Issue 3

Permanent URI for this collection

https://diglib7.eg.org/handle/10.2312/56
EG 1993 Conference Proceedings

BibTeX (Issue 3)
                
@article{
10.1111:1467-8659.1230001,

journal = {Computer Graphics Forum},
title = {{
A Dynamic Gesture Language and Graphical Feedback for Interaction in a 3D User Interface}},

author = {
Bordegoni, Monica
 and 
Hemmje, Matthias
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230001}

}
                
@article{
10.1111:1467-8659.1230115,

journal = {Computer Graphics Forum},
title = {{
3D Computational Morphology}},

author = {
Veltkamp, Remco C.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230115}

}
                
@article{
10.1111:1467-8659.1230129,

journal = {Computer Graphics Forum},
title = {{
Parallel 3D Delaunay Triangulation}},

author = {
Cignoni, P.
 and 
Montani, C.
 and 
Perego, R.
 and 
Scopigno, R.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230129}

}
                
@article{
10.1111:1467-8659.1230143,

journal = {Computer Graphics Forum},
title = {{
Updating Polygonizations*}},

author = {
Abellanas, M.
 and 
Garcia, J.
 and 
Hernbandez, G.
 and 
Hurtado, F.
 and 
Serra, O.
 and 
Urrutia, J.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230143}

}
                
@article{
10.1111:1467-8659.1230177,

journal = {Computer Graphics Forum},
title = {{
A New Paradigm for Geometric Processing}},

author = {
Yamaguchi, Fujio
 and 
Niizeki, Masatoshi
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230177}

}
                
@article{
10.1111:1467-8659.1230189,

journal = {Computer Graphics Forum},
title = {{
Modeling of Skylight and Rendering of Outdoor Scenes}},

author = {
Tadamura, Katsumi
 and 
Nakamae, Eihachiro
 and 
Kaneda, Kazufumi
 and 
Baba, Masashi
 and 
Yamashita, Hideo and Nishita, Tomoyuki
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230189}

}
                
@article{
10.1111:1467-8659.1230153,

journal = {Computer Graphics Forum},
title = {{
Boolean Operations and Spatial Complexity of Face Octrees.}},

author = {
Pla-Garcia, Nuria
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230153}

}
                
@article{
10.1111:1467-8659.1230165,

journal = {Computer Graphics Forum},
title = {{
Introducing blending operations in feature models}},

author = {
Laakko, Timo
 and 
Mantyla, Martti
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230165}

}
                
@article{
10.1111:1467-8659.1230211,

journal = {Computer Graphics Forum},
title = {{
An Integrated System for Modeling, Animating and Rendering Hair}},

author = {
Daldegan, Agnes
 and 
Thalmann, Nadia Magnenat
 and 
Kurihara, Tsuneya
 and 
Thalmann, Daniel
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230211}

}
                
@article{
10.1111:1467-8659.1230201,

journal = {Computer Graphics Forum},
title = {{
A Rendering Algorithm for Discrete Volume Density Objects}},

author = {
Blasi, Philippe
 and 
Le Saec, Bertrand
 and 
Schlick, Christophe
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230201}

}
                
@article{
10.1111:1467-8659.1230223,

journal = {Computer Graphics Forum},
title = {{
A Declarative Design Method for 3D Scene Sketch Modeling}},

author = {
Donikian, Stephane
 and 
Hegron, Gerard
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230223}

}
                
@article{
10.1111:1467-8659.1230013,

journal = {Computer Graphics Forum},
title = {{
DIGIS A Graphical User Interface Design Environment for Non-Programmers}},

author = {
de Bruin, Hans
 and 
Bouwman, Peter
 and 
van den Bos, Jan
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230013}

}
                
@article{
10.1111:1467-8659.1230249,

journal = {Computer Graphics Forum},
title = {{
Extracting contour lines from a hierarchical surface model}},

author = {
De Floriani, Leila
 and 
Mirra, Daniela
 and 
Puppo, Enrico
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230249}

}
                
@article{
10.1111:1467-8659.1230237,

journal = {Computer Graphics Forum},
title = {{
Direct 3D Manipulation Techniques for Interactive Constraint-based Solid Modelling}},

author = {
Fa, Mingxian
 and 
Fernando, Terrence
 and 
Dew, Peter M.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230237}

}
                
@article{
10.1111:1467-8659.1230295,

journal = {Computer Graphics Forum},
title = {{
GKS-9x: Some Implementation Considerations}},

author = {
Damnjanovic, L.B.
 and 
Duce, D.A.
 and 
Robinson, S.K.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230295}

}
                
@article{
10.1111:1467-8659.1230285,

journal = {Computer Graphics Forum},
title = {{
A 4D Ray Tracing}},

author = {
Maurel, Herve
 and 
Duthen, Yves
 and 
Caubet, Rene
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230285}

}
                
@article{
10.1111:1467-8659.1230261,

journal = {Computer Graphics Forum},
title = {{
The Cone of Normals Technique for Fast Processing of Curved Patches}},

author = {
Shirmun, Leon A.
 and 
Abi-Ezzi, Salim S.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230261}

}
                
@article{
10.1111:1467-8659.1230273,

journal = {Computer Graphics Forum},
title = {{
Accurate and Consistent Reconstruction of Illumination Functions Using Structured Sampling}},

author = {
Drettakis, George
 and 
Fiume, Eugene
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230273}

}
                
@article{
10.1111:1467-8659.1230315,

journal = {Computer Graphics Forum},
title = {{
DaScript3D Integrating 3D Graphics in a Page Description Language}},

author = {
Samara, Veronika
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230315}

}
                
@article{
10.1111:1467-8659.1230329,

journal = {Computer Graphics Forum},
title = {{
Pseudo-Satellitefilm Using Fractal Clouds to Enhance Animated Weather Forecasting}},

author = {
Sakas, Georgios
 and 
Schroder, Florian
 and 
Koppert, Hans-Joachim
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230329}

