bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling the Garden of Perfect Brightness
Authors: Wang LiFeng , Botta David , Ellefson Chris , Fournier Alain
Published: March 2003

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.
The Open Inventor Toolkit and the PREMO Standard
Authors: Wang D. , Herman I. , Reynolds G. J.
Published: March 2003

PREMO is an emerging international standard for the presentations of multimedia objects including computer graphics. Open Inventor™ is a commercially available “de facto” standard for interactive computer graphics packaged as a library of objects. In this paper, we consider whether the concepts and objects of PREMO are sufficient to represent a professional quality system, such as Open Inventor.

By comparing PREMO with Open Inventor, we hope to show that PREMO's computer graphics environment model and event model can properly describe Open Inventor's rendering action and event model. The scene graph is very important in Open Inventor. Most Open Inventor functions rely on various operations over scene graphs. The construction, edition and traversal of the scene graphs are implemented as a set of newly defined PREMO objects. Graphics rendering, event handling and scene graphs constitute the fundamental parts of Open Inventor, other Open Inventor functionalities can be constructed from these. We conclude that since these three fundamental parts of Open Inventor can be properly modelled and implemented by means of PREMO, that the concepts and objects of PREMO are sufficient to represent Open Inventor.
Modeling and Rendering of the Atmosphere Using Mie‐Scattering
Authors: Jackèl D. , Walter B.
Published: March 2003

This paper presents a method for rendering of the atmosphere by means of Mie‐scattering. The method is based on a concentric atmospheric model, which is divided into four submodels: for clear air, aerosol, ozone, and rain. In order to simulate and visualize the various atmospheric effects, each of these submodels can be parameterized by the user as desired. The process of rendering an outdoor scene requires an enormous amount of computing power. In order to make this method suitable for efficient implementation, some simplifications and approximations are discussed. In addition, a selection of the rendering results are presented, and our further activities in the field of atmospheric rendering are discussed.
Optical Flow Rendering
Authors: Park Tae‐Joon , Shin Sung Yong , Lee Seungyong
Published: March 2003

This paper proposes a new approach to image‐based rendering that generates an image viewed from an arbitrary camera position and orientation by rendering optical flows extracted from reference images. To derive valid optical flows, we develop an analysis technique that improves the quality of stereo matching. Without using any special equipments such as range cameras, this technique constructs reliable optical flows from a sequence of matching results between reference images. We also derive validity conditions of optical flows and show that the obtained flows satisfy those conditions. Since environment geometry is inferred from the optical flows, we are able to generate more accurate images with this additional geometric information. Our approach makes it possible to combine an image rendered from optical flows with an image generated by a conventional rendering technique through a simple Z‐buffer algorithm.
Importance Driven Texture Coordinate Optimization
Authors: Sloan Peter‐Pike J. , Weinstein David M. , Brederson J.
Published: March 2003

Traditionally, texture coordinates have been generated based solely on the model’s geometry, often even before a model’s textures have been created. With the arrival of new technologies, such as 3D paint programs, weaknesses of a static optimization pre‐process are becoming apparent. These weaknesses arise from constructing a parameterization based solely on the model’s geometry, ignoring the fact that detail is not uniformly spaced throughout the texture space. In fact, certain regions of the texture are more important than other regions. In this paper we introduce the notion of the "importance map" and describe how importance values are derived from both intrinsic properties of the texture and user‐guided highlights. Furthermore, we describe how importance maps are used to drive the texture coordinate optimization. Finally, we show how this optimization process can be integrated into a 3D painting environment, enabling periodic optimization at any stage of texture design.
Simulating Wood Using a Voxel Approach
Authors: Buchanan John W.
Published: March 2003

In this paper we present a technique for generating three‐dimensional wood textures using a regular texture array. Currently three‐dimensional wood textures are generated using procedural textures. Procedural textures are flexible and require little memory, however the modeling of local artifacts such as knots is difficult using the procedural approach. By representing the wood as a texture array and growing the wood in this array we can easily simulate local phenomena such as knots. Our growth model is an approximation to the biological model and assumes that there are several similar wood cells per array element. This means that we can model artifacts that are defined by groups of similar cells. In particular our model is well suited for the modeling of soft‐woods.
A Two‐Pass Hardware‐Based Method for Hierarchical Radiosity
Authors: Martín I. , Pueyo X. , Tost D.
Published: March 2003

