Showing papers in "The Visual Computer in 1999"
TL;DR: This paper proposes an adaptive approach to the fast reconstruction of iso-surfaces from regular volume data at arbitrary levels of detail, designed to enable real-time navigation through complex structures while providing user-adjustable resolution levels.
Abstract: Recent advances in the technology of 3D sensors and in the performance of numerical simulations result in the generation of volume data at ever growing size. In order to allow real-time exploration of even the highest resolution data sets, adaptive techniques benefiting from the hierarchical nature of multi-resolution representations have gained special attention. In this paper we propose an adaptive approach to the fast reconstruction of iso-surfaces from regular volume data at arbitrary levels of detail. The algorithm has been designed to enable real-time navigation through complex structures while providing user-adjustable resolution levels. Since adaptive on-the-fly reconstruction and rendering is performed from a hierarchical octree representation of the volume data, the method does not depend on pre-processing with respect to a specific iso-value thus allowing the user to interactively browse through the set of all possible iso-surfaces. Special attention is paid to the fixing of cracks in the surface where the adaptive reconstruction level changes and to the efficient estimation of the iso-surface’s curvature.
173 citations
TL;DR: The results show that FA aids users in understanding spoken text in noisy conditions; that it can effectively make waiting times more acceptable to the user; and that it makes services more attractive to the users, particularly when they compare directly the same service with or without the FA.
Abstract: Computer simulation of human faces has been an active research area for a long time. However, it is less clear what the applications of facial animation (FA) will be. We have undertaken experiments on 190 subjects in order to explore the benefits of FA. Part of the experiment was aimed at exploring the objective benefits, i.e., to see if FA can help users to perform certain tasks better. The other part of the experiment was aimed at subjective benefits. At the same time comparison of different FA techniques was undertaken. We present the experiment design and the results. The results show that FA aids users in understanding spoken text in noisy conditions; that it can effectively make waiting times more acceptable to the user; and that it makes services more attractive to the users, particularly when they compare directly the same service with or without the FA.
104 citations
TL;DR: A methodology and framework to simulate facial animation and skin aging, taking into account skin texture and wrinkle dynamics is described, and the wrinkle generation and rendering can be incorporated into real-time facial animation systems.
Abstract: We describe a methodology and framework to simulate facial animation and skin aging, taking into account skin texture and wrinkle dynamics. We split the facial simulation process into facial surface deformation and wrinkle generation. The first of these is based on a three-layered facial structure (muscle, connective tissue, and skin layers). The layer of B-spline patch muscles provides the relevant contraction forces to enable the skin deformation, while the layer of connective tissues constrains the range of skin movement. The wrinkle generation uses a synthetic texture, and wrinkles are formed dynamically, thanks to a linear plastic model. The wrinkle generation and rendering can be incorporated into real-time facial animation systems.
98 citations
TL;DR: A comprehensive analysis of various convolution kernels is presented, with a special attention to polynomial kernels.
Abstract: A comprehensive analysis of various convolution kernels is presented. Computational complexity and compatibility between the kernels and a number of modeling primitives are examined. A number of practical suggestions are given how to choose the proper kernel function, with a special attention to polynomial kernels. Mathematical formulations for convolved line segments are given.
89 citations
TL;DR: A new approach for establishing correspondence for morphing between two homeomorphic polyhedral models by defining morphing trajectories between the feature pairs and by interpolating them across the merged polyhedron.
Abstract: We present a new approach for establishing correspondence for morphing between two homeomorphic polyhedral models. The user can specify corresponding feature pairs on the polyhedra with a simple and intuitive interface. Based on these features, our algorithm decomposes the boundary of each polyhedron into the same number of morphing patches. A 2D mapping for each morphing patch is computed in order to merge the topologies of the polyhedra one patch at a time. We create a morph by defining morphing trajectories between the feature pairs and by interpolating them across the merged polyhedron. The user interface provides high-level control, as well as local refinement to improve the morph. The implementation has been applied to several polyhedra composed of thousands of polygons. The system can also handle homeomorphic non-simple polyhedra that are not genuszero (or have holes).
88 citations
TL;DR: An integrated system for 3D computer graphics (CG) hair image synthesis based on a trigonal prism wisp model is presented, which can successfully and efficiently synthesize realistic CG hair style images.