}
                
@article{
10.1111:1467-8659.1230339,

journal = {Computer Graphics Forum},
title = {{
Automatic Reconstruction of Buildings from Stereoscopic Image Sequences}},

author = {
Koch, Reinhard
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230339}

}
                
@article{
10.1111:1467-8659.1230363,

journal = {Computer Graphics Forum},
title = {{
Photo-Realistic Imaging of Digital Terrains}},

author = {
Cohen, Daniel
 and 
Shaked, Amit
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230363}

}
                
@article{
10.1111:1467-8659.1230375,

journal = {Computer Graphics Forum},
title = {{
Landscapes Synthesis Achieved through Erosion and Deposition Process Simulation}},

author = {
Roudier, P.
 and 
Peroche, B.
 and 
Perrin, M.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230375}

}
                
@article{
10.1111:1467-8659.1230351,

journal = {Computer Graphics Forum},
title = {{
On the Application of Quantization and Dithering Techniques to History of Arts}},

author = {
Coltelli, P.
 and 
Faconti, G.
 and 
Marfori, F.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230351}

}
                
@article{
10.1111:1467-8659.1230025,

journal = {Computer Graphics Forum},
title = {{
Abstract Interaction Objects}},

author = {
Duke, D.J.
 and 
Harrison, M.D.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230025}

}
                
@article{
10.1111:1467-8659.1230385,

journal = {Computer Graphics Forum},
title = {{
A New Radiosity Approach Using Area Sampling for Parametric Patches}},

author = {
Nishita, Tomoyuki
 and 
Nakamae, Eihachiro
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230385}

}
                
@article{
10.1111:1467-8659.1230399,

journal = {Computer Graphics Forum},
title = {{
A Progressive Radiosity Algorithm for Scenes Containing Curved Surfaces}},

author = {
Bao, Hujun
 and 
Peng, Qunsheng
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230399}

}
                
@article{
10.1111:1467-8659.1230409,

journal = {Computer Graphics Forum},
title = {{
An Integral Geometry Based Method for Fast Form-Factor Computation}},

author = {
Sbert, Mateu
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230409}

}
                
@article{
10.1111:1467-8659.1230421,

journal = {Computer Graphics Forum},
title = {{
Form Factor Calculation: a New Expression with Implementations on a Parallel T.Node Computer}},

author = {
Michelin, Sylvain
 and 
Maffeis, Gualtiero
 and 
Arques, Didier
 and 
Grossetie, Jean Claude
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230421}

}
                
@article{
10.1111:1467-8659.1230433,

journal = {Computer Graphics Forum},
title = {{
Nonsplitting Macro Patches for Implicit Cubic Spline Surfaces}},

author = {
Guo, B.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230433}

}
                
@article{
10.1111:1467-8659.1230461,

journal = {Computer Graphics Forum},
title = {{
Quality Control of an Interpolation Method for Discontinuous Parametric Surfaces}},

author = {
Seron, F.J.
 and 
Torrens, J.J
 and 
Magallon, J.A.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230461}

}
                
@article{
10.1111:1467-8659.1230447,

journal = {Computer Graphics Forum},
title = {{
Variational Surface Design and Surface Interrogation}},

author = {
Hagen, H.
 and 
Hahmann, St.
 and 
Bonneau, G.-P.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230447}

}
                
@article{
10.1111:1467-8659.1230485,

journal = {Computer Graphics Forum},
title = {{
A Prototype of a Cooperative Visualization Workplace for the Aerodynamicist}},

author = {
Pagendarm, H.-G.
 and 
Walter, B.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230485}

}
                
@article{
10.1111:1467-8659.1230049,

journal = {Computer Graphics Forum},
title = {{
Interactive Neural Network Texture Analysis and Visualization for Surface Reconstruction in Medical Imaging}},

author = {
Busch, C.
 and 
Gro?, M.H.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230049}

}
                
@article{
10.1111:1467-8659.1230473,

journal = {Computer Graphics Forum},
title = {{
Scale-Invariant Minimum-Cost Curves: Fair and Robust Design Implements}},

author = {
Moreton, Henry P.
 and 
Sequin, Carlo H.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230473}

}
                
@article{
10.1111:1467-8659.1230497,

journal = {Computer Graphics Forum},
title = {{
Cooperative Visualization of Computational Fluid Dynamics}},

author = {
Gerald-Yamasaki, Michael J.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230497}

}
                
@article{
10.1111:1467-8659.1230037,

journal = {Computer Graphics Forum},
title = {{
Verve}},

author = {
Knittel, Gunter
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230037}

}
                
@article{
10.1111:1467-8659.1230061,

journal = {Computer Graphics Forum},
title = {{
Fast Spheres}},

author = {
Patterson, John W.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230061}

}
                
@article{
10.1111:1467-8659.1230089,

journal = {Computer Graphics Forum},
title = {{
Storage Support for Multidimensional Discrete Data in Multimedia Databases}},

author = {
Furtado, Paula
 and 
Teixeira, Jose Carlos
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230089}

}
                
@article{
10.1111:1467-8659.1230073,

journal = {Computer Graphics Forum},
title = {{
Using Multimedia to Support Cooperative Editing}},

author = {
Santos, A.
 and 
Tritsch, B.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230073}

