Issue 3

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/62
EG 1994 Conference Proceedings

BibTeX (Issue 3)
                
@article{
10.1111:1467-8659.1330001,

journal = {Computer Graphics Forum},
title = {{
3D Visualization for 2D GIS: an Analysis of the Users  Needs and a Review of Techniques*}},

author = {
Giertsen, Christopher
 and 
Lucas, Anne
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330001}

}
                
@article{
10.1111:1467-8659.1330097,

journal = {Computer Graphics Forum},
title = {{
Spectral Data Modeling for a Lighting Application}},

author = {
Deville, Pascal M.
 and 
Merzouk, Slimane
 and 
Cazier, Dorothee
 and 
Paul, Jean C.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330097}

}
                
@article{
10.1111:1467-8659.1330127,

journal = {Computer Graphics Forum},
title = {{
Chebyshev Polynomials for Boxing and Intersections of Parametric Curves and Surfaces}},

author = {
Fournier, Alain
 and 
Buchanan, John
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330127}

}
                
@article{
10.1111:1467-8659.1330143,

journal = {Computer Graphics Forum},
title = {{
Variational Design and Fairing of Spline Surfaces}},

author = {
Greiner, Gunther
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330143}

}
                
@article{
10.1111:1467-8659.1330107,

journal = {Computer Graphics Forum},
title = {{
Fast Dynamic Tessellation of Trimmed NURBS Surfaced1}},

author = {
Abi-Ezzi, Salim S.
 and 
Subramaniam, Srikanth
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330107}

}
                
@article{
10.1111:1467-8659.1330167,

journal = {Computer Graphics Forum},
title = {{
A Hand Control and Automatic Grasping System for Synthetic Actors}},

author = {
Sanso, Ramon Mas
 and 
Thalmann, Daniel
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330167}

}
                
@article{
10.1111:1467-8659.1330155,

journal = {Computer Graphics Forum},
title = {{
Efficient self-collision detection on smoothly discretized surface animations using geometrical shape regularity}},

author = {
VOLINO, Pascal
 and 
THALMANN, Nadia Magnenat
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330155}

}
                
@article{
10.1111:1467-8659.1330179,

journal = {Computer Graphics Forum},
title = {{
AGRELs and BIPs: Metamorphosis as a Bezier curve in the space of polyhedra}},

author = {
Rossignac, Jarek
 and 
Kaul, Anil
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330179}

}
                
@article{
10.1111:1467-8659.1330185,

journal = {Computer Graphics Forum},
title = {{
Beyond WYSIWYG: Display of Hidden Information in Graphics Editors}},

author = {
Schleich, R.
 and 
Durst, M.J.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330185}

}
                
@article{
10.1111:1467-8659.1330195,

journal = {Computer Graphics Forum},
title = {{
A Semantics-based Approach for the Design and Implementation of Interaction Objects}},

author = {
Paterno , F.
 and 
Leonardi, A.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330195}

}
                
@article{
10.1111:1467-8659.1330205,

journal = {Computer Graphics Forum},
title = {{
Real Time Fitting of Hand-Sketched Pressure Brushstrokes}},

author = {
Pudet, Thierry
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330205}

}
                
@article{
10.1111:1467-8659.1330233,

journal = {Computer Graphics Forum},
title = {{
An Inexpensive BRDF Model for Physically-based Rendering}},

author = {
Schlick, Christophe
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330233}

}
                
@article{
10.1111:1467-8659.1330013,

journal = {Computer Graphics Forum},
title = {{
COMPUTER GRAPHICS AND REMOTE SENSING - A SYNTHESIS FOR ENVIRONMENTAL PLANNING AND CIVIL ENGINEERING}},

author = {
Graf, K.Ch.
 and 
Suter, M.
 and 
Hagger, J.
 and 
Nuesch, D.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330013}

}
                
@article{
10.1111:1467-8659.1330221,

journal = {Computer Graphics Forum},
title = {{
Parallel ray tracing based upon a multilevel topological knowledge acquisition of the scene}},

author = {
RIS, Philippe
 and 
ARQUES, Didier
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330221}

}
                
@article{
10.1111:1467-8659.1330271,

journal = {Computer Graphics Forum},
title = {{
A Method for Displaying Metaballs by using Bezier Clipping}},

author = {
Nishita, Tomoyuki
 and 
Nakamae, Eihachiro
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330271}

}
                
@article{
10.1111:1467-8659.1330259,

journal = {Computer Graphics Forum},
title = {{
Designing and Implementing a Grid-Distortion Mapping Based on Variational Principles}},

author = {
Arad, Nur
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330259}

}
                
@article{
10.1111:1467-8659.1330247,

journal = {Computer Graphics Forum},
title = {{
Volume Rendering on Non-regular Grids}},

author = {
Tabatabai, Behnam
 and 
Sessarego, Emanuela A.
 and 
Mayer, Harald F.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330247}

}
                
@article{
10.1111:1467-8659.1330281,

journal = {Computer Graphics Forum},
title = {{
Triangulating multiply-connected polygons: A simple, yet efficient algorithm.}},

author = {
Ronfard, Remi P.
 and 
Rossignac, Jarek R.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330281}

}
                
@article{
10.1111:1467-8659.1330293,

journal = {Computer Graphics Forum},
title = {{
Raycasting of Nonregularly Structured Volume Data}},

author = {
Fruhauf, Thomas
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330293}

}
                
@article{
10.1111:1467-8659.1330305,

journal = {Computer Graphics Forum},
title = {{
Visualization of Regular Polytopes in Three and Four Dimensions}},

author = {
Hausmann, Barbara
 and 
Seidel, Hans-Peter
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330305}

}
                
@article{
10.1111:1467-8659.1330023,

journal = {Computer Graphics Forum},
title = {{
Towards Context- Dependent Interpolation of Digital Elevation Models}},

author = {
Dixon, A.R.
 and 
Kirby, G.H.
 and 
Wills, D.P.M.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330023}

}
                
@article{
10.1111:1467-8659.1330339,

journal = {Computer Graphics Forum},
title = {{
Selective Visualization of Vector Fields}},

author = {
van Walsum, Theo
 and 
Post, Frits H.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330339}