Abstract: Hair plays an important role in the image of the human face. However, it is still difficult and time consuming to synthesize realistic 3D CG hair images. In this paper, we present an integrated system for 3D computer graphics (CG) hair image synthesis based on a trigonal prism wisp model. By applying the trigonal prism wisp model, 2D hair distribution maps and other CG techniques to our system, we can successfully and efficiently synthesize realistic CG hair style images. A 3D hair style editing tool (HET) is incorporated into the system to support the creation of 3D hair styles. We have also integrated this system with other research results to construct a system for 3D CG character synthesis.
79 citations
TL;DR: The method is general in that there are no restrictions on the number of boundary curves, and the cross-boundary derivatives can be specified independently.
Abstract: -sided region with Gɛ continuous NURBS patches that interpolate boundary curves and approximate given cross-boundary derivatives. The NURBS surfaces joining along inner or boundary curves have normal vectors that do not deviate more than the user-specified angular tolerance ɛ. The method is general in that there are no restrictions on the number of boundary curves, and the cross-boundary derivatives can be specified independently. To satisfy all conditions, only one degree elevation is needed.
52 citations
TL;DR: This paper aims to demonstrate the efforts towards in-situ applicability of EMMARM, which aims to provide real-time information about the physical properties of EMTs and their applications in the field of information science.
Abstract: 1 Hiroshima City University, Faculty of Information Sciences, 3-4-1 Ozukahigashi, Asaminami-ku, Hiroshima, 731-3194, Japan E-mail: {doba, okita}@im.hiroshima-cu.ac.jp 2 The University of Tokyo, Department of Information Science, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan E-mail: nis@is.s.u-tokyo.ac.jp 3 Hiroshima University, Faculty of Engineering, 1-4-1 Kagamiyama, Higashi-Hiroshima, 739-8527, Japan E-mail: yama@eml.hiroshima-u.ac.jp
47 citations
TL;DR: A new system dedicated to the real-time production ofimedia products and TV shows involving multiple virtual actors and presenters, named VHD (Virtual Human Director), may also be used for character animation on high-level systems and interaction with Webbased applications.
Abstract: In this paper, we present a new system dedicated to the real-time production ofmultimedia products and TV shows involving multiple virtual actors and presenters. This system, named VHD (Virtual Human Director), may also be used for character animation on high-level systems and interactionwithWebbased applications. The user can create virtual stories by directing all actions in real time. It is similar to a movie producer directing actors during filming but with more control given to the director in the sense that everything is decided and controlled by the same person. To make this complicated task possible, in a useable way, we based the interaction on the high-level control of the virtual actor.
46 citations
TL;DR: A new refinement method is introduced for computing the triangle sequences of a mesh that generates the triangulation and the triangle strip simultaneously, using a mesh refinement scheme, and is able to produce a hierarchy of triangle strips defined at each refinement level.
Abstract: This paper introduces a new refinement method for computing the triangle sequences of a mesh. We apply the method to construct a single generalized triangle strip that completely covers a parametric or implicit surface. A remarkable feature of this application is that our method generates the triangulation and the triangle strip simultaneously, using a mesh refinement scheme. As a consequence, we are able to produce a hierarchy of triangle strips defined at each refinement level. This data structure has many applications in geometry compression and rendering.
41 citations
TL;DR: DeepMatrix, a shared 3D virtual environment system based on two open technologies, Java and the Virtual Reality Modeling Language (VRML), is presented and authoring for DeepMatrix environments is introduced.
Abstract: In this paper we present DeepMatrix, a shared 3D virtual environment system based on two open technologies, Java and the Virtual Reality Modeling Language (VRML). The system is designed for use on current consumer hardware and requires only a standard Web browser with VRML plug-in. Due to a lean client-server implementation, system performance is superior to comparable approaches and easily extensible. This paper also introduces authoring for DeepMatrix environments and discusses results drawn from a large experimental implementation of widely varying and interconnected virtual worlds.
TL;DR: This work introduces and explores the edge-covering problem; the guards are required to observe the edges of P; metaphorically the paintings on the walls of the art gallery, and not necessarily every interior point.
Abstract: so that each point of P is seen by at least one guard. We introduce and explore the edge-covering problem; the guards are required to observe the edges of P; metaphorically the paintings on the walls of the art gallery, and not necessarily every interior point. We compare minimum edge and interior covers for a given polygon and analyze the bounds and complexity for the edge-covering problem. We also introduce and analyze a restricted edge covering problem, where full visibility of each edge from at least one guard is required. For this problem we present an algorithm that computes a set of regions where a minimum set of guards must be located. The algorithm can also deal with the external visibility of a set of polygons.
TL;DR: The proposed approach is a constrained finite element method that successfully introduces a geometric constraint into the geometrical, nonlinear, finite element equations and obtains an approximate solution satisfying the mechanical properties and the geometric constraint of cloth deformation.
