Volume 19 (2000)

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https://diglib.eg.org/handle/10.2312/93

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    Hierarchical Reconstruction of BRDFs using Locally Supported Functions
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Noe, N.; Peroche, B.
    BRDFs are the backbone of realistic rendering algorithms. Analytical models are sometimes ineffective since they frequently cannot represent very particular material characteristics (retro-reflection, anisotropy, off-specularity, .). Consequently one might want to use measured BRDF data directly; this leads to solving the problem of BRDF reconstruction. In this paper, we propose a new solution which uses locally supported functions that lead to a hierarchical approach able to take irregular distributions of sampled data into account. This method is not computationally expensive and guarantees a physically valid reconstruction. We also discuss the quality of the reconstruction, introducing some new error parameters.
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    Constructive Volume Geometry
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Chen, Min; Tucker, John V.
    We present an algebraic framework, called Constructive Volume Geometryn (CVG), for modelling complex spatial objects using combinational operations. By utilising scalar fields as fundamental building blocks, CVG provides high-level algebraic representations of objects that are defined mathematically or built upon sampled or simulated datasets. It models amorphous phenomena as well as solid objects, and describes the interior as well as the exterior of objects. We also describe a hierarchical representation scheme for CVG, and a direct rendering method with a new approach for consistent sampling. The work has demonstrated the feasibility of combining a variety of graphics data types in a coherent modelling scheme.
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    Eurographics
    (Blackwell Publishers Ltd and the Eurographics Association, 2000)
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    An Interactive Approach to Point Cloud Triangulation
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Kobbelt, Leif P.; Botsch, Mario
    We present an interactive system for the generation of high quality triangle meshes that allows us to handle hybrid geometry (point clouds, polygons,. . .) as input data. In order to be able to robustly process huge data sets, we exploit graphics hardware features like the raster manager and the z-buffer for specific sub-tasks in the overall procedure. By this we significantly accelerate the stitching of mesh patches and obtain an algorithm for sub-sampling the data points in linear time. The target resolution and the triangle alignment in sub-regions of the resulting mesh can be controlled by adjusting the screen resolution and viewing transformation. An intuitive user interface provides a flexible tool for application dependent optimization of the mesh.
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    Robust Motion Watermarking based on Multiresolution Analysis
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Kim, Tae-hoon; Lee, Jehee; Shin, Sung yong
    Digital watermarking is one of commonly used solutions for copyright protection. A watermark should be imperceptible and robust to various attacks. In this paper, we address watermarking for motion data. Our watermarking scheme is based on two well-known ideas, so called multiresolution representation and spread spectrum. We embed a watermark into a motion signal by perturbing large detail coefficients of its multiresolution representation, and extract the watermark by analyzing perturbation of coefficients from a suspected signal. For more effective watermark extraction, we align suspected motion data to the original using dynamic time warping. Our scheme has merits of spread spectrum such as the resilience to common signal processing as well as the robustness to time warping.
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    Modeling the Motion of Dense Smoke in the Wind Field
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Rudolf, Marcin J.; Raczkowski, Jacek
    This paper presents a volumetric animation technique for modeling the turbulent motion of very dense and turbulent smoke such as one coming from a steam engine. A new method of the wind field generation is proposed. Gas motion is determined by the integration of two independent vector layers. The first one is a combination of flow primitives and the second is created by stochastically generated turbulence. Special attention is taken of the proper construction of the turbulent layer. For the visualization purposes a simple volume raytracer is applied. Many light sources are taken into account to achieve photorealistic effects. Finally some interesting animations are overviewed. Computation times for a PC Pentium 200 and an SGI O2 workstation are compared to demonstrate the high efficiency of the method.
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    The Impulse Graph: A New Dynamic Structure For Global Collisions
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Baciu, George; Keung Wong, Sai
    In interactive virtual environments and dynamic simulations, collisions between complex objects and articulated bodies may occur simultaneously at multiple points or regions of interference. Many solutions to the collision response problem are formulated based on the local pair-wise contact dynamics. In this article, we present a new solution to the global interactions and dynamic response between multiple structures in a three-dimensional environment. This is based on a new dynamic impulse graph that tracks the reaction forces through the entire system and gives a global view of all the interactions in a multibody system.
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    Filtered Jitter
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Klassen, R. Victor
    Jitter is one popular way of generating samples for stochastic sampling in computer graphics. The Poisson disk distribution better approximates that of the human photomosaic. In this paper we examine the spatial and frequency space behaviour of a number of existing algorithms for generating stochastic samples and propose a new algorithm based on low pass filtering a jittered set of displacements. The distribution is at least as much like that of the human photomosaic as any existing algorithm, while being fast to compute.
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    Eurographics
    (Blackwell Publishers Ltd and the Eurographics Association, 2000)
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    Haptic Cues for Image Disambiguation
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Faconti, G.; Massink, M.; Bordegoni, M.; De Angelis, F.; Booth, S.
    Haptic interfaces represent a revolution in human computer interface technology since they make it possible for users to touch and manipulate virtual objects. In this work we describe a cross-model interaction experiment to study the effect of adding haptic cues to visual cues when vision is not enough to disambiguate the images. We relate the results to those obtained in experimental psychology as well as to more recent studies on the subject.
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    Context-based Space Filling Curves
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Dafner, Revital; Cohen-Or, Daniel; Matias, Yossi
    A context-based scanning technique for images is presented. An image is scanned along a context-based space filling curve that is computed so as to exploit inherent coherence in the image. The resulting one-dimensional representation of the image has improved autocorrelation compared with universal scans such as the Peano-Hilbert space filling curve. An efficient algorithm for computing context-based space filling curves is presented. We also discuss the potential of improved autocorrelation of context-based space filling curves for image and video lossless compression.
