Issue 3

Permanent URI for this collection

https://diglib7.eg.org/handle/10.2312/80
EG 1997 Conference Proceedings

BibTeX (Issue 3)
                
@article{
-,

journal = {Computer Graphics Forum},
title = {{
Preface and Table of Contents (EG 1997, CGF 16-3)}},

author = {
Fellner, Dieter W.
 and 
Szirmay-Kalos, László
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
-}

}
                
@article{
10.1111:1467-8659.00145,

journal = {Computer Graphics Forum},
title = {{
Computing Volumes of Solids Enclosed by Recursive Subdivision Surfaces}},

author = {
Peters, Jorg
 and 
Nasri, Ahmad
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00145}

}
                
@article{
10.1111:1467-8659.00144,

journal = {Computer Graphics Forum},
title = {{
Robust Computation of Intersection Graph between Two Solids}},

author = {
Nakamura, Hiroyuki
 and 
Higashi, Masatake
 and 
Hosaka, Mamoru
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00144}

}
                
@article{
10.1111:1467-8659.00146,

journal = {Computer Graphics Forum},
title = {{
Compression Domain Volume Rendering for Distributed Environments}},

author = {
Lippert, L.
 and 
Gross, M.H.
 and 
Kurmann, C.
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00146}

}
                
@article{
10.1111:1467-8659.00147,

journal = {Computer Graphics Forum},
title = {{
Deformable Surface Techniques for Field Visualization}},

author = {
Sadarjoen, I.
 and 
Post, Frits H.
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00147}

}
                
@article{
10.1111:1467-8659.00148,

journal = {Computer Graphics Forum},
title = {{
A Multiscale Approach to Integrated Volume Segmentation and Rendering}},

author = {
Westermann, Rudiger
 and 
Ertl, Thomas
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00148}

}
                
@article{
10.1111:1467-8659.00150,

journal = {Computer Graphics Forum},
title = {{
An Algorithmic Reflectance and Transmittance Model for Plant Tissue}},

author = {
Baranoski, Gladimir V.G.
 and 
Rokne, Jon G.
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00150}

}
                
@article{
10.1111:1467-8659.00149,

journal = {Computer Graphics Forum},
title = {{
A Procedural Description of Geometric Textures by Spectral and Spatial Analysis of Profiles}},

author = {
Dischler, J.-M.
 and 
Ghazanfarpour, D.
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00149}

}
                
@article{
10.1111:1467-8659.00151,

journal = {Computer Graphics Forum},
title = {{
Growing and Animating Polygonal Models of Animals}},

author = {
Walter, Marcelo
 and 
Fournier, Alain
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00151}

}
                
@article{
10.1111:1467-8659.00153,

journal = {Computer Graphics Forum},
title = {{
A Muscle-based Feed-forward Controller of the Human Body}},

author = {
Komura, Taku
 and 
Shinagawa, Yoshihisa
 and 
Kunii, Tosiyasu L.
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00153}

}
                
@article{
10.1111:1467-8659.00152,

journal = {Computer Graphics Forum},
title = {{
Stochastic Dynamics: Simulating the Effects of Turbulence on Flexible Structures}},

author = {
Stam, Jos
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00152}

}
                
@article{
10.1111:1467-8659.00136,

journal = {Computer Graphics Forum},
title = {{
Finally Everyone Can Work With Highly Complex 3D Models}},

author = {
Rossignac, Jarek
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00136}

}
                
@article{
10.1111:1467-8659.00154,

journal = {Computer Graphics Forum},
title = {{
A Flexible Architecture for Virtual Humans in Networked Collaborative Virtual Environments}},

author = {
Sunday Pandzic, Igor
 and 
Lee, Elwin
 and 
Magnenat Thalmann, Nadia
 and 
Capin, Tolga K.
 and 
Thalmann, Daniel
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00154}

}
                
@article{
10.1111:1467-8659.00155,

journal = {Computer Graphics Forum},
title = {{
Building Telepresence Systems: Translating Science Fiction Ideas into Reality}},

author = {
Fuchs, Henry
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00155}

}
                
@article{
10.1111:1467-8659.00157,

journal = {Computer Graphics Forum},
title = {{
Selective Pixel Transmission for Navigating in Remote Virtual Environments}},

author = {
Mann, Yair
 and 
Cohen-Or, Daniel
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00157}

}
                
@article{
10.1111:1467-8659.00156,

journal = {Computer Graphics Forum},
title = {{
Automatic Hierarchical Level of Detail Optimization in Computer Animation}},

author = {
Mason, Ashton E.W.
 and 
Blake, Edwin H.
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00156}

}
                
@article{
10.1111:1467-8659.00158,

journal = {Computer Graphics Forum},
title = {{
Efficient Impostor Manipulation for Real-Time Visualization of Urban Scenery}},

author = {
Sillion, Francois
 and 
Drettakis, George
 and 
Bodelet, Benoit
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00158}

}
                
@article{
10.1111:1467-8659.00159,

journal = {Computer Graphics Forum},
title = {{
Interactive High-Quality Soft Shadows in Scenes with Moving Objects}},

author = {
Loscos, Celine
 and 
Drettakis, George
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00159}

}
                
@article{
10.1111:1467-8659.00161,

journal = {Computer Graphics Forum},
title = {{
Steering Image Generation with Wavelet Based Perceptual Metric}},

author = {
Gaddipatti, Ajeetkumar
 and 
Machiraju, Raghu
 and 
Yagel, Roni
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00161}

}
                
@article{
10.1111:1467-8659.00160,

journal = {Computer Graphics Forum},
title = {{
Fast Analytic Shading and Shadowing for Area Light Sources}},

author = {
Tanaka, Toshimitsu
 and 
Takahashi, Tokiichiro
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00160}

}
                
@article{
10.1111:1467-8659.00154-16-3,

journal = {Computer Graphics Forum},
title = {{
Tunnel-Free Supercover 3D Polygons and Polyhedra}},

author = {
Andres, Eric
 and 
Nehlig, Philippe
 and 
Francon, Jean
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00154-16-3}

