EG2007

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Shape Analysis for Augmented Topological Shape Descriptor
(The Eurographics Association, 2007) Symonova, Olga; Amicis, Raffaele De; Paolo Cignoni and Jiri Sochor
In this work we propose a scheme for analysis of the shape of a 3D model.We use Extended Reeb Graph to describe the topological structure of the model which we further enrich with extracted geometrical features. The nodes of the graph represent different components of the model, and we propose to analyze their shape separately. Shape characteristics such as taper/enlargement, average curvature, bending are revealed through tracing changes in cross sections of each shape component. Finally the topological structure together with the associated geometrical characteristics represents the shape descriptor of the 3D model.
State of the Art in Ray Tracing Animated Scenes
(The Eurographics Association, 2007) Wald, Ingo; Mark, William R.; Günther, Johannes; Boulos, Solomon; Ize, Thiago; Hunt, Warren; Parker, Steven G.; Shirley, Peter; Dieter Schmalstieg and Jiri Bittner
Ray tracing has long been a method of choice for off-line rendering, but traditionally was too slow for interactive use. With faster hardware and algorithmic improvements this has recently changed, and real-time ray tracing is finally within reach. However, real-time capability also opens up new problems that do not exist in an off-line environment. In particular real-time ray tracing offers the opportunity to interactively ray trace moving/animated scene content. This presents a challenge to the data structures that have been developed for ray tracing over the past few decades. Spatial data structures crucial for fast ray tracing must be rebuilt or updated as the scene changes, and this can become a bottleneck for the speed of ray tracing. This bottleneck has received much recent attention by researchers that has resulted in a multitude of different algorithms, data structures, and strategies for handling animated scenes. The effectiveness of techniques for ray tracing dynamic scenes vary dramatically depending on details such as scene complexity, model structure, type of motion, and the coherency of the rays. Consequently, there is so far no approach that is best in all cases, and determining the best technique for a particular problem can be a challenge. In this STAR, we aim to survey the different approaches to ray tracing animated scenes, discussing their strengths and weaknesses, and their relationship to other approaches. The overall goal is to help the reader choose the best approach depending on the situation, and to expose promising areas where there is potential for algorithmic improvements.
New Trends in 3D Video
(The Eurographics Association, 2007) Theobalt, Christian; Würmlin, Stephan; Aguiar, Edilson de; Niederberger, Christoph; Karol Myszkowski and Vlastimil Havran
3D Video is an emerging and challenging research discipline that lives on the boundary between computer vision and computer graphics. The goal of researchers working in the field is to extract spatio-temporal models of dynamic scenes from multi-video footage in order to display them from user-controlled synthetic perspectives. 3D Video technology has the potential to lay the algorithmic foundations for a variety of intriguing new applications. This includes stunning novel visual effects for movies and computer games, as well as, facilitating the entire movie production pipeline by enabling virtual rearranging of cameras and lighting during post-processing. Furthermore, 3D Video processing will revolutionize visual media by enabling 3D TV and movies with interactive viewpoint control, or by enabling virtual fly-arounds during sports-broadcasts. To achieve this purpose, several challenging problems from vision and graphics have to be solved simultaneously. The speakers in this course will explain the foundations of dynamic scene acquisition, dynamic scene reconstruction and dynamic scene rendering based on their own seminal work, as well as related approaches from the literature. They will explain in more detail three important categories of algorithms for dynamic shape and appearance reconstruction, namely silhouette-based, stereobased, and model- based approaches. Alternative methods, such as data-driven approaches, will also be reviewed. The tutorial will focus on latest 3D Video techniques that were not yet covered in a tutorial, including algorithms for freeviewpoint video relighting, model-based deformable mesh tracking, as well as highquality scene reconstruction with camera/projector setups. The course keeps a balance between the explanation of theoretical foundations, engineering problems and emerging applications of 3D Video technology. We therefore believe that the course will be a valuable and entertaining source of information for students, researchers and practitioners alike.
Object-Oriented Shader Design
(The Eurographics Association, 2007) Kuck, Roland; Paolo Cignoni and Jiri Sochor
We present an extremely lightweight object-oriented framework for writing shaders. It provides a way to invoke methods of objects from the shading language and to use references of objects as normal variables. Classes are declared and instantiated in the application language using proxy classes. We then apply object-oriented design to several typical shading problems showing their strength compared to the standard methods.