Finite elements methods for radiosity are aimed at computing global illumination solutions efficiently. However these methods are not suitable for obtaining high quality images due to the lack of error control. Two‐pass methods allow to achieve that level of quality computing illumination at each pixel and thus introducing a high computing overhead. We present a two‐pass method for radiosity that allows to produce high quality images avoiding most of the per‐pixel computations. The method computes a coarse hierarchical radiosity solution and then performs a second pass using current graphics hardware accelerators to generate illumination as high definition textures.
Perception Based Color Image Difference
Authors: Neumann László , Matkovic Kresimir , Purgathofer Werner
Published: March 2003

A good image metric is often needed in digital image synthesis. It can be used to check the convergence behavior in progressive methods, to compare images rendered using various rendering methods etc. Since images are rendered to be observed by humans, an image metric should correspond to human perception as well. We propose here a new algorithm which operates in the original image space. There is no need for Fourier or wavelet transforms. Furthermore, the new metric is view distance dependent. The new method uses the contrast sensitivity function. The main idea is to place a number of various rectangles in images, and to compute the CIE LUV average color difference between corresponding rectangles. Errors are then weighted according to the rectangle size and the contrast sensitivity function.
Real‐time Biomechanically‐based Muscle Volume Deformation using FEM
Authors: Zhu Qing‐hong , Chen Yan , Kaufman Arie
Published: March 2003

This paper presents a voxel‐based biomechanical model for muscle deformation using finite element method (FEM) and volume graphics. Hierarchical voxel meshes are reconstructed from filtered segmented muscle images followed by FEM simulation and volume rendering. Physiological muscle force is considered and linear elastic muscle models for both static and dynamic cases are simulated by FEM. Voxel‐based wireframe, polygon surface rendering, and volume rendering techniques are applied to show real‐time muscle deformation processes as well as realistic animations.
Mass‐Spring Simulation using Adaptive Non‐Active Points
Authors: Howlett P. , Hewitt W.T.
Published: March 2003

This paper introduces an adaptive component to a mass‐spring system as used in the modelling of cloth for computer animation. The new method introduces non‐active points to the model which can adapt the shape of the cloth at inaccuracies. This improves on conventional uniform mass‐spring systems by producing more visually pleasing results when simulating the drape of cloth over irregular objects. The computational cost of simulation is decreased by reducing the complexity of collision handling and enabling the use of coarser mass‐spring networks.
Tetrahedra Based Adaptive Polygonization of Implicit Surface Patches
Authors: Hui K. C. , Jiang Z. H.
Published: March 2003

This paper presents a tetrahedra based adaptive polygonization technique for tessellating implicit surface patches. An implicit surface patch is defined as an implicit surface bounded by its intersections with a set of clipping surfaces and which lies within an enclosing tetrahedron. To obtain the polygonization of an implicit surface patch, the tetrahedron containing the patch is adaptively subdivided into smaller tetrahedra according to the criteria introduced in the paper. The result is a set of tetrahedra each containing a facet approximating the surface. The intersections between the facets and the clipping surfaces are used to locate the surface patch boundary. Ambiguous results in generating the facets for highly curved surfaces or surfaces with singular points are also addressed. The result of the polygonization is a set of triangular facets that can be used for visualization and numerical analysis. The proposed method is also suitable for locating the intersection of two implicit surfaces.
Interactive Line Art Rendering of Freeform Surfaces
Authors: Elber Gershon
Published: March 2003

In recent years, synthetically created line art renderings have reached quality levels that are aesthetically pleasing. Moreover, the sketch based approach was found to be quite capable at conveying geometrical information in an intuitive manner. While a growing interest in this type of rendering method has yielded successful and appealing results, the developed techniques were, for the most part, too slow to be embedded in real time interactive display. This paper presents a line art rendering method for freeform polynomial and rational surfaces that is capable of achieving real time and interactive display. A careful preprocessing stage that combines an a‐priori construction of line art strokes with proper classification of these strokes, allows one to significantly alleviate the computational cost, in real time, of the sketch based rendering, and enables interactive line art display.
Multi‐layered impostors for accelerated rendering
Authors: Decoret Xavier , Sillion Franĉois , Schaufler Gernot , Dorsey Julie
Published: March 2003