}
                
@article{
10.1111:1467-8659.00164,

journal = {Computer Graphics Forum},
title = {{
An Analysis of Quasi-Monte Carlo Integration Applied to the Transillumination Radiosity Method}},

author = {
Szirmay-Kalos, Laszlo
 and 
Foris, Tibor
 and 
Neumann, Laszlo
 and 
Csebfalvi, Balazs
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00164}

}
                
@article{
10.1111:1467-8659.00165,

journal = {Computer Graphics Forum},
title = {{
A Rendering Equation for Specular Transfers and Its Integration into Global Illumination}},

author = {
Yu, Yizhou
 and 
Wu, Hong
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00165}

}
                
@article{
10.1111:1467-8659.00162,

journal = {Computer Graphics Forum},
title = {{
Painting-like Image Emphasis based on Human Vision Systems}},

author = {
Tanaka, Toshimitsu
 and 
Ohnishi, Noboru
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00162}

}
                
@article{
10.1111:1467-8659.00163,

journal = {Computer Graphics Forum},
title = {{
Radiosity with Well Distributed Ray Sets}},

author = {
Neumann, Laszlo
 and 
Neumann, Attila
 and 
Bekaert, Philippe
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00163}

}
                
@article{
10.1111:1467-8659.00170,

journal = {Computer Graphics Forum},
title = {{
A Framework for Interacting with Paper}},

author = {
Robinson, Peter
 and 
Sheppard, Dan
 and 
Watts, Richard
 and 
Harding, Robert
 and 
Lay, Steve
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00170}

}
                
@article{
10.1111:1467-8659.00169,

journal = {Computer Graphics Forum},
title = {{
Virtually Documented Environments: A New Interface Paradigm for Task-oriented Access to Information}},

author = {
Kakez, Samory
 and 
Conan, Vania
 and 
Bisson, Pascal
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00169}

}
                
@article{
10.1111:1467-8659.00166,

journal = {Computer Graphics Forum},
title = {{
Generating Reflected Directions from BRDF Data}},

author = {
Lalonde, Paul
 and 
Fournier, Alain
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00166}

}
                
@article{
10.1111:1467-8659.00167,

journal = {Computer Graphics Forum},
title = {{
Optimal Source Selection in Shooting Random Walk Monte Carlo Radiosity}},

author = {
Sbert, Mateu
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00167}

}
                
@article{
10.1111:1467-8659.00168,

journal = {Computer Graphics Forum},
title = {{
Bounded Radiosity - Illumination on General Surfaces and Clusters}},

author = {
Stamminger, Marc
 and 
Slusallek, Philipp
 and 
Seidel, Hans-Peter
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00168}

}
                
@article{
10.1111:1467-8659.00138,

journal = {Computer Graphics Forum},
title = {{
Normal Computation for Discrete Surfaces in 3D Space}},

author = {
Thürmer, Grit
 and 
Wüthrich, Charles A.
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00138}

}
                
@article{
10.1111:1467-8659.00137,

journal = {Computer Graphics Forum},
title = {{
The Personal Interaction Panel - a Two-Handed Interface for Augmented Reality}},

author = {
Szalavari, Zsolt
 and 
Gervautz, Michael
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00137}

}
                
@article{
10.1111:1467-8659.00173,

journal = {Computer Graphics Forum},
title = {{
A Modeling and Rendering Method for Snow by Using Metaballs}},

author = {
Nishita, Tomoyuki
 and 
Iwasaki, Hiroshi
 and 
Dobashi, Yoshinori
 and 
Nakamae, Eihachiro
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00173}

}
                
@article{
10.1111:1467-8659.00172,

journal = {Computer Graphics Forum},
title = {{
Using Subdivision on Hierarchical Data to Reconstruct Radiosity Distribution}},

author = {
Kobbelt, Leif
 and 
Stamminger, Marc
 and 
Seidel, Hans-Peter
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00172}

}
                
@article{
10.1111:1467-8659.00139,

journal = {Computer Graphics Forum},
title = {{
Orthogonal Decomposition of Non-Uniform Bspline Spaces using Wavelets}},

author = {
Kazinnik, Roman
 and 
Elber, Gershon
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00139}

}
                
@article{
10.1111:1467-8659.00174,

journal = {Computer Graphics Forum},
title = {{
Modelling the Garden of Perfect Brightness}},

author = {
Wang, LiFeng
 and 
Botta, David
 and 
Ellefson, Chris
 and 
Fournier, Alain
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00174}

}
                
@article{
10.1111:1467-8659.00175,

journal = {Computer Graphics Forum},
title = {{
A Million Polygons, a Million Pixels: Which is Heavier?}},

author = {
Sillion, Francois X.
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00175}

}
                
@article{
10.1111:1467-8659.00142,

journal = {Computer Graphics Forum},
title = {{
Animation by Deformation of Space-Time Objects}},

author = {
Aubert, Fabrice
 and 
Bechmann, Dominique
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00142}

}
                
@article{
10.1111:1467-8659.00140,

journal = {Computer Graphics Forum},
title = {{
Polyhedral Surface Modeling with a Diffusion System}},

author = {
Kuriyama, Shigeru
 and 
Tachibana, Keihachiro
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00140}

}
                
@article{
10.1111:1467-8659.00141,

journal = {Computer Graphics Forum},
title = {{
Interactive Rendering of Deforming NURBS Surfaces}},

author = {
Li, Frederick W. B.
 and 
Lau, Rynson W. H.
 and 
Green, Mark
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00141}

}
                
@article{
10.1111:1467-8659.00143,

journal = {Computer Graphics Forum},
title = {{
Interactive Boundary Computation of Boolean Combinations of Sculptured Solids}},

author = {
Krishnan, S.
 and 
Gopi, M.
 and 
Manocha, D.
 and 
Mine, M.
},
year = {
1997},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.00143}

