EG2004

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https://diglib.eg.org/handle/10.2312/243

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Acquisition, Synthesis and Rendering of Bidirectional Texture Functions
(Eurographics Association, 2004) Müller, Gero; Meseth, Jan; Sattler, Mirko; Sarlette, Ralf; Klein, Reinhard
One of the main challenges in computer graphics is still the realistic rendering of complex materials such as fabric or skin. The difficulty arises from the complex meso structure and reflectance behavior defining the unique look-and-feel of a material. A wide class of such realistic materials can be described as 2D-texture under varying light- and view direction namely the Bidirectional Texture Function (BTF). Since an easy and general method for modeling BTFs is not available, current research concentrates on image-based methods which rely on measured BTFs (acquired real-world data) in combination with appropriate synthesis methods. Recent results have shown that this approach greatly improves the visual quality of rendered surfaces and therefore the quality of applications such as virtual prototyping. This STAR will present in detail the state-of-the-art techniques for the main tasks involved in producing photo-realistic renderings using measured BTFs
Adaptive Brush Stroke Generation for Painterly Rendering
(Eurographics Association, 2004) Park ChungAng, Youngsup; Yoon, Kyunghyun; M. Alexa and E. Galin
We propose adaptive brush stroke generation for source images, using reference data. Colors used are formed by actual palette colors from artists. To create the palette, we have referred mostly to colors used in Van Gogh’s works and determined the color of brush strokes by transferring it to the most similar one, through comparing colors used in source images and the palette colors. Also, by referring to the edge orientation of source images, we have applied a brush stroke orientation that surrounds the edges. The sizes were determined depending on the different sizes of the objects from wide to narrow brushes. Finally, we applied spline curve shapes. The brush strokes created in such method, were applied separately according to its segmented images, and composed after rendering.
Advanced Virtual Medicine: Techniques and Applications for Medicine Oriented Computer Graphics
(Eurographics Association, 2004) Delingette, H.; Linney, A.; Magnenat-Thalmann, N.; Wu, Yin; Bartz, D.; Hauth, M.; Mueller, K.
The course will introduce techniques of modelling and simulating human tissue for medical applications. The course includes basic and advanced techniques of segmentation, registration, reconstruction and motion simulation in medical applications from disease detection to surgery simulation and surgery in virtual reality. This tutorial introduces various methods along with concrete clinic cases and present examples to convert research work to commercial applications.
Automatic Generation of Animated Population in Virtual Environments
(Eurographics Association, 2004) Thalmann, D.; Magnenat-Thalmann, N.; Donikian, S.
The necessity to model virtual population appears in many applications of computer animation and simulation. Such applications encompass several different domains - representative or autonomous agents in virtual environments, human factors analysis, training, education,simulation-based design, and entertainment. Reproduce in simulation the dynamic life of virtual environments in realtime is also a great challenge.
Classification of Illumination Methods for Mixed Reality
(Eurographics Association, 2004) Jacobs, Katrien; Loscos, Céline
A mixed reality (MR) represents an environment composed both by real and virtual objects. MR applications are more and more used, for instance in surgery, architecture, cultural heritage, entertainment, etc. For some of these it is important to merge the real and virtual elements using consistent illumination. In this paper, we propose a classification of illumination methods for MR applications that aim at generating a merged environment in which illumination and shadows are consistent. Three different illumination methods can be identified: common illumination, relighting and methods based on inverse illumination. In this report a classification of the illumination methods for MR is given based on their input requirements: the amount of geometry and radiance known from the real environment. This led us to define four categories of methods that vary depending on the type of geometric model used for representing the real scene, and the different radiance information available for each point of the real scene. Various methods are described within their category. The classification points out that in general the quality of the illumination interactions increases with the amount of input information available. On the other hand, the accessibility of the method decreases since its pre-processing time increases to gather the extra information. Recent developed techniques managed to compensate unknown data with clever techniques using an iterative algorithm, hardware illumination or recent progress in stereovision. We complete the review of illumination techniques for MR with a discussion on important properties such as the possibility of interactivity or the amount of complexity in the simulated illumination.
Collision Detection for Deformable Objects
(Eurographics Association, 2004) Teschner, M.; Kimmerle, S.; Heidelberger, B.; Zachmann, G.; Raghupathi, L.; Fuhrmann, A.; Cani, M.-P.; Faure, F.; Magnenat-Thalmann, N.; Strasser, W.; Volino, P.
Interactive environments for dynamically deforming objects play an important role in surgery simulation and entertainment technology. These environments require fast deformable models and very efficient collision handling techniques. While collision detection for rigid bodies is well-investigated, collision detection for deformable objects introduces additional challenging problems. This paper focusses on these aspects and summarizes recent research in the area of deformable collision detection. Various approaches based on bounding volume hierarchies, distance fields, and spatial partitioning are discussed. Further, image-space techniques and stochastic methods are considered. Applications in cloth modeling and surgical simulation are presented.