Abstract: This paper presents a new method for modeling cloth deformation. The proposed approach is a constrained finite element method. We successfully introduce a geometric constraint into the geometrical, nonlinear, finite element equations. The assumed constraint is that lengths of all threads in a cloth object remain unchanged after deformation. Using the proposed method, we obtain an approximate solution satisfying the mechanical properties and the geometric constraint of cloth deformation. Further, the long computing time and solution distortion problems involved in the large rotation of cloth deformation can be solved. We also present several examples to verify the mode.
TL;DR: The main goal has been to provide a classification of computer animation systems focused on motion and behaviour modelling from the point of view of control techniques.
Abstract: The main task of a computer animator is to make the objects of a purely synthetic 3D world move realistically. The great number of computer animation techniques that already exist and the new ones that are continuously appearing, are the result of a multidisciplinary exchange of ideas. Our main goal has been to provide a classification of computer animation systems focused on motion and behaviour modelling from the point of view of control techniques. We also present the historical evolution in these areas, providing an extensive bibliography and highlighting some historical milestones. Finally, a set of Internet adresses of the most relevant research groups in this area present on the Web is also given.
TL;DR: In this article, the authors present a dynamic systems approach to modeling and generating low-level behaviors for autonomous agents such as real-time target tracking and obstacle avoidance in time-varying environments.
Abstract: We present a dynamic systems approach to modeling and generating low-level behaviors for autonomous agents Such behaviors include real-time target tracking and obstacle avoidance in time-varying environments The novelty of the method lies on the integration of distinct non-linear dynamic systems to model the agent's interaction with the environment An angular velocity control dynamic system guides the agent's direction angle, while another dynamic system selects the environmental input that will be used in the control system The agent interacts with the environment through its knowledge of the position of stationary and moving objects In our system agents automatically avoid stationary and moving obstacles to reach the desired target(s) This approach allows us to prove the stability conditions that result in a principled methodology for the computation of the system's dynamic parameters We present a variety of real-time simulations that illustrate the power of our approach
TL;DR: The prototype, extract information from the World Wide Web from query engines, automatically categorizes and clusters the information and allows the user to visualize.
Abstract: relevance measures of the objects are not significant. We flatten the multidimensionality of the feature space into a 2D relevance map, capturing the inter-relations among the features. The prototype, extract information from the World Wide Web from query engines, automatically categorizes and clusters the information and allow the user to visualize.
TL;DR: An algebraic specification of the operators needed to handle the topological models and refinements of 2D and 3D subdivisions is presented, thanks to the use of rewrite systems.
Abstract: The geometric refinements of 2D and 3D subdivisions are basic operations in geometric programming. They consist in partitioning their cells, until no intersection exists between them and in achieving their topological restructuring. We present new methods to formalize their design. We present an algebraic specification of the operators needed to handle the topological models and refinements. We completely describe the refinement processes, thanks to the use of rewrite systems. This approach allows us to exhibit integrity constraints for the objects handled and to focus on the conceptual and logical aspects of the refinement. Finally, we show how the systems are enhanced to reflect choices of implementations and algorithmic improvements.
TL;DR: This article describes aPolyFormeso, the first software member of this family to have reached a sufficient degree of development to show that declarative techniques can be applied and to demonstrate the potential of these methods in the field of computer graphics and to convince those waiting for practical achievements.
Abstract: The notion of declarative generation first mentioned by the Nantes research team in computer graphics has noticeably progressed of late (Lucas et al. 1990). After a first concept-developing phase, the project ExploFormes moved into active research to define techniques able to bring these new ideas into play. At present, the first application programs for declarative generation from the research team clearly show the potential of the approach. This article describes aPolyFormeso, the first software member of this family to have reached a sufficient degree of development to show that declarative techniques can be applied. By means of the following description, we wish to demonstrate the potential of these methods in the field of computer graphics and to convince those waiting for practical achievements. In Sect. 2, the main principles of the declarative generation of scenes are recalled. A definition and the objectives of declarative modelization are given. After defining what universe of forms is, we define the universe of semiregular polyhedra and explain the choice of this universe as the field of experimentation. In Sect. 3, the PolyFormes software is described. In this paragraph, the software is presented from the user's point of view so that the declarative paradigm for modelling complex objects is emphasized. In Sect. 4, we present PolyFormes from the inside. We explain the use of an inference engine, using rules and facts that model all the knowledge about a polyhedron or a family of polyhedra. Correctness and completeness in this geometrical context are defined and discussed. Finally, the main rules of the system are given with symbolic notation. The body that achieves the mathematical calculus of the geometrical entities is also given. In Sect. 5, one can find a discussion about existing work and systems related to the declarative approach. Section 6 presents some of the problems encountered and discusses how PolyFormes resolves them. We conclude with some information about implementation.
