EG 1995 Conference Proceedings

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https://diglib.eg.org/handle/10.2312/13894

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The HUMANOID Environment for Interactive Animation of Multiple Deformable Human Characters
(Blackwell Science Ltd and the Eurographics Association, 1995) Boulic, R.; Capin, T.; Huang, Z.; Kalra, P.; Lintermann, B.; Magnenat-Thalmann, N.; Moccozet, L. and Molet, T. and Pandzic, I. and Saar, K. and Schmitt, A. and Shen, J. and Thalmann, D.
We describe the HUMANOID environment dedicated to human modeling and animation for general multimedia, VR, and CAD applications integrating virtual humans. We present the design of the system and the integration of the various features: generic modeling of a large class of entities with the BODY data structure, realistic skin deformation for body and hands, facial animation, collision detection, integrated motion control and parallelization of computation intensive tasks.
Discrete Ray-Tracing of Huge Voxel Spaces
(Blackwell Science Ltd and the Eurographics Association, 1995) Stolte, Nilo; Caubet, Rene
The quality of images produced by Discrete Ray-Tracing voxel spaces is highly dependent on 3d grid resolution. The huge amount of memory needed to store such grids often discards discrete Ray-Tracing as a practical visualization algorithm. The use of an octree can drastically change this when most of space is empty, as such is the case in most scenes.Although the memory problem can be bypassed using the octree, the performance problem still remains. A known fact is that the performance of discrete traversal is optimal for quite low resolutions. This problem can be easily solved by dividing the task in two steps, working in two low resolutions instead of just one high resolution, thus taking advantage of optimal times in both steps. This is possible thanks to the octree property of representing the same scene in several different resolutions. This article presents a two step Discrete Ray-Tracing method using an octree and shows, by comparing it with the single step version, that a substantial gain in performance is achieved.
An Adaptive Spatial Subdivision of the Object Space for Fast Collision Detection of Animated Rigid Bodies
(Blackwell Science Ltd and the Eurographics Association, 1995) Bandi, Srikanth; Thalmann, Daniel
Collision detection tests between objects dominate run time simulation of rigid body animation. Traditionally, hierarchical bounding box tests are used to minimize collision detection time. But the bounding boxes do not take shapes of the objects into account which results in a large number of collision detection tests. We propose an adaptive spatial subdivision of the object space based on octree structure to rectify this problem. We also present a technique for efficiently updating this structure periodically during the simulation.
An Incremental Alignment Algorithm for Parallel Volume Rendering
(Blackwell Science Ltd and the Eurographics Association, 1995) Or, Daniel Cohen; Fleishman, Shachar
This paper introduces a data distribution scheme and an alignment algorithm for parallel volume rendering. The algorithm performs a single wrap-around shear transformation which requires only a regular inter-processor communication pattern. The alignment can be implemented incrementally consisting of short distance shifts, thus significantly reducing the communication overhead. The alignment process is a non-destructive transformation, consisting of a single non-scaling shear operation. This is a unique feature which provides the basis for the incremental algorithm.
A Graph-Based Approach to Surface Reconstruction
(Blackwell Science Ltd and the Eurographics Association, 1995) Mencl, Robert
A new approach to the reconstruction of a surface from an unorganized set of points in space is presented. The point set may for example be obtained with a laser scanner or a manual digitizing tool, and is the only source of information about the shape of the acquired object. The basic idea is to calculate the Euclidean minimum spanning tree (EMST) of the given points. The EMST is then augmented to the so-called surface description graph (SDG). Finally the wire frame defined by the SDG are filled with triangles. The advantage of our approach is that also highly non-convex and even disconnected surfaces are reconstructed quite reliably. This is demonstrated for a variety of data sets.
Multiresolution B-spline Radiosity
(Blackwell Science Ltd and the Eurographics Association, 1995) Yu, Yizhou; Peng, Qunsheng
This paper introduces a kind of new wavelet radiosity method called multiresolution B-spline radiosity, which uses B-splines of different scales to represent radiosity distribution functions. A set of techniques and algorithms, such as function extrapolation, adaptive quadrature, scale adjustment and octree, are proposed to implement it. This method sets up hierarchical structures on surfaces, keeps radiosity distribution continuous at element boundaries, does not need postprocessing, and does not prevent the use of any surface whose parameter domain is rectilinear.
A rational model of the surface swept by a curve*
(Blackwell Science Ltd and the Eurographics Association, 1995) Johnstone, John K.; Williams, James P.
