Issue 3

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/74
EG 1996 Conference Proceedings

BibTeX (Issue 3)
                
@article{
10.1111:1467-8659.1530003,

journal = {Computer Graphics Forum},
title = {{
Three-Dimensional Modeling and Effects on Still Images}},

author = {
Zakait, Yaron
 and 
Rappoport, Ari
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530003}

}
                
@article{
10.1111:1467-8659.1530097,

journal = {Computer Graphics Forum},
title = {{
Special Effects with Half-Toning}},

author = {
Buchanan, John W.
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530097}

}
                
@article{
10.1111:1467-8659.1530119,

journal = {Computer Graphics Forum},
title = {{
An Image based Measurement System for Anisotropic Reflection}},

author = {
Karner, Konrad F.
 and 
Mayer, Heinz
 and 
Gervautz, Michael
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530119}

}
                
@article{
10.1111:1467-8659.1530109,

journal = {Computer Graphics Forum},
title = {{
Method for Calculation of Sky Light Luminance Aiming at an Interactive Architectural Design}},

author = {
Dobashi, Yoshinori
 and 
Kaneda, Kazufumi
 and 
Yamashita, Hideo
 and 
Nishita, Tomoyuki
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530109}

}
                
@article{
10.1111:1467-8659.1530143,

journal = {Computer Graphics Forum},
title = {{
Blob Metamorphosis based on Minkowski Sums}},

author = {
Galin, E.
 and 
Akkouche, S.
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530143}

}
                
@article{
10.1111:1467-8659.1530129,

journal = {Computer Graphics Forum},
title = {{
Matching and Interpolation of Shapes using Unions of Circles}},

author = {
Ranjan, V.
 and 
Fournier, A.
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530129}

}
                
@article{
10.1111:1467-8659.1530165,

journal = {Computer Graphics Forum},
title = {{
Implicit Sweep Objects}},

author = {
Crespin, Benoit
 and 
Blanc, Carole
 and 
Schlick, Christophe
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530165}

}
                
@article{
10.1111:1467-8659.1530187,

journal = {Computer Graphics Forum},
title = {{
Generation of Smooth Surfaces by Controlling Curvature Variation}},

author = {
Higashi, Masatake
 and 
Tsutamori, Hideo
 and 
Hosaka, Mamoru
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530187}

}
                
@article{
10.1111:1467-8659.1530175,

journal = {Computer Graphics Forum},
title = {{
Data Dependent Thin Plate Energy and its use in Interactive Surface Modeling}},

author = {
Greiner, Gunther
 and 
Loos, Joachim
 and 
Wesselink, Wieger
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530175}

}
                
@article{
10.1111:1467-8659.1530155,

journal = {Computer Graphics Forum},
title = {{
Physically-Based Deformations Constrained in Displacements and Volume}},

author = {
Promayon, E.
 and 
Baconnier, P.
 and 
Puech, C.
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530155}

}
                
@article{
10.1111:1467-8659.1530207,

journal = {Computer Graphics Forum},
title = {{
CCD-Camera Based Optical Beacon Tracking for Virtual and Augmented Reality}},

author = {
Madritsch, Franz
 and 
Gervautz, Michael
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530207}

}
                
@article{
10.1111:1467-8659.1530197,

journal = {Computer Graphics Forum},
title = {{
Head-Tracked Stereo Viewing with Two-Handed 3 D Interaction for Animated Character Construction}},

author = {
Turner, Russell
 and 
Gobbetti, Enrico
 and 
Soboroff, Ian
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530197}

}
                
@article{
10.1111:1467-8659.1530011,

journal = {Computer Graphics Forum},
title = {{
Interactive Occlusion and Automatic Object Placement for Augmented Reality}},

author = {
Breen, David E.
 and 
Whitaker, Ross T.
 and 
Rose, Eric
 and 
Tuceryan, Mihran
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530011}

}
                
@article{
10.1111:1467-8659.1530217,

journal = {Computer Graphics Forum},
title = {{
Intelligent Control for Haptic Displays}},

author = {
Munch, Stefan
 and 
Stangenberg, Martin
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530217}

}
                
@article{
10.1111:1467-8659.1530227,

journal = {Computer Graphics Forum},
title = {{
A Three Dimensional Image Cache for Virtual Reality}},

author = {
Schaufler, Gernot
 and 
Sturzlinger, Wolfgang
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530227}

}
                
@article{
10.1111:1467-8659.1530237,

journal = {Computer Graphics Forum},
title = {{
Radiosity for dynamic scenes in flatland with the visibility complex}},

author = {
ORTI, Rachel
 and 
RIVIERE, Stephane
 and 
DURAND, Fredo
 and 
PUECH, Claude
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530237}

}
                
@article{
10.1111:1467-8659.1530249,

journal = {Computer Graphics Forum},
title = {{
Output-SensitiveVisibility Algorithms for Dynamic Scenes with Applications to Virtual Reality}},

author = {
Sudarsky, Oded
 and 
Gotsman, Craig
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530249}

}
                
@article{
10.1111:1467-8659.1530259,

journal = {Computer Graphics Forum},
title = {{
Extraction of Typographic Elements from Outline Representations of Fonts}},

author = {
Shainir, Ariel
 and 
Rappoport, Ari
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530259}

}
                
@article{
10.1111:1467-8659.1530269,

journal = {Computer Graphics Forum},
title = {{
Fractal modeling using free form techniques}},

author = {
Zair, Chems Eddine
 and 
Tosan, Eric
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530269}

}
                
@article{
10.1111:1467-8659.1530279,

journal = {Computer Graphics Forum},
title = {{
Modelling Megalithic Sites}},

author = {
POULET, Francois
 and 
LUCAS, Michel
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530279}

}
                
@article{
10.1111:1467-8659.1530289,

journal = {Computer Graphics Forum},
title = {{
Vector Field Based Texture Mapping of Animated Implicit Objects}},

author = {
Smets-Solanes, Jean-Paul
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530289}

}
                
@article{
10.1111:1467-8659.1530301,

journal = {Computer Graphics Forum},
title = {{
Surface Graph Sketching}},

author = {
Hutchinson, D.
 and 
Lin, F.
 and 
Hewitt, W.T.
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530301}