TL;DR: A fast polygon-oriented algorithm is presented that allows the use of curved perspectives in order to overcome several drawbacks, but at the cost of non-linearity.
Abstract: Classic ultra-wide-angle perspectives are not realistic and often misleading, nevertheless, they have to be used in many applications where the viewer needs a survey of the scene. Current hardware, however, only supports classic perspectives. We present a fast polygon-oriented algorithm that allows the use of curved perspectives in order to overcome several drawbacks, but at the cost of non-linearity. Space is projected onto a sphere rather than onto an image plane. The spherical coordinates are then interpreted two-dimensionally. We discuss the advantages and drawbacks of several approaches to curved perspectives. Time measurements show that real-time animation of reasonably complicated scenes can still be done; the overhead (additional cost of CPU-time) is less than 20%. Thus, curved perspectives are a good choice in virtual reality applications where ultra-wide-angle lenses have to be used.
TL;DR: This paper presents a method for generating the draft on a free-form surface, which is a ruled surface with a nonrational Bspline form that is first defined, then generated approximately.
Abstract: When a CAD system is used to design a model manufactured by die casting, injection mould or another method, and the finished product is drawn out of a mould, it may be necessary to give the model draft. This paper presents a method for generating the draft on a free-form surface. An isocline curve and an isocline surface are first defined, then generated approximately. The approximate isocline surface, which becomes the draft on the free-form surface, is a ruled surface with a nonrational Bspline form.
TL;DR: A constrained inverse kinematics algorithm for real-time motion capture in virtual environments, that has its origins in the simulation of multi-body systems is presented and the possibility of capturing fast gestures is investigated by analysing the convergence patterns of the algorithm with the motion tracking sampling frequency for a range of actions.
Abstract: In this paper we present a constrained inverse kinematics algorithm for real-time motion capture in virtual environments, that has its origins in the simulation of multi-body systems. We apply this algorithm to an articulated human skeletal model using an electromagnetic motion tracking system with a small number of sensors to create avatar postures. The method offers efficient inverse kinematics computation and it is also generalised for the configurations of an articulated skeletal model. We investigate the possibility of capturing fast gestures by analysing the convergence patterns of the algorithm with the motion tracking sampling frequency for a range of actions.
TL;DR: A Delaunay triangulation-based algorithm to search for the nearest line or polygonal boundary to an arbitrary point, being quite similar with respect to the numbers of distance-based calculations and faster with regard to execution time.
Abstract: We describe a Delaunay triangulation-based algorithm to search for the nearest line or polygonal boundary to an arbitrary point. We use geographical data to compare the algorithm experimentally with a linear quadtree search procedure. Both algorithms use priority queues. The rich proximity relations of the triangulation result in run-time performance that is clearly competitive with the quadtree, being quite similar with respect to the numbers of distance-based calculations and faster with regard to execution time. It is envisaged that the main benefits of triangulation for neighbourhood search are in applications in which the data are permanently triangulated or in which a triangulation assists in an application-specific analysis or transformation.
TL;DR: Polynomial functions in three space that are equivariant with respect to the symmetries of a dodecahedron are determined andRaytracing techniques enable the rendering of the three-dimensional attractors so that both their complexity and symmetry can be observed.
Abstract: Polynomial functions in three space that are equivariant with respect to the symmetries of a dodecahedron are determined. These are constructed with a sum of functions under changes of coordinates with respect to the group. Monte Carlo searches through parameter space lead to functions that are experimentally chaotic and that have visually appealing attractors. Raytracing techniques enable the rendering of the three-dimensional attractors so that both their complexity and symmetry can be observed.
TL;DR: This work has transformed a system designed for the realistic offline biomechanical/behavioral animation of artificial fishes into a real-time, interactive, stereoscopic, virtual undersea experience.
Abstract: Biomechanical simulation enables the realistic animation of animals in virtual worlds, but at significant computational cost. Synthetic motion capture is a low-cost technique that prescribes (i) the capture of motion data through the systematic simulation of biomechanical animal models and (ii) compilation of the captured data into kinematic action repertoires rich enough to support elaborate behavioral animation. Synthetic motion capture in conjunction with level-of-detail geometric modeling and object culling during rendering has enabled us to transform a system designed for the realistic offline biomechanical/behavioral animation of artificial fishes into a real-time, interactive, stereoscopic, virtual undersea experience.