}
                
@article{
10.1111:1467-8659.1330317,

journal = {Computer Graphics Forum},
title = {{
Magicsphere: an insight tool for 3D data visualization}},

author = {
Cignoni, P.
 and 
Montani, C.
 and 
Scopigno, R.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330317}

}
                
@article{
10.1111:1467-8659.1330329,

journal = {Computer Graphics Forum},
title = {{
Vector Fields: an Interactive Tool for Animation, Modeling and Simulation with Physically Based 3D Particle Systems and Soft Objects}},

author = {
Hilton, Travis L.
 and 
Egbert, Parris K.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330329}

}
                
@article{
10.1111:1467-8659.1330381,

journal = {Computer Graphics Forum},
title = {{
GKS-9x: The Design Output Primitive, an Approach to a Specification.}},

author = {
Nehlig, Ph. W.
 and 
Duce, D. A.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330381}

}
                
@article{
10.1111:1467-8659.1330361,

journal = {Computer Graphics Forum},
title = {{
Improved Visualisation of Marine Data: Algae and Acid Rain}},

author = {
Day, A.M.
 and 
Turner, S.M.
 and 
Arnold, D.B.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330361}

}
                
@article{
10.1111:1467-8659.1330371,

journal = {Computer Graphics Forum},
title = {{
A Formal Approach to the Specification of Graphic Object Functions}},

author = {
Torres, J.C.
 and 
Clares, B.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330371}

}
                
@article{
10.1111:1467-8659.1330349,

journal = {Computer Graphics Forum},
title = {{
An Integrated Line Tracking and Vectorization Algorithm}},

author = {
van Nieuwenhuizen, Peter R.
 and 
Kiewiet, Olaf
 and 
Bronsvoort, Willem F.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330349}

}
                
@article{
10.1111:1467-8659.1330407,

journal = {Computer Graphics Forum},
title = {{
Fast Wavelet Radiosity Method}},

author = {
Pattanaik, Sumanta N.
 and 
Bouatouch, Kadi
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330407}

}
                
@article{
10.1111:1467-8659.1330393,

journal = {Computer Graphics Forum},
title = {{
PREMO - An Initial Approach to a Formal Definition}},

author = {
DUCE, D.A.
 and 
DUKE, D.J.
 and 
ten HAGEN, P.J.W.
 and 
REYNOLDS, G.J.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330393}

}
                
@article{
10.1111:1467-8659.1330433,

journal = {Computer Graphics Forum},
title = {{
A Median Cut Algorithm for Efficient Sampling of Radiosity Functions}},

author = {
Feda, Martin
 and 
Purgathofer, Werner
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330433}

}
                
@article{
10.1111:1467-8659.1330443,

journal = {Computer Graphics Forum},
title = {{
Implementing RenderMan - Practice, Problems and Enhancements}},

author = {
Slusallek, Philipp
 and 
Pflaum, Thomas
 and 
Seidel, Hans-Peter
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330443}

}
                
@article{
10.1111:1467-8659.1330421,

journal = {Computer Graphics Forum},
title = {{
Adaptive mesh generation for progressive radiosity: A ray-tracing based algorithm.}},

author = {
PAULIN, Mathias
 and 
JESSEL, Jean-Pierre
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330421}

}
                
@article{
10.1111:1467-8659.1330489,

journal = {Computer Graphics Forum},
title = {{
Sketching 3D models with 2D interaction devices}},

author = {
Branco, Vasco
 and 
Costa, Antonio
 and 
Ferreira, F. Nunes
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330489}

}
                
@article{
10.1111:1467-8659.1330503,

journal = {Computer Graphics Forum},
title = {{
Reducing The Latency In Head-Mounted Displays By A Novel Prediction Method Using Grey System Theory}},

author = {
Wu, Jiann-Rong
 and 
Ouhyoung, Ming
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330503}

}
                
@article{
10.1111:1467-8659.1330455,

journal = {Computer Graphics Forum},
title = {{
How to Render Frames and Influence People}},

author = {
Strothotte, Thomas
 and 
Preim, Bernhard
 and 
Raab, Andreas
 and 
Schumann, Jutta
 and 
Forsey, David R.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330455}

}
                
@article{
10.1111:1467-8659.1330467,

journal = {Computer Graphics Forum},
title = {{
Cross Scan Buffer and its Applications}},

author = {
Tanaka, Toshimitsu
 and 
Takahashi, Tokiichiro
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330467}

}
                
@article{
10.1111:1467-8659.1330033,

journal = {Computer Graphics Forum},
title = {{
A Paradigm for the Robust Design of Algorithms for Geometric Modeling}},

author = {
Agrawal, Amitabh
 and 
Requicha, Aristides A. G.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330033}

}
                
@article{
10.1111:1467-8659.1330477,

journal = {Computer Graphics Forum},
title = {{
Computer Graphics System for Reproducing Three- Dimensional Shape from Idea Sketch}},

author = {
Akeo, Makoto
 and 
Hashimoto, Hiroshi
 and 
Kobayashi, Taisuke
 and 
Shibusawa, Tetsuo
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330477}

}
                
@article{
10.1111:1467-8659.1330055,

journal = {Computer Graphics Forum},
title = {{
Solid Modeling Based on a New Paradigm}},

author = {
Yoshida, Norimasa
 and 
Shiokawa, Masato
 and 
Yamaguchi, Fujio
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330055}

}
                
@article{
10.1111:1467-8659.1330045,

journal = {Computer Graphics Forum},
title = {{
A Robust and Consistent Algorithm for Intersecting Convex Polyhedra}},

author = {
Sugihara, Kokichi
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330045}

}
                
@article{
10.1111:1467-8659.1330065,

journal = {Computer Graphics Forum},
title = {{
The Mesh Propagation Algorithm for Isosurface Construction}},

author = {
Howic, C.T.
 and 
Blake, E.H.
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330065}

}
                
@article{
10.1111:1467-8659.1330085,

journal = {Computer Graphics Forum},
title = {{
Skylight for Interior Lighting Design}},

author = {
Dobashi, Yoshinori
 and 
Kaneda, Kazufumi
 and 
Nakashima, Takanobu
 and 
Yamashita, Hideo
 and 
Nishita, Tomoyuki and Tadamura, Kastumi
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330085}