Construction of Non-Blobby Surface from Particles
(The Eurographics Association, 2007) Harada, Takahiro; Koshizuka, Seiichi; Kawaguchi, Yoichiro; Paolo Cignoni and Jiri Sochor
This paper presents a method that can construct a surface with a thin region or sharp edges from particles. The surface is constructed in two stages. An implicit surface is generated by assigning a density distribution to each particle in the first step and then the surface constructed from the density distribution is changed to a surface with a thin region or sharp edges. Furthermore, the method can generate various kinds of surfaces because a surface is controlled by several parameters. Therefore, the present technique increases the range of expression of particle-based simulations. In this paper, some calculation results are presented and finally an application from the results of particle-based fluid simulation is discussed.
Computational Photography
(The Eurographics Association, 2007) Raskar, Ramesh; Tumblin, Jack; Mohan, Ankit; Agrawal, Amit; Li, Yuanzen; Karol Myszkowski and Vlastimil Havran
Computational photography combines plentiful computing, digital sensors, modern optics, actuators, probes and smart lights to escape the limitations of traditional film cameras and enables novel imaging applications. Unbounded dynamic range, variable focus, resolution, and depth of field, hints about shape, reflectance, and lighting, and new interactive forms of photos that are partly snapshots and partly videos are just some of the new applications found in Computational Photography. The computational techniques encompass methods from modification of imaging parameters during capture to sophisticated reconstructions from indirect measurements. We provide a practical guide to topics in image capture and manipulation methods for generating compelling pictures for computer graphics and for extracting scene properties for computer vision, with several examples. Many ideas in computational photography are still relatively new to digital artists and programmers and there is no upto- date reference text. A larger problem is that a multi-disciplinary field that combines ideas from computational methods and modern digital photography involves a steep learning curve. For example, photographers are not always familiar with advanced algorithms now emerging to capture high dynamic range images, but image processing researchers face difficulty in understanding the capture and noise issues in digital cameras. These topics, however, can be easily learned without extensive background. The goal of this presentation is to present both aspects in a compact form. The new capture methods include sophisticated sensors, electromechanical actuators and on-board processing. Examples include adaptation to sensed scene depth and illumination, taking multiple pictures by varying camera parameters or actively modifying the flash illumination parameters. A class of modern reconstruction methods is also emerging. The methods can achieve a photomontage by optimally fusing information from multiple images, improve signal to noise ratio and extract scene features such as depth edges. The presentation briefly reviews fundamental topics in digital imaging and then provides a practical guide to underlying techniques beyond image processing such as gradient domain operations, graph cuts, bilateral filters and optimizations. The participants learn about topics in image capture and manipulation methods for generating compelling pictures for computer graphics and for extracting scene properties for computer vision, with several examples. We hope to provide enough fundamentals to satisfy the technical specialist without intimidating the curious graphics researcher interested in recent advances in photography. The intended audience is photographers, digital artists, image processing programmers and vision researchers using or building applications for digital cameras or images. They will learn about camera fundamentals and powerful computational tools, along with many real world examples.
Haptic Simulation, Perception and Manipulation of Deformable Objects
(The Eurographics Association, 2007) Magnenat-Thalmann, Nadia; Volino, Pascal; Bonanni, Ugo; Summers, Ian R.; Brady, A. C.; Qu, J.; Allerkamp, D.; Fontana, M.; Tarri, F.; Salsedo, F.; Bergamasco, Massimo; Karol Myszkowski and Vlastimil Havran
This tutorial addresses haptic simulation, perception and manipulation of complex deformable objects in virtual environments (VE). We first introduce HAPTEX, a research project dealing with haptic simulation and perception of textiles in VEs. Then, we present state-of-the-art techniques concerning haptic simulation and rendering, ranging from physically based modelling to control issues of tactile arrays and force-feedback devices. In the section on cloth simulation for haptic systems we describe techniques for simulating textiles adapted to the specific context of haptic applications. The section concerning tactile aspects of virtual objects shows how arrays of contactors on the skin can be used to provide appropriate spatiotemporal patterns of mechanical excitation to the underlying mechanoreceptors. Finally, the last section addresses the problem of developing suitable force feedback technologies for the realistic haptic rendering of the physical interaction with deformable objects, addressing the design of novel force feedback systems, innovative concepts for curvature simulation and control algorithms for accuracy improvement.
Inverse Kinematics and Kinetics for Virtual Humanoids
(The Eurographics Association, 2007) Boulic, Ronan; Kulpa, Richard; Karol Myszkowski and Vlastimil Havran
The present tutorial deals with the use of inverse kinematics and kinetics for postural adaptations of virtual hu- manoids to different kind of constraints. It first proposes an overview of the problematic of this thematic and then of the existing techniques. Then it technically describes two key approaches: the prioritized inverse kinematics for accurate and realistic adaptation and a CCD-like algorithm based on groups for fast and realistic adaptation of hundreds of characters in real-time.