}
                
@article{
10.1111:1467-8659.1230101,

journal = {Computer Graphics Forum},
title = {{
An Object Model for Multimedia Programming}},

author = {
Arbab, F.
 and 
Herman, I.
 and 
Reynolds, G.J.
},
year = {
1993},

publisher = {
Blackwell Science Ltd and the Eurographics Association},


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1230101}

}

Browse

Recent Submissions

Now showing 1 - 41 of 41
  • Thumbnail Image
    Item
    A Dynamic Gesture Language and Graphical Feedback for Interaction in a 3D User Interface
    (Blackwell Science Ltd and the Eurographics Association, 1993) Bordegoni, Monica; Hemmje, Matthias
    In user interfaces of modern systems, users get the impression of directly interacting with application objects. In 3D based user interfaces, novel input devices, like hand and force input devices, are being introduced. They aim at providing natural ways of interaction. The use of a hand input device allows the recognition of static poses and dynamic gestures performed by a user s hand.This paper describes the use of a hand input device for interacting with a 3D graphical application. A dynamic gesture language, which allows users to teach some hand gestures, is presented. Furthermore, a user interface integrating the recognition of these gestures and providing feedback for them, is introduced. Particular attention has been spent on implementing a tool for easy specification of dynamic gestures, and on strategies for providing graphical feedback to users interactions. To demonstrate that the introduced 3D user interface features, and the way the system presents graphical feedback, are not restricted to a hand input device, a force input device has also been integrated into the user interface.
  • Thumbnail Image
    Item
    3D Computational Morphology
    (Blackwell Science Ltd and the Eurographics Association, 1993) Veltkamp, Remco C.
    Computational Morphology is the analysis of form by computational means. This discipline typically uses techniques from Computational Geometry and Computer Aided Geometric Design. The present paper is more specifically about the construction and manipulation of closed object boundaries through a set of scattered points in 3D. Original results are developed in three stages of computational morphology: * impose a geometrical structure on the set of points- * construct a polyhedral boundary surface from this geometrical structure- * build a hierarchy of polyhedral approximations together with localization information-The economic advantage of this approach is that there is no dependency on any specific data source. It can be used for various types of data sources or when the source is unknown.
  • Thumbnail Image
    Item
    Parallel 3D Delaunay Triangulation
    (Blackwell Science Ltd and the Eurographics Association, 1993) Cignoni, P.; Montani, C.; Perego, R.; Scopigno, R.
  • Thumbnail Image
    Item
    Updating Polygonizations*
    (Blackwell Science Ltd and the Eurographics Association, 1993) Abellanas, M.; Garcia, J.; Hernbandez, G.; Hurtado, F.; Serra, O.; Urrutia, J.
    In this paper we consider polygonizations that are robust when faced with changes in the vertices that are present or in their position. We analyze the dynamic maintenance of different types of polygonizations (monotone, star-shaped.) and we introduce monotone half-convex polygonizations that are specially interesting because they provide minimum cost per insertion or deletion. If we had to delete not only one point but several external layers of the set, then the onion polygonizations would be suited, because they can be updated in constant time. We also consider the case of points that can be moved to contiguous positions and we show how to polygonize the set for updating in linear time. We deal too with security problems for a polygon: What is the maximum distance the vertices of a polygon could be moved away of their position in such a way that the topology on the boundary of the polygon (or its convexity) remains the same?.
  • Thumbnail Image
    Item
    A New Paradigm for Geometric Processing
    (Blackwell Science Ltd and the Eurographics Association, 1993) Yamaguchi, Fujio; Niizeki, Masatoshi
    A new paradigm for geometric processing is proposed. The paradigm can be featured by the four key phrases: (1) Totally Four Dimensional Homogeneous Processing, (2) 4 ? 4 Matrix Method and 4 ? 4 Determinant Method, (3) Integer Arithmetic with Adaptive Data-Length Control Technique, (4) Systematic Paradigm Structures Based on the Duality.
  • Thumbnail Image
    Item
    Modeling of Skylight and Rendering of Outdoor Scenes
    (Blackwell Science Ltd and the Eurographics Association, 1993) Tadamura, Katsumi; Nakamae, Eihachiro; Kaneda, Kazufumi; Baba, Masashi; Yamashita, Hideo and Nishita, Tomoyuki
    Photorealistic animated images are extremely effective for pre-evaluating visual impact of city renewal and construction of tall buildings. In order to generate a photorealistic image not only the direct sunlight but also skylight must be considered.This paper proposes a method of high-fidelity image generation for photorealistic outdoor scenes based on the following ideas: * 1The intensity distribution of skylight taking account of scattering and absorption due to particles in the atmosphere which coincides with CIE standard skylight luminance functions is sought, and realistic images considering about spectrum distribution of skylight for any altitude of the sun can be easily and accurately displayed. * 2A rectangular parallelepiped with a specialized distribution of intensity simulating the skylight is introduced for efficient calculation of illumination due to skylight, and by employing a graphics hardware calculation of the skylight illuminance taking into account shadow effects is obtained with high efficiency- these techniques can be used to generate sequences of images, making animations possible at far lower calculation cost than previous methods.
  • Thumbnail Image
    Item
    Boolean Operations and Spatial Complexity of Face Octrees.
    (Blackwell Science Ltd and the Eurographics Association, 1993) Pla-Garcia, Nuria
    Most of the existing representation schemes of free form surfaces or objects with free form boundary are not capable to compute efficiently boolean operations and other usual geometric interrogations. Classical octrees, proposed to overcome this drawback, require large amounts of memory. Face Octrees was a proposal suitable in the case of smooth surfaces or objects with smooth boundary. In this paper, different aspects of this model are discussed. In fact, it is focussed on the description of boolean operation algorithms using this model, proving that it solves the first problems, and on the computation of spatial complexity bounds. These bounds allow an evaluation of the fitness of each of the existing octree models in a given situation, showing the advantage of Face Octrees when the boundaries are smooth (curvatures are small).
  • Thumbnail Image
    Item
    Introducing blending operations in feature models
    (Blackwell Science Ltd and the Eurographics Association, 1993) Laakko, Timo; Mantyla, Martti
