Issue 3

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https://diglib.eg.org/handle/10.2312/96

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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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    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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    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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    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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    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.
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    Towards Blind Detection of Robust Watermarks in Polygonal Models
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Benedens, Oliver; Busch, Christoph
    We describe a Digital Watermarking system dedicated for embedding watermarks into 3D polygonal models. The system consists of three watermarking algorithms, one named Vertex Flood Algorithm (VFA) suitable for embedding fragile public readable watermarks with high capacity and offering a way of model authentication, one realizing affine invariant watermarks, named Affine Invariant Embedding (AIE) and a third one, named Normal Bin Encoding (NBE) algorithm, realizing watermarks with robustness against more complex operations, most noticeably polygon reduction. The watermarks generated by these algorithms are stackable. We shortly discuss the implementation of the system, which is realized as a 3D Studio MAX plugin.
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    Representing Animations by Principal Components
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Alexa, Marc; Muller, Wolfgang
    In this paper, we present a representation for three-dimensional geometric animation sequences. Different from standard key-frame techniques, this approach is based on the determination of principal animation components and decouples the animation from the underlying geometry. The new representation supports progressive animation compression with spatial, as well as temporal, level-of-detail and high compression ratios. The distinction of animation and geometry allows for mapping animations onto other objects.
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    Surface Reconstruction based on Lower Dimensional Localized Delaunay Triangulation
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Gopi, M.; Krishnan, S.; Silva, C.T.
    We present a fast, memory efficient algorithm that generates a manifold triangular mesh S passing through a set of unorganized points P R 3. Nothing is assumed about the geometry, topology or presence of boundaries in the data set except that P is sampled from a real manifold surface. The speed of our algorithm is derived from a projection-based approach we use to determine the incident faces on a point. We define our sampling criteria to sample the surface and guarantee a topologically correct mesh after surface reconstruction for such a sampled surface. We also present a new algorithm to find the normal at a vertex, when the surface is sampled according our given criteria. We also present results of our surface reconstruction using our algorithm on unorganized point clouds of various models.
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    Tone Reproduction for Interactive Walkthroughs
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Scheel, A.; Stamminger, M.; Seidel, H.-P.
    When a rendering algorithm has created a pixel array of radiance values the task of producing an image is not yet completed. In fact, to visualize the result the radiance values still have to be mapped to luminances, which can be reproduced by the used display. This step is performed with the help of tone reproduction operators. These tools have mainly been applied to still images, but of course they are just as necessary for walkthrough applications, in which several images are created per second. In this paper we illuminate the physiological aspects of tone reproduction for interactive applications. It is shown how tone reproduction can also be introduced into interactive radiosity viewers, where the tone reproduction continuously adjusts to the current view of the user. The overall performance is decreased only moderately, still allowing walkthroughs of large scenes.
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    Floating Points: A Method for Computing Stipple Drawings
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Deussen, Oliver; Hiller, Stefan; Van Overveld, Cornelius; Strothotte, Thomas
    We present a method for computer generated pen-and-ink illustrations by the simulation of stippling. In a stipple drawing, dots are used to represent tone and also material of surfaces. We create such drawings by generating an initial dot set which is then processed by a relaxation method based on Voronoi diagrams. The point patterns generated are approximations of Poisson disc distributions and can also be used for integrating functions or the positioning of objects. We provide an editor similar to paint systems for interactively creating stipple drawings. This makes it possible to create such drawings within a matter of hours, instead of days or even weeks when the drawing is done manually.
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    Modelling virtual cities dedicated to behavioural animation
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Thomas, Gwenola; Donikian, Stephane
    In order to populate virtual cities, it is necessary to specify the behaviour of dynamic entities such as pedestrians or car drivers. Since a complete mental model based on vision and image processing cannot be constructed in real time using purely geometrical information, higher levels of information are needed in a model of the virtual environment. For example, the autonomous actors of a virtual world would exploit the knowledge of the environment topology to navigate through it. In this article, we present a model of virtual urban environments using structures and information suitable for behavioural animations. Thanks to this knowledge, autonomous virtual actors can behave like pedestrians or car drivers in a complex city environment. A city modeler has been designed, using this model of urban environment, and enables complex urban environments for behavioural animation to be automatically produced.
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    Real Time Local Approximation of Deformations using Rotations
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Maillot, Jerome
    Additional realism can be achieved in computer generated images using smooth and increasingly complex deformations. Though significant effort has been spent on improving these deformations, no general method has been proposed yet to deal with rigid pieces connected to soft objects. This paper proposes a general framework to solve this problem. We will present several types of applications, such as flowing small objects in a deformation field, animating rigid features connected to some deformed object, or smoothly attached limbs to a deforming body. All the calculations presented here can be applied to any type of deformation, provided that the deformation at each point only depends on the point itself. Even though we can directly compute the result for some analytical deformation fields, we will show that a good sampling of the deformation in the area of interest is generally enough. One intermediate result consists of a practical method to find the best rotation that approximates a linear transformation. The proposed method is a superset of the Gram-Schmidt orthonormalization process, and is much easier to compute than global methods based on Taylor series.
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    Integration of Multidimensional Interaction Devices in Real-Time Computer Graphics Applications
    (Blackwell Publishers Ltd and the Eurographics Association, 2000) Frohlich, Torsten; Roth, Marcus
    Modern CAD/CAM and Virtual Reality applications cannot be imagined without the new class of interaction devices allowing the user direct interaction with computer generated scenes. Integrating such devices into existing or newly developed software is a complex task for a number of reasons. The set of devices is very heterogeneous in functionality and data formats. Most devices are difficult to handle by inexperienced users or need careful handling and calibration. After reviewing a number of existing systems, a novel approach to this problem is presented. A device interface that allows the flexible, hardware independent configuration and error robust operation, even reconfiguration and exchanges of interaction devices during operation, will be introduced. The system structure is discussed and novel communication protocols reducing latency are invented.