bluuebunny/crossref_metadata_2025 huggingface dataset:
Children and Welfare Reform: A View from an Experimental Welfare Program in Minnesota
Authors: Gennetian Lisa A. , Miller Cynthia
Published: March 2003

Little is known about the effects of the most recent welfare reform initiatives—which include work mandates, time limits, and enhanced earnings disregards—on children’s outcomes. This is partly because the ways in which maternal employment and income affect children more generally are not well understood. This article describes the effects on child development of the Minnesota Family Investment Program (MFIP), a welfare program that began prior to 1996 federal welfare reform legislation. The present study utilized MFIP’s unique, three‐group research design to untangle the effects of different components of the program, and, in turn, discover how each component’s effects on parents’ income or employment affected children’s development. This study’s findings showed that MFIP increased employment rates and decreased poverty and, according to reports from mothers, children were less likely to exhibit problem behaviors and more likely to perform better and be more highly engaged in school. These findings, based on a total of 879 participants, bolster the long‐standing literature that has associated poverty with worse outcomes for children by confirming, in a rigorous experiment, that incremental increases in income for working poor parents bring benefits to children.
Evidence for Knowledge–Based Category Discrimination in Infancy
Authors: Pauen Sabina
Published: March 2003

Two studies examined whether infants’ category discrimination in an object–examination task was based solely on an ad hoc analysis of perceptual similarities among the experimental stimuli. In Experiment 1A, 11–month–olds examined four different exemplars of one superordinate category (animals or furniture) twice, followed by a new exemplar of the familiar category and an exemplar of the contrasting category. Group A (N= 39) explored natural–looking toy replicas with low between–category similarity, whereas group B (N= 40) explored artificial–looking toy models with high between–category similarity. Experiment 1B (N= 40) tested a group of 10–month–olds with the same design. Experiment 1C (N= 20) reversed the order of test trials. For Experiment 2 (N= 20), the same artificial–looking toy animals as in Experiment 1 (group B) were used for familiarization), but no category change was introduced at the end of the session. Infants’ responses varied systematically only with the presence of a category change, and not with the degree of between–category similarity. This supports the hypothesis that performance was knowledge based.
Distributed Reputation Management for Electronic Commerce
Authors: Yu Bin , Singh Munindar P.
Published: March 2003

One of the major challenges for electronic commerce is how to establish a relationship of trust between different parties. Establishing trust is nontrivial, because the traditional physical or social means of trust cannot apply directly in virtual settings. In many cases, the parties involved may not ever have interacted before. Reputation systems seek to address the development of trust by recording the reputations of different parties. However, most existing reputation systems are restricted to individual market websites. Further, relevant information about a party may come from several websites and from interactions that were not mediated by any website.

This paper considers the problem of automatically collecting ratings about a given party from others. Our approach involves a distributed agent architecture and adapts the mathematical theory of evidence to represent and propagate the ratings that participants give to each other. When evaluating the trustworthiness of a given party, a peer combines its local evidence (based on direct prior interactions with the party) with the testimonies of others regarding the same party. This approach satisfies certain important properties of distributed reputation management and is experimentally evaluated through simulations.
A Muscle‐based Feed‐forward Controller of the Human Body
Authors: Komura Taku , Shinagawa Yoshihisa , Kunii Tosiyasu L.
Published: March 2003

There is an increasing demand for human body motion data. Motion capture and physical animation have been used to generate such data. It is, however, apparent that such methods cannot automatically generate arbitrary human body motions. A human body is a redundant multi‐linked body controlled by a number of muscles. For this reason, the muscles must work appropriately and cooperatively for controlling the whole body. It is well‐known that the human body control system is composed of two parts: The open‐loop feed‐forward control system and the closed‐loop feedback control system. Many researchers have investigated the characteristics of the latter by analyzing the response of a human body to various external perturbations. However, for the former, very few studies have been done. This paper proposes an open‐loop feed‐forward model of the lower extremities which includes postural control for accurate animation of a human body. Assumptions are made here that the feed‐forward controller minimizes a certain objective value while keeping the balance of the body stable. The actual human motion data obtained using a motion capturing technique is compared with the trajectory calculated using our method for verification. The best criteria which is based on muscle dynamics is proposed. Using our method, dynamically correct human animation can be created by merely specifying a few key postures.
Interactive High‐Quality Soft Shadows in Scenes with Moving Objects
Authors: Loscos Céline , Drettakis George
Published: March 2003