    We describe the implementation of a blending facility in the context of a feature modelling system where solid and feature-based modelling operations can be utilized in parallel during the design process of a part. The definition of blends can be done in a graphical user interface by selecting edges to be blended. Feature recognition of blends facilitates the definition process of blends. Alternatively, a special feature editor can be used to add blends to the feature model. The particular implementation style chosen gives rise to aflexible and easy-to-use modelling tool.
  • Thumbnail Image
    Item
    An Integrated System for Modeling, Animating and Rendering Hair
    (Blackwell Science Ltd and the Eurographics Association, 1993) Daldegan, Agnes; Thalmann, Nadia Magnenat; Kurihara, Tsuneya; Thalmann, Daniel
    There are basically four problems to solve in order to produce realistic animated synthetic actors with hair: hair modeling and creation, hair motion, collision detection and hair rendering. This paper describes a complete methodology to solve these basic four problems. We present how hair styles may be designed with our Hair Styler module. Then we survey the animation model and emphasize a method of collision processing. Finally, we explain how hair may be rendered using an extension of a standard ray-tracing program. We also show applications of our synthetic actors with various hair styles and different styles of mustaches and beards.
  • Thumbnail Image
    Item
    A Rendering Algorithm for Discrete Volume Density Objects
    (Blackwell Science Ltd and the Eurographics Association, 1993) Blasi, Philippe; Le Saec, Bertrand; Schlick, Christophe
    We present a new algorithm for simulating the effect of light travelling through volume objects. Such objects (haze, fog, clouds.) are usually modelized by voxel grids which define their density distribution in a discrete tridimensional space. The method we propose is a two-pass Monte-Carlo ray-tracing algorithm that does not make any restrictive assumptions neither about the characteristics of the objects (both arbitrary density distributions and phase functions are allowed) nor about the physical phenomena included in the rendering process (multiple scattering is accounted for). The driving idea of the algorithm is to use the phase function for Monte-Carlo sampling, in order to modify the direction of the ray during scattering.
  • Thumbnail Image
    Item
    A Declarative Design Method for 3D Scene Sketch Modeling
    (Blackwell Science Ltd and the Eurographics Association, 1993) Donikian, Stephane; Hegron, Gerard
    In this paper, we present a dynamic model associated with an intelligent CAD system aiming at the modeling of an architectural scene sketch. Our design methodology has been developed to simulate the process of a user who tries to give a description of a scene from a set of mental images. The scene creation is based on a script which describes the environment from the point of view of an observer who moves across the scene. The system is based on a declarative method viewed as a stepwise refinement process. For the scene representation, a qualitative model is used to describe the objects in terms of attributes, functions, methods and components. The links between objects and their components are expressed by a hierarchical structure, and a description of spatial configurations is given by using locative relations. The set of solutions consistent with the description is usually infinite. So, either one scene consistent with this description is calculated and visualized, or reasons of inconsistency are notified to the user. The resolution process consists of two steps: firstly a logical inference checks the consistency of the topological description, and secondly an optimization algorithm deals with the global description and provides a solution. Two examples illustrate our design methodology and the calculation of a scene model.
  • Thumbnail Image
    Item
    DIGIS A Graphical User Interface Design Environment for Non-Programmers
    (Blackwell Science Ltd and the Eurographics Association, 1993) de Bruin, Hans; Bouwman, Peter; van den Bos, Jan
    DIGIS (Direct Interactive Generation of Interactive Systems) is a graphical UI design environment for non-programmers that facilitates the design of all aspects of a UI with direct manipulation techniques. DIGIS is based on four models: an object model, a system task model, an interaction model and a dialogue control model. These four models describe an interactive system at a high conceptual level which allows a UI designer to quickly construct a high quality direct manipulation UI that supports undo-redo, context-sensitive help and guidance, and connect the UI with the (existing) application.
  • Thumbnail Image
    Item
    Extracting contour lines from a hierarchical surface model
    (Blackwell Science Ltd and the Eurographics Association, 1993) De Floriani, Leila; Mirra, Daniela; Puppo, Enrico
    The Hierarchical Triangulated Irregular Network (HTIN) is a structure for representing 2?-dimensional surfaces at different levels of detail through piecewise-linear approximations based on triangulations of the surface domain. In this paper, we present two algorithms that allow extracting a representation of the surface and contour lines at a given level of detail, directly from the HTIN.
  • Thumbnail Image
    Item
    Direct 3D Manipulation Techniques for Interactive Constraint-based Solid Modelling
    (Blackwell Science Ltd and the Eurographics Association, 1993) Fa, Mingxian; Fernando, Terrence; Dew, Peter M.
    This paper presents a novel constraint-based 3D manipulation approach to interactive constraint-based solid modelling. This approach employs a constraint recognition process to automatically recognise assembly relationships and geometric constraints between entities from 3D manipulation. A technique referred to as allowable motion is used to achieve accurate 3D positioning of a solid model by automatically constraining its 3D manipulation without menu interaction. A set of virtual design tools, which can be used to construct constraint-based solid models within a virtual environment, are also supported. These tools have been implemented as functional 3D objects associated with several pre-defined modelling functions to simulate physical tools such as a drilling tool and T-square. They can be directly manipulated by the user, and precisely positioned relative to other solid models through the constraint-based 3D manipulation approach. Their modelling functions can be automatically triggered, depending upon their associated constraints and the user s manipulation manner. A prototype system has been implemented to demonstrate the feasibility of these techniques for model construction and assembly operations.
  • Thumbnail Image
    Item
    GKS-9x: Some Implementation Considerations
    (Blackwell Science Ltd and the Eurographics Association, 1993) Damnjanovic, L.B.; Duce, D.A.; Robinson, S.K.
    The Graphical Kernel System (GKS) was published as an ISO standard for computer graphics programming in August 1985. GKS is now undergoing revision in ISO/IEC and at the time of writing the text of the Draft International Standard of GKS-9x was being finalized. This paper presents a way in which a key part of the new functionality in GKS-9x, namely namesets and selection criteria, can be implemented effectively.
  • Thumbnail Image
    Item
    A 4D Ray Tracing
    (Blackwell Science Ltd and the Eurographics Association, 1993) Maurel, Herve; Duthen, Yves; Caubet, Rene