}
                
@article{
10.1111:1467-8659.1530023,

journal = {Computer Graphics Forum},
title = {{
Compositing Computer and Video Image Sequences: Robust Algorithms for the Reconstruction of the Camera Parameters}},

author = {
Berger, M.-O.
 and 
Chevrier, C.
 and 
Simon, G.
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530023}

}
                
@article{
10.1111:1467-8659.1530311,

journal = {Computer Graphics Forum},
title = {{
Generation of 3D Texture Using Multiple 2D Models Analysis}},

author = {
GHAZANFARPOUR, Djamchid
 and 
DISCHLER, Jean-Michel
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530311}

}
                
@article{
10.1111:1467-8659.1530327,

journal = {Computer Graphics Forum},
title = {{
Computation of Higher Order Illumination with a Non-Deterministic Approach}},

author = {
Bouatouch, Kadi
 and 
Pattanaik, S. N.
 and 
Zeghers, Eric
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530327}

}
                
@article{
10.1111:1467-8659.1530347,

journal = {Computer Graphics Forum},
title = {{
Reusable Radiosity Objects}},

author = {
Ouhyoung, Ming
 and 
Chuang, Yung-Yu
 and 
Liang, Rung-Huei
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530347}

}
                
@article{
10.1111:1467-8659.1530339,

journal = {Computer Graphics Forum},
title = {{
Simplification of Global-Illumination Meshes}},

author = {
Hughes, Merlin
 and 
Lastra, Anselmo A.
 and 
Saxe, Edward
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530339}

}
                
@article{
10.1111:1467-8659.1530357,

journal = {Computer Graphics Forum},
title = {{
An Energy-Based Approach for Contact Force Computation}},

author = {
Faure, Francois
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530357}

}
                
@article{
10.1111:1467-8659.1530409,

journal = {Computer Graphics Forum},
title = {{
Interpolatory Subdivision on Open Quadrilateral Nets with Arbitrary Topology}},

author = {
Kobbelt, Leif
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530409}

}
                
@article{
10.1111:1467-8659.1530367,

journal = {Computer Graphics Forum},
title = {{
Incremental constraint modelling in a feature modelling system}},

author = {
Laakko, Timo
 and 
Mantyla, Martti
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530367}

}
                
@article{
10.1111:1467-8659.1530387,

journal = {Computer Graphics Forum},
title = {{
BOXTREE: A Hierarchical Representation for Surfaces in 3D}},

author = {
Barequet, Gill
 and 
Chazelle, Bernard
 and 
Guibas, Leonidas J.
 and 
Mitchell, Joseph S.B.
 and 
Tal, Ayellet
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530387}

}
                
@article{
10.1111:1467-8659.1530397,

journal = {Computer Graphics Forum},
title = {{
3D Reconstruction of Complex Polyhedral Shapes from Contours using a Simplified Generalized Voronoi Diagram}},

author = {
Oliva, J-M.
 and 
Perrin, M.
 and 
Coquillart, S.
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530397}

}
                
@article{
10.1111:1467-8659.1530377,

journal = {Computer Graphics Forum},
title = {{
Integrating Computer Animation and Multimedia}},

author = {
Preston, Martin
 and 
Hewitt, Terry
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530377}

}
                
@article{
10.1111:1467-8659.1530033,

journal = {Computer Graphics Forum},
title = {{
3D Interactive Topological Modeling using Visible Human Dataset}},

author = {
Beylot, P
 and 
Gingins, P
 and 
Kalra, P
 and 
Thalmann, N Magnenat
 and 
Maurel, W
 and 
Thalmann, D
 and 
Fasel, J
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530033}

}
                
@article{
10.1111:1467-8659.1530421,

journal = {Computer Graphics Forum},
title = {{
Demand-Driven Geometry Transmission for Distributed Virtual Environments}},

author = {
Schmalstieg, Dieter
 and 
Gervautz, Michael
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530421}

}
                
@article{
10.1111:1467-8659.1530433,

journal = {Computer Graphics Forum},
title = {{
A Platform for User-Tailored Interaction Development in 2D, 3D, and VR}},

author = {
Encarnacao, L. Miguel
 and 
Fechter, Jurgen
 and 
Grunert, Thomas
 and 
Strasser, Wolfgang
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530433}

}
                
@article{
10.1111:1467-8659.1530443,

journal = {Computer Graphics Forum},
title = {{
Symbiosis of Virtual Reality and Scientific Visualization System}},

author = {
Haase, Helmut
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530443}

}
                
@article{
10.1111:1467-8659.1530045,

journal = {Computer Graphics Forum},
title = {{
Incremental Volume Rendering Using Hierarchical Compression}},

author = {
Haley, Michael B.
 and 
Blake, Edwin H.
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530045}

}
                
@article{
10.1111:1467-8659.1530067,

journal = {Computer Graphics Forum},
title = {{
Full-range approximation of triangulated polyhedra.}},

author = {
Ronfard, Remi
 and 
Rossignac, Jarek
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530067}

}
                
@article{
10.1111:1467-8659.1530057,

journal = {Computer Graphics Forum},
title = {{
Real-time Volumetric Deformable Models for Surgery Simulation using Finite Elements and Condensation}},

author = {
Bro-Nielsen, Morten
 and 
Cotin, Stephane
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530057}

}
                
@article{
10.1111:1467-8659.1530087,

journal = {Computer Graphics Forum},
title = {{
Automatic Generation of Multiresolution Boundary Representations}},

author = {
Andujar, C.
 and 
Ayala, D.
 and 
Brunet, P.
 and 
Arinyo, R. Joan
 and 
Sole, J.
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530087}