This paper describes the successful combination of pre‐generated and dynamically updated image‐based representations to accelerate the visualization of complex virtual environments. We introduce a new type of impostor, which has the desirable property of limiting de‐occlusion errors to a user‐specified amount. This impostor, composed of multiple layers of textured meshes, replaces the distant geometry and is much faster to draw. It captures the relevant depth complexity in the model without resorting to a complete sampling of the scene. We show that layers can be dynamically updated during visualization. This guarantees bounded scene complexity in each frame and also exploits temporal coherence to improve image quality when possible. We demonstrate the strengths of this approach in the context of city walkthroughs.
Compact Metallic Reflectance Models
Authors: Neumann László , Neumannn Attila , Szirmay‐Kalos László
Published: March 2003

The paper presents simple, physically plausible, but not physically based reflectance models for metals and other specular materials. So far there has been no metallic BRDF model that is easy to compute, suitable for fast importance sampling and is physically plausible. This gap is filled by appropriate modifications of the Phong, Blinn and the Ward models. The Phong and the Blinn models are known not to have metallic characteristics. On the other hand, this paper also shows that the Cook‐Torrance and the Ward models are not physically plausible, because of their behavior at grazing angles. We also compare the previous and the newly proposed models. Finally, the generated images demonstrate how the metallic impression can be provided by the new models.
Texturing 3D Models of Real World Objects from Multiple Unregistered Photographic Views
Authors: Neugebauer Peter J. , Klein Konrad
Published: March 2003

As the efficiency of computer graphic rendering methods is increasing, generating realistic models is now becoming a limiting factor. In this paper we present a new technique to enhance already existing geometry models of real world objects with textures reconstructed from a sparse set of unregistered still photographs. The aim of the proposed technique is the generation of nearly photo‐realistic models of arbitrarily shaped objects with minimal effort. In our approach, we require neither a prior calibration of the camera nor a high precision of the user's interaction. Two main problems have to be addressed of which the first is the recovery of the unknown positions and parameters of the camera. An initial estimate of the orientation is calculated from interactively selected point correspondences. Subsequently, the unknown parameters are accurately calculated by minimising a blend of objective functions in a 3D‐2D projective registration approach. The key point of the proposed method of registration is a novel filtering approach which utilises the spatial information provided by the geometry model. Second, the individual images have to be combined yielding a set of consistent texture maps. We present a robust method to recover the texture from the photographs thereby preserving high spatial frequencies and eliminating artifacts, particularly specular highlights. Parts of the object not seen in any of the photographs are interpolated in the textured model. Results are shown for three complex example objects with different materials and numerous self‐occlusions.
A Translucent Sketchpad for the Virtual Table Exploring Motion‐based Gesture Recognition
Authors: Encarnaĉão L. M. , Bimber O. , Schmalstieg D. , Chandler S. D.
Published: March 2003

The Virtual Table presents stereoscopic graphics to a user in a workbench‐like setting. For this device, a user interface and new interaction techniques have been developed based on transparent props ‐a tracked hand‐held pen and a pad. These props, particularly the pad, are augmented with 3D graphics from the Virtual Table’s display that can serve as a palette for tools and controls as well as a window‐like see‐through interface, a plane‐shaped and through‐the‐plane tool, supporting a variety of new interaction techniques. This paper reports on an extension of this user‐interface design space which uses gestural input to create and control solid geometries for CAD and conceptual design. The application of gestural interfaces is a common method for interacting with virtual environments on a habitual and natural basis. The motion‐based gesture recognition presented here uses Fuzzy Logic to support a predictable, flexible, and efficient learning process. This new interaction paradigm greatly increases the Virtual Table’s suitability for design tasks. Traditional CAD dialogue can be combined with intuitive rapid sketching of geometry on the pad. Additionally, the resulting events and objects can be associated with scene details below the translucent tablet.
Seamless Integration of Databases in VR for Constructing Virtual Environments
Authors: Soetebier Ingo , Dörner Ralf , Braun Norbert
Published: March 2003