}

Browse

Recent Submissions

Now showing 1 - 41 of 41
  • No Thumbnail Available
    Item
    Preface and Table of Contents (EG 1997, CGF 16-3)
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Fellner, Dieter W.; Szirmay-Kalos, László
    -
  • No Thumbnail Available
    Item
    Computing Volumes of Solids Enclosed by Recursive Subdivision Surfaces
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Peters, Jorg; Nasri, Ahmad
    The volume of a solid enclosed by a recursive subdivision surface can be approximated based on the closed-form representation of regular parts of the subdivision surface and a tight estimate of the local convex hull near extraordinary points. The approach presented is efficient, i.e. non-exponential, and robust in that it yields rapidly contracting error bounding boxes. An extension to measuring higher-order moments is sketched.
  • No Thumbnail Available
    Item
    Robust Computation of Intersection Graph between Two Solids
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Nakamura, Hiroyuki; Higashi, Masatake; Hosaka, Mamoru
    We propose a new robust algorithm for Boolean operations on solid models. The algorithm produces a consistent intersection graph between two input solids whose geometrical data are represented in floating point numbers. In order to prevent numerical calculation errors and inaccuracy of input data from causing inconsistency of the output, we put higher priority on symbolical connectivity of the edge-face intersection points than their numerical nearness. Each edge-face intersection point is symbolically represented using face names, which generate connectivity relations between the intersection points and the intersection line segments. The symbols with the same connectivity are made into clusters. The intersection line segments connected together at their end clusters form the intersection graph of two solids. Inconsistency of the connectivity of the clusters is detected and the intersection graph is corrected automatically. We describe the algorithm in detail for polyhedral solids, discuss extension to curves solids, and show its effectiveness by some examples of Boolean operations for two solids whose faces intersect at a very small angle.
  • Thumbnail Image
    Item
    Compression Domain Volume Rendering for Distributed Environments
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Lippert, L.; Gross, M.H.; Kurmann, C.
    This paper describes a method for volume data compression and rendering which bases on wavelet splats. The underlying concept is especially designed for distributed and networked applications, where we assume a remote server to maintain large scale volume data sets, being inspected, browsed through and rendered interactively by a local client. Therefore, we encode the serverâ s volume data using a newly designed wavelet based volume compression method. A local client can render the volumes immediately from the compression domain by using wavelet footprints, a method proposed earlier. In addition, our setup features full progression, where the rendered image is refined progressively as data comes in. Furthermore, framerate constraints are considered by controlling the quality of the image both locally and globally depending on the current network bandwidth or computational capabilities of the client. As a very important aspect of our setup, the client does not need to provide storage for the volume data and can be implemented in terms of a network application. The underlying framework enables to exploit all advantageous properties of the wavelet transform and forms a basis for both sophisticated lossy compression and rendering. Although coming along with simple illumination and constant exponential decay, the rendering method is especially suited for fast interactive inspection of large data sets and can be supported easily by graphics hardware.
  • Thumbnail Image
    Item
    Deformable Surface Techniques for Field Visualization
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Sadarjoen, I.; Post, Frits H.
    Surface extraction from data fields is often used in scientific visualization, as surfaces can represent meaningful information and they are well suited for display. This paper describes a general method for localized surface extraction from scalar and vector fields. An initial polygonal surface is placed within the field, and the shape of the surface is adapted to the field by iterative displacement of surface nodes according to a displacement criterion. To achieve a good approximation of a smooth surface, the polygon mesh can be locally refined during iteration. The type of surface extracted depends on the displacement criterion, which can be any function of the available field variables. Techniques for displacement and mesh refinement are discussed in detail. The results we show are generation of a local isosurface and extraction of a vortex tube. Finally, we will draw conclusions and discuss some issues for further development.
  • No Thumbnail Available
    Item
    A Multiscale Approach to Integrated Volume Segmentation and Rendering
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Westermann, Rudiger; Ertl, Thomas
    A number of techniques have been proposed for rendering volumetric scalar data sets. Techniques have also been proposed for analyzing the three dimensional information contents of the underlying domain, but traditionally the data analysis part is left as a post-processing step which only involves the rendered two dimensional images. In this paper, we describe a visualization method for scalar volume data which integrates explicit knowledge of the underlying domain into the rendering process. The key of this approach lies in a hierarchical description of the discrete signal, which is decomposed into a sequence of multiscale representations. We describe a technique for the analysis of structures within the data. This allows for the segmentation and classification of the relevant features and can be used to improve their visual sensation. We also address the problem of accelerating the final rendering pass by integrating the extracted object space information into the ray traversal process.
  • No Thumbnail Available
    Item
    An Algorithmic Reflectance and Transmittance Model for Plant Tissue
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Baranoski, Gladimir V.G.; Rokne, Jon G.
    Recent developments in rendering have provided very realistic images. However, these images rarely show organic objects. We believe that one of the main difficulties of rendering these objects realistically is the lack of reflectance and transmittance models oriented to organic materials. In this paper an algorithmic reflectance and transmittance model for plant tissue oriented to computer graphics applications is presented. The model accounts for the three components of light propagation in plant tissues, namely surface reflectance, subsurface reflectance and transmittance, and mechanisms of light absorption by pigments present in these tissues. The model design is based on the available biological information, and it is controlled by a small number of biologically meaningful parameters. Its formulation, based on standard Monte Carlo techniques, guarantees its easy incorporation into most rendering systems. The spectral curves of reflectance and transmittance computed by the model are compared with measured curves from actual experiments.
  • Thumbnail Image
    Item
    A Procedural Description of Geometric Textures by Spectral and Spatial Analysis of Profiles
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Dischler, J.-M.; Ghazanfarpour, D.