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    Video-based Approach to Human Animation
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Lao, Zhiqiang; Li, Ling
    A method based on computer vision technologies is presented to determine the 3-D spatial locations of joints or feature points of a human body from human motion video. The proposed method first applies the geometric projection theory to obtain a set of feasible postures in some key frames according to predefined 2D video features and 3D-model features correspondence. Next it makes use of the available skeleton controlled human model to get a feasible posture for each key frame. The method is applied to a series of video images to animate artificial 3D human models.
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    Variable Resolution 4-k Meshes: Concepts and Applications
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Velho, Luiz; Gomes, Jonas
    In this paper we introduce variable resolution 4-k meshes, a powerful structure for the representation of geometric objects at multiple levels of detail. It combines most properties of other related descriptions with several advantages, such as more flexibility and greater expressive power. The main unique feature of the 4-k mesh structure lies in its variable resolution capability, which is crucial for adaptive computation. We also give an overview of the different methods for constructing the 4-k mesh representation, as well as the basic algorithms necessary to incorporate it in modeling and graphics applications.
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    Generating Animatable 3D Virtual Humans from Photographs
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Lee, WonSook; Gu, Jin; Magnenat-Thalmann, Nadia
    We present an easy, practical and efficient full body cloning methodology. This system utilizes photos taken from the front, side and back of a person in any given imaging environment without requiring a special background or a controlled illuminating condition. A seamless generic body specified in the VRML H-Anim 1.1 format is used to generate an individualized virtual human. The system is composed of two major components: face-cloning and body-cloning. The face-cloning component uses feature points on front and side images and then applies DFFD for shape modification. Next a fully automatic seamless texture mapping is generated for 360? coloring on a 3D polygonal model. The body-cloning component has two steps: (i feature points specification, which enables automatic silhouette detection in an arbitrary background (ii two-stage body modification by using feature points and body silhouette respectively. The final integrated human model has photo-realistic animatable face, hands, feet and body. The result can be visualized in any VRML compliant browser.
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    Editorial
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Coquillart, Sabine; Duke, David
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    A Vector-based Representation for Image Warping
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Froumentin, Max; Labrosse, Frederic; Willis, Philip
    A method for image analysis, representation and re-synthesis is introduced. Unlike other schemes it is not pixel based but rather represents a picture as vector data, from which an altered version of the original image can be rendered. Representing an image as vector data allows performing operations such as zooming, retouching or colourising, avoiding common problems associated with pixel image manipulation. This paper brings together methods from the areas of computer vision, image compositing and image based rendering to prove that this type of image representation is a step towards accurate and efficient image manipulation.
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    Binding Virtual Environments to Toolkit Capabilities
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Smith, Shamus P.; Duke, David J.
    There are many toolkits and development environments that aid the process of constructing virtual environment applications. Many of these development environments encourage customising a virtual environment's design while rapid prototyping within the confines of a toolkit's capabilities. Thus the choice of the technology and its associated support has been made independent of the end-use requirements of the final system. This can bias a virtual environment's design by implementation based constraints. We propose that an alternative approach is the consideration of virtual environment requirements in the context of an inspectable design model, to identify the requirements that a toolkit will need to support. In the context of an example, we present a selection of design requirements that we consider important for virtual environment design in general. We explore how these requirements might be mapped to different capabilities using Virtual Reality Modelling Language (VRML) as a concrete example of a platform technology.
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    Versatile Tuning of Humanoid Agent Activity
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Emering, Luc; Boulic, Ronan; Molet, Tom; Thalmann, Daniel
    In this paper, we present an integration framework for heterogeneous motion generators. The objective is to outline issues that are currently easily solved in professional post-processing systems used in film and game production but which cannot be transposed as is to real-time systems with autonomous agents. We summarise our approach for articulated agent-modelling and their animation by combining heterogeneous motion generators, such as real-time motion capturing, key-framing, inverse kinematics, procedural walking. We propose an agent/action-oriented framework. Activity properties such as action simultaneity and motion blending, spatial coherence, motion-flow update schemes, agent attachments, and location corrections, are the main topics handled by our generic animation framework. Numerous examples throughout the paper illustrate our approach and outline encountered problems and solutions or open research directions.
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    Generating Consistent Motion Transition via Decoupled Framespace Interpolation
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Ashraf, G.; Wong, K. C.
    The framespace interpolation algorithm abstracts motion sequences as 1D signals, and interpolates between them to create higher dimension signals, with weights drawn from a user specified curve in a bounded region. We reformulate the algorithm to achieve motion-state based transition via dynamic warping of framespaces and automatic transition timing via framespace frequency interpolation. Basis motions displaying diverse coordination configurations between upper and lower body-halves, cannot be consistently corresponded at a macro level. We address this problem here, through decoupled blending of these halves to achieve true consistency, and eliminate accumulated phase differences via cosine phase warp functions. This generalization enables interpolation of motions with diverse coordinations between the upper and lower bodies.
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    Subdivision Surface Tesselation on the Fly using a versatile Mesh Data Structure
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Muller, Kerstin; Havemann, Sven
    Subdivision surfaces have become a standard technique for freeform shape modeling. They are intuitive to use and permit designers to flexibly add detail. But with larger control meshes, efficient adaptive rendering techniques are indispensable for interactive visualization and shape modeling. In this paper, we present a realization of tesselation-on-the-fly for Loop subdivision surfaces as part of a framework for interactive visualization.