An approach for authoring virtual environments within the virtual environments themselves is presented, integrating a database containing arbitrary components that are used to construct the 3D scene. The issues important to a seamless integration of the database, such as multimedia data storage and database linkage are discussed, with the focus on the human‐computer interaction component. A concept for a 3D database interface is described for query, presentation and usage of query results in the virtual environment. Finally, an implementation of the concept using VRML and Java is presented.
An Efficient 2½ D rendering and Compositing System
Authors: Froumentin M. , Willis P.
Published: March 2003

We describe a method for doing image compositing using either 2D geometric shapes or raster images as input primitives. The resolution of the final image is virtually unlimited but, as no frame buffer is used, performance is much less dependant on resolution than with standard painting programs, allowing rendering very large images in reasonable time. Many standard features found in compositing programs have been implemented, like hierarchical data structures for input primitives, lighting control for each layer and filter operations (for antialiasing or defocus).
Adaptable Splatting for Irregular Volume Rendering
Authors: Wang Wencheng , Wu Enhua
Published: March 2003

By employment of a footprint table in conducting intensity integration, splatting method has been very successful in rendering regular data volumes. Recently, the method has also been extended to render irregular data volumes. However, since samples in irregular volumes vary greatly in size and shape, the footprint table is unable to be employed in an efficient manner. This hinders the application of splatting approach from being used in the irregular volume case. In this paper, an adaptable splatting method is proposed, which provides an efficient way to integrate color intensity in terms of footprint table for the samples in various sizes. Experiments show that the new method may be used to produce better images without extra expense.
G1 Hierarchical Bézier Surface over Arbitrary Meshes
Authors: Bercovier M. , Volpin O.
Published: March 2003

This paper presents a method for constructing composite surfaces based on a collection of quadrilateral patches. A global parameterization using bilinear quadrilateral meshes and FEM like minimization procedure are introduced. Smoothing conditions such as C1 and G1 are handled by constraint equation and a related duality argument is implemented. The surfaces that can be constructed in this way include conforming and non‐conforming connections (3 n 6, T‐nodes) between elementary patches. Non‐manifold surfaces are automatically treated also by this data structure. The underlying quadratic programming with linear constraints is solved by duality methods. Hierarchical data structure with bordering matrices methods are implemented to deal with local refinement (subdivision). The present work details the actual implementation for the case of Bézier patches.
LCTS: Ray Shooting using Longest Common Traversal Sequences
Authors: Havran V. , Bittner J.
Published: March 2003

We describe two new techniques of ray shooting acceleration that exploit the traversal coherence of a spatial hierarchy. The first technique determines a sequence of adjacent leaf‐cells of the hierarchy that is pierced by all rays contained within a certain convex shaft. This sequence is used to accelerate ray shooting for all remaining rays within the shaft. The second technique establishes a cut of the hierarchy that contains nodes where the hierarchy traversal can no longer be predetermined for all rays contained within a given shaft. This cut is used to initiate the traversal for all remaining rays contained in the shaft. The description of the methods is followed by results evaluated by their practical implementation.
Realistic Collision Avoidance of Upper Limbs Based on Neuroscience Models
Authors: Nebel Jean‐Christophe
Published: March 2003

When articulated figures interact in a 3D environment, collisions are highly likely and must often be avoided. We present a method automatically producing realistic collision‐free animation of the upper arms. Based on the latest models of collision avoidance provided by neuroscience, our method allows realistic interpolation of keyframes at interactive speed. In order to validate our scheme we compared computer generated motions with motions performed by a sample of ten humans. These motions were defined by start and final postures and by an obstacle which had to be passed. In each case the generated positions are the same as those chosen by 30% of real humans, we therefore consider our method provides realistic motions. Moreover, the collision‐free paths are automatically generated in a few seconds. Hence, our method can be very beneficial to animators by reducing the level of detail needed to define motions of articulated figures. It can also be used for the automatic generation of realistic animations for virtual reality applications.
Gradient Estimation in Volume Data using 4D Linear Regression
Authors: Neumann László , Csébfalvi Balázs , König Andreas , Gröller Eduard
Published: March 2003

