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
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.
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.
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.
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.
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.
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.
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.
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.
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.
Tone Mapping in VR Environments
(Eurographics Association, 2004) Hausner, Alexander; Stamminger, Marc; M. Alexa and E. Galin
Tone mapping is the process of mapping high dynamic range images to the low dynamic range of current displays. So far, tone mapping research was focused on static images, but with powerful graphics hardware available today, real time tone mapping becomes possible. In this paper we describe tone mapping within a VR environment. The tone mapping operator utilizes information about the user's line of sight obtained by a tracking system. Adaptation is optimized for the current view point and costly image operations are restricted to the central view field. Since all computations are completely performed by graphics hardware, we achieve interactive frame rates.
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.
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.
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.
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.
A Spectral Gamut-Mapping Environment with Rendering Parameter Feedback
(Eurographics Association, 2004) Bell, Ian E.; Alexander, Simon K.; M. Alexa and E. Galin
This paper proposes a prototypical environment for gamut mapping in spectral space. Images are rendered in terms of light and material parameters by a symbolic ray tracer, and the parameter ranges are adjusted, without re-rendering, to bring the image into the output device's spectral gamut. There is a growing disparity between the high dynamic range images produced by spectral renderers and the limitations of display gamuts and lowdimensional colour management standards. While in rendering tone mapping has helped compress luminance ranges, and in colour science 3D gamut mapping has helped compress chrominance ranges, only high-dimensional spectral methods will fully bridge the gap. This paper's environment for gamuts in spectral space is a step toward spectral gamut mapping, which we demonstrate by using the ray tracer to predict feasible ranges of rendering parameters for an in-gamut image. The environment can be easily extended to support interactive or automatic image correction, and more sophisticated rendering and gamut-mapping methods of arbitrary dimensionality.
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.

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