}
                
@article{
10.1111:1467-8659.1530077,

journal = {Computer Graphics Forum},
title = {{
Mesh Simplification}},

author = {
Algorri, Maria-Elena
 and 
Schmitt, Francis
},
year = {
1996},

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


ISSN = {1467-8659},

DOI = {
10.1111/1467-8659.1530077}

}

Browse

Recent Submissions

Now showing 1 - 42 of 42
  • Thumbnail Image
    Item
    Three-Dimensional Modeling and Effects on Still Images
    (Blackwell Science Ltd and the Eurographics Association, 1996) Zakait, Yaron; Rappoport, Ari
    Designers and creative artists use computer graphics and image processing effects on stall photographs in application areas such as advertising entertainment broadcasting and the arts Most of the effects available in research arid commercial work are two-dimensional in nature, for example image processing filters [blur, edge enhancement) and creative effects (tilings, reflections) There is almost no usage of information taken from the 3-D world in which the objects appearing an the image are located.In this paper we present a novel method for creating 3-D effects on photographs or in general on any image created by rendering a 3-D world The artist interacts with the image using a set of intuitive direct manipulation interface objects These objects let the user define a 3-D model, display at, and manipulate it in a 3-D space which is correlated with that of the input image.The generated model can be an arbitrarily complex 3-D polyhedron Any texture, including texture taken from the input photograph, can be mapped into any of its faces arid used for special effects We discuss and show examples for effects such as copy and paste, motion blur, model editing and deformations lighting effects, and shadows.
  • Thumbnail Image
    Item
    Special Effects with Half-Toning
    (Blackwell Science Ltd and the Eurographics Association, 1996) Buchanan, John W.
    Half-toning is the process by which gray-scale images are approximated with sets of black and white pixels. The process works because our eyes perceive a local average, thus half-toning seeks to approximate the local average. Ideally this approximation should be accomplished without introducing undesirable artifacts.In many situations the stylized display of images is desired. Often this stylized display is accomplished by the addition of semi-structured artifacts. In current applications the designer processes the image using tools provided by some image processing package. The resulting image is then half-toned and printed. Half-toning these processed images can reduce the visual impact of the special effects that have been introduced in the image.In this paper we show that the processes of controlled artifact introduction and half-toning can successfully be combined. By combining these two processes we ensure that the printed image is what the designer intended. We present a brief overview of the current error-diffusion half-toning techniques. We then propose several ways in which artifacts can be introduced to the image. This discussion is accompanied by a set of illustrative images.In particular, we discuss the introduction of false edges and the alteration of the scan pattern. We illustrate these techniques with a variety of images.We conclude the paper with a discussion on these new half-toning methods for the generation of binary gray-scale textures. In addition to showing how to generate these binary gray-scale textures we also show how these gray-scale textures can be used to half-tone images.
  • Thumbnail Image
    Item
    An Image based Measurement System for Anisotropic Reflection
    (Blackwell Science Ltd and the Eurographics Association, 1996) Karner, Konrad F.; Mayer, Heinz; Gervautz, Michael
    This paper introduces an image based method for measuring bidirectional reflectance distribution functions (BRDF). The measurement system uses a CCD camera connected to a workstation to capture images from the material under investigation. The evaluation of the BRDF is performed in an image processing step, gathering BRDF values with a broad range of incident and reflected angles, followed by a fitting process, where these values are approximated by a chosen reflectance model. Absolute BRDF values are obtained by the usage of a diffuse reflectance standard. It is shown that the proposed measurement system produces very reasonable results compared to accurate measurements. Thus, it is an easy and cost efficient way to measure material properties needed for physically based rendering algorithms.
  • Thumbnail Image
    Item
    Method for Calculation of Sky Light Luminance Aiming at an Interactive Architectural Design
    (Blackwell Science Ltd and the Eurographics Association, 1996) Dobashi, Yoshinori; Kaneda, Kazufumi; Yamashita, Hideo; Nishita, Tomoyuki
    Recently, computer graphics are frequently used for both architectural design and visual environmental assessment. Using computer graphics, designers can easily compare the effect of the natural light on their architectural designs under various conditions, such as different times of day, seasons, atmospheric conditions (clear or overcast sky) or building wall materials. In traditional methods of calculating the luminance due to sky light, however, all calculation must be performed from scratch if such conditions undergo change. Therefore, to compare the architectural designs under different conditions, a great deal of time has to be spent on generating the images.This paper proposes a new method of quickly generating images of an outdoor scene, taking into account glossy specular reflection, even if such conditions change. In this method, luminance due to sky light is expressed by a series of basis functions, and basis luminances corresponding to each basis function are precalculated and stored in a compressed form in the preprocess. Once the basis luminances are calculated, the luminance due to sky light can be quickly calculated by the weighted sum of the basis luminances. Several examples of an architectural design demonstrate the usefulness of the proposed method.
  • Thumbnail Image
    Item
    Blob Metamorphosis based on Minkowski Sums
    (Blackwell Science Ltd and the Eurographics Association, 1996) Galin, E.; Akkouche, S.
    This paper addresses the metamorphosis of soft objects built from skeletons. We propose a new approach that may be split into three steps. The first step consists in an original splitting of the initial and the final shapes with a view to creating a bijective graph of correspondence. In the second step, we assume that the skeletons are convex polygonal shapes, and thus take advantage of the properties of Minkowski sums to characterize the skeletons of intermediate shapes. Eventually, we characterize the intermediate distance and field functions- we describe a set of interpolation methods and propose to use a restricted class of parametrized distance and field functions so as to preserve coherence and speed-up computations.We show that we can easily extend those results to achieve a Bezier like metamorphosis where control points are replaced by control soft objects- in this scope, we have adapted existing accelerated techniques that build a Bezier transformation from a set of convex polyhedra to any kind of convex polygonal shapes.Eventually, we point out that matching all components of the initial and the final shapes generates amorphous intermediate shapes based on an overwhelming number of intermediate sub-components. Thus, we propose heuristics with a view to preserving coherence during the transformation and accelerating computations. We have implemented and tested our techniques in an experimental ray-tracer.
  • Thumbnail Image
    Item
    Matching and Interpolation of Shapes using Unions of Circles
    (Blackwell Science Ltd and the Eurographics Association, 1996) Ranjan, V.; Fournier, A.