    We are going to present a survey of techniques using temporal coherence in between frames to render animation sequences with ray tracing. A new method using temporal coherence in the ray space (lightpath of rays) is proposed. The goal of this technique is to factorize intersection and illumination calculations over the frames of the sequence. An optical event springing out many times in the sequence is computed once. The method is based upon 4D intersection calculations between temporal rays and moving objects. At the end of this paper, we present measurements showing the number of rays we need not calculate with our solution. These results come from simulating the algorithm behavior through a graphic and statistic ray analyser tool.
  • Thumbnail Image
    Item
    The Cone of Normals Technique for Fast Processing of Curved Patches
    (Blackwell Science Ltd and the Eurographics Association, 1993) Shirmun, Leon A.; Abi-Ezzi, Salim S.
    The cone of normals technique for curved surface patches allows to perform various quick tests at the patch level such as front- or backfacing test, light influence test, and existence of silhouette edges test. For a given patch, a truncated cone of normals is constructed at creation time, which contains all points and all normal directions of the patch. At traversal time, a simple scalar product test determines whether the whole patch is backfacing or frontfacing, so that the costly step of tessellating the patch is avoided in case of patch level face culling. In addition, the technique quickly determines which light sources have no influence on a patch, and which patches have no silhouette edges. The technique can also be used for other surface primitives, such as triangular strips and quadrilateral meshes,
  • Thumbnail Image
    Item
    Accurate and Consistent Reconstruction of Illumination Functions Using Structured Sampling
    (Blackwell Science Ltd and the Eurographics Association, 1993) Drettakis, George; Fiume, Eugene
    The study of common classes of diffuse emitters, such as planar convex polygons, reveals several interesting properties of the functions of illumination these emitters cast on receiver surfaces. Some properties, such as the position of the maximum and the curvature are of particular interest for sampling and reconstruction of illumination across receivers. A computationally efficient approach is presented that identifies these properties, and uses them to select samples of illurnination. In addition these properties are used to determine upper bounds on the error due to linear and quadratic interpolants. These bounds are then used to adaptively subdivide the non-uniform sampling grid, resulting in accurate reconstruction. Results show that the method reduces the error compared to uniform approaches, and produces more consistent animated sequences.
  • Thumbnail Image
    Item
    DaScript3D Integrating 3D Graphics in a Page Description Language
    (Blackwell Science Ltd and the Eurographics Association, 1993) Samara, Veronika
    Despite the necessity of producing high-quality documents comprising all aspects of electronic publishing, there is still no system available that can generate and integrate two-dimensional (2D) graphics, three-dimensional (3D) graphics and high-quality text electronically. This situation becomes especially critical in the area of technical documentation where graphics as well as text play a major role. DaScript3D introduces 3D extensions able to handle and integrate 2D and 3D graphics as well as text in one tool. Based on the page description language PostScript, DaScript3D offers the power of PostScript on the one hand, and, on the other hand, all the characteristics and advantages of a 3D system.
  • Thumbnail Image
    Item
    Pseudo-Satellitefilm Using Fractal Clouds to Enhance Animated Weather Forecasting
    (Blackwell Science Ltd and the Eurographics Association, 1993) Sakas, Georgios; Schroder, Florian; Koppert, Hans-Joachim
    We have developed a system enabling the National German Meteorological Office to generate pseudo-satellite images and video sequences based on their weather forecasting simulation data. With our system meteorologists can visualize the past and the current weather situation, evaluate their simulation results, and produce animated weather forecast videos broadcasted by several television stations. Realistic images are generated by interpolating the extremely coarse weather simulation data grid and enhancing the result using fractal clouds. It also enables the meteorologists to interactively change the forecast data in order to compensate the lack of accuracy or the known errors in their simulation models. Our system TRITON enables the visualization of complex weather simulations in a more natural way by presenting an intuitively understandable forecast.
  • Thumbnail Image
    Item
    Automatic Reconstruction of Buildings from Stereoscopic Image Sequences
    (Blackwell Science Ltd and the Eurographics Association, 1993) Koch, Reinhard
    A vision-based 3-D scene analysis system is described that is capable to model complex real-world scenes like streets and buildings automatically from stereoscopic image pairs. Input to the system is a sequence of stereoscopic images taken with two standard CCD Cameras and TV lenses. The relative orientation of both cameras to each other is known by calibration. The camerapair is then moved throughout the scene and a long sequence of closely spaced views is recorded. Each of the stereoscopic image pairs is rectified and a dense map of 3-D suface points is obtained by area correlation, object segmentation, interpolation, and triangulation. 3-D camera motion relative to the scene coordinate system is tracked directly from the image sequence which allows to fuse 3-D surface measurements from different viewpoints into a consistent 3-D model scene. The surface geometry of each scene object is approximated by a triangular surface mesh which stores the suface texture in a texture map. From the textured 3-D models, realistic looking image sequences from arbitrary view points can be synthesized using computer graphics.
  • Thumbnail Image
    Item
    Photo-Realistic Imaging of Digital Terrains
    (Blackwell Science Ltd and the Eurographics Association, 1993) Cohen, Daniel; Shaked, Amit
    We present a method for the generation of photo-realistic images of views over terrain datasets by mapping a digital aerial photograph on a perspective projection of a digital elevation map. We use high resolution for both digital maps to increase the quality and the realism of the image at the cost of the overhead of processing very large data bases. In the core of this paper we present an accelerated ray casting technique based on a new algorithm of traversing a pyramidal data structure. Unlike other known traversal techniques, the cost of a single step of the algorithm consists of a few additions, shifts and comparisons only.
  • Thumbnail Image
    Item
    Landscapes Synthesis Achieved through Erosion and Deposition Process Simulation
    (Blackwell Science Ltd and the Eurographics Association, 1993) Roudier, P.; Peroche, B.; Perrin, M.