Interactive rendering of soft shadows (or penumbra) in scenes with moving objects is a challenging problem. High quality walkthrough rendering of static scenes with penumbra can be achieved using pre‐calculated discontinuity meshes, which provide a triangulation well adapted to penumbral boundaries, and backprojections which provide exact illumination computation at vertices very efficiently. However, recomputation of the complete mesh and back‐projection structures at each frame is prohibitively expensive in environments with changing geometry. This recomputation would in any case be wasteful: only a limited part of these structures actually needs to be recalculated. We present a novel algorithm which uses spatial coherence of movement as well as the rich visibility information existing in the discontinuity mesh to avoid unnecessary recomputation after object motion. In particular we isolate all modifications required for the update of the discontinuity mesh by using an augmented spatial subdivision structure and we restrict intersections of discontinuity surfaces with the scene. In addition, we develop an algorithm which identifies visibility changes by exploiting information contained in the planar discontinuity mesh of each scene polygon, obviating the need for many expensive searches in 3D space. A full implementation of the algorithm is presented, which allows interactive updates of high‐quality soft shadows for scenes of moderate complexity. The algorithm can also be directly applied to global illumination.
A Modeling and Rendering Method for Snow by Using Metaballs
Authors: Nishita Tomoyuki , Iwasaki Hiroshi , Dobashi Yoshinori , Nakamae Eihachiro
Published: March 2003

The display of natural scenes such as mountains, trees, the earth as viewed from space, the sea, and waves have been attempted. Here a method to realistically display snow is proposed.

In order to achieve this, two important elements have to be considered, namely the shape and shading model of snow, based on the physical phenomenon. In this paper, a method for displaying snow fallen onto objects, including curved surfaces and snow scattered by objects, such as skis, is proposed. Snow should be treated as particles with a density distribution since it consists of water particles, ice particles, and air molecules. In order to express the material property of snow, the phase functions of the particles must be taken into account, and it is well‐known that the color of snow is white because of the multiple scattering of light.

This paper describes a calculation method for light scattering due to snow particles taking into account both multiple scattering and sky light, and the modeling of snow.
Interactive Sculpting with Deformable Nonuniform B‐splines
Authors: Vassilev Tzvetomir Ivanov
Published: March 2003

This paper describes an efficient method for manipulating deformable B‐spline surfaces, based on minimizing an energy functional. The major benefit of the proposed new fairness norm is that it preserves the natural representation of the B‐spline surface control points (a two dimensional array) which has an efficiency advantage over other methods. The designer uses forces as a main sculpting tool and is free to specify a single force, a set of isolated forces, forces situated on a line or curve or area of the deformable surface. The user is allowed to modify several parameters and in this way to change the physical properties of the object.
Maximum Intensity Projection Using Splatting in Sheared Object Space
Authors: Cai Wenli , Sakas Georgios
Published: March 2003

In this paper we present a new Maximum Intensity Projection (MIP) algorithm which was implemented employing splatting in a shear‐warp context. This algorithm renders a MIP image by first splatting each voxel on two intermediate spaces called "worksheet" and "shear image". Then, the maximum value is evaluated between worksheet and shear image. Finally, shear image is warped on the screen to generate the result image. Different footprints implementing different quality modes are discussed. In addition, we introduced a line encoded indexing speed‐up method to obtain interactive speed. This algorithm allows for a quantitative, predictable trade‐off between interactivity and image quality.
Conservative Visibility and Strong Occlusion for Viewspace Partitioning of Densely Occluded Scenes
Authors: Cohen‐Or Daniel , Fibich Gadi , Halperin Dan , Zadicario Eyal
Published: March 2003

Computing the visibility of out‐door scenes is often much harder than of in‐door scenes. A typical urban scene, for example, is densely occluded, and it is effective to precompute its visibility space, since from a given point only a small fraction of the scene is visible. The difficulty is that although the majority of objects are hidden, some parts might be visible at a distance in an arbitrary location, and it is not clear how to detect them quickly. In this paper we present a method to partition the viewspace into cells containing a conservative superset of the visible objects. For a given cell the method tests the visibility of all the objects in the scene. For each object it searches for a strong occluder which guarantees that the object is not visible from any point within the cell. We show analytically that in a densely occluded scene, the vast majority of objects are strongly occluded, and the overhead of using conservative visibility (rather than visibility) is small. These results are further supported by our experimental results. We also analyze the cost of the method and discuss its effectiveness.
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.
An Enhanced Spring Model for Information Visualization
Authors: Theisel Holger , Kreuseler Matthias
Published: March 2003

