bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Library for Developing PHIGS Programming Tools in a PEX Environment
Authors: Wainer Michael , Tan Ting 
Published: March 2003

AbstractThe merger of three‐dimensional graphics with the X Window System has recently been standardized by adapting PHIGS, the Programmer's Hierarchical Interactive Graphics System, to the X Window System with PEX, the PHIGS Extension to X. The standard programming library for PEX has been defined to be identical to PHIGS PLUS allowing PHIGS programs to port directly to the X environment. X uses a client server model to run applications as client processes which communicate with a server to perform graphical display and input. For improved performance, the PEX extension defines new server resources to reduce network traffic and to take advantage of graphics hardware existing on high‐end servers. A side effect of this distributed model of computation is a distribution of PHIGS structures leading to a relaxation of the exclusive access which a PHIGS application usually maintains over its Central Structure Store.We exploit the distributed nature of a PEX/PHIGS client's Central Structure Store to provide access to it for other applications besides the originating PEX/PHIGS client. We refer to these other applications as tools since one of our primary goals is to create development tools for PHIGS programmers. Rather than concentrate on particular debugging tools, we focus upon easing the process of actually developing tools. Our goal is to supply a collection of routines which can be used by PHIGS programmers to create custom tools or other programs which require access to the graphics data of remote PHIGS processes.Our Tool Development Library provides the PHIGS programmer a small number of management routines which orchestrate the connection and mapping to the data of one or more remote PHIGS applications. Manipulation of remote PHIGS structures is accomplished just as easily as local operations and is performed using standard PHIGS calls. The remote application being accessed requires no changes to its source code. Obvious uses for the Tool Development Library are in the construction of PHIGS tools such as structure browsers, editors and debugging aids. Less obvious is the potential for developing collections of cooperating graphics applications which share graphics data.
Experiments in the Parallel Computation of 3D Convex Hulls
Authors: Claret A.R. , Day A.M. 
Published: March 2003

AbstractTwo parallel implementations of a 3D convex hull algorithm are reported. The paper considers a MIMD distributed memory architecture and the implementations are carried out on the Meiko Computing Surface using T800 transputers and the programming languages Occam and C. The first method uses a simple parallel geometric decomposition strategy and produces encouraging results. With the second approach a parallel generic Divide‐and‐Conquer kernel is incorporated. This is an example of the algorithmic skeleton approach to parallel programming and involves run‐time, dynamic allocation of work to processors. The resulting performances for both methods are measured and compared.
Making Shaders More Physically Plausible
Authors: Lewis Robert R. 
Published: March 2003

AbstractThere is a need to develop shaders that not only “look good”, but are more physically plausible. From physical and geometric considerations, we review the derivation of a shading equation expressing rejected radiance in terms of incident radiance and the bidirectional reflectance distribution function (BRDF). We then examine the connection between this equation and conventional shaders used in computer graphics. Imposing the additional physical constraints of energy conservation and Helmholtz reciprocity allows us to create variations of the conventional shaders that are more physically plausible.
Wavelet Projections for Radiosity
Authors: Schröder Peter , Gortler Steven J. , Cohen Michael F. , Hanrahan Pat 
Published: March 2003

AbstractOne important goal of image synthesis research is to accelerate the process of obtaining realistic images using the radiosity method. Two important concepts recently introduced are the general framework of projection methods and the hierarchical radiosity method.Wavelet theory, which explores the space of hierarchical basis functions, offers an elegant framework that unites these two concepts and allows us to more formally understand the hierarchical radiosity method.Wavelet expansions of the radiosity kernel have negligible entries in regions where high frequency/fine detail information is not needed. A sparse system remains if these entries are ignored. This is similar to applying a lossy compression scheme to the form factor matrix. The sparseness of the system allows for asymptotically faster radiosity algorithms by limiting the number of matrix terms that need to be computed. The application of these methods to 3D environments is described in4. Due to space limitations in that paper many of the subtleties of the construction could not be explored there. In this paper we discuss some of the mathematical details of wavelet projections and investigate the application of these methods to the radiosity kernel of a flatland environment, where many aspect are easier to visualize.
3D Visualization for 2D GIS: an Analysis of the Users' Needs and a Review of Techniques*
Authors: Giertsen Christopher , Lucas Anne 
Published: March 2003