    This paper describes an original approach to terrain evolution in landscapes synthesis. In order to create some realistic landforms, we simulate geologically contrasted terrains and apply to them deterministic erosion processes. This allows us to relate the erosion on any point of the landsurface to local geological parameters. Any height field may be chosen as an initial topographic surface. Small perturbations may be introduced to avoid unpleasant regularities. A 3D model defines the geological parameters of each point according to its elevation. Our method is iterative: at each step, rock removal and possible alluvial deposition are computed at each point of the landsurface. The available erosion laws simulate mechanical erosion, chemical dissolution and alluvial deposition. At the end of each iteration, a new landsurface and the corresponding river network are created. Landsurfaces can be visualized at the final stage by two rendering algorithms including natural textures mapping. The stream network and the ridges may also be visualized.
  • Thumbnail Image
    Item
    On the Application of Quantization and Dithering Techniques to History of Arts
    (Blackwell Science Ltd and the Eurographics Association, 1993) Coltelli, P.; Faconti, G.; Marfori, F.
    The diffusion of computing techniques within humane studies is considerably increasing, due to technological advances and reduction in computing costs, with History of Arts being one of the most interesting fields of application. In fact, several domains related to works of arts might be investigated other than archival and retrieval of information: this includes the planning for the preservation and restoration, the developing of critical examinations of artworks as well as the supporting of less specialized activities such as teaching, presentation of museum exhibitions and spreading of information.Within this framework, it is of particular interest to review already known image compression techniques from other fields and to evaluate their applicability taking into account the peculiarities and the requirements of this specific domain. A distinguishing aspect of History of Arts is the requirement to keep the maximum approximation of the original information on each point of an image. This peculiarity strongly requires that the set of pixels of the same color in the original image is bound to a unique color in the final image and that each color in the final image uniquely determines the set of colors it represents. This requirement constrains the applicability in this domain to those quantization algorithms satisfying this property while still minimizing the quantization error.The paper gives a formal definition of the above requirement and justifies the use of the quantization and dithering algorithms based on the octree reduction technique. Following, the results given by the application of these techniques to several paintings are shown. Finally, the measured quantization errors are compared with those obtained by applying the median-cut algorithm.
  • Thumbnail Image
    Item
    Abstract Interaction Objects
    (Blackwell Science Ltd and the Eurographics Association, 1993) Duke, D.J.; Harrison, M.D.
    The concept of an interactor has been introduced by Faconti and Paterno [6] as an abstraction of an entity in interactive graphics capable of both input and output. However the notion of interaction object need not be confined to graphics systems- it represents a useful structure for thinking and reasoning about the behaviour of interactive systems in general. As part of Esprit Basic Research Action 7040 (Amodeus-2) we are using the concept of interactor, and existing work on state-based processes and agents, to develop a model and theory of interactive systems. In this paper we describe two formal models for interaction objects and sketch how they can be used to build a small vocabulary of operators to support the rigorous specification of a graphics system. Our model differs from the approach of Faconti and Paterno in that it abstracts away from any specific graphics framework and is thus suited to the level of abstraction demanded by formal approaches to system development.
  • Thumbnail Image
    Item
    A New Radiosity Approach Using Area Sampling for Parametric Patches
    (Blackwell Science Ltd and the Eurographics Association, 1993) Nishita, Tomoyuki; Nakamae, Eihachiro
    A high precision illumination model is indispensable for lighting simulation and realistic image synthesis. For the purpose of improving realism, research on global illumination has been done, and several papers on radiosity methods have been presented. In the most recently proposed methods, the shapes of light sources and objects are restricted to polygons or simple curved surfaces. We present a more general method which can handle the kind of free-form surfaces widely used in industrial products and in architecture. The method proposed here solves the problem of the interreflection of light (i.e., radiosities) between patches, and form-factors, which play an important role in this process, are precisely calculated without aliasing through the use of an area sampling method (i.e., pyramid tracing). Furthermore the method can handle both non-uniform intensity curved sources and non-diffuse surfaces.
  • Thumbnail Image
    Item
    A Progressive Radiosity Algorithm for Scenes Containing Curved Surfaces
    (Blackwell Science Ltd and the Eurographics Association, 1993) Bao, Hujun; Peng, Qunsheng
    Based on the theory of light energy transfer between two differential diffuse surface areas, a generalized radiosity approach is presented. Unlike the conventional radiosity method, curved surfaces are subdivided into triangular surface patches, radiosity is assummed to be vary across each triangular surface patch. By adopting linear interpolation scheme over each triangular surface patch, we have established a complete set of approximated radiosity equations. Their unknowns are radiosities of differential surface areas located at all vertices of surface patches. The generalized radiosity equation has also been extended to non-diffuse environments. Theoretical analysis and experimental results demonstrate the great potential of this method,
  • Thumbnail Image
    Item
    An Integral Geometry Based Method for Fast Form-Factor Computation
    (Blackwell Science Ltd and the Eurographics Association, 1993) Sbert, Mateu
    Monte Carlo techniques have been widely used in rendering algorithms for local integration. For example, to compute the contribution of a patch to the luminance of another. In the present paper we propose an algorithm based on Integral geometry where Monte Carlo is applied globally. We give some results of the implementation to validate the proposition and we study the error of the technique, as well as its complexity.
  • Thumbnail Image
    Item
    Form Factor Calculation: a New Expression with Implementations on a Parallel T.Node Computer
    (Blackwell Science Ltd and the Eurographics Association, 1993) Michelin, Sylvain; Maffeis, Gualtiero; Arques, Didier; Grossetie, Jean Claude
    The radiosity technique uses the heat transfer theory to define a view-independent illumination model. For complex scenes, calculation of this model is very time-intensive, due largely to the determination of a geometric factor, defined with a double area integral, and named form factor. This paper presents a new expression of the form factor, which can be reformulated, in a computationally more efficient manner, as a simple line integral for planar polygonal convex surfaces that are perfectly diffuse.Recently, parallel computers have been used to decrease calculation time. Previous work is focused mainly on distributed implementations of a method, the progressive refinement method, widely used for complex environments. The T.Node is a completely reconfigurable MIMD machine, based on the transputer chip. In this paper, we compare a parallel implementation of the progressive refinement method with a direct method which takes into account the memory capabilities of this kind of machine.
