EG2004

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Principles and Applications of Medical Virtual Environments
(Eurographics Association, 2004) Vidal, Franck; Bello, F.; Brodlie, K.; John, N.W.; Gould, D.; Phillips, R.; Avis, N. J.
The medical domain offers many excellent opportunities for the application of computer graphics, visualization, and virtual environments, offering the potential to help improve healthcare and bring benefits to patients. This report provides a comprehensive overview of the state-of-the-art in this exciting field. It has been written from the perspective of both computer scientists and practicing clinicians and documents past and current successes together with the challenges that lie ahead. The report begins with a description of the commonly used imaging modalities and then details the software algorithms and hardware that allows visualization of and interaction with this data. Example applications from research projects and commercially available products are listed, including educational tools; diagnostic aids; virtual endoscopy; planning aids; guidance aids; skills training; computer augmented reality; and robotics. The final section of the report summarises the current issues and looks ahead to future developments.
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.
Visual Supercomputing - Technologies, Applications and Challenges
(Eurographics Association, 2004) Brodlie, K.; Brooke, J.; Chen, M.; Chisnall, D.; Fewings, A.; Hughes, C.; John, N. W.; Jones, M. W.; Riding, M.; Roard, N.
If we were to have a Grid infrastructure for visualization, what technologies would be needed to build such an infrastructure, what kind of applications would benefit from it, and what challenges are we facing in order to accomplish this goal? In this report, we make use of the term `visual supercomputing' to encapsulate a subject domain concerning the infrastructural technology for visualization. We consider a broad range of scientific and technological advances in computer graphics and visualization, which are relevant to visual supercomputing. We identify the state of the art technologies that have prepared us for building such an infrastructure. We examine a collection of applications that would benefit enormously from such an infrastructure, and discuss their technical requirements. We propose a set of challenges that may guide our strategic efforts in the coming years.
A Quick and Automatic Image Based Modeling and Rendering System
(Eurographics Association, 2004) Yerex, Keith; Birkbeck, Neil; Cobzas, Dana; Jagersand, Martin; M. Alexa and E. Galin
We present a complete and automatic system for object capture from video, Internet delivery, and real-time photorealistic rendering. Shape from silhouette is used to capture an approximate enveloping geometry, the visual hull. Texture coordinates are generated automatically under a minimum distortion criterion. To account for the difference between the true shape of the object and the captured visual hull we use Dynamic texturing, a viewdependent texturing method, which explicitly captures geometric deviations and applies a texture based correction. These models are then efficiently coded, and delivered over the Internet.
Realtime Isosurface Extraction with Graphics Hardware
(Eurographics Association, 2004) Reck, Frank; Dachsbacher, Carsten; Grosso, Roberto; Greiner, Günther; Stamminger, Marc; M. Alexa and E. Galin
In this paper we introduce a method for the display of isosurfaces extracted from unstructured tetrahedral grids. Our algorithm completely runs on the graphics hardware. The tetrahedra are streamed into a vertex program, which extracts the surface for the given isovalue and immediately renders it. The triangles are not stored explicitly but are computed during rendering time, so the user can modify the isovalue with immediate feedback. If the tetrahedra entirely fit into video memory, we achieve a throughput of more than nine million tetrahedra per second. Our performance can be further improved by using a hybrid method which pre-selects tetrahedra containing the isovalue. We compare our approach with a pure CPU based implementation which achieves about half the performance of our hardware accelerated method.
The Visualisation and Expression of Virtual 3DSurfaces Explored through Custom Developed Interactive Software, Optically Mixed Coloured Surface Contouring and Fine Art Printmaking
(Eurographics Association, 2004) Lee, Peter John; M. Alexa and E. Galin
This short presentation paper describes an exploration and the visualisation of virtual 3D compositions through custom developed software and fine art printmaking. The author, a trained and practising visual artist considers this innovative visualisation as an exploration into the newly emerging visual language of the computer in similar vein to some of the NPR artists. The comprehension of virtual 3D objects is achieved primarily through linear surface contouring. The colour of these 3D surfaces is created by components intrinsic to the contour structure culminating in optical colour mixtures. The custom software, developed by the author, facilitates the application of the surface contouring to imported pre-constructed 3D object’s surfaces, computing the contouring component configurations and dimensions. Fine art screen-prints are created from DIBs generated within the software from the colour layers comprising the surface contouring. The printed DIBs form monochrome positives that are available for the artist to edit at will, before or following the transfer to screen-print screens and printing in CMYK screen-printing inks. The entire process can be reiterated editing the composition’s coloured contouring using the software, the positives or even the screens themselves until a satisfactory aesthetic result is obtained
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.