This paper shows how to construct a rational Bezier model of a swept surface that interpolates N frames (i.e., N position/orientation pairs) of a fixed rational space curve c(s) and maintains the shape of the curve at all intermediate points of the sweep. Thus, the surface models an exact sweep of the curve, consistent with the given data. The primary novelty of the method is that this exact modeling of the sweep is achieved without sacrificing a rational representation for the surface. Through a simple extension, we also allow the sweeping curve to change its size through the sweep. The position, orientation, and size of the sweeping curve can change with arbitrary continuity (we use C2 continuity in this paper). Our interpolation between frames has the classical properties of Bezier interpolation, such as the convex hull property and linear precision.This swept surface is a useful primitive for geometric design. It encompasses the surface of revolution and extruded surface, but extends them to arbitrary sweeps. It is a useful modeling primitive for robotics and CAD/CAM, using frames generated automatically by a moving robot or tool.
A Multimedia Constraint System1
(Blackwell Science Ltd and the Eurographics Association, 1995) van Hintum, J.E.A.; Reynolds, G.J.
The MADE constraint system provides excellent opportunities to introduce constraints in a multimedia application. Multimedia applications are not only a good place to experiment with constraint systems- constraints in a multimedia environment are almost indispensable. Due to the overwhelming amount of data and the number of relations between several parts of this data, multimedia applications almost demand the support of a constraint management system.The MADE constraint system combines the object oriented programming paradigm, inherited from the mC++ language, the declarative constraint programming paradigm and the special requirements imposed upon the constraint system by the multimedia environment. Among other things, the MADE constraint system provides parallel satisfaction techniques- several constraints may be solved simultaneously and this satisfaction process is performed in parallel with the application. This not only reduces the time needed to solve the constraints, it also allows the multimedia application to proceed with its presentation while (beneath the surface) the constraints are maintained. This not only holds for the parts of the presentation that are not constrained at all, but also for those parts that are. Furthermore, the constraint system is transparent to the multimedia application- no special coding or preparation of the objects in the application is necessary. Constraints can be added later to the application without much work. Besides that, it is also possible to add and remove constraints at runtime- objects may be constrained for only a period of the time the application is running.
Automatic Reconstruction of Unstructured 3D Data: Combining a Medial Axis and Implicit Surfaces
(Blackwell Science Ltd and the Eurographics Association, 1995) Bittar, Eric; Tsingos, Nicolas; Gascuel, Marie-Paule
This paper presents a new method that combines a medial axis and implicit surfaces in order to reconstruct a 3D solid from an unstructured set of points scattered on the object s surface. The representation produced is based on iso-surfaces generated by skeletons, and is a particularly compact way of defining a smooth free-form solid. The method is based on the minimisation of an energy representing a"distance" between the set of data points and the iso-surface, resembling previous reserach19. Initialisation, however, is more robust and efficient since there is computation of the medial axis of the set of points. Instead of subdividing existing skeletons in order to refine the object s surface, a new reconstruction algorithm progressively selects skeleton-points from the pre- computed medial axis using an heuristic principle based on a"local energy" criterion. This drastically speeds up the reconstruction process. Moreover, using the medial axis allows reconstruction of objects with complex topology and geometry, like objects that have holes and branches or that are composed of several connected components. This process is fully automatic. The method has been successfully applied to both synthetic and real data.
Algorithms for Extracting Correct Critical Points and Constructing Topological Graphs from Discrete Geographical Elevation Data
(Blackwell Science Ltd and the Eurographics Association, 1995) Takahashi, Shigeo; Ikeda, Tetsuya; Shinagawa, Yoshihisa; Kunii, Tosiyasu L.; Ueda, Minoru
Researchers in the fields of computer graphics and geographical information systems (GISs) have extensively studied the methods of extracting terrain features such as peaks, pits, passes, ridges, and ravines from discrete elevation data. The existing techniques, however, do not guarantee the topological integrity of the extracted features because of their heuristic operations, which results in spurious features. Furthermore, there have been no algorithms for constructing topological graphs such as the surface network and the Reeb graph from the extracted peaks, pits, and passes. This paper presents new algorithms for extracting features and constructing the topological graphs using the features. Our algorithms enable us to extract correct terrain features; i.e., our method extracts the critical points that satisfy the Euler formula, which represents the topological invariant of smooth surfaces. This paper also provides an algorithm that converts the surface network to the Reeb graph for representing contour changes with respect to the height. The discrete elevation data used in this paper is a set of sample points on a terrain surface. Examples are presented to show that the algorithms also appeal to our visual cognition.
Realizing 3D Visual Programming Environments within a Virtual Environment
(Blackwell Science Ltd and the Eurographics Association, 1995) Van Reeth, F.; Coninx, K.; De Backer, S.; Flerackers, E.