  • Thumbnail Image
    Item
    Nonsplitting Macro Patches for Implicit Cubic Spline Surfaces
    (Blackwell Science Ltd and the Eurographics Association, 1993) Guo, B.
    Macro patches are important for generating quadric or cubic implicit spline surfaces from the input of a polyhedron. All existing macro patches split the triangular facets of the polyhedron- this paper presents cubic nonsplitting macro patches (NMP) that do not split these facets. The NMP s are based on a necessary and sufficient condition for nonsplitting constructions of implicit cubic spline surfaces. This condition can be satisfied for most practical applications, so the NMP s lead to an efficient and powerful spline surface scheme using implicit cubics. The free parameters in an NMP are set using a new technique for excluding topological anomalies such as extraneous sheets, splits, unwanted holes, self-intersections, and unwanted handles. Each cubic patch obtained by this technique best approximates, in a least-squares sense, a quadric patch from a single algebraic component of a monotone polynomial derived from the input data.
  • Thumbnail Image
    Item
    Quality Control of an Interpolation Method for Discontinuous Parametric Surfaces
    (Blackwell Science Ltd and the Eurographics Association, 1993) Seron, F.J.; Torrens, J.J; Magallon, J.A.
    In this paper we study a finite element interpolation method for fitting discontinuous parametric surfaces when the data points are the nodes of a curvilinear grid. Quality control of the interpolating surfaces is also considered, focussing on the display of isophotes and reflection lines using ray tracing techniques. Finally, graphical and numerical examples are given.
  • Thumbnail Image
    Item
    Variational Surface Design and Surface Interrogation
    (Blackwell Science Ltd and the Eurographics Association, 1993) Hagen, H.; Hahmann, St.; Bonneau, G.-P.
    The generation of technical smooth surfaces from a mesh of three-dimensional data points is an important problem in geometric modelling. In this publication we give a survey of some new techniques based on a calculus of variation approach. Apart from the pure construction of these surfaces, the analysis of their quality is equally important in the design and manufacturing process. Generalized focal surfaces are presented here as a new surface interrogation tool.
  • Thumbnail Image
    Item
    A Prototype of a Cooperative Visualization Workplace for the Aerodynamicist
    (Blackwell Science Ltd and the Eurographics Association, 1993) Pagendarm, H.-G.; Walter, B.
    Several feasibility studies for cooperative visualization were performed based on an existing modular visualization system. Two different architectures for the implementation of a cooperative system were identified, implemented and tested.One architectural model, the broadcast model, assumes either one single visualization system running on a central facility driving multiple displays or in case of cooperative work it assumes that each visualization module drives multiple displays.The second model, the synchronized visualization systems, features distributed visualization tools with synchronization mechanisms. The synchronization ensures that all partners create identical images from identical data. This model requires special control features to avoid conflicts created by user-interaction.Both architectures are complete by adding bi-directional video connection and audio communication over the network plus offering remote cursor functionality.Two prototype implementations were produced to compare the two architectures and to evaluate the feasibility of cooperative visualization on existing hardware. Because of the poor access to wide-area networks, the prototypes were tested in a local area network. Visualization protocols, data communication, video and audio ran on a standard Ethernet based on TCP/IP communications. The tests were done using typical data from aerodynamics or numerical flow simulations.In spite of the limits due to low network bandwidth and slow performance of some hardware components the second architecture using the synchronized systems seems to be useful and feasible even under today s circumstances. There are no additional features identified which would be needed to run the cooperative visualization on a wide area network but a higher network throughput would be required.
  • Thumbnail Image
    Item
    Interactive Neural Network Texture Analysis and Visualization for Surface Reconstruction in Medical Imaging
    (Blackwell Science Ltd and the Eurographics Association, 1993) Busch, C.; Gro?, M.H.
    The following paper describes a new approach for the automatic segmentation and tissue classification of anatomical objects such as brain tumors from magnetic resonance imaging (MRI) data sets using artificial neural networks. These segmentations serve as an input for 3D-reconstruction algorithms. Since MR images require a careful interpretation of the underlying physics and parameters, we first give the reader a tutorial style introduction to the physical basics of MR technology. Secondly, we describe our approach that is based on a two-pass method including non-supervised cluster analysis, dimensionality reduction and visualization of the texture features by means of nonlinear topographic mappings. An additional classification of the MR data set can be obtained using a post-processing technique to approximate the Bayes decision boundaries. Interactions between the user and the network allow an optimization of the results. For fast 3D-reconstructions, we use a modified marching cubes algorithm but our scheme can easily serve as a preprocessor for any kind of volume renderer.The applications we present in our paper aim at the automatic extraction and fast reconstruction of brain tumors for surgery and therapy planning. We use the neural networks on pathological data sets and show how the method generalizes to physically comparable data sets.
  • Thumbnail Image
    Item
    Scale-Invariant Minimum-Cost Curves: Fair and Robust Design Implements
    (Blackwell Science Ltd and the Eurographics Association, 1993) Moreton, Henry P.; Sequin, Carlo H.
    Four functionals for the computation of minimum cost curves are compared. Minimization of these functionals result in the widely studied Minimum Energy Curve (MEC), the recently introduced Minimum Variation Curve (MVC), and their scale-invariant counterparts, (SI-MEC, SI-MVC). We compare the stability and fairness of these curves using a variety of simple interpolation problems. Previously, we have shown MVC to possess superior fairness. In this paper we show that while MVC have fairness and stability superior to MEC they are still not stable in all configurations. We introduce the SI-MVC as a stable alternative to the MVC. Like the MVC, circular and helical arcs are optimal shapes for the SI-MVC.Additionally, the application of scale invariance to functional design allows us to investigate locally optimal curves whose shapes are dictated solely by their topology, free of any external interpolation or arc length constraints.