AbstractMost of the existing geographical information systems (GIS) make limited use of algorithms for advanced computer graphics and visualization. One explanation is that few attempts are made to identify the visualization needs for different uses of GIS, and to couple such needs to the available algorithms. Another explanation is that most GIS are designed to handle two‐dimensional (20) data with few obvious relationships to three‐dimensional (30) visualization.In an attempt to provide a better understanding of the application of visualization in GIS, we propose a conceptual framework linking several aspects of the two fields. At the user‐level, we link different uses of GIS to different categories of audience and presentation styles. At the level of implementation, we first propose different ways to create 3D data for visualization from 2D GIS data, and then we review algorithms and techniques for 3D visualization with respect to support of different presentation styles.
Fast Dynamic Tessellation of Trimmed NURBS Surfaced1
Authors: Abi‐Ezzi Salim S. , Subramaniam Srikanth 
Published: March 2003

AbstractTrimmed NURBS (non‐uniform rational B‐splines) surfaces are being increasingly used and standardized in geometric modeling applications. Fast graphical processing of trimmed NURBS at interactive speeds is absolutely essential to enable these applications. which poses some unique challenges in software, hardware, and algorithm design. This paper presents a technique that uses graphical compilation to enable fast dynamic tessellation of trimmed NURBS surfaces under highly varying transforms.We use the concept of graphical data compilation. through which we preprocess the NURBS surface into a compact, view‐independent form amenable for fast per‐frame extraction of triangles. Much of the complexity of processing is absorbed during compilation. Arbitrarily complex trimming regions are broken down into simple regions that are specially designed to facilitate tessellation before rendering. Potentially troublesome cases of degeneracies in the surface are detected and dealt with during compilation. Compilation enables a clean separation of algorithm‐intensive and compute‐intensive operations, and provides for parallel implementations of the latter. Also, we exercise a classification technique while processing trimming loops. which robustly takes care of geometric ambiguities and deals with special cases while keeping the compilation code simple and concise.
AGRELs and BIPs: Metamorphosis as a Bezier curve in the space of polyhedra
Authors: Rossignac Jarek , Kaul Anil 
Published: March 2003

AbstractThe metamorphosis between two user‐specified objects offers an intuitive metaphor for designing animations of deforming shapes. We present a new technique for interactively editing such deformations and for animating them in realtime. Besides the starting and ending shapes, our approach offers easy to use additional control over the deformations. The new Bezier Interpolating Polyhedron (BIP) provides a graphics representation of such a deforming object formulated mathematically as a point describing a Bezier curve in the space of all polyhedra. We replace, in the Bezier formulation, the traditional control points by arbitrary polyhedra and the vector addition by the Minkowski sum. BIPs are composed of Animated GRaphic ELement (AGRELs), which are faces with constant orientation, but with parametrized vertices represented by Bezier curves. AGRELs were designed to efficiently support smooth realtime animation on commercially available rendering hardware. We provide a tested algorithm for automatically computing BIPs from the sequence of control polyhedra and demonstrate its applications to animation design.
Volume Rendering on Non‐regular Grids
Authors: Tabatabai Behnam , Sessarego Emanuela A. , Mayer Harald F. 
Published: March 2003

AbstractIn this article we present the principle methods for volumerendering of non‐regular grids as used in the Finite Element Method or the Method of Control Volumes. Besides linear element types, the methods discussed here also cover the handling of commonly used non‐linear element types but little considered in the Computer Graphics community. The very basic operation in the whole rendering process, namely the interpolation of the geometry and function values is fully based on the element type specific shape functions, ensuring a consistent mathematical treatment of the object in the sense of the underlying numerical simulation. We discuss the implications of this approach and propose optimizations justified by general assumptions on the qualify of the simulation model.
A Method for Displaying Metaballs by using Bézier Clipping
Authors: Nishita Tomoyuki , Nakamae Eihachiro 
Published: March 2003

AbstractFor rendering curved surfaces, one of the most popular techniques is metaballs, an implicit model based on isosurfaces of potential fields. This technique is suitable for deformable objects and CSG model.For rendering metaballs, intersection tests between rays and isosurfaces are required. By defining the higher degree of functions for the field functions, richer capability can be expected, i.e., the smoother surfaces. However, one of the problems is that the intersection between the ray and isosurfaces can not be solved analytically for such a high degree function. Even though the field function is expressed by degree six polynomial in this paper (that means the degree six equation should be solved for the intersection test), in our algorithm, expressing the field function on the ray by Bézier functions and employing Bézier Clipping, the root of this function can be solved very effectively and precisely.This paper also discusses a deformed distribution function such as ellipsoids and a method displaying transparent objects such as clouds.
Improved Visualisation of Marine Data: Algae and Acid Rain
Authors: Day A.M. , Turner S.M. , Arnold D.B. 
Published: March 2003