Capturing Reflectance - From Theory to Practice
(The Eurographics Association, 2007) Lensch, Hendrik P. A.; Goesele, Michael; M¨uller, Gero; Karol Myszkowski and Vlastimil Havran
One important problem in photorealistic or predictive rendering nowadays is to realistically model the light interaction with objects. Measurements can capture the reflection properties of real world surface, i.e., they are one way of obtaining realistic reflection properties. For arbitrary (non-fluorescent, non-phosphorescent) materials, the reflection properties can be described by the 8D reflectance field of the surface, also called BSSRDF. Since densely sampling an 8D function is currently not practical various acquisition methods have been proposed which reduce the number of dimensions by restricting the viewing or relighting capabilities of the captured data sets. In this tutorial we will mainly focus on three different approaches, the first allowing to reconstruct opaque surfaces from a very small set of input images, the second allows for arbitrary surfaces but under the assumption of distant light sources and the last which allows for relighting an arbitrary scene with arbitrary spatially varying light patterns. After a short introduction explaining some fundamental concepts regarding measuring and representing reflection properties, the basics of data acquisition with photographs will be addressed. The tutorial present the set of current state-of-the art algorithms for acquiring and modeling 3D objects. The tutorial investigates the strengths and limitations of each technique and sorts them by their complexity with regard to acquisition costs. Besides describing the theoretical contributions we will furthermore point out the practical issues when acquiring reflectance fields in order to help interested users to build and implement their own acquisition setup.
Bridging Semantic Web and Digital Shapes
(The Eurographics Association, 2007) Papaleo, Laura; Floriani, Leila De; Hendler, Jim; Paolo Cignoni and Jiri Sochor
Since the volume of multimedia content available on the Web is continuously increasing, a clear need for advanced techniques capable of performing an effective retrieval and management of such data. In this context, in order to reason on digital shapes and their associated semantic, we see a growing interest in exploiting the potential of the Semantic Web in different research fields. We present here the design and initial development of our new system, that we call be-SMART for inspecting digital 3D shapes by extracting geometrical and topological information from them and for structuring and annotating these shapes using ontology-driven metadata. We describe the general structure of the system, its modules and their mutual relations. We also provide motivations for further work in developing new techniques for managing 3D models on the Web.
Tangible Heritage: Production of Astrolabes on a Laser Engraver
(The Eurographics Association, 2007) Zotti, Georg; David B. Arnold and Andrej Ferko
The astrolabe, an analog computing device, used to be the iconic instrument of astronomers during the Middle Ages. It allowed a multitude of operations of practical astronomy which were otherwise cumbersome to perform in an epoch when mathematics had apparently almost been forgotten. Usually made from wood or sheet metal, a few hundred instruments, mostly from brass, survived until today and are valuable museum showpieces. This paper explains a procedural modelling approach for the construction of the classical kinds of astrolabes, which allows a wide variety of applications from plain explanatory illustrations to 3D models, and even the production of working physical astrolabes usable for public or classroom demonstrations.
Visualization of Multi-variate Scientific Data
(The Eurographics Association, 2007) Bürger, Raphael; Hauser, Helwig; Dieter Schmalstieg and Jiri Bittner
In this state-of-the-art report we discuss relevant research works related to the visualization of complex, multivariate data. We focus on non-classical approaches, i.e. approaches which haven t been discussed in previous related reports, and we highlight techniques which potentially lead towards new directions in visualization research. We discuss how different techniques take effect at specific stages of the visualization pipeline and how they apply to multi-variate data sets being composed of scalars, vectors, and tensors. We also provide a categorization of these techniques in the aim for a better overview of related approaches. In the second part of this paper we take a look at recent techniques that are useful for the visualization of complex data sets either because they are general purpose or because they can be adapted to specific problems.