    While the notion of shape of an object is very intuitive, its precise definition is very elusive, and defining a useful metric for the shape distance between objects is a difficult endeavor. At the same time many successful techniques have been developed which interpolate between two objects, so in essence interpolate between shapes.W e present here work which uses a representation of objects as union of circles to define a distance between two objects and to base a method to interpolate between the two. This method can be used in a totally automatic fashion (that is, without any user intervention), or users can guide a pre-registration phase as well as a segmentation phase, after which the matched segments are interpolated pair-wise. The union of circles representation of the two objects is obtained from the Delaunay triangulation of their boundary points. The circles can be simplified to obtain smaller data sets. The circles are then optimally matched according to a distance metric between circles which is a function of their position, size, and feature, that is, a local configuration of circles. The interpolation between the two objects is then obtained by interpolating between the matched pairs of circles (the interpolations can be affine or non -affine).Examples with simple and more complex objects show how the technique can give results which correspond closely to the human notion of shape interpolation. The interpolations shown include some between a calf and a cow and between a cow and a giraffe. The examples given are in two dimensions, but all the steps except the segmentation have been implemented as well for three dimensional objects. W e also show the results of computation of distances between the objects used in our examples.
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    Implicit Sweep Objects
    (Blackwell Science Ltd and the Eurographics Association, 1996) Crespin, Benoit; Blanc, Carole; Schlick, Christophe
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    Generation of Smooth Surfaces by Controlling Curvature Variation
    (Blackwell Science Ltd and the Eurographics Association, 1996) Higashi, Masatake; Tsutamori, Hideo; Hosaka, Mamoru
    To satisfy a designer s intention for constructing aesthetic shapes such as automotive bodies, we propose a surface generation method. In the surface design process, designers determine shapes according to their great concern for the reflected images of vehicle surroundings, shade lines and highlight lines. Since reflection and shading are affected by changes of surface normal, the curvature variation of the surface, which represents the change of the surface normal, should be smooth and distributed as designers want. The proposed method controls curvature distribution directly by determining a surface shape from an evolute, which is a locus of the curvature center of the generatrix and moves along directrices to form the surface. It first generates evolutes of boundary curves to be generatrices as rational Bezier curves, then interpolates their shapes with the Bezier polygons, and locates the interpolated shape to the corresponding position of the directrices. By applying this method, we have confirmed that a smooth shape is generated from four boundary curves.
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    Data Dependent Thin Plate Energy and its use in Interactive Surface Modeling
    (Blackwell Science Ltd and the Eurographics Association, 1996) Greiner, Gunther; Loos, Joachim; Wesselink, Wieger
    When modeling spline surfaces of complex shape, one has to deal with an overwhelming number of control points. Modeling by direct manipulation of the control points is a tedious task. In particular, it is very difficult to maintain a generally pleasant looking surface shape. It becomes therefore increasingly important to build tools that allow the designer to specify only a few geometric constraints while automatically determining the explicit representation of the surface. The basic concept of such a tool is simple. In a first step one has to somehow measure the"fairness" (=quality) of a surface. Once this is achieved, an optimization process selects the one surface with optimal fairness from all surfaces satisfying the user specified geometric constraints.To measure the fairness, thin plate energy functionals are a good choice. However, for interactive use these functionals are far too complex. W e will present appropriate approximations to these functionals that allow an optimization nearly in real time. Thefunctionals are obtained by introducing reference surfaces thus leading to data dependent, quadratic approximations to the exact thin plate energy functionals. We apply the method to interactive surface manipulations based on energy constraints.
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    Physically-Based Deformations Constrained in Displacements and Volume
    (Blackwell Science Ltd and the Eurographics Association, 1996) Promayon, E.; Baconnier, P.; Puech, C.
    This paper presents a method of constraining physically-based deformable objects. In this method, an object can be defined locally in terms of kinetic and dynamic (mass, position, speed), and physical parameters (compressibility, elasticity, motor functioning). Several problems are solved: constant volume deformation, displacement constraints (fixed or moving required positions), and real object modelling. An object is described by a set of mass points on its contour. The evolution algorithm runs in two phases dealing successively with forces and constraints (which are presented as reaction forces).The main contribution of the method is the control of object volumes during evolution. We define a function that explicitly gives the inside volume of an object in order to use it as a constraint. Thus, the volume can be kept exactly constant during deformation without using an iterative process, in opposition to lagrangian approaches. Some results are illustrated by examples at the end of the paper.
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    CCD-Camera Based Optical Beacon Tracking for Virtual and Augmented Reality
    (Blackwell Science Ltd and the Eurographics Association, 1996) Madritsch, Franz; Gervautz, Michael
    We introduce a scheme for optical beacon tracking using two CCD-cameras and LED beacons. Due to the sub-pixel accuracy of the beacon detection algorithm a very high precision can be achieved so that the tracking method is suitable for augmented reality applications. We describe the assembly of the equipment needed for the whole tracking system, the behavior of LED-beacons, and how three beacons can be combined to form a 6-DOF tracker. A report on our accuracy evaluation and its results are given. Furthermore we describe two application prototypes in which the tracker was incorporated and tested.
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    Head-Tracked Stereo Viewing with Two-Handed 3 D Interaction for Animated Character Construction
    (Blackwell Science Ltd and the Eurographics Association, 1996) Turner, Russell; Gobbetti, Enrico; Soboroff, Ian
    In this paper, we demonstrate how a new interactive 3 D desktop metaphor based on two-handed 3 D direct manipulation registered with head-tracked stereo viewing can be applied to the task of constructing animated characters. In our configuration, a six degree-of-freedom head-tracker and CrystalEyes shutter glasses are used to produce stereo images that dynamically follow the user head motion. 3 D virtual objects can be made to appear at a fixed location in physical space which the user may view from different angles by moving his head. To construct 3 D animated characters, the user interacts with the simulated environment using both hands simultaneously: the left hand, controlling a Spaceball, is used for 3 D navigation and object movement, while the right hand, holding a 3 D mouse, is used to manipulate through a virtual tool metaphor the objects appearing in front of the screen. In this way, both incremental and absolute interactive input techniques are provided by the system. Hand-eye coordination is made possible by registering virtual space exactly to physical space, allowing a variety of complex 3 D tasks necessary for constructing 3 D animated characters to be performed more easily and more rapidly than is possible using traditional interactive techniques. The system has been tested using both Polhemus Fastrak and Logitech ultrasonic input devices for tracking the head and 3 D mouse.
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    Interactive Occlusion and Automatic Object Placement for Augmented Reality
    (Blackwell Science Ltd and the Eurographics Association, 1996) Breen, David E.; Whitaker, Ross T.; Rose, Eric; Tuceryan, Mihran