A Color Decomposition Method for Preserving Ukiyo-e Woodblocks
(Eurographics Association, 2004) Terai, Tomokazu; Mizuno, Shinji; Okada, Minoru; M. Alexa and E. Galin
In this paper we propose a color decomposition method for multicolor printing of watercolors including areas overlapping each print layer. Watercolors have an important feature that the observed colors are different on the printing order. The proposed method is based on a particle density model for expressing the effects of watercolors. The approach of this method is to solve an inverse problem, that is, determining a printed area corresponding to a watercolor from an observed image. Our purpose in this study is to estimate woodblocks from a woodblock print. The authors have already proposed a non-photorealistic rendering method to produce virtual woodblock prints. This approach can be utilized to Ukiyo-e. An Ukiyo-e print is created from several woodblocks with several watercolors, and has a mixing color expression similar to the effects of watercolor painting. The color decomposition method can be applied to produce virtual woodblocks in the virtual woodblock printing. The results of woodblock estimation will be utilized to preserve the techniques and prints of Ukiyo-e.
Enriching Animation Databases
(Eurographics Association, 2004) Ahmed, Amr; Mokhtarian, Farzin; Hilton, Adrian; M. Alexa and E. Galin
The paper presents a framework for enriching an existing basic animation databse by modifying existing motions to generate a variety of new motions. Intuitively controlled motion varities are generated on demand which reduces the storage requirements, avoids recapturing missing variations, and provides greater flexibility and utilisation of existing clips. An improved root-trajectory blending is introduced that overcomes the limitations of ordinary blending (including flipping of the root trajectory when blending motions of opposite path-curvature or opposite directions). A novel synchronised mirror technique is also introduced.
Frontier Sets: A Partitioning Scheme to Enable Scalable Virtual Environments
(Eurographics Association, 2004) Steed, Anthony; Angus, Cameron; M. Alexa and E. Galin
We present a new spatial partitioning scheme called frontier sets. Frontier sets build on the notion of a potentially visible set (PVS) [ARB90, TS91]. In a PVS a world is sub-divided into cells and for each cell all the other cells that can be seen are computed. Frontier sets represent regions of mutual invisibility. One frontier in a frontier set considers pairs of cells, A and B. It lists two sets of cells, FAB and FBA. From no cell in FAB is any cell in FBA visible and vice-versa. We have used frontier sets to investigate peer-to-peer networking schemes for networked virtual environments. Preliminary investigation of simulations within the Quake II game engine shows that frontiers have significant promise and may allow a new class of scalable peer-to-peer game infrastructures to emerge.
A Generic Method for Geometric Contraints Detection
(Eurographics Association, 2004) Salvati, Marc; Lecallennec, Benoît; Boulic, Ronan; M. Alexa and E. Galin
In this paper, we present a generic method to automatically detect geometric constraints on motion capture animations. At each frame, elementary geometric constraints are computed with respect to a reference which can either be the world coordinate system or any moving object in the scene. We then use constraint-related concepts of union and intersection to merge the elementary constraints together and/or to generate new ones. Finally, our algorithm provides an exhaustive list of geometric constraints with an accurate evaluation of their duration. The detected constraints can characterize virtual human motion (e.g. footprints) as well as interactions with moving objects of the scene (e.g. a hand touching a ball). While our approach also detects sliding geometric constraints, we focus our discussion on detecting positional geometric constraints.
Geometric Algebra and its Application to Computer Graphics
(Eurographics Association, 2004) Hildenbrand, Dietmar; Perwass, Christian; Dorst, Leo; Fontijne, Daniel
In this tutorial we will give an overview of Geometric Algebra and its application to computer graphics. First of all, we want to motivate the topic and give insights into some applications.
Interactive Modeling of Mushrooms
(Eurographics Association, 2004) Desbenoit, Brett; Vanderhaghe, David; Galin, Eric; Grosjean, Jerôme; M. Alexa and E. Galin
This paper presents a fast and efficient method for modeling mushrooms. Starting from a real world image, the designer defines a silhouette and specifies deformation parameters. Our system then automatically generates a textured triangle mesh model using a procedural modeling pipeline. This approach enables us to create a vast variety of shapes easily using shape morphing.
Interactive Physically-based Animation System for Dense Meshes
(Eurographics Association, 2004) Kondo, Ryo; Kanai, Takashi; M. Alexa and E. Galin
In this paper we describe an interactive physically-based animation system for dense meshes. Our method extracts a coarse mesh from an original mesh to make a tetrahedral mesh for the reduction of computational costs. For computing reaction forces we precompute penetration depth values and gradients at mesh vertices by creating a distance field. They are interpolated when collisions are detected and are used for the calculation of forces with a penalty method. Our method can handle dense meshes with physically-based animation and collision response at interactive frame rates.