}
                
@article{
10.1111:1467-8659.1330075,

journal = {Computer Graphics Forum},
title = {{
A New Approach to the Construction of Surfaces from Contour Data}},

author = {
Jones, Mark W.
 and 
Chen, Min
},
year = {
1994},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1330075}

}

Browse

Recent Submissions

Now showing 1 - 44 of 44
  • Thumbnail Image
    Item
    3D Visualization for 2D GIS: an Analysis of the Users Needs and a Review of Techniques*
    (Blackwell Science Ltd and the Eurographics Association, 1994) Giertsen, Christopher; Lucas, Anne
    Most of the existing geographical information systems (GIS) make limited use of algorithms for advanced computer graphics and visualization. One explanation is that few attempts are made to identify the visualization needs for different uses of GIS, and to couple such needs to the available algorithms. Another explanation is that most GIS are designed to handle two-dimensional (20) data with few obvious relationships to three-dimensional (30) visualization.In an attempt to provide a better understanding of the application of visualization in GIS, we propose a conceptual framework linking several aspects of the two fields. At the user-level, we link different uses of GIS to different categories of audience and presentation styles. At the level of implementation, we first propose different ways to create 3D data for visualization from 2D GIS data, and then we review algorithms and techniques for 3D visualization with respect to support of different presentation styles.
  • Thumbnail Image
    Item
    Spectral Data Modeling for a Lighting Application
    (Blackwell Science Ltd and the Eurographics Association, 1994) Deville, Pascal M.; Merzouk, Slimane; Cazier, Dorothee; Paul, Jean C.
    In computer graphics, image generation uses the RGB colorimetric system. However, this system does not produce an accurate simulation of the spectral characteristics of both light and material, due to the fact that it is device dependent. Indeed, to get realistic images, the image calculation process must deal with spectral characteristics of lights and materials and with the problem of sampling the wavelength domain. Methods have been shown that are a good way to solve the two problems mentioned above, however, these approaches do not take into account complex spectrums (discontinuous). In this paper, we propose a method which removes the constraints imposed by the current methods. Our method is based upon an algorithm of spectrum analysis.
  • Thumbnail Image
    Item
    Chebyshev Polynomials for Boxing and Intersections of Parametric Curves and Surfaces
    (Blackwell Science Ltd and the Eurographics Association, 1994) Fournier, Alain; Buchanan, John
    Parametric curves and surfaces are powerful and popular modelling tools in Computer Graphics and Computer Aided Design. Ray-tracing is a versatile and popular rendering technique. There is therefore a strong incentive in developing fast, accurate and reliable algorithms to intersect rays and parametric curves and surfaces.We propose and demonstrate the use of Chebyshev basis functions to speed up the computation of the intersections between rays and parametric curves or surfaces. The properties of Chebyshev polynomials result in the computation of better and tighter enclosing boxes. For surfaces they provide a better termination criterion to decide on the limits of subdivision, and allow the use of bilinear surfaces for the computation of the intersection when needed.The efficiency of the techniques used depends on the relative magnitude of the coefficients of the Chebyshev basis functions. We show from a statistical analysis of the characteristics of several thousands surfaces of different origin that these techniques will result most of the time in significant improvement in speed and accuracy over other other boxing and subdivision techniques.
  • Thumbnail Image
    Item
    Variational Design and Fairing of Spline Surfaces
    (Blackwell Science Ltd and the Eurographics Association, 1994) Greiner, Gunther
    Variational principles have become quite popular in the design of free form surfaces. Among others they are used for fairing purposes. The choice of the right fairness functional is a crucial step. There is always a tradeoff between high quality and computational effort. In this paper we present fairness functionals that allow fairing efficiently, i.e., produce high quality surfaces in a reasonable amount of time. These functionals can be considered as simplified thin plate energy functionals for parametric surfaces or as simplified MVC functionals.
  • Thumbnail Image
    Item
    Fast Dynamic Tessellation of Trimmed NURBS Surfaced1
    (Blackwell Science Ltd and the Eurographics Association, 1994) Abi-Ezzi, Salim S.; Subramaniam, Srikanth
    Trimmed NURBS (non-uniform rational B-splines) surfaces are being increasingly used and standardized in geometric modeling applications. Fast graphical processing of trimmed NURBS at interactive speeds is absolutely essential to enable these applications. which poses some unique challenges in software, hardware, and algorithm design. This paper presents a technique that uses graphical compilation to enable fast dynamic tessellation of trimmed NURBS surfaces under highly varying transforms.We use the concept of graphical data compilation. through which we preprocess the NURBS surface into a compact, view-independent form amenable for fast per-frame extraction of triangles. Much of the complexity of processing is absorbed during compilation. Arbitrarily complex trimming regions are broken down into simple regions that are specially designed to facilitate tessellation before rendering. Potentially troublesome cases of degeneracies in the surface are detected and dealt with during compilation. Compilation enables a clean separation of algorithm-intensive and compute-intensive operations, and provides for parallel implementations of the latter. Also, we exercise a classification technique while processing trimming loops. which robustly takes care of geometric ambiguities and deals with special cases while keeping the compilation code simple and concise.
  • Thumbnail Image
    Item
    A Hand Control and Automatic Grasping System for Synthetic Actors
    (Blackwell Science Ltd and the Eurographics Association, 1994) Sanso, Ramon Mas; Thalmann, Daniel
    In the computer animation field, the interest for grasping has appeared with the development of synthetic actors. Based on a grasp taxonomy, we propose a completely automatic grasping system for synthetic actors. In particular, the system can decide to use a pinch when the object is too small to be grasped by more than two fingers or to use a two-handed grasp when the object is too large. The system also offers both direct and inverse kinematics to control the articulations. In order to ensure realistic looking closing of the hand, several of the joints are constrained. A brief description of the system and results are also presented.
  • Thumbnail Image
    Item
    Efficient self-collision detection on smoothly discretized surface animations using geometrical shape regularity
    (Blackwell Science Ltd and the Eurographics Association, 1994) VOLINO, Pascal; THALMANN, Nadia Magnenat
    We present a new algorithm for detecting self-collisionson highly discretized moving polygonal surfaces. If is based on geometrical shape regularity properties that permit avoiding many useless collision tests. We use an improved hierarchical representation of our surface that, besides the optimizations inherent to hierarchisation, allows us to fake adjacency information to our advantage for applying efficiently our geometrical optimizations. We reduce the computation time between each frame by building automatically the hierarchical structure once as a preprocessing task. We describe the main principles of our algorithm, followed by some performance tests.
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    AGRELs and BIPs: Metamorphosis as a Bezier curve in the space of polyhedra