    We present several techniques for producing two visual and modeling effects in augmented reality. The first effect involves interactively calculating the occlusions between real and virtual objects. The second effect utilizes a collision detection algorithm to automatically move dynamic virtual objects until they come in contact with static real objects in augmented reality. All of the techniques utilize calibrated data derived from images of a real-world environment.
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    Intelligent Control for Haptic Displays
    (Blackwell Science Ltd and the Eurographics Association, 1996) Munch, Stefan; Stangenberg, Martin
    Usually, a mouse is used for input activities only, whereas output from the computer is sent via the monitor and one or two loudspeakers. But why not use the mouse for output, too? For instance, if it would be possible to predict the next interaction object the user wants to click on, a mouse with a mechanical brake could stop the cursor movement at the desired position. This kind of aid is especially attractive for small targets like resize handles of windows or small buttons.In this paper, we present an approach for the integration of haptic feedback in everyday graphical user interfaces. We use a specialized mouse which, is able to apply simple haptic information, to the user s hand and index finger. A multi-agent system has been designed which observes the user in order to predict the next interaction object and launch haptic feedback, thus supporting positioning actions with the mouse. Although primarily designed in order to provide intelligent haptic feedback, the system can be combined with other output modalities as well, due to its modular and flexible architecture.
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    A Three Dimensional Image Cache for Virtual Reality
    (Blackwell Science Ltd and the Eurographics Association, 1996) Schaufler, Gernot; Sturzlinger, Wolfgang
    Despite recent advances in rendering hardware, large and complex virtual environments cannot be displayed with a sufficiently highframe rate, because of limitations in the available rendering performance.This paper presents a new approach of software accelerated rendering which draws from the concepts of impostors, hierarchical scene subdivision and levels of detail. So far software optimization in real-time rendering has merely considered individual objects. This work is actually optimizing the rendering of the whole virtual environment by implementing a three dimensional image cache. It speeds up rendering for large portions of the scene by exploiting the coherence inherent in any smooth frame sequence.The implementation of the three dimensional image cache is discussed and the savings in rendering load achievable on a suitable hardware platform are presented.
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    Radiosity for dynamic scenes in flatland with the visibility complex
    (Blackwell Science Ltd and the Eurographics Association, 1996) ORTI, Rachel; RIVIERE, Stephane; DURAND, Fredo; PUECH, Claude
    The radiosity method is particularly suitable for global illumination calculations in static environments. Nonetheless, recent applications of image synthesis such as architectural simulation or lighting design require the ability to modify environments. Previous methods have attempted to deal with dynamic environments (environments where the geometry, the material properties, etc., can change)but still suffer some limitations in the case of moving objects. One of the main problems remaining is the efficient and accurate detection of which form factors must really be recomputed, since their calculation is the most time-consuming part of the radiosity method. To correctly understand and solve this problem, we start with a method in 2D for polygonal scenes using the visibility complex. It is a powerful data structure representing the visibility relationships between objects in the plane. We have developed and implemented an algorithm which uses this structure to efficiently compute the discontinuity mesh and the form factors for static scenes. We also propose an extension to our algorithm to efficiently update only the modified form factors when an object is moving. This approach enhances our understanding and will hopefully lead to efficient solutions in 3D.
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    Output-SensitiveVisibility Algorithms for Dynamic Scenes with Applications to Virtual Reality
    (Blackwell Science Ltd and the Eurographics Association, 1996) Sudarsky, Oded; Gotsman, Craig
    An output-sensitive visibility algorithm is one whose runtime is proportional to the number of visible graphic primitives in a scene model-not to the total number of primitives, which can be much greater. The known practical output-sensitive visibility algorithms are suitable only for static scenes, because they include a heavy preprocessing stage that constructs a spatial data structure which relies on the model objects positions. Any changes to the scene geometry might cause significant modifications to this data structure. We show how these algorithms may be adapted to dynamic scenes. Two main ideas are used: first, update the spatial data structure to reflect the dynamic objects current positions- make this update efficient by restricting it to a small part of the data structure. Second, use temporal bounding volumes (TBVs) to avoid having to consider every dynamic object in each frame. The combination of these techniques yields efficient, output-sensitive visibility algorithms for scenes with multiple dynamic objects. The performance of our methods is shown to be significantly better than previous output-sensitive algorithms, intended for static scenes.TBVs can be adapted to applications where no prior knowledge of the objects trajectories is available, such as virtual reality (VR), simulations etc. Furthermore, they save updates of the scene model itself- notjust of the auxiliary data structure used by the visibility algorithm. They can therefore be used to greatly reduce the communications overhead in client-server VR systems, as well as in general distributed virtual environments.
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    Extraction of Typographic Elements from Outline Representations of Fonts
    (Blackwell Science Ltd and the Eurographics Association, 1996) Shainir, Ariel; Rappoport, Ari
    Digital typefaces for computer graphics and multimedia applications should be capable of supporting operations such as font variations, transformations. deformations and blending. A powerful implementation of such operations must rely on the inherent typographic attributes of the typeface. However, even today s most advanced typeface representations support only geometric outline representations and basic font variations.In this paper we discuss high-level typeface representations which we term Parametric Typographic Representations (PTRs). We present an algorithm for automatically extracting typographic elements of typefaces from their outline representation, which, is an essential initial step in converting typefaces from outline representations to PTRs. The extracted typographic elements include serifs, bars. sterns, slants, bows, arcs, curve stems and curve bars. Most notable is the treatment of serifs, which are represented by finite-automata. The algorithm only needs to learn a serif type once, and is then capable of automatically recognizing it in different typefaces.We show an application of a PTR for automatic high-quality hinting of fonts, which is one of the most important stages in, digital font production. Our system was used to generate hints for dozens of thousands of Kanji, Roman and Hebrew characters.
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    Fractal modeling using free form techniques
    (Blackwell Science Ltd and the Eurographics Association, 1996) Zair, Chems Eddine; Tosan, Eric
    IFS models have become a powerful tool for the construction of fractal sets. They offer a straightforward way to generate complex, self-similar figures as attractors. However, they present the fundamental disadvantage of providing little control over the global form of the attractor. In contrast, free form techniques give a high control over smooth man-made objects with the use of a set of control points.In this paper, we present a new approach of fractal modeling which is based on IFS theory. We shall use free form techniques to give a practical and efficient way to build controlled fractal attractors. The resulting effect consists on the ability to deform a fractal shape interactively into the desired shape, in the same way as parametric forms (Bezier, splines).