In the visual programming community, many interesting graphical metaphors have been reported upon for representing computer programs graphically. Most of them have a 2D or 2.5D appearance on the screen in order to reflect the inherent multi-dimensionality of the programming constructs being represented. By going into a three-dimensional representation, this reflection can go a stepfurther. With ever increasing3D graphics rendering capabilities on todays computers, it moreover becomes feasible to extend the dimensionality of the program (and data structure) depiction. We follow this approach by realizing 3D graphical programming techniques within CAEL, our interactive Computer Animation Environment Language. The paper elucidates how several concepts, traditionally found within the Virtual Environments area, can be utilized in the realization of three-dimensional Programming Environments.
Sketching 3D Animations
(Blackwell Science Ltd and the Eurographics Association, 1995) Balaguer, Jean-Francis; Gobbetti, Enrico
We are interested in providing animators with a general-purpose tool allowing them to create animations using straight-ahead actions as well as pose-to-pose techniques. Our approach seeks to bring the expressiveness of real-time motion capture systems into a general-purpose multi-track system running on a graphics workstation. We emphasize the use of high-bandwidth interaction with 3D objects together with specific data reduction techniques for the automatic construction of editable representations of interactively sketched continuous parameter evolution. In this paper, we concentrate on providing a solution to the problem of applying data reduction techniques in an animation context. The requirements that must be fulfilled by the data reduction algorithm are analyzed. From the Lyche and Morken knot removal strategy, we derive an incremental algorithm that computes a B-spline approximation to the original curve by considering only a small piece of the total curve at any time. This algorithm allows the processing of the user s captured motion in parallel with its specification, and guarantees constant latency time and memory needs for input motions composed of any number of samples. After showing the results obtained by applying our incremental algorithm to 3D animation paths, we describe an integrated environment to visually construct 3D animations, where all interaction is done directly in three dimensions. By recording the effects of user s manipulations and taking into account the temporal aspect of the interaction, straight-ahead animations can be defined. Our algorithm is automatically applied to continuous parameter evolution in order to obtain editable representations. The paper concludes with a presentation offuture work.
Synthetic Vision and Audition for Digital Actors
(Blackwell Science Ltd and the Eurographics Association, 1995) NOSER, Hansrudi; THALMANN, Daniel
We present an overview of some principles of synthetic vision and audition for digital autonomous actors in virtual worlds. After a short review of the state-of-the-art we focus on some aspects of synthetic vision and virtual world constraints. Then, we present a simple real time structured sound renderer. This sound renderer is used as audition channel for synthetic and real actors and synchronized sound track generator for video film productions.
Morphological Operations for Color-Coded Images
(Blackwell Science Ltd and the Eurographics Association, 1995) Busch, Christoph and Eberle, Michael
The subject of this paper is the semantically based postprocessing of color-coded images such as classification results. We outline why the classical definition of mathematical morphology suffers if it is used for processing of coded image data. Therefore we provide an extension for morphological operations such as dilation, erosion, opening, and closing. With a new understanding of morphology we introduce bridging and tunneling as further combinations of dilation and erosion. The extensions are applied to medical image data, where the semantic rules stem from basic anatomical knowledge.
A Quick Rendering Method Using Basis Functions for Interactive Lighting Design
(Blackwell Science Ltd and the Eurographics Association, 1995) Dobashi, Yoshinori; Kaneda, Kazufumi; Nakatani, Hideki; Yamashita, Hideo; Nishita, Tomoyuki
When designing interior lighting effects, it is desirable to compare a variety of lighting designs involving different lighting devices and directions of light. It is, however, time-consuming to generate images with many different lighting parameters, taking interreflection into account, because all luminances must be calculated and recalculated. This makes it difficult to design lighting effects interactively. To address this problem, this paper proposes a method of quickly generating images of a given scene illustrating an interreflective environment illuminated by sources with arbitrary luminous intensity distributions. In the proposed method, the luminous intensity ditribution is expressed with basis functions. The proposed method uses a series of spherical harmonic functions as basis functions, and calculates in advance each intensity on surfaces lit by the light sources whose luminous intensity distribution are the same as the spherical harmonic functions. The proposed method makes it possible to generate images so quickly that we can change the luminous intensity distribution interactively. Combining the proposed method with an interactive walk-through that employs intensity mapping, an interactive system for lighting design is implemented. The usefulness of the proposed method is demonstrated by its application to interactive lighting design, where many images are generated by altering lighting devices and/or direction of light.
