bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using Wavefront Tracing for the Visualization and Optimization of Progressive Lenses
Authors: Loos J. , Slusallek Ph. , Seidel H.‐P. 
Published: March 2003

Progressive addition lenses are a relatively new approach to compensate for defects of the human visual system. While traditional spectacles use rotationally symmetric lenses, progressive lenses require the specification of free‐form surfaces. This poses difficult problems for the optimal design and its visual evaluation.This paper presents two new techniques for the visualization of optical systems and the optimization of progressive lenses. Both are based on the same wavefront tracing approach to accurately evaluate the refraction properties of complex optical systems.We use the results of wavefront tracing for continuously re‐focusing the eye during rendering. Together with distribution ray tracing, this yields high‐quality images that accurately simulate the visual quality of an optical system. The design of progressive lenses is difficult due to the trade‐off between the desired properties of the lens and unavoidable optical errors, such as astigmatism and distortions. We use wavefront tracing to derive an accurate error functional describing the desired properties and the optical error across a lens. Minimizing this error yields optimal free‐form lens surfaces.While the basic approach is much more general, in this paper, we describe its application to the particular problem of designing and evaluating progressive lenses and demonstrate the benefits of the new approach with several example images.
Virtual Dunhuang Art Cave: A Cave within a CAVE
Authors: Lutz B. , Weintke M. 
Published: March 2003

Virtual Reality can present historical places in a three‐dimensional and interactive way, giving visitors a photorealistic impression of objects. Not only existing scenarios can be shown, but VR can also be used to rebuild scenarios that were damaged or destroyed a long time ago, giving new life to the cultural heritage. We used Virtual Reality to present the Mogao Grottos in Dunhuang. This cave site is one of the most important cultural and religious places by the ancient Silk Road. The presentation is to give visitors the impression of visiting the cave site and provide information about the caves, paintings and statues in an interesting way. To achieve this, we developed a new, intuitive interaction paradigm, which enables the user to explore the caves. To give observers a photorealistic impression of the caves and to create a feeling of immersion, innovative rendering techniques were integrated.The resulting presentation combines Virtual Reality and archaeology to give tourists a realistic experience of this cave site and to support scientists in their research work.
Visibility Driven Rasterization
Authors: Meißner M. , Bartz D. , Günther R. , Straßer W. 
Published: March 2003

We present a new visibility driven rasterization scheme that significantly increases the rendering performance of modern graphic subsystems. Instead of rasterizing, texturing, lighting, and depth‐testing each individual pixel, we introduce a two‐level visibility mask within the rasterization stage which facilitates the removal of groups of pixels and triangles from rasterization and subsequent pipeline stages.Local visibility information is stored within the visibility mask that is updated several times during the generation of a frame. The update can easily be accomplished by extending already available (in hardware) occlusion culling mechanisms (i.e. those of HP and SGI), where it is possible to integrate the additional functionality without any additional delay cycles. In addition to these existing hardware based occlusion culling approaches—which cull only geometry contained in bounding volumes determined as occluded—we are able to significantly accelerate the rendering of the geometry determined as visible. However, our approach does not specifically rely on such occlusion culling hardware.The proposed new rasterization scheme is well suited for hardware implementation, can easily be integrated into low‐cost rasterizers, and its scalability can vary upon available chip real estate. Only incremental modifications of modern graphics subsystems are required to achieve a significant improvement in rendering performance.
An Object Model for Multimedia Programming
Authors: Arbab F. , Herman I. , Reynolds G.J. 
Published: March 2003

AbstractThe development of multimedia applications is a complex task. Much of this complexity stems from requirements associated with programming multiple media objects and the control of dependences and inter‐relationships between these media objects and the user(s). It is clearly necessary to have a basic framework on which to build multimedia applications in the face of such complexities. Such a conceptual model is what we have called an object model and it is the main subject of this paper. The MADE object model represents a novel approach to multimedia application programming that is founded on the two principal concepts of active objects and delegation. Although these concepts are not novel in themselves, we believe that their combined use in a multimedia development environment represents a substantial enhancement to more traditional approaches to programming in this area.
A Progressive Radiosity Algorithm for Scenes Containing Curved Surfaces
Authors: Bao Hujun , Peng Qunsheng 
Published: March 2003