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    Modelling Megalithic Sites
    (Blackwell Science Ltd and the Eurographics Association, 1996) POULET, Francois; LUCAS, Michel
    In this paper, we present the MegaFormes project which deals with the modelling of megalithic sites. The goal is to enable virtual visits of megalithic sites and to help archaeologists in picturing the evolution of a monument. A megalithic site is made of a set of elements that can be: fogous, dolmens, chamber tombs, stone alignments or circles. The description of such a site is done in two stages: during the first stage, a draft of the site is drawn, each stone being represented by its bounding box. The second stage allows the user to describe the content of the boxes (the stones).To describe fogous and chamber tombs, basic models of these monuments are used. These basic types are simplified representations of the monuments (walls only). The models can be modified by changing the dimensions and locations of the walls and by cutting the initial walls into individual stones. The definition of stone alignments or circles calls for the use of a one-dimensional position vocabulary (along simple geometric primitives or curves). The different elements (alignments, circles, fogous, and chamber tombs) are then combined to obtain the draft of the site. A two-dimensional vocabulary allowing to position the elements in the site is used. The paper is illustrated with examples obtained with the developed software.
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    Vector Field Based Texture Mapping of Animated Implicit Objects
    (Blackwell Science Ltd and the Eurographics Association, 1996) Smets-Solanes, Jean-Paul
    This paper shows that an adequate use of vectorfields can solve most inconsistencies related to texture mapping that appear in current animation and rendering systems based on implicit objects. The method used is based on the concept of a virtual skin. A skin with its own texture mapping is spread over an implicit object and is constrained to stick to the deformation of the implicit object. A vectorfield is used to compute the relationship between the motion of the skin and the deformation of the object. Visual and implementation issues are discussed with respect to typical applications of implicit objects in computer graphics.
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    Surface Graph Sketching
    (Blackwell Science Ltd and the Eurographics Association, 1996) Hutchinson, D.; Lin, F.; Hewitt, W.T.
    The production of patterns and designs upon surfaces has received only limited attention, with texturing techniques being accepted as adequate. Texturing, however, can be a very unsatisfactory and clumsy method of producing complex and accurate designs upon a surface, even more so with surfaces such as NURBS where a texture may appear very much distorted when mapped to a surface. This paper introduces a new approach called surface graph sketching which draws upon ideas from planar graph sketching for the construction of complex curve networks across parametrically defined surfaces. Surface curves can be created by a number of methods and stored in the parameter space of the surface thereby allowing intricate and more importantly accurate surface designs to be created. Regions of the surface may be assigned a property such as colour or texture, or cut away to produce holes. Surface graph sketching has a number of applications, in the design of trimming curves, surface patterning and texture map definitions.
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    Compositing Computer and Video Image Sequences: Robust Algorithms for the Reconstruction of the Camera Parameters
    (Blackwell Science Ltd and the Eurographics Association, 1996) Berger, M.-O.; Chevrier, C.; Simon, G.
    Augmented reality shows great promises in fields where a simulation in situ would be impossible or too expensive. When mixing synthetic and real objects in the same animated sequence, we must be sure that the geometrical coherence as well as the photometrical coherence is ensured. One major challenge is to compute the camera viewpoint with sufficient accuracy to ensure a satisfactory composition. We especially address this point in this paper using computer vision techniques and robust statistical methods. We prove that such techniques make it possible to compute almost automatically the viewpoint for long video sequences even for bad quality images in outdoor environments. Significant results on the lighting simulation of the bridges of Paris are shown.
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    Generation of 3D Texture Using Multiple 2D Models Analysis
    (Blackwell Science Ltd and the Eurographics Association, 1996) GHAZANFARPOUR, Djamchid; DISCHLER, Jean-Michel
    Solid (30) texturing is commonly used in computer graphics for producing more realistic images. It is often more attractive than the conventional 20 texture mapping but remains more complex on some points. Its major difficulty concerns the generation of 30 texture in a general and efficient way. The well-known traditional procedural methods use generally a simplified mathematical model of a natural texture. No reliable way for the choice of the mathematical model parameters, which characterise directly the produced 30 texture, is given. Therefore, 30 texture generation becomes a more or less experimental process with these methods.Our recently published methodfor an automatic 30 texture generation avoids this problem by the use of the spectral analysis of one 2D model texture. The resulting 30 texture is of good quality but one open problem remains: the aspect of the produced texture cannot be fully controlled over the entire 30 space by only one 20 spectral analysis. This may be considered as a serious limitation for some kinds of textures representing important variations in any direction.In this paper we present a new and more powerful analytical approach for an automatic 30 texture generation. Contrarily to our previous method, this new approach is not exclusively based on the spectral analysis of only one 20 model. It uses two or three 2D models corresponding to different slices of a 30 texture block, so, the aspect of the produced 3D texture can be controlled more efficiently over the entire 30 space. In addition, a more efficient 30 texture antialiasing, well adapted to this new method is presented.
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    Computation of Higher Order Illumination with a Non-Deterministic Approach
    (Blackwell Science Ltd and the Eurographics Association, 1996) Bouatouch, Kadi; Pattanaik, S. N.; Zeghers, Eric
    In spite of the number of efforts made by the computer graphics researchers, till today the computation of view-independent global illumination in an environment containing non-diffusely reflecting objects is a non-resolved problem. In general, non-deterministic techniques seem to be capable of solving this problem. In this article we propose one such non-deterministic method which will permit such calculation by using a combined technique of higher order function approximation and particle tracing. We have used multi-wavelets as basis functions and have calculated the illumination function approximation coefficients by exploiting the adjointness between the radiance equation and the potential equation.
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    Reusable Radiosity Objects
    (Blackwell Science Ltd and the Eurographics Association, 1996) Ouhyoung, Ming; Chuang, Yung-Yu; Liang, Rung-Huei
    Because of the view independence and photo realistic image generation in a diffuse environment, radiosity is suitable for an interactive walk through system. The drawback of radiosity is that it is time-consuming in form factor estimation, and furthermore, inserting, deleting or moving an object makes the whole costly rendering process repeat itself. To solve this problem, we encapsulate necessary information for form factor calculation and visibility estimation in each object, which is called a reusable radiosity object. An object is defined as a cluster or clusters of triangles. Whenever a scene updates, the radiosity algorithm looks up the prestored information in each object, thus speeding itself up by two orders of magnitude. Besides, solution time based on cluster representatives is linear to the number of objects since each object is reusable, encapsulated with preprocessed data in every level of hierarchy. We also analyze the unregarded error on visibility estimation and propose a statistically optimal adaptive algorithm to maintain the same error for each link.