AbstractRecent studies have shown a connection between seasonal phytoplankton activity and generation of atmospheric sulphur products known to contribute towards acid rain [1]. Although anthropogenic sources of sulphur dioxide and sulphate dominate in acid &position on land surfaces, for some less industrialised areas of Europe, during the summer, there may be a significant contribution from natural marine sources.This paper describes briefly the nature of the marine processes thought to be taking place and survey cruises in the Southern North Sea used to collect data. Such field studies pose peculiar difficulties in both collection and processing of data. A critique on the nature of data generated under such conditions is included and some implications drawn for visualisation and interpretation techniques. Some initial results, with basic interpolation and approximation techniques, are compared. The paper concludes with suggestions on the way in which the research projects described are intended to befurther developed.
GKS‐9x: The Design Output Primitive, an Approach to a Specification.
Authors: Nehlig Ph. W. , Duce D. A. 
Published: March 2003

AbstractThis paper describes an approach to the formal definition of the design primitive introduced in the revision of the ISO/IEC computer graphics standard, GKS. The paper starts with a general description of the design primitive and then describes the specification (which is given in the Z notation) and the motivation for the approach taken in some detail. The paper concludes with a reflection on the contribution of this work, and the descriptive style adopted an the GKS revision, to the role of formal description in the presentation of graphics standards.
The Design and Specification of a Visual Language: An Example for Customising Geographic Information Systems Functionalities
Authors: Paterna' F. , Campari I. , Scopigno R. 
Published: March 2003

AbstractIn this paper the design of a visual program editor and its specification using formal grammars are discussed. We consider an environment to specify, analyse and execute visual programs for a Geographical Information System (GIS). The lack of sophisticated user interfaces is one of the major drawbacks to Geographical Information Systems, particularly for people without a sound background in computer science. The use of a visual language approach is useful in order to hide the plethora of basic GIS functions, while providing ready‐ to‐use tools to solve users' tasks. The visual environment provides users with higher level interfaces; it is based on the module concept, which is conceived as a software building block that implements a solution to a general basic task and is presented to the user through an interactive frame. Complex GIS queries can be carried out by interconnecting modules into flow networks, using a direct manipulation approach.
Deriving Spectral, Reflectance Functions of Computer‐Simulated Object Colours
Authors: Schettini R. 
Published: March 2003

AbstractA method is presented which, given the RGB values of a colour stimulus displayed on a given cathode ray tube (to which a CIE XYZ triple corresponds), makes it possible to find a spectral reflectance function characterizing an object colour. Such an object when “illuminated” by a given illuminant produces a metameric spectral power distribution, that is, one with the same XYZ tristimulus values. The method is useful in the colorimetric matching of colours on different media or supports.
Computation of Offset Curves by the Huygens Principle
Authors: Mikheev A. , Nozik M. , Rubinstein J. 
Published: March 2003

AbstractA new algorithm for computing offset curves is proposed. The algorithm is based on the Huygens principle for propagating wave‐fronts. It automatically avoids the topological singularities that appear in conventional methods. The algorithm is simple to implement and it does not require any multiplication or other floating number operations.
Multiresolution Tiling
Authors: Meyers David 
Published: March 2003

AbstractThis paper describes an efficient method for constructing a tiling between a pair of planar contours. The problem is of interest in a number of domains, including medical imaging, biological research and geological reconstructions. Our method, based on ideas from multiresolution analysis and wavelets, requires O(n) space and appears to require O(n log n) time for average inputs, compared to the O(n2) space and O(n2 log n) time required by the optimizing algorithm of Fuchs, Kedem and Uselton1. The results computed by our algorithm are in many cases nearly the same as those of the optimizing algorithm, but at a small fraction of the computational cost. The performance improvement makes the algorithm usable for large contours in an interactive system. The use of multiresolution analysis provides an efficient mechanism for data compression by discarding wavelet coefficients smaller than a threshold value during reconstruction. The amount of detail lost can be controlled by appropriate choice of the threshold value. The use of lower resolution approximations to the original contours yields significant savings in the time required to display a reconstructed object, and in the space required to store it.
An Algorithm for Perspective Viewing of Objects Represented by Octrees
Authors: Aref Walid G. , Samet Hanan 
Published: March 2003

AbstractA new algorithm is presented for viewing three‐dimensional objects, represented by an octree, from an arbitrary location. The algorithm generates aperspective view of the objects while eliminating hidden surfaces. The viewer can be located anywhere inside or outside the objects. The algorithm presented in this short notefixes an artifact that is generated by a previously published algorithm due to Meagher when the viewer is located in certain regions in space. The new algorithm traverses the octree in a back‐to‐front order and recursively chooses correct orders for visiting the sons of non‐leaf nodes.
Fast Generation of Leakproof Surfaces from Well‐Defined Objects by a Modified Marching Cubes Algorithm
Authors: Roll Stefan , Haase Axel , von Kienlin Markus 
Published: March 2003