    (Blackwell Science Ltd and the Eurographics Association, 1994) Rossignac, Jarek; Kaul, Anil
    The metamorphosis between two user-specified objects offers an intuitive metaphor for designing animations of deforming shapes. We present a new technique for interactively editing such deformations and for animating them in realtime. Besides the starting and ending shapes, our approach offers easy to use additional control over the deformations. The new Bezier Interpolating Polyhedron (BIP) provides a graphics representation of such a deforming object formulated mathematically as a point describing a Bezier curve in the space of all polyhedra. We replace, in the Bezier formulation, the traditional control points by arbitrary polyhedra and the vector addition by the Minkowski sum. BIPs are composed of Animated GRaphic ELement (AGRELs), which are faces with constant orientation, but with parametrized vertices represented by Bezier curves. AGRELs were designed to efficiently support smooth realtime animation on commercially available rendering hardware. We provide a tested algorithm for automatically computing BIPs from the sequence of control polyhedra and demonstrate its applications to animation design.
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    Beyond WYSIWYG: Display of Hidden Information in Graphics Editors
    (Blackwell Science Ltd and the Eurographics Association, 1994) Schleich, R.; Durst, M.J.
    Graphics editors such as computer aided design systems are complex and difficult to use. We attribute this to the fact that only a small part of the information is visible and therefore accessible and understandable. Only the graphics objects themselves are visible, but the relations between these objects remain hidden. We propose an effective way to visualise this information in the form of trees and graphs in so-called structure browsers. A prototype implements this proposal based on an object-oriented application framework for graphics editors.
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    A Semantics-based Approach for the Design and Implementation of Interaction Objects
    (Blackwell Science Ltd and the Eurographics Association, 1994) Paterno , F.; Leonardi, A.
    Although tools for developing graphical user interfaces are becoming increasingly popular, they do not usually highlight precisely which key elements developers should take into account. This still entails considerable expertise in developing user interfaces. In this paper we present an approach to overcome these problems. Our approach is based on a model for interaction objects and a corresponding design space. This is supported by a toolkit where the available interaction objects are initially classified by their semantics whereas in most current toolkits they are investigated by their appearance. This facilitates designers and developers in identifying the interactors needed in order to obtain an Interactive System supporting user tasks.
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    Real Time Fitting of Hand-Sketched Pressure Brushstrokes
    (Blackwell Science Ltd and the Eurographics Association, 1994) Pudet, Thierry
    A method is described for fitting the outline of hand-sketched pressure brushstrokes with Bezier curves. It combines the brush-trajectory model, in which a stroke is generated by dragging a brush along a given trajectory, with a fast curve fitting algorithm.The method has been implemented for a vector-based drawing program in which the user draws with a cordless pressure-sensitive stylus on a digitizing tablet. From the trajectory followed by the stylus, its associated pressure data, and a specified brush, a stroke of variable width is computed and displayed in real time.First, the digitized trajectory is fitted, thus removing noise. Then, from polygonal approximations of the fitted trajectory and the brush outline, a polygonal approximation of the stroke outline is computed. Working with polygonal approximations reduces computations to simple geometric operations and greatly simplifies the treatment of dynamic, pressure-controlled brushes. Last, the polygonal approximation of the stroke outline is fitted. The result is a closed piecewise Bezier curve approximating the brushstroke outline to within an arbitrary error tolerance.Several examples of hand-sketched drawings realized with this method are presented.
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    An Inexpensive BRDF Model for Physically-based Rendering
    (Blackwell Science Ltd and the Eurographics Association, 1994) Schlick, Christophe
    A new BRDF model is presented which can be viewed as an kind of intermediary model between empirism and theory. Main results of physics are observed (energy conservation, reciprocity rule, microfacet theory) and numerous phenomena involved in light reflection are accounted for, in a physically plausible way (incoherent and coherent reflection, spectrum modifications, anisotropy, self-shadowing, multiple surface and subsurface reflection, differences between homogeneous and heterogeneous materials). The model has been especially intended for computer graphics applications and therefore includes two main features: simplicity (a small number of intuitively understandable parameters controls the model) and efficiency (the formulation provides adequation to Monte-Carlo rendering techniques and/or hardware implementations).
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    COMPUTER GRAPHICS AND REMOTE SENSING - A SYNTHESIS FOR ENVIRONMENTAL PLANNING AND CIVIL ENGINEERING
    (Blackwell Science Ltd and the Eurographics Association, 1994) Graf, K.Ch.; Suter, M.; Hagger, J.; Nuesch, D.
    This paper presents efforts undertaken in the field of photo-realistic visualization of natural landscapes using digital elevation models (DEM) and images generated by remote sensing techniques. The remote sensing systems used in this work include Landsat Thematic Mapper, SPOT HRV and aerial photographs. After an appropriate preprocessing, including radiometric corrections and image enhancement procedures, a precise geometric correction is performed in order to achieve a very high co-registration of the images with the elevation model. A mosaic of several images at various resolutions is stored together with the DEM in a data set covering an extensive area. These data are then input to an efficient hardware-independent terrain rendering algorithm based on a forward projection. Atmospheric effects can be simulated. The concept of a virtual scene allows an automated embedding of raytraced 3D objects. The results show that these methods can be used in the field of environmental planning, civil engineering and other applications where terrain visualization is required.
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    Parallel ray tracing based upon a multilevel topological knowledge acquisition of the scene
    (Blackwell Science Ltd and the Eurographics Association, 1994) RIS, Philippe; ARQUES, Didier
    Including the standard parallelization by grouping primary rays, this paper presents a new parallel ray-timing method based upon a topological knowledge acquisition of the scene. This topological knowledge focuses on relative positions between objects and processes and uses a new type of message. Indeed, instead of exchanging database pages or rays, processes exchange topological information. This information is used by each process to decrease its own list of objects to test against rays The acquisition of information about relative positions between objects and processes is obtained by a careful ordering of he pixel calculation. The processes are dispatched on a computer network including a parallel computer The organization of the processes on this network is a multilevel one leading to different levels of topological message exchanges This method is characterized by topological messages describing the scene, dynamic optimization of the database, easy parallelization on any network (no deadlock, fault tolerance, easily expandable and simple routing), and gives interesting results with true or simulated parallelism.