    In this paper we describe a method for automatically generating procedural "geometric" textures, using a hybrid (spectral and spatial) analysis of profiles (ID curves). The profile describes a certain height variation for a certain abscissa. We call "geometric" textures a class of textures including "Bump" textures and "hypertextures". In dealing with this challenge (automatic synthesis), we introduce two new key ideas.The first is to compute efficiently a compact and procedural description of the texture, by using a spectral (Fourier transform based) and spatial (histogram based) analytical approach of profiles. The resulting texture is defined as a sum of elementary random functions. This sum is generated according to the profile. The procedural description allows the direct computation of the texture values at any co-ordinates in the Euclidean space and the stochastic aspect of the elementary functions also allows for the processing of highly random textures, with no considerable increase of computation time.The second key idea consists of using analysis in the particular and more complex case of geometric textures. For most analytical methods, underlying geometry is never considered. Using profiles as models, the resulting geometric texture is obtained by extending this profile to 2D or 3D space. The resulting texture directly matches the supplied 1D model. Hence, our method promises to be a very useful tool for easily and efficiently "modelling" any kind of geometric textures including rocks, bumps, peaks, fur, cotton and so on.
  • No Thumbnail Available
    Item
    Growing and Animating Polygonal Models of Animals
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Walter, Marcelo; Fournier, Alain
    While there exist many computer models of animal bodies, as polygonal meshes and parametric surfaces, these are difficult to modify to take growth into account, or to animate. Growth data available from the literature usually is expressed as very sparse measurements over the body at various ages of the animal. We present here basic techniques to transfer growth data to computer models (especially polygonal meshes), which allows animation of the growth as well as animation of the body in the traditional sense.The main technique consists of defining local coordinate systems around the growing parts of the body, each one being transformed according to the relevant growth data while maintaining their relationship with the adjoining parts and the continuity of the surface. The local coordinates also permit ordinary animation mainly as relative rotation such as in articulated objects.We present examples with polygonal models of horses and cows, growth data from same, and motion from Muybridgeâ s classic photographic data.
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    A Muscle-based Feed-forward Controller of the Human Body
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Komura, Taku; Shinagawa, Yoshihisa; Kunii, Tosiyasu L.
    There is an increasing demand for human body motion data. Motion capture and physical animation have been used to generate such data. It is, however, apparent that such methods cannot automatically generate arbitrary human body motions. A human body is a redundant multi-linked body controlled by a number of muscles. For this reason, the muscles must work appropriately and cooperatively for controlling the whole body. It is well-known that the human body control system is composed of two parts: The open-loop feed-forward control system and the closed-loop feedback control system. Many researchers have investigated the characteristics of the latter by analyzing the response of a human body to various external perturbations. However, for the former, very few studies have been done. This paper proposes an open-loop feed-forward model of the lower extremities which includes postural control for accurate animation of a human body. Assumptions are made here that the feed-forward controller minimizes a certain objective value while keeping the balance of the body stable. The actual human motion data obtained using a motion capturing technique is compared with the trajectory calculated using our method for verification. The best criteria which is based on muscle dynamics is proposed. Using our method, dynamically correct human animation can be created by merely specifying a few key postures.
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    Stochastic Dynamics: Simulating the Effects of Turbulence on Flexible Structures
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Stam, Jos
    This paper addresses the problem of realistically simulating the motion of tree-branches subjected to turbulence. Since the resulting motion is random in nature, we model it as a stochastic process. We synthesize this process directly by filtering a white noise in the Fourier domain. The filter is constructed by performing a modal analysis of the tree. We use a sophisticated numerical technique which is able to compute the first few significant modes of large trees. The main advantage of our technique over previous methods is that we are able to compute complicated motions without the necessity of integrating dynamical equations over time. Consequently, a user can view and manipulate tree-motions in real-time. Our technique can be further extended to other flexible structures such as two-dimensional plates.
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    Finally Everyone Can Work With Highly Complex 3D Models
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Rossignac, Jarek
    In the past, access to 3D databases was restricted to few specialists having the appropriate CAD skills, software, and graphics hardware.The availability of inexpensive graphics support on personal computers, the Internetâ s impact on private and commercial communication, and the emergence of multimedia standards provide the basis for linking CAD databases with other personal productivity and communication tools and for making them accessible to everyone at home, in schools, in hospitals, or in the industry. For example, employees that have no design expertise, customers, and suppliers would benefit from having an easy access to the 3D databases of a company for: collaborative design review, 3D-based multi-media problem reports, collaborative problem solving and tracking, online training and documentation, internet-based part purchasing and subcontracting, demonstration to customers, or advertising. This presentation will address three of the key issues that have so far limited the non-specialistâ s access to 3D databases.First-time or occasional non-expert users need to become instant experts in 3D navigation through Virtual Environments or in the interactive manipulation of digital 3D models, so that they may immediately focus on their tasks, and not waste precious time learning and fighting an unnatural user interface. Immersive VR is not the panacea - other more effective techniques show promise.The data complexity found in commercial CAD databases, especially in the automotive, aerospace, and construction industries, significantly exceeds the capabilities of any interactive graphics system. This situation is not likely to change, since the growth of the complexity and availability of 3D models outpaces the performance improvement of personal computers. Research on the automatic simplification of 3D models and on the use of levels of detail to accelerate the rendering of distant portions of the scene is growing rapidly.The still limited bandwidth of internet communication channels prohibits a pervasive access to large amounts of 3D data. Recent 3D compression techniques reduce the storage requirements for polyhedral 3D models by two orders of magnitudes.
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    A Flexible Architecture for Virtual Humans in Networked Collaborative Virtual Environments
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Sunday Pandzic, Igor; Lee, Elwin; Magnenat Thalmann, Nadia; Capin, Tolga K.; Thalmann, Daniel
    Complex virtual human representation provides more natural interaction and communication among participants in networked virtual environments, hence it is expected to increase the sense of being together within the same virtual world. We present a flexible framework for the integration of virtual humans in networked collaborative virtual environments. A modular architecture allows flexible representation and control of the virtual humans, whether they are controlled by a physical user using all sorts of tracking and other devices, or by an intelligent control program turning them into autonomous actors. The modularity of the system allows for fairly easy extensions and integration with new techniques making it interesting also as a testbed for various domains from "classic" VR to psychological experiments. We present results in terms of functionalities, example applications and measurements of performance and network traffic with an increasing number of participants in the simulation.