In this paper a new gradient estimation method is presented which is based on linear regression. Previous contextual shading techniques try to fit an approximate function to a set of surface points in the neighborhood of a given voxel. Therefore a system of linear equations has to be solved using the computationally expensive Gaussian elimination. In contrast, our method approximates the density function itself in a local neighborhood with a 3D regression hyperplane. This approach also leads to a system of linear equations but we will show that it can be solved with an efficient convolution. Our method provides at each voxel location the normal vector and the translation of the regression hyperplane which are considered as a gradient and a filtered density value respectively. Therefore this technique can be used for surface smoothing and gradient estimation at the same time.
Collaborative Virtual Simulation Environment for Radiotherapy Treatment Planning
Authors: Cai Wenli , Walter Stefan , Karangelis Grigorios , Sakas Georgios
Published: March 2003

The simulation of Radiotherapy Treatment Planning (RTP) is a normal procedure in oncology clinics carried out on a Simulator machine. The Virtual Simulation of RTP replaces the real Simulator machine with a virtual one by using the CT data sets of a patient instead of the real patient. In this paper, we present a collaborative virtual simulation environment of RTP, named EU‐VIRTUOSO, which is based on volume rendering and telecommunication techniques. The RTP procedure is visualised on a virtual patient, which is created by using the CT data of the patient. Different volume rendering and volume interaction techniques, such as DRR, MIP, gradient surface, and iso‐surface, supply physicians with high quality rendering images to simulate the real working environment of the Simulator machine. In the collaborative environment, physicians distributed at different locations can work together via network to plan the treatment or to validate the treatment plan on‐line by a collaborative application sharing approach. Both concepts virtualised planning and collaborative planning improve the efficiency and accuracy of a radiotherapy treatment while reducing the effort for an individual patient.
Representing Animations by Principal Components
Authors: Alexa Marc , Müller Wolfgang
Published: March 2003

In this paper, we present a representation for three‐dimensional geometric animation sequences. Different from standard key‐frame techniques, this approach is based on the determination of principal animation components and decouples the animation from the underlying geometry. The new representation supports progressive animation compression with spatial, as well as temporal, level‐of‐detail and high compression ratios. The distinction of animation and geometry allows for mapping animations onto other objects.
A Hybrid Approach for Stroke‐Based Letterform Composition Including Outline‐Based Methods
Authors: Schneider Uwe
Published: March 2003

For three decades a number of computer‐aided systems have been developed in order to assist in the design of digital type. Even though some of them are used by typographers in commercial type design, they are not yet widely accepted. One reason is the lack of appropriate design metaphors in systems which provide low‐level operations (e.g. the manipulation of outlines). Another reason is the lack of essential functionality in high‐level approaches (not all characters can be modeled). While these two reasons correspond with the underlying paradigms of those systems, namely the outline and the stroke approach, the presented model provides a synthesis of both. By exploring the high‐level semantics of the stroke‐based paradigm, letterforms can be composed by individual strokes. Properties like round corners at stroke intersections, as they typically appear in the design of Western type, can be modeled via outline segments attached to the associated stroke elements. As a consequence, Latin characters as well as characters incorporating hand‐written characters, like Kanji, can be expressed using a single model. These two classes of types are considered by the typographic community to be fundamentaly different.
Perceptual Principles and Computer Graphics
Authors: May Jon
Published: March 2003

Now that technology allows us to present photorealistic animations of scenically lit objects acting in real‐time, the problem of computer graphics has changed from making displays recognisable, to ensuring that users notice what they are intended to see, without being distracted by irrelevant information. Worse than that, the use of veridical displays that are intended to be lifelike runs the risk of introducing unpredictable sources of information, that can lead users to infer all sorts of unwanted details. Traditional visual theory, based upon bottom‐up models of feature extraction from the retinal image, cannot inform us about these aspects of perception. Broader based cognitive theories are required that integrate visual perception with attention, memory, emotion and inference. Theories such as Barnard's Interacting Cognitive Subsystems enable phenomena such as change blindness and the craft principles of film editing to be interpreted within a common framework, supporting extrapolation to computer graphics.
Rendering Caustics on Non‐Lambertian Surfaces
Authors: Jensen Henrik Wann
Published: March 2003