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    A Method for Displaying Metaballs by using Bezier Clipping
    (Blackwell Science Ltd and the Eurographics Association, 1994) Nishita, Tomoyuki; Nakamae, Eihachiro
    For rendering curved surfaces, one of the most popular techniques is metaballs, an implicit model based on isosurfaces of potential fields. This technique is suitable for deformable objects and CSG model.For rendering metaballs, intersection tests between rays and isosurfaces are required. By defining the higher degree of functions for the field functions, richer capability can be expected, i.e., the smoother surfaces. However, one of the problems is that the intersection between the ray and isosurfaces can not be solved analytically for such a high degree function. Even though the field function is expressed by degree six polynomial in this paper (that means the degree six equation should be solved for the intersection test), in our algorithm, expressing the field function on the ray by Bezier functions and employing Bezier Clipping, the root of this function can be solved very effectively and precisely.This paper also discusses a deformed distribution function such as ellipsoids and a method displaying transparent objects such as clouds.
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    Designing and Implementing a Grid-Distortion Mapping Based on Variational Principles
    (Blackwell Science Ltd and the Eurographics Association, 1994) Arad, Nur
    A grid-distortion mapping based on variational principles is described. The mapping is first defined between any two equivalent regular grids with minor geometric restrictions, and is then optimally extended to the interior of the source grid in a sense to be defined. The result is independent of the particular representation of the curves, and depends only on geometric properties of the grids. We then proceed to construct an approximation to the mapping defined and demonstrate its implementation. Finally, this algorithm is compared to several competing ones, in particular separable (scanline) algorithms.
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    Volume Rendering on Non-regular Grids
    (Blackwell Science Ltd and the Eurographics Association, 1994) Tabatabai, Behnam; Sessarego, Emanuela A.; Mayer, Harald F.
    In this article we present the principle methods for volumerendering of non-regular grids as used in the Finite Element Method or the Method of Control Volumes. Besides linear element types, the methods discussed here also cover the handling of commonly used non-linear element types but little considered in the Computer Graphics community. The very basic operation in the whole rendering process, namely the interpolation of the geometry and function values is fully based on the element type specific shape functions, ensuring a consistent mathematical treatment of the object in the sense of the underlying numerical simulation. We discuss the implications of this approach and propose optimizations justified by general assumptions on the qualify of the simulation model.
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    Triangulating multiply-connected polygons: A simple, yet efficient algorithm.
    (Blackwell Science Ltd and the Eurographics Association, 1994) Ronfard, Remi P.; Rossignac, Jarek R.
    We present a new, simple, yet efficient algorithm for triangulating multiply-connected polygons. The algorithm requires sorting only local concave minima (sags). The order in which triangles are created mimics a flooding process of the interior of the polygon. At each stage, the algorithm analyses the positions and neighborhoods of two vertices only, and possibly checks for active sags, so as to determine which of five possible actions to take. Actions are based on a local decomposition of the polygon into monotonic regions, or gorges (raise the water level in the current gorge, spill into an adjacent gorge, jump to the other bank of a filled gorge, divide a gorge into two, and fill a gorge to its top). The implementation is extremely simple and numerically robust for a large class of polygons. It has been tested on millions of cases as a preprocessing step of a walkthrough and inspection program for complex mechanical and architectural scenes. Extensive experimental results indicate that the observed complexity in terms of the number of vertices, remains under in all cases.
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    Raycasting of Nonregularly Structured Volume Data
    (Blackwell Science Ltd and the Eurographics Association, 1994) Fruhauf, Thomas
    Raycasting is an efficient, but computation-intensive technique for the direct rendering of volumetric data. Nonregularly structured volume data is produced in a variety of applications, such as numerical simulation, ultrasonic inspection, or seismic measurement. Unfortunately, in raycasting nonregulary structured grids, sampling data along the rays is even more computation-intensive. One idea might be to resample the data onto a regular grid for further processing. It is shown, that resampling typical grids results either in extreme sub- sampling of the most interesting areas or in data sets too huge to handle. Additionally, no better hardware will overcome the fact that all topology and context information is lost through resampling. Therefore, dedicated algorithms for the raycasting of nonregularly structured volumes are required.We present a new approach for this task, which is based on sending rays through the computational space of a nonregular grid, instead of conventionally raycasting the physical space. This technique overcomes the difficulties in sampling data along the rays, since the computational space is regular by definition. The paper outlines the mathematical operations of this technique as well as its embedding in a rendering algorithm. We have implemented the new raycasting strategy as a module of our interactive visualization system, providing the users with an additional tool for the efficient exploration of their data.
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    Visualization of Regular Polytopes in Three and Four Dimensions
    (Blackwell Science Ltd and the Eurographics Association, 1994) Hausmann, Barbara; Seidel, Hans-Peter
    Nontrivial regular polytopes only exist in three and four dimensions. This paper describes a software package that allows to interactively visualize and analyze these regular polytopes. The following four tools are available: Display of the Schlegel diagrams, perspective projections with the possibility of interactively rotating the polytope in three-/four-dimensional space before projection, interactive slicing along various directions, cut-throughs and fold-downs. Various examples illustrate the approach.
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    Towards Context- Dependent Interpolation of Digital Elevation Models
    (Blackwell Science Ltd and the Eurographics Association, 1994) Dixon, A.R.; Kirby, G.H.; Wills, D.P.M.
    The fractional Brownian motion (fBm) model has become increasingly popular in recent years as a mechanism for the synthesis of many natural phenomena. Unfortunately, the required interdependence of neighbouring points over an unbounded area (context dependence) renders valid approximations to fBm extremely inefficient. This paper describes a technique for the interpolation of digital elevation models to an arbitrarily high spatial resolution. This is achieved using an efficient recursive subdivision algorithm which has the ability to permit some degree of context dependence within, and across the boundaries of interpolation areas. The application of this technique to flight simulation is described and the technique is evaluated based on its ability to reduce run-time storage requirements.