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    Simplification of Global-Illumination Meshes
    (Blackwell Science Ltd and the Eurographics Association, 1996) Hughes, Merlin; Lastra, Anselmo A.; Saxe, Edward
    We present a methodfor simplifying the meshes produced as solutions to global illumination problems, reducing geometric complexity while retaining the perceived imagefidelity. The method has been applied to produce meshes of linearly, quadratically and cubically colour-interpolated triangles. The goal of our work is to permit interactive rendering of more complex global illumination solutions through the application of simplification algorithms as well as the use of more powerful rendering primitives.
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    An Energy-Based Approach for Contact Force Computation
    (Blackwell Science Ltd and the Eurographics Association, 1996) Faure, Francois
    A new approach for computing resting contact forces between solids is presented, which handles both static and sliding friction, while avoiding the problems arising from previous approaches. Each iteration provides values for all unknowns and needs a constant computation time. The first iteration is a global dynamic solution involving inertia and external forces. The subsequent iterations consist of global redistributions of energy through the solids in order to restrict the values within correct bounds, leading to a progressive refinement of the solution. This allows the termination of the computation when a user-defined level of precision is reached. Convergence is proven in the frictionless case.The method is concise and is easily usable in a motion control system. It was implemented and tested on some examples involving simultaneously static and sliding friction along with motion control.
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    Interpolatory Subdivision on Open Quadrilateral Nets with Arbitrary Topology
    (Blackwell Science Ltd and the Eurographics Association, 1996) Kobbelt, Leif
    A simple interpolatory subdivision scheme for quadrilateral nets with arbitrary topology is presented which generates C1 surfaces in the limit. The scheme satisfies important requirements for practical applications in computer graphics and engineering. These requirements include the necessity to generate smooth surfaces with local creases and cusps. The scheme can be applied to open nets in which case it generates boundary curves that allow a C0-join of several subdivision patches. Due to the local support of the scheme, adaptive refinement strategies can be applied. We present a simple device to preserve the consistency of such adaptively refined nets.
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    Incremental constraint modelling in a feature modelling system
    (Blackwell Science Ltd and the Eurographics Association, 1996) Laakko, Timo; Mantyla, Martti
    The techniques of constraint propagation have recently been successfully applied to feature-based design. Because of their speed, constraint propagation methods allow incremental design and rapid local modifcations of the part. However, cyclic constraints cause serious problems to current constraint propagation algorithms. Variational geometric design systems can, in principle, manage these cases. Unfortunately, this typically requires complete re-evaluation of the underlying set of constraint equations, making the method unsuitable for interactive use.The proposed system aims to localize the problem of constraint solving and maintenance. The constraint graph of the part or assembly is divided into several independent partial graphs, subsystems. Afterwards, each subsystem is handled separately using a selected constraint solving technique for the subsystem.
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    BOXTREE: A Hierarchical Representation for Surfaces in 3D
    (Blackwell Science Ltd and the Eurographics Association, 1996) Barequet, Gill; Chazelle, Bernard; Guibas, Leonidas J.; Mitchell, Joseph S.B.; Tal, Ayellet
    We introduce the boxtree, a versatile data structure for representing triangulated or meshed surfaces in 3D. A boxtree is a hierarchical structure of nested boxes that supports efficient ray tracing and collision detection. It is simple and robust, and requires minimal space. In situations where storage is at a premium, boxtrees are effective alternatives to octrees and BSP trees. They are also more flexible and efficient than R-trees, and nearly as simple to implement.
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    3D Reconstruction of Complex Polyhedral Shapes from Contours using a Simplified Generalized Voronoi Diagram
    (Blackwell Science Ltd and the Eurographics Association, 1996) Oliva, J-M.; Perrin, M.; Coquillart, S.
    We are interested in modelling the suface of very irregular objects known through a few planar polygonal cross-sections. This problem is considered difficult when severe topology and morphology variations appear between neighbouring cross-sections (multi-branching, holes, disconnected areas). Only few methods deal with this problem in a systematic way.The paper describes an original method allowing to build, in a fully automatic and systematic way, an external surface with a valid topology in any case. It moreover allows to adjust details of the reconstructed surface in view of the morphologies and topologies of the various initial cross-sectional contours.At first, a global correspondence is operated between each couple of adjacent cross-sections by extracting polygonal areas of difference. Next steps are based on the computation in each area of difference of the bisector network, a well-defined simplified generalised Voronoi diagram. This structure is used both for connecting initial contour points and for interpolating new intermediate portions of contours. It depends on the complexity of initial 2D shapes. Interpolation stage is then recursively operated until a satisfactory surface has been obtained or until a maximum number of new intermediate cross-sectional contours have been built. The valid final suface is directly obtained by concatenating all the tiling areas of difference without need of any post processing step. The processing of several real data related to geological bodies or human organs has proved that the described method allows detailed modelling of irregular objects with very performing CPU times. The reconstruction appears insensitive to severe variations of the object shape, including apparitions of holes or disconnections.
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    Integrating Computer Animation and Multimedia
    (Blackwell Science Ltd and the Eurographics Association, 1996) Preston, Martin; Hewitt, Terry
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    3D Interactive Topological Modeling using Visible Human Dataset
    (Blackwell Science Ltd and the Eurographics Association, 1996) Beylot, P; Gingins, P; Kalra, P; Thalmann, N Magnenat; Maurel, W; Thalmann, D; Fasel, J
    Availability of Visible Human Dataset (VHD)has provided numerous possibilities for its exploitation in both medical applications and 3D animation. In this paper, we present our interactive tools which enable extraction of surfaces for different organs, including bones, muscles, fascia, and skin, from the VHD. The reconstructed surfaces then are used for defining the inter-relationship of organs, a process we refer to as topological modeling. A data base is constructed, which encapsulates structural, topological, mechanical and other relevant information about organs. A 3D interactive tool enables the building and editing of this data base. Such a data base can later be used for different applications in fields such as medicine, sports, education, and entertainment.