AbstractBased on the theory of light energy transfer between two differential diffuse surface areas, a generalized radiosity approach is presented. Unlike the conventional radiosity method, curved surfaces are subdivided into triangular surface patches, radiosity is assummed to be vary across each triangular surface patch. By adopting linear interpolation scheme over each triangular surface patch, we have established a complete set of approximated radiosity equations. Their unknowns are radiosities of differential surface areas located at all vertices of surface patches. The generalized radiosity equation has also been extended to non‐diffuse environments. Theoretical analysis and experimental results demonstrate the great potential of this method,
An Integral Geometry Based Method for Fast Form‐Factor Computation
Authors: Sbert Mateu 
Published: March 2003

AbstractMonte Carlo techniques have been widely used in rendering algorithms for local integration. For example, to compute the contribution of a patch to the luminance of another. In the present paper we propose an algorithm based on Integral geometry where Monte Carlo is applied globally. We give some results of the implementation to validate the proposition and we study the error of the technique, as well as its complexity.
Scale‐Invariant Minimum‐Cost Curves: Fair and Robust Design Implements
Authors: Moreton Henry P. , Séquin Carlo H. 
Published: March 2003

AbstractFour functionals for the computation of minimum cost curves are compared. Minimization of these functionals result in the widely studied Minimum Energy Curve (MEC), the recently introduced Minimum Variation Curve (MVC), and their scale‐invariant counterparts, (SI‐MEC, SI‐MVC). We compare the stability and fairness of these curves using a variety of simple interpolation problems. Previously, we have shown MVC to possess superior fairness. In this paper we show that while MVC have fairness and stability superior to MEC they are still not stable in all configurations. We introduce the SI‐MVC as a stable alternative to the MVC. Like the MVC, circular and helical arcs are optimal shapes for the SI‐MVC.Additionally, the application of scale invariance to functional design allows us to investigate locally optimal curves whose shapes are dictated solely by their topology, free of any external interpolation or arc length constraints.
Computer Graphics System for Reproducing Three‐ Dimensional Shape from Idea Sketch
Authors: Akeo Makoto , Hashimoto Hiroshi , Kobayashi Taisuke , Shibusawa Tetsuo 
Published: March 2003

AbstractThis paper describes the technical features and method of implementation of our designer support system which enables reproducing a three‐dimensional shape from an idea sketch speedily and modifying the reproduced shape easily, thereby facilitating the consistency of the shape to be checked from a design viewpoint.The designer support system was developed as a tool to cut the time and labor designers have to spend in the design process and help designers to fully display their creativity–the essential attribute of designers.This system uses cross‐section lines of an idea sketch of an object drawn by an industrial designer as input data to reproduce automatically a three‐dimensional wireframe model of the object by a newly developed three‐dimensional graphic algorithm including graphic constraints. In addition, it automatically creates planes by scanning the area enclosed by reproduced curved lines and subjects them to shading. In this process, the dimensions of the object need not be input to the system. The designer can operate the system simply by using the mouse to input appropriate data.Thus, the system permits the designer to easily express his idea in the form of a three‐dimensional shape and study idea variations on the display screen without creating a mockup.
Sketching 3D models with 2D interaction devices
Authors: Branco Vasco , Costa António , Ferreira F. Nunes 
Published: March 2003

AbstractThe creation of a 3D shape using CAD tools, namely solid modelers, is difficult and time‐consuming. Therefore, these systems are kept away from the conceptual phases of design, perhaps the most important in any product life cycle.The sketch is considered by many people as one of the fundamental techniques during a design's conceptual stages, as it enables high level design options to be explored at low cost. In general, this technique IS under‐appreciated in the computer graphics world.In this paper, we present a system called IDeS that tries to combine simplicity and intuition while drawing, with the useful features of the solid modelers, for example, CSG operators.
Function Representation of Solids Reconstructed from Scattered Surface Points and Contours
Authors: Savchenko Vladimir V. , Pasko Alexander A. , Okunev Oleg G. , Kunii Tosiyasu L. 
Published: March 2003

AbstractThis paper presents a novel approach to the reconstruction of geometric models and surfaces from given sets of points using volume splines. It results in the representation of a solid by the inequality f(x,y,z) ≥ 0. The volume spline is based on use of the Green's function for interpolation of scalar function values of a chosen “carrier” solid. Our algorithm is capable of generating highly concave and branching objects automatically. The particular case where the surface is reconstructed from cross‐sections is discussed too. Potential applications of this algorithm are in tomography, image processing, animation and CAD for bodies with complex surfaces.
An Efficient Algorithm for Line Clipping by Convex and Non‐convex Polyhedra in E3
Authors: Skala Václav 
Published: March 2003