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    Selective Visualization of Vector Fields
    (Blackwell Science Ltd and the Eurographics Association, 1994) van Walsum, Theo; Post, Frits H.
    In this paper, we present an approach to selective vector field visualization. This selective visualization approach consists of three stages: selectdon creation, selection processing and selective visualization mapping. It is described how selected regions, called selections, can be represented and created, how selections can be processed and how they can be used in the visualization mapping. Combination of these techniques with a standard visualization pipeline improves the visualization process and offers new facilities for visualization. Examples of selective visualization of fluid flow datasets are provided.
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    Magicsphere: an insight tool for 3D data visualization
    (Blackwell Science Ltd and the Eurographics Association, 1994) Cignoni, P.; Montani, C.; Scopigno, R.
    How to render very complex datasets, and yet maintain interactive response times, is a hot topic in computer graphics. The MagicSphere idea originated as a solution to this problem, but its potential goes much further than this original scope. In fact, it has been designed as a very generical 3D widget: it defines a spherical volume of interest in the dataset modeling space. Then, several filters can be associated with the Magicsphere, which apply different visualization modalities to the data contained in the volume of interest. The visualization of multi-resolution datasets is selected here as a case study and an ad hoc filter has been designed, the MultiRes filter. Some results of a prototipal implementation are presented and discussed.
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    Vector Fields: an Interactive Tool for Animation, Modeling and Simulation with Physically Based 3D Particle Systems and Soft Objects
    (Blackwell Science Ltd and the Eurographics Association, 1994) Hilton, Travis L.; Egbert, Parris K.
    Vectorfields have traditionally been used in computer graphics as a means of visualizing models over time. This paper presents a system which extends the use of vector fields as an interactive tool for physically based three dimensional particle systems and soft objects. The techniques implemented in the system provide the user with new flexibility in animation, modeling and simulation. This paper describes bounded interactive vectorfields and how they can be used to manipulate particle systems and a class of soft objects. Applications to animation, modeling and simulation are also presented.
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    GKS-9x: The Design Output Primitive, an Approach to a Specification.
    (Blackwell Science Ltd and the Eurographics Association, 1994) Nehlig, Ph. W.; Duce, D. A.
    This paper describes an approach to the formal definition of the design primitive introduced in the revision of the ISO/IEC computer graphics standard, GKS. The paper starts with a general description of the design primitive and then describes the specification (which is given in the Z notation) and the motivation for the approach taken in some detail. The paper concludes with a reflection on the contribution of this work, and the descriptive style adopted an the GKS revision, to the role of formal description in the presentation of graphics standards.
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    Improved Visualisation of Marine Data: Algae and Acid Rain
    (Blackwell Science Ltd and the Eurographics Association, 1994) Day, A.M.; Turner, S.M.; Arnold, D.B.
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    A Formal Approach to the Specification of Graphic Object Functions
    (Blackwell Science Ltd and the Eurographics Association, 1994) Torres, J.C.; Clares, B.
    Graphic objects are an abstract mathematical model for graphic systems. The model is an algebraic approach to represent graphic information, which include modelling operations. This formalism require some method to describe normal graphic procedures, such as changing the object colour or texture mapping, as these procedures are essential to represent graphic processes.This paper extends the theory by introducing the concept of graphic object functions. A graphic object function transforms one graphic object into another, changing its visual appearance or its geometric properties. A formal definition of graphic functions is given, with a characterization of two special kinds of graphic object functions: filters and object transference functions. These two kinds of functions can be used to perform normal graphic operations, such as changing colours, texture mapping or clipping.Equivalence relationships between graphic objects induced by functions are also studied. These relationships establish an hierarchical structure on the graphic object set.
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    An Integrated Line Tracking and Vectorization Algorithm
    (Blackwell Science Ltd and the Eurographics Association, 1994) van Nieuwenhuizen, Peter R.; Kiewiet, Olaf; Bronsvoort, Willem F.
    A method is presented to compute a vector representation of an arbitrary line in a bi-level raster image The line may have varying line width and irregular borders. Furthermore, at line crossings and branches the user is offered the opportunity to choose from the directions in which line tracking may he continued The method avoids thinning and vectorization of chain codes. Instead, a contour follower is used at both sides of the line, and median line calculation is integrated with contour following. This leads to an efficient algorithm, in particular when individual lines have to be interactively extracted from a raster image.
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    Fast Wavelet Radiosity Method
    (Blackwell Science Ltd and the Eurographics Association, 1994) Pattanaik, Sumanta N.; Bouatouch, Kadi
    Wavelet analysis has been found [1] to be very useful for functional representation and accurate global solution of radiosity. In radiosity we deal with functions in 2D and 4D spaces. Under such conditions, the biggest bottleneck in applying this wavelet analysis seems to be the large number of multidimensional inner products. In this paper, we propose (i) the use of interpolating wavelets for fast inner product computation and consequently for faster wavelet radiosity solution (ii) the use of hierarchical decomposition technique for determining the smoothness of the radiosity function for optimal adaptive subdivision.
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    PREMO - An Initial Approach to a Formal Definition
    (Blackwell Science Ltd and the Eurographics Association, 1994) DUCE, D.A.; DUKE, D.J.; ten HAGEN, P.J.W.; REYNOLDS, G.J.
    Many descriptions of multimedia programming systems are starting to appear in the literature, but little work has yet been done on how to formally specify and reason about such systems. This paper is a contribution on the use of formal description techniques for the specification of multimedia systems and explores a style in which the Object-Z notation from the University of Queensland can be used to specify some of the properties and functionality of such systems. The work has been carried out with reference to the role of formal description techniques in the presentation of ISO/IEC International Standards and in particular to the Premo project in ISO/IEC JTCl/SC24.
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    A Median Cut Algorithm for Efficient Sampling of Radiosity Functions
    (Blackwell Science Ltd and the Eurographics Association, 1994) Feda, Martin; Purgathofer, Werner