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    Building Telepresence Systems: Translating Science Fiction Ideas into Reality
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Fuchs, Henry
    Many people feel that at some time in the distant future it will be possible to see and interact with remote individuals so realistically that they will appear to be standing next to us, that it will also be possible for physicians to look inside their patients and see organs and tumors, as if they possessed Supermanâ s X-ray vision.Although we are far from the realization of such dreams, we are witnessing some encouraging progress toward them. For example, we understand that two aspects common to these systems are a) the acquisition and synthesis of complex 3D information (whether from cameras at a distant scene or medical imaging devices inside a patient), and b) reconstruction and presentation of the 3D information to the observer (whether a distant collaborator or a nearby physician). Early results from several institutions are encouraging.It is now possible to walk around distant scenes, although the visual data still needs to be preprocessed, the scene still needs to be static and the reconstruction still has gaps. It is possible to look inside patients, although with crude ultrasound imaging and with very limited visualization, or not naturally from the physicianâ s own point of view. It is not yet possible to view any of this kind of information with high degree of immersive 3D realism without wearing cumbersome visualization aids. Truly compelling realization of these long-held dreams will take careful analysis of the remaining problems, creative thinking about new approaches, and innovative and sustained development of the required acquisition and display technologies.
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    Selective Pixel Transmission for Navigating in Remote Virtual Environments
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Mann, Yair; Cohen-Or, Daniel
    This paper presents a technique to improve the performance of a walkthrough in remote virtual environments, where a scene is rendered jointly by the server and the client, in order to reduce the network requirements as much as possible. The client generates novel views by extrapolating a reference view based on the locally available geometric model, while the server transmits data necessary to prevent an accumulation of errors. Within this concept, we show that by transmitting only a selected subset of pixels, the quality of the extrapolated views can be improved while requiring less bandwidth. We focus on the selection process in which the visibility gaps between the reference view and novel view are detected, packed and transmitted compressed to the client.
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    Automatic Hierarchical Level of Detail Optimization in Computer Animation
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Mason, Ashton E.W.; Blake, Edwin H.
    We show that the hierarchical level of detail optimization problem is equivalent to a constrained version of the Multiple Choice Knapsack Problem, and present a new algorithm whose solution to it is at least half as good as the optimal one. The advantage of the hierarchical algorithm is that it allows the use of hierarchical level of detail descriptions in which shared representations may be provided for groups of objects. Rendering cost may then be saved to afford better renderings of more important objects, and the algorithm is capable of providing a complete representation of the visible scene even when the visible scene complexity is very high. Our algorithm has a worst case time complexity of O(nlogn), and is incremental so that it typically completes in only a few iterations. We introduce the use of perceptual evaluation to demonstrate the effectiveness of the use of representations for groups of objects that our algorithm allows.
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    Efficient Impostor Manipulation for Real-Time Visualization of Urban Scenery
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Sillion, Francois; Drettakis, George; Bodelet, Benoit
    Urban environments present unique challenges to interactive visualization systems, because of the huge complexity of the geometrical data and the widely varying visibility conditions. This paper introduces a new framework for real-time visualisation of such urban scenes. The central concept is that of a dynamic segmentation of the dataset, into a local three-dimensional model and a set of impostors used to represent distant scenery. A segmentation model is presented, based on inherent urban structure. A new impostor structure is introduced, derived from the level-of-detail approach. Impostors combine three-dimensional geometry to correctly model large depth discontinuities and parallax, and textures to rapidly display visual detail. We present the algorithms necessary for the creation of accurate and efficient three-dimensional impostors. The implementation of our algorithms allows interactive navigation in complex urban databases, as required by many applications.
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    Interactive High-Quality Soft Shadows in Scenes with Moving Objects
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Loscos, Celine; Drettakis, George
    Interactive rendering of soft shadows (or penumbra) in scenes with moving objects is a challenging problem. High quality walkthrough rendering of static scenes with penumbra can be achieved using pre-calculated discontinuity meshes, which provide a triangulation well adapted to penumbral boundaries, and backprojections which provide exact illumination computation at vertices very efficiently. However, recomputation of the complete mesh and back-projection structures at each frame is prohibitively expensive in environments with changing geometry. This recomputation would in any case be wasteful: only a limited part of these structures actually needs to be recalculated. We present a novel algorithm which uses spatial coherence of movement as well as the rich visibility information existing in the discontinuity mesh to avoid unnecessary recomputation after object motion. In particular we isolate all modifications required for the update of the discontinuity mesh by using an augmented spatial subdivision structure and we restrict intersections of discontinuity surfaces with the scene. In addition, we develop an algorithm which identifies visibility changes by exploiting information contained in the planar discontinuity mesh of each scene polygon, obviating the need for many expensive searches in 3D space. A full implementation of the algorithm is presented, which allows interactive updates of high-quality soft shadows for scenes of moderate complexity. The algorithm can also be directly applied to global illumination.
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    Steering Image Generation with Wavelet Based Perceptual Metric
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Gaddipatti, Ajeetkumar; Machiraju, Raghu; Yagel, Roni
    It is often the case that images generated by image synthesis algorithms are judged by visual examination. The user resorts to an iterative refinement process of inspection and rendering until a satisfactory image is obtained. In this paper we propose quantitative metrics to compare images that arise from an image synthesis algorithm. The intent is to be able to guide the refinement process inherent in image synthesis. The Mean-Square-Error (MSE) has been traditionally employed to guide this process. However, it is not a viable metric for image synthesis control. We propose the use of a wavelet based perceptual metric which incorporates the frequency response of the Human Visual System. A useful aspect of the wavelet based metric is its ability to selectively measure the changes to structures of different sizes and scales in specific locations. Also, by resorting to the use of wavelets of various degrees of regularity, one can seek different levels of smoothness in an image. It is rare that such level of control can be obtained from a metric other than a wavelet based metric. We show the usefulness of our metric by examining its effectiveness in providing insights for common operations of an image synthesis algorithm (e.g., blurring). We also provide some examples of its use in rendering algorithms frequently used in graphics.