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    Demand-Driven Geometry Transmission for Distributed Virtual Environments
    (Blackwell Science Ltd and the Eurographics Association, 1996) Schmalstieg, Dieter; Gervautz, Michael
    We present a strategy for rendering in distributed virtual environments. A geometry database is maintained by a server, while users invoke individual clients to interact with the environment. Instead of downloading a complete copy of the geometry data, the data is distributed on demand, thus gaining signifcant savings in network bandwidth. Our strategy combines several techniques, including levels of detail, progressive refinement and graceful degradation to deliver the data"just in time" over the network to the rendering process. The method allows operate on a tight resource budget, which important if attempting to use low cost systems for virtual reality applications.
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    A Platform for User-Tailored Interaction Development in 2D, 3D, and VR
    (Blackwell Science Ltd and the Eurographics Association, 1996) Encarnacao, L. Miguel; Fechter, Jurgen; Grunert, Thomas; Strasser, Wolfgang
    The discussion on the advantages and disadvantages of 2D, 3D, and VR interfaces and their applicability to different types of systems, users, and information led to a series of stand-alone implementations that lack the possibility of realizing an integrated approach. The acceptance of the different interaction techniques will depend on their success in practical applications, i.e. with systems that are used by different users for different purposes. Since this acceptance is especially hard to achieve in computer-critical environments, such as medicine, we developed a software environment that allows for the development, integration, and user-centered evaluation of existing and new interaction techniques for their use in medical applications. This environment is equipped with an innovative message-passing functionality that provides the communication to and among application objects in 2D, 3D, and VR. Furthermore, the environment contains a component for user-adapted interaction and system support at runtime.
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    Symbiosis of Virtual Reality and Scientific Visualization System
    (Blackwell Science Ltd and the Eurographics Association, 1996) Haase, Helmut
    This paper describes a concept for the symbiosis of a virtual reality system and a system for scientific visualization, as well as an implementation (called ISVAS-VR) to evaluate the concept. The idea is to preserve the strengths of both systems in order to help scientists in analyzing their data by means of the joint synergy of both approaches.Motivation for this work is given along with a description of the two individual systems (ISVAS? and Virtual Design). Possible communication schemes are discussed and the communication techniques which were utilized in the implementation are presented, namely shared memory and pipes. Finally, interaction of the user with the compound system is described and a number of application examples are given.
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    Incremental Volume Rendering Using Hierarchical Compression
    (Blackwell Science Ltd and the Eurographics Association, 1996) Haley, Michael B.; Blake, Edwin H.
    We present a new algorithm here for efficient incremental rendering of volumetric datasets. The primary goal of this algorithm is to give average workstations the ability to efficiently render volume data received over relatively low bandwidth network links in such a way that rapid user feedback is maintained. Common limitations of workstation rendering of volume data include: large memory overheads, the requirement of expensive rendering hardware, and high speed processing ability. The rendering algorithm presented here overcomes these problems by making use of the efficient Shear-Warp Factorisation method which does not require specialised graphics hardware. However the original Shear-Warp algorithm suffers from a high memory overhead and does not provide for incremental rendering which is required should rapid user feedback be maintained. Our algorithm represents the volumetric data using a hierarchical data structure which provides for the incremental classification and rendering of volume data. This exploits the multiscale nature of the octree data structure. The algorithm reduces the memory footprint of the original Shear-Warp Factorisation algorithm by a factor of more than two, while maintaining good rendering performance. These factors make our octree algorithm more suitable for implementation on average desktop workstations for the purposes of interactive exploration of volume models over a network. Results from tests using typical volume datasets will be presented which demonstrate the ability of the algorithm to achieve high rendering rates for both incremental rendering and standard rendering while reducing the runtime memory requirements.
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    Full-range approximation of triangulated polyhedra.
    (Blackwell Science Ltd and the Eurographics Association, 1996) Ronfard, Remi; Rossignac, Jarek
    We propose a new algorithm for automatically computing approximations of a given polyhedral object at different levels of details. The application for this algorithm is the display of very complex scenes. where many objects are seen with a range of varying levels of detail. Our approach is similar to the region-merging method used for image segmentation. We iteratively collapse edges, based on a measure of the geometric deviation from the initial shape. When edges are merged in the right order, this strategy produces a continuum of valid approximations of the original object, which can be used for faster rendering at vastly different scales.
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    Real-time Volumetric Deformable Models for Surgery Simulation using Finite Elements and Condensation
    (Blackwell Science Ltd and the Eurographics Association, 1996) Bro-Nielsen, Morten; Cotin, Stephane
    This paper discusses the application of 3D solid volumetric Finite Element models to surgery simulation. In particular it introduces three new ideas for solving the problem of achieving real-time performance for these models. The simulation system we have developed is described and we demonstrate real-time deformation using the methods developed in the paper.
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    Automatic Generation of Multiresolution Boundary Representations
    (Blackwell Science Ltd and the Eurographics Association, 1996) Andujar, C.; Ayala, D.; Brunet, P.; Arinyo, R. Joan; Sole, J.
    The paper focuses on automatic simplification algorithms for the generation of a multiresolution family of solid models from an initial boundary representation of a polyhedral solid. An algorithm for general polyhedra based on an intermediate octree representation is proposed. Simplified elements of the multiresolution family approximate the initial solid within increasing tolerances. A discussion among different octree-based simplification methods and the standard marching cubes algorithm is presented.
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    Mesh Simplification
    (Blackwell Science Ltd and the Eurographics Association, 1996) Algorri, Maria-Elena; Schmitt, Francis
    Mesh simplification is an important stage after surface reconstruction since the models produced can contain a large number of polygons making them difficult to manipulate. In this paper we present a mesh simplification algorithm to reduce the number of vertices in a dense mesh of triangles. The algorithm is based on edge operations that are performed in the inside of independent clusters distributed over the entire mesh. The clusters are well-characterized regions that can successfully accept simplification operations. The simplification operations produce only local transformations on the mesh. This region-based, distributed approach permits to easily track and control the changes in the triangulation and avoids the appearance of particular cases that would require a special handling. The algorithm uses two user-specified parameters to guide the operations. These parameters allow various simplification strategies that are illustrated on several dense triangulations.