Synthesizing Feather Textures in Galliformes
(Blackwell Science Ltd and the Eurographics Association, 1995) Dai, Wen-Kai; Shih, Zen-Chung; Chang, Ruei-Chuan
The texture of feather is one of the most fascinating, complicated, and beautiful texture patterns in nature. In this paper, we propose a new and effective texture generation approach that uses the traits of iteration behavior to synthesize the textures of Galliformes feathers realistically. We also propose an interactive feather modeling approach which provides a close connection between the user s intuition and the resulting branching pattern. In texturing the feather structure, we use an object-space mapping technique. Experimental results are presented to show the effectiveness of our method.
Distributed Augmented Reality for Collaborative Design Applications
(Blackwell Science Ltd and the Eurographics Association, 1995) Ahlers, Klaus H.; Kramer, Andre; Breen, David E.; Chevalier, Pierre-Yves; Crampton, Chris; Rose, Eric; Tuceryan, Mihran; Whitaker, Ross T.; Greer, Douglas
This paper presents a system for constructing collaborative design applications based on distributed augmented reality. Augmented reality interfaces are a natural method for presenting computer-based design by merging graphics with a view of the real world. Distribution enables users at remote sites to collaborate on design tasks. The users interactively control their local view, try out design options, and communicate design proposals. They share virtual graphical objects that substitute for real objects which are not yet physically created or are not yet placed into the real design environment.We describe the underlying augmented reality system and in particular how it has been extended in order to support multi-user collaboration. The construction of distributed augmented reality applications is made easier by a separation of interface, interaction and distribution issues. An interior design application is used as an example to demonstrate the advantages of our approach.
VR-VIBE: A Virtual Environment for Co-operative Information Retrieval
(Blackwell Science Ltd and the Eurographics Association, 1995) Benford, Steve; Snowdon, Dave; Greenhalgh, Chris; Ingram, Rob; Knox, Ian; Brown, Chris
We present a virtual reality application called VR-VIBE which is intended to support the co-operative browsing and filtering of large document stores. VR-VIBE extends a visualisation approach proposed in a previous two dimensional system called VIBE into three dimensions, allowing more information to be visualised at one time and supporting more powerful styles of interaction, The essence of VR-VIBE is that multiple users can explore the results of applying several simultaneous queries to a corpus of documents. By arranging the queries into a spatial framework, the system shows the relative attraction of each document to each query by its spatial position and also shows the absolute relevance of each document to all of the queries. Users may then navigate the space, select individual documents, control the display according to a dynamic relevance threshold and dynamically drag the queries to new positions to see the effect on the document space. Co-operative browsing is supported by directly embodying users and providing them with the ability to interact over live audio connections and to attach brief textual annotations to individual documents. Finally, we conclude with some initial observations gleaned from our experience of constructing VR-VIBE and using it in the laboratory setting.
Generating a Texture Map from Object-Surface Texture Data
(Blackwell Science Ltd and the Eurographics Association, 1995) Maruya, Makoto
A number of 3D digitizing methods, including stereopsis, are capable of measuring not only an object s shape but also its surface texture. Measured shape data can be expressed as a polyhedron whose faces are triangular, and object-surface texture data can be represented in the form of color data for each of the vertices of the various triangles. The ability to apply object-surface texture data directly to the creation of computer graphics images has been severely limited by the extreme difficulty of expressing such texture data in the image from which conventional texture mapping proceeds (commonly referred to as a texture map). Proposed here is a method that generates a texture map from object-surface texture data. First, the method reduces the number of triangles in the polyhedron while preserving essentially all the color data that it originally contained. Next, it arranges the triangles in the simplified triangle mesh onto a plane, and generates a texture map from this arrangement. This method preserves the full texture of an object, no matter how complex its shape, an advantage over the conventional cylindrical texture representation approach. Furthermore, since essentially all color data has been retained, the reduction in the number of triangles does not produce any significant reduction in the texture-realism of the object image produced.
A new radiosity approach for regular objects: application to ruled surfaces
(Blackwell Science Ltd and the Eurographics Association, 1995) ARQUES, Didier; MICHELIN, Sylvain
This paper introduces a new approach in the radiosity method. The main principle applied here, is the improvement of form factor computation by the knowledge of the model properties. More precisely, if surfaces describing a scene are"regular", the values of the form factor and its"derivatives" between any patch B and a patch A intervening in the meshing of a given surface, enable us to evaluate (with a required precision) the form factors values between B and the neighboring patches of A. We will also show that the mathematical relation we have obtained, 1) is especially efficient with ruled surfaces, 2) significantly decreases the computation time, 3) is well-adapted to refinement or subdivision techniques and 4) gives us an interesting variety of surfaces. Calculation times are equivalent to those obtained with a projective method (hemi-cube for example) but with an efficient control of the generated errors.

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