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    Fast Analytic Shading and Shadowing for Area Light Sources
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Tanaka, Toshimitsu; Takahashi, Tokiichiro
    This paper describes a fast analytic algorithm that generates exact highlights and soft shadows from area light sources. In order to realize fast shadowing, we propose the ray-oriented buffer which segments 3D space by following light rays from polygonal sources. Each cell of the buffer stores objects that intersect a related subspace. Candidate objects which may cast shadows onto a point are selected by referring to the buffer. The candidates are then tested with their shadow bounding volumes to suppress objects that never occlude light sources.In addition, we propose the cross scanline clipping algorithm. It quickly determines the exact regions of uncovered area light sources with simple silhouette generation. Both diffuse and specular reflections are computed by integrating light rays from the uncovered sources. Experimental results confirm the high performance of the proposed method.
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    Tunnel-Free Supercover 3D Polygons and Polyhedra
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Andres, Eric; Nehlig, Philippe; Francon, Jean
    A new discrete 3D line and 3D polygon, called Supercover 3D line and Supercover 3D polygon, are introduced. Analytical definitions are provided. The Supercover 3D polygon is a tunnel free plane segment defined by vertices and edges. An edge is a Supercover 3D line segment. Two different polygons can share a common edge and if they do, the union of both polygons is tunnel free. This definition of discrete polygons has the "most" properties in common with the continuous polygons. It is particularly interesting for modeling of discrete scenes, especially using tunnel-free discrete polyhedra. Algorithms for computing Supercover 3D Lines and Polygons are given and illustrated.
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    An Analysis of Quasi-Monte Carlo Integration Applied to the Transillumination Radiosity Method
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Szirmay-Kalos, Laszlo; Foris, Tibor; Neumann, Laszlo; Csebfalvi, Balazs
    This paper presents an enhanced transillumination radiosity method that can provide accurate solutions at relatively low computational cost. The proposed algorithm breaks down the double integral of the gathered power to an area integral that is computed analytically and to a directional integral that is evaluated by quasi-Monte Carlo techniques. Since the analytical integration results in a continuous function of finite variation, the quasi-Monte Carlo integration that follows the analytical integration will be efficient and its error can be bounded by the Koksma-Hlawka inequality. The paper also analyses the requirements of the convergence, presents theoretical error bounds and proposes error reduction techniques. The theoretical bounds are compared with simulation results.
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    A Rendering Equation for Specular Transfers and Its Integration into Global Illumination
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Yu, Yizhou; Wu, Hong
    In this paper, we present a rigorous theoretical formulation of the fundamental problem-indirect illumination from area sources via curved ideal specular surfaces. Intensity and area factors are introduced to clarify this problem and to rectify the radiance from these specular surfaces. They take surface geometry, such as Gaussian curvature, into account. Based on this formulation, an algorithm for integrating ideal specular transfers into global illumination is also presented. This algorithm can deal with curved specular reflectors and transmitters. An implementation is described based on wavefront tracing and progressive radiosity. Sample images generated by this method are presented.
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    Painting-like Image Emphasis based on Human Vision Systems
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Tanaka, Toshimitsu; Ohnishi, Noboru
    Regional image emphasis is often evident in paintings and illustrations. This technique increases local contrast while reducing global contrast by amplifying image intensity on shadowed surfaces, reducing intensity on illuminated surfaces, and then expanding contrast at intensity edges. The effects are assumed to result from the visual processing needed to interpolate the real world onto canvas. Therefore, we propose an intensity emphasis method based on human vision. This method simulates the adaptation of photoreceptor cells and the lateral inhibition of receptive fields. These attributes of a vision system are realized by computation of relative intensity and differential intensity in small areas.The proposed method can successfully generate painting-like artifacts, which greatly improves the perception of visual elements displayed in an image. Since the method efficiently reduces the dynamic range of images, it can be used for displaying highlighted images on standard graphic monitors. Experiments on a computer-generated image and a photograph confirm the advantages of our method.
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    Radiosity with Well Distributed Ray Sets
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Neumann, Laszlo; Neumann, Attila; Bekaert, Philippe
    In this paper we present a new radiosity algorithm, based on the notion of a well distributed ray set (WDRS). A WDRS is a set of rays, connecting mutually visible points and patches, that forms an approximate representation of the radiosity operator and the radiosity distribution. We propose an algorithm that constructs an optimal WDRS for a given accuracy and mesh. The construction is based on discrete importance sampling as in previously proposed stochastic radiosity algorithms, and on quasi Monte Carlo sampling. Quasi Monte Carlo sampling leads to faster convergence rates and the fact that the sampling is deterministic makes it possible to represent the well distributed ray set very efficiently in computer memory. Like previously proposed stochastic radiosity algorithms, the new algorithm is well suited for computing the radiance distribution in very complex diffuse scenes, when it is not feasible to explicitly compute and store form factors as in classical radiosity algorithms. Experiments show that the new algorithm is often more efficient than previously proposed Monte Carlo radiosity algorithms by half an order of magnitude and more.
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    A Framework for Interacting with Paper
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Robinson, Peter; Sheppard, Dan; Watts, Richard; Harding, Robert; Lay, Steve
    This paper reports on ways of using digitised video from television cameras in user interfaces for computer systems. The DigitalDesk is built around an ordinary physical desk and can be used as such, but it has extra capabilities. A video camera mounted above the desk, pointing down at the work surface, is used to detect where the user is pointing and to read documents that are placed on the desk. A computer-driven projector is also mounted above the desk, allowing the system to project electronic objects onto the work surface and onto real paper documents. The animated paper documents project is considering particular applications of the technology in electronic publishing. The goal is to combine electronic and printed documents to give a richer presentation than that afforded by either separate medium.This paper describes the framework that has been developed to assist with the preparation and presentation of these mixed-media documents. The central component is a registry that associates physical locations on pieces of paper with actions. This is surrounded by a number of adaptors that assist with the creation of new documents either from scratch or by translating from conventional hypermedia, and also allow the documents to be edited. Finally the DigitalDesk itself identifies pieces of paper and animates them with the actions described in the registry.
