikita; Savchenko, Vladimir; Senin, Mikhail; Hagiwara, Ichiro
We present an approach to real-time animation of deformable objects. Optimization of algorithms using compactly supported radial basis functions (CSRBF) allows us to generate deformations performed fast enough for such real-time applications as computer games. The algorithm described in detail in this paper uses space mapping technique. Smooth local deformations of animation objects can be defined by only a moderate number of control vectors and locality of deformations can be defined by radius of support. We also present examples of animations and speed benchmarks.
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.
From Textual Chats to Interest Groups in 3D Virtual Space
(Eurographics Association, 2002) Masa, Michal; Zara, Jiri
While the textual chat is a highly popular tool for various kinds of social interactions, its extension to the visual three-dimensional domain remains almost untouched and without practical utilization yet. This paper discusses advantages and disadvantages of spatial virtual environment when used as a platform for connecting people and serving for social and cultural interaction. The differences between textual chat and interest groups in virtual reality are highlighted with the aim to overcome the gap between well-established chat technology and promising but still a bit exotic virtual reality approach. Theoretical analysis is followed by several examples taken from experimental setup.
Tone Reproduction and Physically Based Spectral Rendering
(Eurographics Association, 2002) Devlin, Kate; Chalmers, Alan; Wilkie, Alexander; Purgathofer, Werner
The ultimate aim of realistic graphics is the creation of images that provoke the same responses that a viewer would have to a real scene. This STAR addresses two related key problem areas in this effort which are located at opposite ends of the rendering pipeline, namely the data structures used to describe light during the actual rendering process, and the issue of displaying such radiant intensities in a meaningful way. The interest in the first of these subproblems stems from the fact that it is common industry practice to use RGB colour values to describe light intensity and surface reflectancy. While viable in the context of methods that do not strive to achieve true realism, this approach has to be replaced by more physically accurate techniques if a prediction of nature is intended. The second subproblem is that while research into ways of rendering images provides us with better and faster methods, we do not necessarily see their full effect due to limitations of the display hardware. The low dynamic range of a standard computer monitor requires some form of mapping to produce images that are perceptually accurate. Tone reproduction operators attempt to replicate the effect of real-world luminance intensities. This STAR report will review the work to date on spectral rendering and tone reproduction techniques. It will include an investigation into the need for spectral imagery synthesis methods and accurate tone reproduction, and a discussion of major approaches to physically correct rendering and key tone mapping algorithms. The future of both spectral rendering and tone reproduction techniques will be considered, together with the implications of advances in display hardware.

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