    This paper presents an efficient method for sampling the illumination functions in higher order radiosity algorithms. In such algorithms, the illumination function is not assumed to be constant across each patch, but it is approximated by a function which is at least C1 continuous. Our median cut sampling algorithm is inspired by the observation that many form factors are computed at higher precision than is necessary. While a high sampling rate is necessary in regions of high illumination, dark areas can be sampled at a much lower rate to compute the received radiosity within a given precision. We adaptively subdivide the emitter into regions of approximately equal influence on the result. Form factors are evaluated by the disk approximation and a ray tracing based test for occlusion detection. The implementation of a higher order radiosity system using B-splines as radiosity function is described. The median cut algorithm can also be used for radiosity algorithms based on the constant radiosity assumption.
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    Implementing RenderMan - Practice, Problems and Enhancements
    (Blackwell Science Ltd and the Eurographics Association, 1994) Slusallek, Philipp; Pflaum, Thomas; Seidel, Hans-Peter
    The RenderMan interface has been proposed as a general interface to rendering systems, yet only a few implementations of the interface exist. In this paper we describe the implementation of the RenderMan interface on a general rendering architecture that supports various rendering algorithms. Specifically we discuss the implementation of the RenderMan Shading Language and its integration into our rendering architecture. Special attention is focused on the problems that we have encountered and how they can be solved. Additionally, we suggest extensions and enhancements to the current interface definition, which would make RenderMan easier to implement and more flexible to use.
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    Adaptive mesh generation for progressive radiosity: A ray-tracing based algorithm.
    (Blackwell Science Ltd and the Eurographics Association, 1994) PAULIN, Mathias; JESSEL, Jean-Pierre
    The radiosity method is one of the most popular rendering algorithms. It allows to simulate interreflections of light accurately between surfaces as energy transfers are well designed. However, this algorithm and its derivatives need to break scenes into a relatively large number of small elements to approximate the illumination function. Even with a very large number of elements, not all the illumination effects can be simulated. In fact, there are always artefacts when modelling sharp shadows, besides shadows falling between mesh vertices can be missed entirely. To reduce the computational cost of such methods and to increase the accuracy of the radiosity solution, adaptive mesh generation is well suited. In this paper, we present a ray-tracing based algorithm for adaptive mesh generation which resolves all the illumination problems without lengthening computation time too much. This method allows a small number of initial elements and increases element density in critical locations while solving the illumination problem.
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    Sketching 3D models with 2D interaction devices
    (Blackwell Science Ltd and the Eurographics Association, 1994) Branco, Vasco; Costa, Antonio; Ferreira, F. Nunes
    The creation of a 3D shape using CAD tools, namely solid modelers, is difficult and time-consuming. Therefore, these systems are kept away from the conceptual phases of design, perhaps the most important in any product life cycle.The sketch is considered by many people as one of the fundamental techniques during a design s conceptual stages, as it enables high level design options to be explored at low cost. In general, this technique IS under-appreciated in the computer graphics world.In this paper, we present a system called IDeS that tries to combine simplicity and intuition while drawing, with the useful features of the solid modelers, for example, CSG operators.
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    Reducing The Latency In Head-Mounted Displays By A Novel Prediction Method Using Grey System Theory
    (Blackwell Science Ltd and the Eurographics Association, 1994) Wu, Jiann-Rong; Ouhyoung, Ming
    In this paper we propose a novel prediction method for the head motion using Grey System theory, where a 6D tracker is attached to an HMD on a user s head in virtual reality applications. Our prediction method using Grey System Model can greatly reduce the latency by at least one half and reduce image jittering. A system latency below 100 ms or even 50 ins can be achieved, even though without prediction the latency is around 200 ms. Using 6 points in prediction with Grey System Model is currently the best in tracker prediction as we tried from 2 points to 10 points.In order to measure the latency, we also propose a way to measure it in an HMD system precisely and conveniently. During the process, we have implemented four different prototypes respectively on a PC486, a SUN SparcStation10, an SGI IndigoR4000, and a high performance computer image generator. The computation complexity of our prediction method is relatively low and therefore real time requirement is easily met.
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    How to Render Frames and Influence People
    (Blackwell Science Ltd and the Eurographics Association, 1994) Strothotte, Thomas; Preim, Bernhard; Raab, Andreas; Schumann, Jutta; Forsey, David R.
    Rendering systems generally treat the production of images as an objective process governed by the laws of physics. However, perception and understanding on the part of viewers are subjective processes influenced by a variety offactors. For example, in the presentation of architectural drawings, the apparent precision with which the drawings are made will affect whether the viewer considers the design as part of a preliminary design or as part of a final polished project, and to some extent the level of confidence the viewer has in the encoded information.In this paper we develop techniques for rendering images in a way that differs from the usual photorealistic or wire-frame output of renderers. In particular, our techniques allow a user to adjust the rendering of a scene to produce images using primitives with variable degrees of precision, from approximations that resemble vague"five-minute-sketches" to more mature but still hand-drawn images. We provide a theoretical framework for analysing the information flow from the computer to the user via such images. Finally, we describe the design and implementation of a prototypical renderer and show examples of its output.
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    Cross Scan Buffer and its Applications
    (Blackwell Science Ltd and the Eurographics Association, 1994) Tanaka, Toshimitsu; Takahashi, Tokiichiro
    We propose the Cross Scanline Buffer which preserves the result of hidden surface removal as performed by the Cross Scanline Algorithm. The Cross Scan Buffer reduces image re-generation time and eliminates aliasing artifacts even if the image is arbitrarily scaled. Perfect anti-aliasing is achieved because the Cross Scanline Algorithm analytically determines visible polygonal surfaces and divides them into sets of triangles and trapezia. The Cross Scan Buffer supports the various applications that currently use the conventional buffering methods for anti-aliasing. This paper introduces and tests three applications: image scaling, shadow creation, and texture mapping. Experimental results verify that the Cross Scan Buffer is very powerful yet efficient.
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    A Paradigm for the Robust Design of Algorithms for Geometric Modeling
    (Blackwell Science Ltd and the Eurographics Association, 1994) Agrawal, Amitabh; Requicha, Aristides A. G.