Virtual Agent Navigation in Open Spaces using Iterative Shrinking Polygons
(The Eurographics Association, 2007) Haciomeroglu, Murat; Laycock, Robert; Day, Andy; Paolo Cignoni and Jiri Sochor
Populating an urban environment with a virtual crowd provides a dynamic element to an otherwise static scene; bringing the virtual environment to life. One of the fundamental components governing the fidelity of the scene is the realistic simulation of the crowd behaviour. To create a believable crowd simulation one group of methods considers constructing a graph covering the space available to the virtual agents and subsequently performing path planning to allow the agents to navigate their environment by traversing the edges of the graph. To avoid computationally expensive path planning algorithms there exists a tradeoff between the number of edges in the graph and the amount of available space which an agent can visit. In order to alleviate this problem we propose to compute the straight skeleton to provide an initial covering of the environment. This is subsequently augmented using iterative shrinking polygons to generate additional edges in the larger open spaces. The technique developed requires limited knowledge of the urban environment, processes the relevant information automatically and is illustrated in this paper to control the behaviour of a virtual crowd in real time.
An E-Learning Course on Scientific Visualization
(The Eurographics Association, 2007) Taras, Christiane; Rotard, Martin; Ertl, Thomas; Isabel Navazo and Petr Felkel
In this paper we present an e-learning course on scientific visualization. Based on over ten years of teaching experiences in this field, we have created a multimedia online course which we use as additional material for our lecture. The course will be made publicly available so that not only our students but all people interested in the field of scientific visualization can benefit from the materials we have prepared. In the course important visualization techniques and algorithms are discussed. The main goal is to lay the foundamentals for future specialists and researchers in the field of scientific visualization.
Preface and Table of Contents
(The Eurographics Association, 2007) -; Isabel Navazo and Petr Felkel
Preface and Table of Contents
A Discussion of the CGE06 Workshop Report
(The Eurographics Association, 2007) Cunningham, Moderator: Steve; Isabel Navazo and Petr Felkel
The CGE06 workshop, held after the EG06 conference in Vienna, recommended a structure for first cycle an and second cycle education in computer graphics. The workshop report is online at d http://education.siggraph.org/conferences/eurographics/2006/cge2006. This discussion will present an overview of the recommended structure by four European workshop participa participants. They will present their views on the workshop recommendations and will discuss any nts. steps that have been taken to implement them in their own or in other universities.
Color Pages
(The Eurographics Association, 2007) Arnold, David B.; Ferko, Andrej; David B. Arnold and Andrej Ferko
Color Pages
Automated Combination of Real-Time Shader Programs
(The Eurographics Association, 2007) Trapp, Matthias; Döller, Jürgen; Paolo Cignoni and Jiri Sochor
This work proposes an approach for automatic and generic runtime-combination of high-level shader programs. Many of recently introduced real-time rendering techniques rely on such programs. The fact that only a single program can be active concurrently becomes a main conceptual problem when embedding these techniques into middleware systems or 3D applications. Their implementations frequently demand for a combined use of individual shader functionality and, therefore, need to combine existing shader programs. Such a task is often timeconsuming, error-prone, requires a skilled software engineer, and needs to be repeated for each further extension. Our extensible approach solves these problems efficiently: It structures a shader program into code fragments, each typed with a predefined semantics. Based on an explicit order of those semantics, the code fragments of different programs can be combined at runtime. This technique facilitates the reuse of shader code as well as the development of extensible rendering frameworks for future hardware generations. We integrated our approach into an object-oriented high-level rendering system.
Volumetric Normal Mapping in Rendering of Multivariate Volume Data
(The Eurographics Association, 2007) Seipel, Stefan; Paolo Cignoni and Jiri Sochor
The work presented in this paper introduces volumetric normal maps for producing visual structure in direct volume rendering (DVR) of 3D data for the purpose of visualizing multiple attributes in a 3D volume. We use volumetric normal maps to represent normal vector glyphs that are subsequently applied to warp the gradients in the primary volume data. This method is intended to visualize some secondary attribute in DVR. We demonstrate that our method can render visual structures in DVR without the need of explicit surface reconstruction and texturing.
3D Shape Description and Matching Based on Properties of Real Functions
(The Eurographics Association, 2007) Biasotti, Silvia; Falcidieno, Bianca; Frosini, Patrizio; Giorgi, Daniela; Landi, Claudia; Marini, Simone; Patané, Giuseppe; Spagnuolo, Michela; Karol Myszkowski and Vlastimil Havran
This tutorial covers a variety of methods for 3D shape matching and retrieval that are characterized by the use of a real-valued function defined on the shape (mapping function) to derive its signature. The methods are discussed following an abstract conceptual framework that distinguishes among the three main components of these class of shape matching methods: shape analysis, via the application of the mapping function, shape description, via the construction of a signature, and comparison, via the definition of a distance measure. Goal of the tutorial is to facilitate the understanding of the performance of the various methods by a methodical analysis of the properties of various methods at the three different stages.

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