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    Virtually Documented Environments: A New Interface Paradigm for Task-oriented Access to Information
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Kakez, Samory; Conan, Vania; Bisson, Pascal
    We present a suitable virtually documented environment system providing the user with high level interaction possibilities. The system is dedicated to applications where the operator needs to have his hands free in order to access information, carry out measurements and/or operate on a device (e.g. maintenance, instruction). The system merges video images acquired through a head-mounted video camera with synthetic data (multimedia documents including CAD models and text) and presents these merged images to the operator. Registration techniques allow the operator to visualise information properly correlated to the real world: this is an essential aspect in order to achieve a feeling of presence in a real environment.We increase the sense of immersion through high level Human-Computer Interaction (HCI) allowing hands-free access to information through vocal commands as well as multimodal interaction associating speech and gesture. In this way, the user can access information and manipulate it in a very natural manner. We discuss the construction of the documentation system and the requested functionalities which led to the system architecture.
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    Generating Reflected Directions from BRDF Data
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Lalonde, Paul; Fournier, Alain
    Monte-Carlo path tracing algorithms for computer graphics require that given an incident light ray at a surface an outgoing direction can be computed with a distribution given by the magnitude of the bidirectional reflectance distribution function (BRDF). For analytic reflectance functions this can be done using various techniques including inverting the function, or tabulating some representation of the inverse. However, measured BRDF data sets are too large for this to be practical.We present a method to generate reflection rays distributed according to the magnitude of the BRDF. The method relies on a wavelet-based representation of the BRDF. This representation is efficient and compact, allowing large, anisotropic measured BRDF data sets to be represented with a few thousand coefficients. In particular, we exploit the wavelet representation to quickly compute integrals over ranges of the BRDF.
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    Optimal Source Selection in Shooting Random Walk Monte Carlo Radiosity
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Sbert, Mateu
    In this paper we study how to optimally select between different sources in shooting random walk Monte Carlo Radiosity. Until now the probability of selecting a source has been made proportional to the importance of that source for the region of interest. We will show here that, whenever the transition probabilities are the Form Factors, this is not optimal, and will consequently give the optimal case. This will correspond to probabilities proportional to the square root of importances, rather than to importances themselves.
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    Bounded Radiosity - Illumination on General Surfaces and Clusters
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Stamminger, Marc; Slusallek, Philipp; Seidel, Hans-Peter
    Traditionally, Radiosity algorithms have been restricted to scenes made from planar patches. Most algorithms for computing form factors and the subdivision criterion for hierarchical methods implicitly assume planar patches. In this paper, we present a new radiosity algorithm that is solely based on simple geometric information about surface elements, namely their bounding boxes and cone of normals. Using this information allows to compute efficient error bounds that can be used for the subdivision oracle and for computing the energy transfer. Due to the simple interface to geometric objects, our algorithm not only allows for computing illumination on general curved surfaces, but it can also be directly applied to a hieararchy of clusters. Several examples demonstrate the advantages of the new approach.
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    Normal Computation for Discrete Surfaces in 3D Space
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Thürmer, Grit; Wüthrich, Charles A.
    Associating normal vectors to surfaces is essential for many rendering algorithms. We introduce a new method to compute normals on discrete surfaces in object space. Assuming that the surface separates space locally into two disjoint subsets, each of these subsets contains implicitly information about the surface inclination. Considering one of these subsets in a small neighbourhood of a surface point enables us to derive the surface normal from this set. We show that this leads to exact results for C1 continuous surfaces in R3. Furthermore, we show that good approximations can be obtained numerically by sampling the considered area. Finally, we derive a method for normal computation on surfaces in discrete space.
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    The Personal Interaction Panel - a Two-Handed Interface for Augmented Reality
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Szalavari, Zsolt; Gervautz, Michael
    This paper describes the introduction of a new interaction paradigm to augmented reality applications. The everyday tool handling experience of working with pen and notebooks is extended to create a three dimensional two-handed interface, that supports easy-to-understand manipulation tasks in augmented and virtual environments. In the design step we take advantage from the freedom, given by our very low demands on hardware and augment form and functionality to this device. On the basis of examples from object manipulation, augmented research environments and scientific visualization we show the generality of applicability. Although being in the first stages implementation, we consider the wide spectrum of suitability for different purposes.
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    A Modeling and Rendering Method for Snow by Using Metaballs
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Nishita, Tomoyuki; Iwasaki, Hiroshi; Dobashi, Yoshinori; Nakamae, Eihachiro
    The display of natural scenes such as mountains, trees, the earth as viewed from space, the sea, and waves have been attempted. Here a method to realistically display snow is proposed.In order to achieve this, two important elements have to be considered, namely the shape and shading model of snow, based on the physical phenomenon. In this paper, a method for displaying snow fallen onto objects, including curved surfaces and snow scattered by objects, such as skis, is proposed. Snow should be treated as particles with a density distribution since it consists of water particles, ice particles, and air molecules. In order to express the material property of snow, the phase functions of the particles must be taken into account, and it is well-known that the color of snow is white because of the multiple scattering of light.This paper describes a calculation method for light scattering due to snow particles taking into account both multiple scattering and sky light, and the modeling of snow.
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    Using Subdivision on Hierarchical Data to Reconstruct Radiosity Distribution
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Kobbelt, Leif; Stamminger, Marc; Seidel, Hans-Peter