This paper presents a new technique for rendering caustics on non‐Lambertian surfaces. The method is based on an extension of the photon map which removes previous restrictions limiting the usage to Lambertian surfaces. We add information about the incoming direction to the photons and this allows us to combine the photon map with arbitrary reflectance functions. By using a cone‐filter we improve the quality of the radiance estimate in particular at discontinuities. Furthermore we introduce balancing of the photon map which not only reduces the memory requirements but also significantly reduces the rendering time. We have used the method to render caustics on surfaces with reflectance functions varying from Lambertian to glossy specular.
Modeling of Skylight and Rendering of Outdoor Scenes
Authors: Tadamura Katsumi , Nakamae Eihachiro , Kaneda Kazufumi , Baba Masashi , Yamashita Hideo , Nishita Tomoyuki
Published: March 2003

Photorealistic animated images are extremely effective for pre‐evaluating visual impact of city renewal and construction of tall buildings. In order to generate a photorealistic image not only the direct sunlight but also skylight must be considered.

This paper proposes a method of high‐fidelity image generation for photorealistic outdoor scenes based on the following ideas:

The intensity distribution of skylight taking account of scattering and absorption due to particles in the atmosphere which coincides with CIE standard skylight luminance functions is sought, and realistic images considering about spectrum distribution of skylight for any altitude of the sun can be easily and accurately displayed.

A rectangular parallelepiped with a specialized distribution of intensity simulating the skylight is introduced for efficient calculation of illumination due to skylight, and by employing a graphics hardware calculation of the skylight illuminance taking into account shadow effects is obtained with high efficiency; these techniques can be used to generate sequences of images, making animations possible at far lower calculation cost than previous methods.
Strands, Gravity and Botanical Tree Imagery
Authors: Holton Matthew
Published: March 2003

This paper presents a technique for the modelling and rendering of realistic botanical tree images. A strand model is used that is analogous to the internal vascular structure of a tree. The model is “grown” under the simulated influence of gravity and light. The strand densities at each branching point are used to determine branching angles, branch lengths and branch thicknesses, taking into account stored, user definable parameters that characterize the species of tree being modelled. These parameters address such factors as gravimorphism, phototropism, orthotropism, plagiotropism, planartropism and phyllotaxis, and are distributed according to a branch ordering system.

Branch segments and joints are modelled by Bézier splines, with an assumed circular cross‐section. Leaves are made up from numbers of sample ranges from vector plane equations. The trees are rendered using a surface sampling algorithm with a light Z buffer for shadows and autoregression textures for tree bark and grass.
Spectral Data Modeling for a Lighting Application
Authors: Deville Pascal M. , Merzouk Slimane , Cazier Dorothée , Paul Jean C.
Published: March 2003

In computer graphics, image generation uses the RGB colorimetric system. However, this system does not produce an accurate simulation of the spectral characteristics of both light and material, due to the fact that it is device dependent. Indeed, to get realistic images, the image calculation process must deal with spectral characteristics of lights and materials and with the problem of sampling the wavelength domain. Methods have been shown that are a good way to solve the two problems mentioned above, however, these approaches do not take into account complex spectrums (discontinuous). In this paper, we propose a method which removes the constraints imposed by the current methods. Our method is based upon an algorithm of spectrum analysis.
Pertinent Data for Modelling Pigmented Materials in Realistic Rendering
Authors: Callet Patrick
Published: March 2003

This article discusses the important problem of determining pertinent data to describe a pigmented medium. The first part deals with optical characteristics of pigments and the general properties of binders and fillers. It also exposes the limits and conditions of applicability of single scattering. In the second part the connection between individual optical properties, size, and form of particles is made with phenomenological theories of multiple scattering in absorbing media, Progressively, it appears that pertinent data in realistic modelling are always in relation with true or effective complex refractive indices and size parameters.
Energy Duality Methods for Piecewise Bézier Curve Construction
Authors: Bercovier M. , Volpin O.
Published: March 2003

Piecewise Bézier Curves are constructed using a minimization principle. Ck and GCk continuity is imposed by linear constraints. The corresponding quadratic programming with linear constraints problem is introduced and solved by duality methods. Bordering matrices methods are implemented to deal with local refinement (subdivision). The result is a versatile tool for defining/editing contours made of piecewise Bézier curves.
Incremental Line Labelling for Sketch Input of Solid Models
Authors: Grimstead I. J. , Martin R. R.
Published: March 2003