    Geometric modelers are becoming faster and more powerful, but they still suffer from reliability problems because of floating point errors. Previous work in the field of robust geometric modeling tends to be problem specific and has proven hard to generalize. The approach described here is a general paradigm for handling the accuracy problem for a large set of geometric algorithms. This approach brings together ideas and techniques from interval arithmetic, constraint management, randomization, and algebraic geometry. It acknowledges that input values have tolerances, that objects within tolerance are equivalent, and that certain geometric singularities must be maintained because they reflect design intent or the laws of geometry. Our approach is systematic, and can be applied almost mechanically to the large domain of problems that can be solved by algorithms using the operations +, ?, * and /. The required theory and algorithms have been developed, and the viability of the concepts has been demonstrated by an experimental implementation involving linear half-spaces in Euclidean 2-dimensional space. The implementation focuses on algorithms for computing the boundaries of objects defined by Constructive Solid Geometry (CSG) trees.
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    Computer Graphics System for Reproducing Three- Dimensional Shape from Idea Sketch
    (Blackwell Science Ltd and the Eurographics Association, 1994) Akeo, Makoto; Hashimoto, Hiroshi; Kobayashi, Taisuke; Shibusawa, Tetsuo
    This paper describes the technical features and method of implementation of our designer support system which enables reproducing a three-dimensional shape from an idea sketch speedily and modifying the reproduced shape easily, thereby facilitating the consistency of the shape to be checked from a design viewpoint.The designer support system was developed as a tool to cut the time and labor designers have to spend in the design process and help designers to fully display their creativity-the essential attribute of designers.This system uses cross-section lines of an idea sketch of an object drawn by an industrial designer as input data to reproduce automatically a three-dimensional wireframe model of the object by a newly developed three-dimensional graphic algorithm including graphic constraints. In addition, it automatically creates planes by scanning the area enclosed by reproduced curved lines and subjects them to shading. In this process, the dimensions of the object need not be input to the system. The designer can operate the system simply by using the mouse to input appropriate data.Thus, the system permits the designer to easily express his idea in the form of a three-dimensional shape and study idea variations on the display screen without creating a mockup.
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    Solid Modeling Based on a New Paradigm
    (Blackwell Science Ltd and the Eurographics Association, 1994) Yoshida, Norimasa; Shiokawa, Masato; Yamaguchi, Fujio
    The technique of solid modeling is essential in CAD/CAM applications, and is currently well established. However, problems remain, such as the lack of uniformity in geometric computations and the lack of stability of Boolean operations of two solids. In this paper, we introduce a theoretical solid modeling system that operates on boundary representations of polyhedral objects and is based on a new paradigm. The characteristics of the system are the following: (I) in Boolean Operations and modeling transformations, all geometric computations are performed by the 4 ? 4 determinant method or the 4 ? 4 matrix method in homogeneous space, which allows the system to avoid division operations, (2) all geometric computations are performed by the exact integer arithmetic, which makes the geometric algorithms stable and simple, and (3) primitive solids are constructed consistently in the integer domain, and the consistency is assured throughout Boolean operations and transformations.
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    A Robust and Consistent Algorithm for Intersecting Convex Polyhedra
    (Blackwell Science Ltd and the Eurographics Association, 1994) Sugihara, Kokichi
    This paper presents a numerically robust and topologically consistent algorithm for intersecting convex polyhedra. This algorithm is new in the sense that the consistency issue is completely separated from the numerical error issue. The intersection operation is combinatorially abstracted as the operation of changing the vertex-edge graphs associated with the input polyhedra, and numerical computation is employed only for choosing the branch of processing which is most likely to lead to the correct solution of the problem. Hence, the resultant algorithm is completely free from topological inconsistency.
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    The Mesh Propagation Algorithm for Isosurface Construction
    (Blackwell Science Ltd and the Eurographics Association, 1994) Howic, C.T.; Blake, E.H.
    A new algorithm, Mesh Propagation, is presented for the generation of isosurfaces from three-dimensional discrete data sets. While producing the same surface mesh as that generated by a corrected Marching Cubes algorithm, its characteristic is that it constructs an isosurface using connected strips of dynamically triangulated polygons. This compact data structure speeds up surface construction and reduces surface storage requirements. The surface can also be displayed more quickly, particularly where there is hardware support for rendering triangle strips.With engineering as well as medical imaging applications in mind, the algorithm can be used with both irregular and rectilinear grids of data, the primitive volume elements need not be hexahedral only, and volumes of heterogeneous polyhedral elements are supported without traversal complications.The algorithm propagates through the cells in the grid and uses the same lookup table topologies as Marching Cubes to determine patches of surface-element intersection- additional tables are used for non-hexahedral elements. The surface patches are dynamically coded into triangle strips which are then concatenated and linked to construct the surface. The data structures used for propagating through the volume overcome the topological ambiguities associated with table-based methods of surface construction and no holes are generated in the final mesh.
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    Skylight for Interior Lighting Design
    (Blackwell Science Ltd and the Eurographics Association, 1994) Dobashi, Yoshinori; Kaneda, Kazufumi; Nakashima, Takanobu; Yamashita, Hideo; Nishita, Tomoyuki and Tadamura, Kastumi
    It is inevitable for indoor lighting design to render a room lit by natural light, especially for an atelier or an indoor pool where there are many windows. This paper proposes a method for calculating the illuminance due to natural light, i.e. direct sunlight and skylight, passing through transparent planes such as window glass. The proposed method makes it possible to efficiently calculate such illuminance accurately, because it takes into account both non-uniform luminous intensity distribution of skylight and the distribution of transparency of glass according to incident angles of light. Several examples including the lighting design in an indoor pool, are shown to demonstrate the usefulness of the proposed method.
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    A New Approach to the Construction of Surfaces from Contour Data
    (Blackwell Science Ltd and the Eurographics Association, 1994) Jones, Mark W.; Chen, Min
    This paper presents a new approach to the construction of a surface from a stack of contour slices. Unlike most existing methods, this new approach handles ambiguous conditions consistently without employing an algorithm to establish a correspondence between vertices on one contour and those on the next. It is easy to implement and fast to compute, requiring only basic geometric properties, namely closedness and simplicity, to be available with contour data. The advantages of this new approach have also been demonstrated with solutions to a few classical problems from the literature and some practical problems in medical imaging. It can also be applied to geographical surveying and keyframe animations.