In this paper we present a new technique for visualizing multidimensional information. We describe objects of a higher dimensional information space as small closed free‐form‐surfaces in the visualization. The location, size and shape of these surfaces describe the original objects in information space uniquely. The underlying enhanced spring model is introduced. The technique is applied to two test data sets.
Comprehensive Halftoning of 3D Scenes
Authors: Veryovka O. , Buchanan J.
Published: March 2003

The display of images on binary output hardware requires a halftoning step. Conventional halftoning algorithms approximate image values independently from the image content and often introduce artificial texture that obscures fine details. The objective of this research is to adapt a halftoning technique to 3D scene information and thus to enhance the display of computer generated 3D scenes. Our approach is based on the control of halftoning texture by the combination of ordered dithering and error diffusion techniques. We extend our previous work and enable a user to specify the shape, scale, direction, and contrast of the halftoning texture using an external buffer. We control texture shape by constructing a dither matrix from an arbitrary image or a procedural texture. Texture direction and scale are adapted to the external information by the mapping function. Texture contrast and the accuracy of tone reproduction are varied across the image using the error diffusion process. We halftone images of 3D scenes by using the geometry, position, and illumination information to control the halftoning texture. Thus, the texture provides visual cues and can be used to enhance the viewer's comprehension of the display.
Computer‐Generated Graphite Pencil Rendering of 3D Polygonal Models
Authors: Sousa Mario Costa , Buchanan John W.
Published: March 2003

Researchers in non‐photorealistic rendering have investigated the display of three‐dimensional worlds using various display models. In particular, recent work has focused on the modeling of traditional artistic media and styles such as pen‐and‐ink illustration and watercolor painting. By providing 3D rendering systems that use these alternative display models users can generate traditional illustration renderings of their three‐dimensional worlds. In this paper we present our graphite pencil 3D renderer. We have broken the problem of simulating pencil drawing down into four fundamental parts: (1) simulating the drawing materials (graphite pencil and drawing paper, blenders and kneaded eraser), (2) modeling the drawing primitives (individual pencil strokes and mark‐making to create tones and textures), (3) simulating the basic rendering techniques used by artists and illustrators familiar with pencil rendering, and (4) modeling the control of the drawing composition. Each part builds upon the others and is essential to developing the framework for higher‐level rendering methods and tools. In this paper we present parts 2, 3, and 4 of our research. We present non‐photorealistic graphite pencil rendering methods for outlining and shading. We also present the control of drawing steps from preparatory sketches to finished rendering results. We demonstrate the capabilities of our approach with a variety of images generated from 3D models.
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.
Floating Points: A Method for Computing Stipple Drawings
Authors: Deussen Oliver , Hiller Stefan , Van Overveld Cornelius , Strothotte Thomas
Published: March 2003

We present a method for computer generated pen‐and‐ink illustrations by the simulation of stippling. In a stipple drawing, dots are used to represent tone and also material of surfaces. We create such drawings by generating an initial dot set which is then processed by a relaxation method based on Voronoi diagrams. The point patterns generated are approximations of Poisson disc distributions and can also be used for integrating functions or the positioning of objects. We provide an editor similar to paint systems for interactively creating stipple drawings. This makes it possible to create such drawings within a matter of hours, instead of days or even weeks when the drawing is done manually.
Physically‐Based Patination for Underground Objects
Authors: Chang Yao‐Xun , Shih Zen‐Chung
Published: March 2003