TL;DR: A new, fast, triangular mesh approximation method for the 3D visualization of surface data is proposed using spatiofrequency localization characteristics and directional information of wavelet coefficients to approximate the data to a proper triangular mesh.
Abstract: This paper proposes a new, fast, triangular mesh approximation method for the 3D visualization of surface data. Using spatiofrequency localization characteristics and directional information of wavelet coefficients, we determine local complexities of surface data and approximate the data to a proper triangular mesh. The proposed algorithm is quite simple, and the computational cost is low due to the direct use of wavelet coefficients for vertex removal. The computer simulation results for terrain data show that the proposed algorithm is excellent for fast 3D visualization.
TL;DR: The control of the postures are reduced to some intuitive parameters, simplifying the animator's work enormously and the algorithm can be integrated in inverse kinematics-based systems since it has the same order of time complexity and a similar structure.
Abstract: We addresse the problem of articulated character positioning with dynamic and kinematic constraints and with an emphasis on balancing. The balance of the figure is controlled by the precise manipulation of joint torques. The control of the postures are reduced to some intuitive parameters, simplifying the animator's work enormously. The algorithm can easily be integrated in inverse kinematics-based systems since it has the same order of time complexity and a similar structure. The presented technique can find applications in all computer animation systems, virtual environments including articulated figures such as synthetic humans, and robotics.
TL;DR: The scanline principle is a general technique for efficiently converting any display algorithm that is based on polygon scan conversion into scanline mode, i.e., the image is produced in scanline order with required memory proportional to one scanline.
Abstract: The scanline principle is a general technique for efficiently converting any display algorithm that is based on polygon scan conversion into scanline mode, i.e., the image is produced in scanline order with required memory proportional to one scanline. Based on critical-points scan conversion, the technique reduces the Z-buffer or its variants to one scanline. Current scanline depth buffers are inefficient in both time and space. The scanline principle can also transform listpriority methods, such as BSP trees, into scanline mode. The scanline mode enables efficient supersampling and averaging, and low latency in image generation, compression and transmission.
TL;DR: Several energy formulations are derived, including Kirchhoff-Love plate energy, firstorder energy and jerk energy, based on a new paradigm for free-form surface over arbitrary quadrilateral meshes.
Abstract: We derive several energy formulations, including Kirchhoff-Love plate energy, firstorder energy and jerk energy. These formulations are based on a new paradigm for free-form surface over arbitrary quadrilateral meshes. The present work briefly recalls the underlying principles of the energy formulation, then considers the various behaviors and resulting surfaces through examples. Each energy term is used separately, or energy terms are combined, to obtain the samples.
TL;DR: A new approach for better estimation of normal deviations between different levels of detail is described, which allows for accurate lighting with a minimum number of triangles.
Abstract: Recently, output-sensitive rendering algorithms have gained a lot interest. While some years ago the number of triangles describing a scene was smaller than the number of pixels on the screne, this relation has changed to the opposite. The size of the models has become significantly larger while the screen resolution remained more or less constant. One way to get output-sensitivity, is the view-dependent use of multiresolution models. The key idea is to determine the lowest resolution for each part of the object that is necessary to get good images that are visually indistinguishable from rendering the original mesh. To take care of the illumination of the objects there are approaches that use cones of normal vectors to perform illumination dependent selective refinement. This allows the correct rendering of highlights and transitions between lit and unlit areas of an object. The drawback of these approaches is that using only the normal cone for the detection gives only a very poor criteria to detect the problematic cases. Therefore, too much refinement has to be performed which in most cases prevents real time update rates between successive frames. In this paper we describe a new approach for better estimation of normal deviations between different levels of detail. This allows for accurate lighting with a minimum number of triangles.
TL;DR: This work compacts existing outline-based oriental fonts and preserves original design with a parametric representation using quantization in parametric space, and introduces automatic classification and optimization using topological signature mapping between element shapes.
Abstract: The ideographic, oriental alphabets have many more symbols and are more complex than Western alphabets. Composing glyphs from radicals and radicals from strokes can simplify their digital representation. We compact existing outline-based oriental fonts and preserve original design with a parametric representation. Our method comprises: classification of elements to groups, parameterization of representative elements, optimization of the parametric representatives to match all group elements, and compaction using quantization. We introduce automatic classification and optimization using topological signature mapping between element shapes. We control the trade-off between compacting and preserving quality simply and naturally by using quantization in parametric space.