AbstractA new algorithm for clipping lines against convex polyhedron with O(N) complexity is given with modification for non‐convex polyhedron. The suggested algorithm is faster for higher number of facets of the given polyhedron than the traditional Cyrus‐Beck's algorithm. Some principal results of comparison of all algorithms are shown and give some ideas how the proposed algorithm could be used effectively.
Mesh Simplification
Authors: Algorri Maria‐Elena , Schmitt Francis 
Published: March 2003

AbstractMesh 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.
Matching and Interpolation of Shapes using Unions of Circles
Authors: Ranjan V. , Fournier A. 
Published: March 2003

AbstractWhile 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.
Blob Metamorphosis based on Minkowski Sums
Authors: Galin E. , Akkouche S. 
Published: March 2003

AbstractThis 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 Bézier like metamorphosis where control points are replaced by control soft objects; in this scope, we have adapted existing accelerated techniques that build a Bézier 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.
Radiosity for dynamic scenes in flatland with the visibility complex
Authors: ORTI Rachel , RIVIERE Stéphane , DURAND Frédo , PUECH Claude 
Published: March 2003

AbstractThe 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.
Fractal modeling using free form techniques
Authors: Zair Chems Eddine , Tosan Eric 
Published: March 2003

AbstractIFS 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 (Bézier, splines).
Simplification of Global‐Illumination Meshes
Authors: Hughes Merlin , Lastra Anselmo A. , Saxe Edward 
Published: March 2003

AbstractWe 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.
Interpolatory Subdivision on Open Quadrilateral Nets with Arbitrary Topology
Authors: Kobbelt Leif 
Published: March 2003

AbstractA 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.
The Postnational Constellation: Democratic Governance in the Era of Globalization
Authors: Schmalz‐Bruns Rainer 
Published: March 2003

Books reviewed in this article:Daniele Archibugi, David Held, and Martin K??hler, (ed.) Re‐imagining Political Community: Studies in Cosmopolitan Democracy.Max Pensky, (ed.) The Postnational Constellation: Political Essays. By J??rgen Habermas.Beate Kohler‐Koch, Regieren in entgrenzten R??umen. (Governance in Debordered Spaces.) Politische Vierteljahresschrift, special issue 29.Wolfgang Streeck, (ed.) Internationale Wirtschaft, nationale Demokratie. Herausforderungen f??r die Demokratietheorie. (International Economy, National Democracy: Challenges for Democratic Theory.)Michael Z??rn, Regieren jenseits des Nationalstaates. (Governance Beyond the Nation‐State.)
The Strategic Board: the changing role of directors in developing and maintaining corporate capability
Authors: Ingley C. B. , Van der Walt N. T. 
Published: March 2003

Faced with major shifts in public opinion and societal change on an international scale, together with the strategic requirements of newly emergent forms of business structure, new technologies, globalisation and new forms of competition, modern companies are facing a crisis in their boardrooms. Traditional forms of governance architecture are being challenged and boards are under pressure to develop a broader mindset and new skills to deal with the uncertainty of higher‐level issues such as direction‐giving and implementation of strategy.The paper proposes a framework developed from research which examines the selection, evaluation and performance of boards of directors in New Zealand. From this research a need for strategic vision and leadership has clearly emerged as a key requirement in director capability, but in practice there is an acknowledged variation among individual directors in terms of their competence in this regard. Implications for further research suggest the need to explore the strategic role of the modern board in value creation, the extent to which directors perceive a link between strategy and corporate governance and their level of participation in this process.
Work Orientations and Women's Work: A Critique of Hakim's Theory of the Heterogeneity of Women
Authors: Procter Ian , Padfield Maureen 
Published: March 2003

This paper is a critique of Hakim's theory of the gendered character of work with its key idea of the ‘heterogeneity of women’ centring on the distinction between those who are ‘family oriented’ and those who are ‘career oriented’. Such patterns of work commitment are claimed to be developed by early adulthood and to steer women in one direction or the other.Our critique is based on interviews with two groups of young adult women generating rich data on their attitudes to employment, families and the relationship between the two. The first group (‘single workers’) when first interviewed were single, childless and employed full‐time. The second (‘early mothers’) were partnered mothers with at most part‐time employment.The substance of the critique is threefold:1.The single workers could not be clearly separated by ‘career’ or ‘family’ orientation. They wanted both, which then left them in Hakim's residual category as ‘drifters’, a wholly inappropriate characterization.2.The early mothers were certainly homemakers but our data doubted that this was by choice and suggested that many were becoming more career oriented.3.Longitudinal data from the single workers show the importance of analysing ‘orientation’ or other aspects of agency in the context of social structure rather than as a prime mover in itself.