Although current photorealistic rendering techniques can produce very impressive images, the rendered objects are often too clean and shiny. Thus, the resulting images look unnatural. This paper proposes a physically‐based model to simulate the appearance of patinas on ancient Chinese bronzes. Buried in the soil for thousands of years, many patinas are found on the surface of ancient bronzes as a result of the aging process and the physical and chemical conditions of the soil environment. The development of patinas is modulated herein by L‐systems according to tendencies based on the environmental factors and object geometry. The tendencies are employed to represent the accumulative effect of all factors on patination. The proposed model can be extended to simulate a variety of metallic patinas including the ancient Chinese bronzes discovered at San‐hsing‐tui, Sichuan, China.
Multiresolution Shape Deformations for Meshes with Dynamic Vertex Connectivity
Authors: Kobbelt Leif P. , Bareuther Thilo , Seidel Hans‐Peter
Published: March 2003

Multiresolution shape representation is a very effective way to decompose surface geometry into several levels of detail. Geometric modeling with such representations enables flexible modifications of the global shape while preserving the detail information. Many schemes for modeling with multiresolution decompositions based on splines, polygonal meshes and subdivision surfaces have been proposed recently. In this paper we modify the classical concept of multiresolution representation by no longer requiring a global hierarchical structure that links the different levels of detail. Instead we represent the detail information implicitly by the geometric difference between independent meshes. The detail function is evaluated by shooting rays in normal direction from one surface to the other without assuming a consistent tesselation. In the context of multiresolution shape deformation, we propose a dynamic mesh representation which adapts the connectivity during the modification in order to maintain a prescribed mesh quality. Combining the two techniques leads to an efficient mechanism which enables extreme deformations of the global shape while preventing the mesh from degenerating. During the deformation, the detail is reconstructed in a natural and robust way. The key to the intuitive detail preservation is a transformation map which associates points on the original and the modified geometry with minimum distortion. We show several examples which demonstrate the effectiveness and robustness of our approach including the editing of multiresolution models and models with texture.
Visualizing Stars and Emission Nebulas
Authors: Nadeau David R. , Genetti Jon D. , Napear Steve , Pailthorpe Bernard , Emmart Carter , Wesselak Erik , Davidson Dennis
Published: March 2003

We describe star and nebula visualization techniques used to create a 3D volumetric visualization of the Orion Nebula. The nebula's ionization layer is modeled first as a surface model, derived from infrared and visible light observations. The surface model is imported into a volume scene graph‐based visualization system that uses procedural volume modeling to simulate the nebula's emissive gas layers. Additional scene graphs model proplyds and shock fronts within the nebula. Stars are rendered using Gaussian spots that are attenuated with distance. Finally, eighty‐six separate volumes are voxelized from these scene graphs, then simultaneously volume rendered.
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

The 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

Based 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

Monte 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

Four 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

This paper describes the technical features and method of implementation of our designer support system which enables reproducing a three‐dimensional shape from an idea sketch speedily and modifying the reproduced shape easily, thereby facilitating the consistency of the shape to be checked from a design viewpoint.

The designer support system was developed as a tool to cut the time and labor designers have to spend in the design process and help designers to fully display their creativity–the essential attribute of designers.

This system uses cross‐section lines of an idea sketch of an object drawn by an industrial designer as input data to reproduce automatically a three‐dimensional wireframe model of the object by a newly developed three‐dimensional graphic algorithm including graphic constraints. In addition, it automatically creates planes by scanning the area enclosed by reproduced curved lines and subjects them to shading. In this process, the dimensions of the object need not be input to the system. The designer can operate the system simply by using the mouse to input appropriate data.

Thus, the system permits the designer to easily express his idea in the form of a three‐dimensional shape and study idea variations on the display screen without creating a mockup.
Sketching 3D models with 2D interaction devices
Authors: Branco Vasco , Costa António , Ferreira F. Nunes
Published: March 2003

The creation of a 3D shape using CAD tools, namely solid modelers, is difficult and time‐consuming. Therefore, these systems are kept away from the conceptual phases of design, perhaps the most important in any product life cycle.

The sketch is considered by many people as one of the fundamental techniques during a design's conceptual stages, as it enables high level design options to be explored at low cost. In general, this technique IS under‐appreciated in the computer graphics world.