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.
Steerable Texture Synthesis
(Eurographics Association, 2004) Taponecco, Francesca; Alexa, Marc; M. Alexa and E. Galin
Texture synthesis is typically concerned with the creation of an arbitrarily sized texture from a small sample, where the pattern of the generated texture should be perceived as resembling the example. Most of the current work follows a Markov model approach. The texture is generated by finding best matching pixels or patches in the sample and then copying them to the target. Here we extend this concept to incorporate arbitrary filters acting on the sample before matching and transferring. The filters may vary over the generated texture. Steering the filters with properties connected to the output image allows generating a variety of effects.
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.
Programming Graphics Hardware
(Eurographics Association, 2004) Zeller, Cyril; Fernando, Randy; Wloka, Matthias; Harris, Mark
The presentation gives the big picture for the entire tutorial. It introduces the notions and frameworks that will be revisited in more details during the following presentations: Overview of the tutorial. Real-time graphics concept. Graphics pipeline concept.How the graphics pipeline maps to the PC architecture (CPU <-> GPU). Controlling the GPU from the CPU: The driver and 3D API (OpenGL, Direct3D). Evolution of the PC graphics pipeline and 3D APIs through time from fixed function pipeline to today's programmable pipeline, with introduction to z-buffering, texturing, TnL, multi-texturing, anti-aliasing, vertex and pixel shaders. Review of real-time graphics applications.
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
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.
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.
Simulation of Clothes for Real-time Applications
(Eurographics Association, 2004) Magnenat-Thalmann, N.; Cordier, F.; Keckeisen, M.; Kimmerle, S.; Klein, R.; Meseth, J.
This presentation gives an overview of the whole tutorial. It introduces the different techniques that will be presented in the next sessions. An overview of previous work is given as well.
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.
SP-Octrees Visualization Using Impostors
(Eurographics Association, 2004) Melero Rus, Francisco J.; Cano Olivares, Pedro; Torres Cantero, Juan Carlos; M. Alexa and E. Galin
SP-Octrees (Space-Partition Octrees) allow a multiresolution representation of polyhedral objects, and have been successfully used in progressive transmission. Nonetheless, the SP-Octree is a solid modeling structure, intended to solve problems as solid intersections and point inclusion tests. At intermediate levels of the SP-Octree, the visualization is a rough approximation of the object due to the fact that grey nodes are shown as the convex hull of the part of the solid included in that node. In this paper we present an approach to use SP-Octrees for adaptative visualization, that improves the visualization of these multiresolution models by applying impostors over those planes of the hierarchical structure that belongs to the convex hull but are not part of the solid boundary (ficticious planes). By doing so, it is possible to obtain a better approximating visualization of the object, although the maximum LOD is not used. At every moment, the impostor is selected depending on the viewpoint.
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.
Region Completion in a Single Image
(Eurographics Association, 2004) Zhang, Yunjun; Xiao, Jiangjian; Shah, Mubarak; M. Alexa and E. Galin
Natural images and Photographs sometimes may contain stains or undesired objects covering significant portions of the images. Region completion is a method to fill in such significant portions of an image by using the information from the remaining area of the image. We propose a novel approach to achieve the completion in three steps. First, a spatial-range model is determined to establish the searching order of the target patch. Second, a source patch is selected by measuring the adjusted appearance of the source patch with the target patch and enforcing the searching area in the neighborhood around the previous source patch. Third, a graphcut patch updating algorithm is designed to ensure the non-blurring updating. A number of examples are given to demonstrate the effectiveness of our method.
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.

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