Modeling clouds shape
(Eurographics Association, 2004) Bouthors, Antoine; Neyret, Fabrice; M. Alexa and E. Galin
We propose a model for representing the shape of cumulus clouds.We draw on several approaches that we combine and extend: We store a hierarchy of quasi-spherical particles (or blobs) living on top of each other. The shape of these particles is defined by an implicit field which deforms under the influence of neighbor particles. We define a set of shaders to simulate a volumetric appearance in the spirit of Gardner's textured ellipsoids, to make the shape appear continuous, and to account for dedicated shading effects. In this paper we deal only with the definition of the shape. However, we believe that this model is well suited to be integrated with particle animation and advanced rendering.
Modern Approaches to Augmented Reality
(Eurographics Association, 2004) Bimber, Oliver; Raskar, Ramesh
This tutorial provides a survey of modern techniques for augmented reality (AR) systems. Novel approaches have taken AR beyond traditional eye-worn or hand-held displays, enabling new application areas. We discuss conventional AR displays and present alternative augmented reality approaches that are overcoming some of their limitations. These practical alternatives are spatially augmented displays that exploit large optical elements, video-projectors, holograms, and tracking technologies. Due to the fall in the cost of these devices and graphics resources, there has been a considerable interest in exploiting such augmented reality systems in universities, labs, museums and in the art community.
Modulating View-dependent Textures
(Eurographics Association, 2004) Jagersand, Martin; Cobzas, Dana; Yerex, Keith; M. Alexa and E. Galin
We present a texturing approach for image-based modeling and rendering, where instead of using one (or a blend of a few) sample images, new view dependent textures are synthesized by modulating a differential texture basis. The texture basis models the first order intensity variation due to image projection errors and parallax for a nonlinear projective camera. Experimentally we compare rendered views to ground truth real images and quantify how the texture basis can generate a more accurate rendering compared to conventional view dependent textures.
Multi-resolution Modeling, Visualization and Streaming of Volume Meshes
(Eurographics Association, 2004) Cignoni, P.; De Floriani, L.; Lindstrom, P.; Pascucci, V.; Rossignac, J.; Silva, C.
Volume meshes are widely used in geometric modeling, object reconstruction, level set methods and accurate simulations of physical behaviors like deformable materials, objects under stress, fracture dynamics, optical effects and reproduction of smoke and fluid dynamics.
An Oriented Particle and Generalized Spring Model for Fast Prototyping Deformable Objects
(Eurographics Association, 2004) Jeong, Il-Kwon; Lee, Inho; M. Alexa and E. Galin
We present a new mass-spring system, in particular, by using an oriented particle and generalized spring model, which can be used for fast prototyping or animation of deformable objects. Conventional mass-spring system is widely used especially in cloth animation. However animating deformable objects such as a jelly cube requires extra diagonal springs in addition to structural springs in order to provide shear strain force and guarantee stability on the original shape formation. One has to use his a priori knowledge or trial-anderror method to construct a stable spring network for a given deformable object. This is due to the inherent one-dimensional nature of the conventional spring model. In order to overcome the difficulty in designing a spring network and make it possible to construct a stable network easily and intuitively, we propose an oriented particle and generalized spring model that reacts against bending and twisting force as well as stretching. By using our new mass-spring system, one can easily construct a spring network from a given geometric model. Moreover, one can animate one-dimensional flexible object such as a mobile as well as a thin twodimensional object with sharp folds or creases. In addition, we present an offsetting method for tweaking mass-spring system to have valuable properties that help animating deformable objects with various shapes.
Packing Square Tiles into One Texture
(Eurographics Association, 2004) Decaudin, Philippe; Neyret, Fabrice; M. Alexa and E. Galin
This paper deals with the packing of square tiles of the same size into one texture. Texture size is constrained by the graphics hardware. In particular, width and height resolutions must be powers of two. To cover the whole texture and avoid space loss, common schemes pack a number of tiles that is a power of two. We show that numbers of tiles like 5, 13, 17, 25, 34 and others can also be reached without wasting memory. To achieve this, our scheme takes advantage of texture rotation and the wrapping capability of texture-addressing, which gives a torus topology to the texture space.
Perceptually Adaptive Graphics
(Eurographics Association, 2004) O’Sullivan, Carol; Howlett, Sarah; McDonnell, Rachel; Morvan, Yann; O’Conor, Keith
In recent years, the Graphics community has come to realise the importance of taking human perception into account when striving for realism in images, animations and Virtual Environments. In May 2001, a EUROGRAPHICS/ SIGGRAPH Campfire brought together a group of researchers from various fields, including computer graphics and visualisation, psychology, neuroscience, eye-movements and medicine to discuss the future and current state of the field. Since then, many researchers have been very active in furthering the field of perceptually adaptive graphics. In this report, we outline the state of the art as discussed at that event and the progress that has been made since.

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