In this paper, we present a system called IDeS that tries to combine simplicity and intuition while drawing, with the useful features of the solid modelers, for example, CSG operators.
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

This 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

A 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

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

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

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 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

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

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

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

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.
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 Emergence of Fiduciary Capitalism
Authors: Hawley James , Williams Andrew
Published: March 2003

The twentieth century has seen a sea change in the concentration of ownership of U.S. corporations. Early in the century Berle and Means identified the divorce of ownership from control as the central corporate governance problem, but since the 1970’s ownership has been re’rating into the hands of fiduciary institutions – most notably pension funds and mutual funds. By the 1990s fiduciaries collectively owned over 50% of the outstanding equity of the 1,000 largest corporations. This new pattern of ownership, fiduciary capitalism, has begun to raise important policy questions including: How can agents (fiduciaries) effectively monitor other agents (boards of directors)? What are the social implications of universal ownership where fiduciaries own substantial stakes in virtually all of the corporations in a country, and, finally, What does it mean to maximize shareholder wealth when fiduciaries are universal owners?
Institutional Investor Heterogeneity: Implications for Strategic Decisions
Authors: Sherman Hugh , Beldona Sam , Joshi Maheshkumar
Published: March 2003

There has been much attention given to the growing activism of institutional investors in corporate governance. However, past research has been unable to establish a consistent relationship between institutional investors and firm behavior. This may have occurred because institutional investors have been assumed to be a homogenous group possessing the same objectives and behaviors. For a sample of 271 U.S. Fortune 500 firms for the years 1990 to 1992, we categorized the firms' institutional investors into four distinct types: pension funds, mutual funds, banks, and insurance companies. We found significantly different relationships between these categories of institutional investors and firms' strategic investments.
Board Roles in the Strategic Management of Non‐profit Organisations: theory and practic
Authors: Cornforth Chris , Edwards Charles
Published: March 2003

This paper presents findings from an in‐depth empirical study of the role of boards and their relations with senior managers in four organisations from the public and non‐profit sectors. The findings are interpreted using a conceptual framework which sees the outputs of boards as shaped by board inputs, processes and contextual factors, in particular wider institutional pressures. The results indicate that the strategic contribution of boards varies widely and depends on a complex interplay of factors: the system of regulation, sectoral traditions and norms of governance, the way board members are chosen, board members skill and experience, organisational size and status, and the way boards are organised and run. The wider institutional pressures that shape these factors can result in boards facing tensions and trade‐offs that can result in their contribution to stragegy being squeezed by other board roles.
A Framework for Determining the Influence of the Corporate Board of Directors in Accounting Studies
Authors: Cravens Karen , Wallace Wanda
Published: March 2003

Accounting, auditing, and tax professionals constantly evaluate the integrity, competence, and financial performance of clients as factors in practice that influence both client acceptance decisions and the manner in which professional services are rendered. Yet, from an accounting perspective, previous research investigating the corporate board of directors as a governance mechanism has focused only on the representational role of board members. Moreover, many of these studies resulted in conflicting findings according to these attributes. Other disciplines address the particular influence of the board with respect to overall corporate performance, but arrive at little agreement on either the effect of or the most critical of board attributes. This literature review synthesizes the existing research to provide a framework in which to evaluate the effect of the board of directors in accounting settings and, in particular, when conducting future research that employs elements of corporate governance as dependent or independent variables in accounting studies.
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.
What Makes Boards Effective? An examination of the relationships between board inputs, structures, processes and effectiveness in non‐profit organisations
Authors: Cornforth Chris
Published: March 2003

Based on a survey of charity boards in England and Wales this paper examines what influence board inputs, structures and processes have on board effectiveness. The findings provide mixed support for the normative literature on board effectiveness. Using stepwise logistic regression the research suggests that board inputs and three process variables are important in explaining board effectiveness, namely: board members have the time, skills and experience to do the job; clear board roles and responsibilities; the board and management share a common vision of how to achieve their goals; and the board and management periodically review how they work together.
Corporate Governance and Intellectual Capital: some conceptualisations
Authors: Keenan James , Aggestam Maria
Published: March 2003

One of the persistent problems facing corporate governance is the increasing shift toward knowledge‐intensive organisations. This article focuses on the fiduciary responsibility of corporate governance for creating, developing, and leveraging the intellectual capital existing and embedded in the people, structures, and processes of the firm. Research and practice, traditionally concerned with governance responsibility for financial and physical capitals, has not much focused on the relations between governance and intellectual capital. Here, the authors’ intellectual capital paradigm is overlayered on a recent taxonomy of systems and features of corporate governance. The result is an explication of the role and characteristics of corporate governance in relation to the intellectual capital of the firm.