  • Thumbnail Image
    Item
    Cooperative Visualization of Computational Fluid Dynamics
    (Blackwell Science Ltd and the Eurographics Association, 1993) Gerald-Yamasaki, Michael J.
    Tempus Fugit/Interview is a computational fluid dynamics visualization application for which processing is distributed between high performance graphics workstations and supercomputers. Facilities are provided in the application for more than one user to view shared images creating a cooperative visualization environment. The way in which the computation is partitioned between the super computer and the workstations is critical to the capability of the application to present simultaneous, identical, animated images of fluid dynamics to more than one user.
  • Thumbnail Image
    Item
    Verve
    (Blackwell Science Ltd and the Eurographics Association, 1993) Knittel, Gunter
    The design principles of a hardware acceleratorfor volume rendering are described. The architecture represents a voxel subsystem which interfaces easily to any existing workstation. Host requirements are low since it contains a multiport memory holding the complete data set and all arithmetic units needed to perform an effective visualization.Our approach aims at virtual reality by providing some"real-world" examination techniques. The user (e.g., a physician) is enabled to analyze the data set from an arbitrary viewpoint and, even more, to"walk through" the volume model. For a realistic impression, the machine produces perspective projections, supports the illumination by non-parallel light comingfrom a freely movable point light source and provides depth cueing. The objects are Phong shaded at a rate of 107 operations/s and can be displayed semitransparently. One unit achieves interactive speed: for real-time operation only a small number of units (typically 4-16) must be placed in parallel.
  • Thumbnail Image
    Item
    Fast Spheres
    (Blackwell Science Ltd and the Eurographics Association, 1993) Patterson, John W.
    A new method for generating sphere-like images, using parabolic surfaces delimited by Bresenham s circle- generation algorithm, is presented. In many cases the resultant images are indistinguishable from spheres illuminated from a given single direction. The main form of the algorithm uses first and second integer differences to minimise computation and uses typically not more than one floating-point calculation per sphere. Two variants of the algorithm are given, one optimized for the special case of the light-source being behind the view-point, and one in which values are calculated for a z-buffer hidden-surface algorithm at the same time as the pixel values. The difference formulae can be exploited by differencing hardware or digital signal processors although very little arithmetic, typically five low-weight integer operations, including address calculation operations, is required per pixel on a conventional architecture.
  • Thumbnail Image
    Item
    Storage Support for Multidimensional Discrete Data in Multimedia Databases
    (Blackwell Science Ltd and the Eurographics Association, 1993) Furtado, Paula; Teixeira, Jose Carlos
    Multidimensional discrete data (MDD) is enormously important for multimedia applications since diverse types of such data are used simultaneously by any multimedia application. However, multidimensional discrete data is not adequately supported by most existing database systems.In this paper we discuss the major management requirements imposed by such data on multimedia database management systems both at the conceptual level and at the internal level. At the internal level, the spatial structure of the data must also be preserved and special emphasis must be given to the efficient spatial access to subrectangles of very large data of arbitrary dimensionality.Our major contribution is the presentation of a Storage Manager for this kind of data which preserves the spatial nature of the data at the internal level of the database management system and provides efficient spatial access. This Storage Manager is based on an innovative combination of the subdivision of data in multidimensional tiles and of a spatial index to access those tiles. Furthermore, it supports advanced registration data.The lower level modules of the Storage Manager are responsible for the access to the data stored in secondary storage. The implementation of these modules can rely on any secondary storage access system to access data on disk. The Storage Manager was implemented using the functionality of a relational database system. The implementation of this relational Storage Manager is presented.
  • Thumbnail Image
    Item
    Using Multimedia to Support Cooperative Editing
    (Blackwell Science Ltd and the Eurographics Association, 1993) Santos, A.; Tritsch, B.
    By Cooperative Editing we mean the coordinated manipulation of information by a group of authors. During the editing process the (co-)authors need to communicate their ideas, drafts and constraints (remotely or face-to-face) until a final version of the information is achieved. For the different phases of this process - discussion of ideas, editing, cross-checking - different media or media integration are adequate. Furthermore, analysing the transition from individual work to group work, within different human activities, two pitfalls are often detected if computer support is considered: a) technological communication difficulties, especially if the group is remotely located on heterogeneous hardware, associated with a fall in productivity and frequent social inadequacies of the group s computer support- b) the lack of integrated media processing tools available for group editing.In order to solve these problems, we suggest that Multimedia can be applied in two ways: to effectively support the necessary group communication links- and to enhance the expressiveness of the information edited. To test this statement we have been conceptualising and implementing a prototype system. Most of the techniques involved can be used in other tools that need multimedia capabilities or that support other specific types of group activities.The innovative aspects of the work are the use of multimedia techniques to support demanding applications, possibly on cross-platforms, and the integration of several concepts to support cooperation.
  • Thumbnail Image
    Item
    An Object Model for Multimedia Programming
    (Blackwell Science Ltd and the Eurographics Association, 1993) Arbab, F.; Herman, I.; Reynolds, G.J.
    The development of multimedia applications is a complex task. Much of this complexity stems from requirements associated with programming multiple media objects and the control of dependences and inter-relationships between these media objects and the user(s). It is clearly necessary to have a basic framework on which to build multimedia applications in the face of such complexities. Such a conceptual model is what we have called an object model and it is the main subject of this paper. The MADE object model represents a novel approach to multimedia application programming that is founded on the two principal concepts of active objects and delegation. Although these concepts are not novel in themselves, we believe that their combined use in a multimedia development environment represents a substantial enhancement to more traditional approaches to programming in this area.