    Computing global illumination by finite element techniques usually generates a piecewise constant approximation of the radiosity distribution on surfaces. Directly displaying such scenes generates artefacts due to discretization errors. We propose to remedy this drawback by considering the piecewise constant output to be samples of a (piecewise) smooth function in object space and reconstruct this function by applying a binary subdivision scheme. We design custom taylored subdivision schemes with quadratic precision for the efficient refinement of cell- or pixel-type data. The technique naturally allows to reconstruct functions from non-uniform samples which result from adaptive binary splitting of the original domain (quadtree). This type of output is produced, e.g., by hierarchical radiosity algorithms. The result of the subdivision process can be mapped as a texture on the respective surface patch which allows to exploit graphics hardware for considerably accelerating the display.
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    Orthogonal Decomposition of Non-Uniform Bspline Spaces using Wavelets
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Kazinnik, Roman; Elber, Gershon
    We take advantage of ideas of an orthogonal wavelet complement to produce multiresolution orthogonal decomposition of nonuniform Bspline (NUB) spaces. The editing of NUB curves and surfaces can be handled at different levels of resolutions.Applying Multiresolution decomposition to possibly C1 discontinuous surfaces, one can preserve the general shape on one hand and local features on the other of the free-form models, including geometric discontinuities. The Multiresolution decomposition of the NUB tensor product surface is computed via the symbolic computation of inner products of Bspline basis functions. To find a closed form representation for the inner product of the Bspline basis functions, an equivalent interpolation problem is solved.As an example for the strength of the Multiresolution decomposition, a tool demonstrating the Multiresolution editing capabilities of NUB surfaces was developed and is presented as part of this work, allowing interactive 3D editing of NUB free-form surfaces.
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    Modelling the Garden of Perfect Brightness
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Wang, LiFeng; Botta, David; Ellefson, Chris; Fournier, Alain
    The Yuan Ming Yuan, the Garden of Perfect Brightness, was the culmination of the art of Chinese Imperial gardens. Covering 350 hectares (875 acres) northwest of Beijing, it included 140 distinct sites, 2000 structures, thousands of pieces of furniture and precious objects, countless plants. It was almost totally destroyed in 1860 at the end of the second Opium War by English and French troops in one of the worst acts of cultural vandalism in recorded history.Rebuilding it has proven impossible, but now computer technology, based on 130 years of scholarly documentation makes it possible to build an accurate and detailed model, and will allow us to experience at least virtually the beauty and grandeur that was the Yuan Ming Yuan.This paper describes a project to build such a model, and details the main challenges and difficulties encountered. While commercially available graphics workstations and modelling software can take us most of the way in this task, they fall short with the modelling of natural phenomena such as plants, rocks and bodies of water. In addition the sheer size of the resulting database pushes rendering engines past their limits.
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    A Million Polygons, a Million Pixels: Which is Heavier?
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Sillion, Francois X.
    The impressive progress of rendering software and hardware over the last two decades often leads to the - too rapid - conclusion that high-quality 3D imagery can now be incorporated in all sorts of applications. Interestingly, these advances allow more and more complex applications to be envisioned: however, an increase in processing power is not necessarily used to treat the same problem faster, but also creates a desire to attack larger problems. In many ways the models for visual simulation or engineering applications grow faster than the graphics systems! recent work on image-based rendering and modeling shows a growing awareness that traditional 3D methods may not scale well for the current and coming complexity levels.This talk will examine some of the challenges lying ahead for the development of future graphics applications. Specifically, when is it better to use pixels than polygons? when is a 3D model required? how can we mix and match competing approaches? can image-based approaches help for different applications such as lighting simulations? some issues related to network applications will also be discussed.
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    Animation by Deformation of Space-Time Objects
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Aubert, Fabrice; Bechmann, Dominique
    This article presents the properties of animation with space-time objects. A space-time object means here a geometrical object embedded in R4 with a volumic topology. Resulting animations are obtained by deforming space-time objects with a free-form deformation model. In this way topological modifications, such as disconnecting or hole making, as well as classical geometrical modifications, can be created in an animated object.
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    Polyhedral Surface Modeling with a Diffusion System
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Kuriyama, Shigeru; Tachibana, Keihachiro
    This paper presents a method of generating polyhedral surfaces by using a diffusion system that calculates the positional and normal vectors on their vertices. The system generates smooth shapes that satisfy the minimum norm property, and can be extended to imitate the shape controls of curvature continuous surfaces with bias and tension parameters. The shape of a surface is determined by the stable state of nonlinear and local calculations between vertices, and is easily controlled by adding constraints on arbitrary vertices. Such bottom-up calculation of surfaces enhances flexibility in the interactive design of complicated free-form shapes.
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    Interactive Rendering of Deforming NURBS Surfaces
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Li, Frederick W. B.; Lau, Rynson W. H.; Green, Mark
    Non-uniform rational B-splines (NURBS) has been widely accepted as a standard tool for geometry representation and design. Its rich geometric properties allow it to represent both analytic shapes and free-form curves and surfaces precisely. Moreover, a set of tools is available for shape modification or more implicitly, object deformation. Existing NURBS rendering methods include de Boor algorithm, Oslo algorithm, Shantzâ s adaptive forward differencing algorithm and Silbermannâ s high speed implementation of NURBS. However, these methods consider only speeding up the rendering process of individual frames. Recently, Kumar et al. proposed an incremental method for rendering NURBS surfaces, but it is still limited to static surfaces. In real-time applications such as virtual reality, interactive display is needed. If a virtual environment contains a lot of deforming objects, these methods cannot provide a good solution. In this paper, we propose an efficient method for interactive rendering of deformable objects by maintaining a polygon model of each deforming NURBS surface and adaptively refining the resolution of the polygon model. We also look at how this method may be applied to multi-resolution modelling.
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    Interactive Boundary Computation of Boolean Combinations of Sculptured Solids
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Krishnan, S.; Gopi, M.; Manocha, D.; Mine, M.
    We present algorithms and systems for interactive boundary computation of Boolean combinations of sculptured solids. The algorithm is applicable to all spline solids and computes an accurate boundary representation. To speed up the computation, the algorithm exploits parallelism at all stages. It has been implemented on a multi-processor SGI and takes one second on average per boolean operation to compute the boundary of high degree primitives. The system has also been integrated with an immersive design and manipulation environment. The resulting system is able to interactively evaluate boundaries of the models, display them for model validation and place them at appropriate position using collision detection algorithms.