Designers need to transfer three‐dimensional objects from their minds via a two‐dimensional interface into a solid modelling system. We propose a system where objects are sketched interactively in two‐dimensions and incrementally line‐labelled as the drawing progresses, as the preliminary stage in constructing a solid model. Once the sketch is complete, the line‐labels are coupled with various inferred constraints to enable us to generate a solid model. In this paper we describe and evaluate a modification to existing line labelling methods to allow them to work incrementally. In this way, the labelling and region information can be built up as the user sketches, rather than all at once at the end of the sketching process, which reduces the delay before the final solid model is built.
3D Interactive Topological Modeling using Visible Human Dataset
Authors: Beylot P , Gingins P , Kalra P , Thalmann N Magnenat , Maurel W , Thalmann D , Fasel J
Published: March 2003

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.
Incremental Volume Rendering Using Hierarchical Compression
Authors: Haley Michael B. , Blake Edwin H.
Published: March 2003

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.
Method for Calculation of Sky Light Luminance Aiming at an Interactive Architectural Design
Authors: Dobashi Yoshinori , Kaneda Kazufumi , Yamashita Hideo , Nishita Tomoyuki
Published: March 2003

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.
Data Dependent Thin Plate Energy and its use in Interactive Surface Modeling
Authors: Greiner Günther , Loos Joachim , Wesselink Wieger
Published: March 2003

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.
Intelligent Control for Haptic Displays
Authors: Munch Stefan , Stangenberg Martin
Published: March 2003

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.
3D Reconstruction of Complex Polyhedral Shapes from Contours using a Simplified Generalized Voronoi Diagram
Authors: Oliva J‐M. , Perrin M. , Coquillart S.
Published: March 2003

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.
Demand‐Driven Geometry Transmission for Distributed Virtual Environments
Authors: Schmalstieg Dieter , Gervautz Michael
Published: March 2003

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.
Symbiosis of Virtual Reality and Scientific Visualization System
Authors: Haase Helmut
Published: March 2003

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.
The Defects of Stakeholder Theory
Authors: Sternberg Elaine
Published: March 2003

Stakeholder theory has been widely offered as a corrective to perceived defects of business and business ethics, and as an alternative model of corporate governance. Indeed, it is now advocated so commonly as to have become a new orthodoxy. Far from being a source of improvements, however, stakeholder theory is fundamentally misguided, incapable of providing better corporate governance, business performance or business conduct. Stakeholder theory is indeed intrinsically incompatible with all substantive objectives, and undermines both private property and accountability.
On the Supposed Independence of Two‐tier Boards: formal structure and reality in the Netherlands
Authors: Maassen Gregory , Van Den Bosch Frans
Published: March 2003

This paper outlines the formal structure of Dutch two‐tier boards and compares the formal structure with the reality of board practices of the largest Dutch companies listed at the Amsterdam Stock Exchanges. This comparison questions the supposed independence of two‐tier boards.
An Organizational Portfolio Theory of Board Composition
Authors: Heslin Peter , Donaldson Lex
Published: March 2003

A new theory of organizational change and success has recently been proposed, organizational portfolio theory (Donaldson, 1999). One purpose of this theory is to provide a fresh perspective on the determinants and consequences of board composition. After outlining organizational portfolio theory, this paper suggests some implications of the new theory for understanding the dynamic relationship between board composition and firm performance.
The Role of Non‐Executive Directors in Cyprus Public Companies and their Subsidiaries
Authors: Aloneftis Andreas
Published: March 2003

Corporate governance practices in Cyprus, despite the shortcomings of the relevant legislation, will continue to evolve to meet changing conditions and increased shareholder awareness but certainly do vary and will persist to vary with those of other nations and cultures.

Gradually, it is being accepted that the main corporate objective is enhancing shareholder value, which not only indicates superior competitive performance, but also generally requires awareness to the expectations and aspirations of other stakeholders.

Wider transparency and independent supervision of management by boards of directors are the central elements of improved corporate governance but board practices should be subject to unforced adaptation and evolution in an environment of globally understood and accepted minimum standards.

There is no single universal model of corporate governance, which could be transplanted nor is there a static final structure which could be easily adopted. The country will have to develop a system of corporate governance which will fit its respective culture and values. Therefore, we can learn a great deal from observing developments in other countries and encourage experimentation and variety.