AbstractLocal surface reconstruction by the Marching Cubes algorithm and its derivatives has a well known ambiguity, which prevents constructed surfaces from being closed and simple. We investigate this ambiguity assuming that a 3D image samples well‐defined objects. In this case it is justified to aim at tiling of extracted object voxels rather than at reconstructing iso surfaces. Compared to iso surface reconstruction, our algorithm provides essentially the same level of confidence with respect to surface location at a lower computational cost. We present a leak detection and mending scheme which resolves the Marching Cubes ambiguity and guarantees a well‐defined behaviour with respect to which objects are covered by which surface. We detail how to implement our leak mending method within a completely tabulated Marching Cubes algorithm. We finally give an example of how the adapted algorithm is of benefit to a recently developed 3D MR spectroscopy technique.
Fractals and Quasi‐Affine Transformations
Authors: Nehlig P. W. , Reveilles J.‐P. 
Published: March 2003

AbstractIn the continuum , contracting affine transformations have a unique fixed point. It is well known that this property is not preserved by dicretization and that the dynamics of discretized functions are very complicated. Discrete geometry allows us to start a theory for these dynamics and to illustrate some of their features by pictures. These pictures, rendered by a simple algorithm, reveal a very large spectrum of fractal structures, from the simplest to the intricatest.
Optimization of a Priority List Algorithm for 3‐D Rendering of Buildings
Authors: Morer Paz , Alonso Alejandro M. Garcia , Flaquer Juan 
Published: March 2003

AbstractArchitectural scenes usually have some peculiar properties, like parallel surfaces, symmetry, instantiation, easy clustering, etc. These properties can be used by visualization algorithms in order to improve the solution of the hidden surface removal problem.This paper presents some practical implementation policies for the binary space partition algorithm proposed by Fuchs. They take advantage of the characteristics found in architectural scenes. These suggestions help to minimize both the time needed to build the tree and the memory space used. Five optimization techniques are presented and applied to fourteen architectural scenes.
Domain Extension of Isothetic Polyhedra with Minimal CSG Representation
Authors: Arinyo Robert Juan 
Published: March 2003

AbstractWe consider the problem of converting boundary representations of isothetic polyhedra into constructive solid geometry (CSG) representations. The CSG representation is a boolean formula based on the half‐spaces supporting the faces of the polyhedron. This boolean formula exhibits two important features: no term is complemented (it is monotone) and each supporting half‐space appears in the formula once and only once. It is known that such formulas do not always exist for general polyhedra in the three‐dimensional space. In this work first we give a procedure that extends the domain of polyhedra for which such a nice representation can be computed. Then we prove that not all cyclic isothetic polyhedra have a CSG representation of the style given above.
Animation of Human Diving
Authors: Wooten Wayne L. , Hodgins Jessica K. 
Published: March 2003

AbstractThe motion of a human platform diver was simulated using a dynamic model and a control system. The dynamic model has 32 actuated degrees of freedom and dynamic parameters within the range of those reported in the literature for humans. The control system uses algorithms for balance, jumping, and twisting to initiate the dive, sequences of desired values for proportional‐derivative servos to perform the aerial portion of the dice, and a state machine to sequence the actions throughout the dice. The motion of the simulated diver closely resembles video footage of dices performed by human athletes. The control and simulation techniques presented in this paper are useful for providing realistic motion for synthetic actors in computer animations and virtual environments and may some day be useful for analysis of sports performance.
Fitting Triangular B‐Splines to Functional Scattered Data
Authors: Pfeifle Ron , Seidel Hans‐Peter 
Published: March 2003

AbstractScattered data is, by definition, irregularly spaced. Uniform surface schemes are not well adapted to the locally varying nature of such data. Conversely, Triangular B‐Spline surfaces 2 are more flexible in that they can be built over arbitrary triangulations and thus can be adapted to the scattered data.This paper discusses the use of DMS spline surfaces for approximation of scattered data. A method is provided for automatically triangulating the domain containing the points and generating basis functions over this triangulation. A surface approximating the data is then found by a combination of least squares and bending energy minimization. This combination serves both to generate a smooth surface and to accommodate for gaps in the data. Examples are presented which demonstrate the eftectiveness of the technique for mathematical, geographical and other data sets.
Three‐Dimensional Modeling and Effects on Still Images
Authors: Zakait Yaron , Rappoport Ari 
Published: March 2003

AbstractDesigners and creative artists use computer graphics and image processing effects on stall photographs in application areas such as advertising entertainment broadcasting and the arts Most of the effects available in research arid commercial work are two‐dimensional in nature, for example image processing filters [blur, edge enhancement) and creative effects (tilings, reflections) There is almost no usage of information taken from the 3‐D world in which the objects appearing an the image are located.In this paper we present a novel method for creating 3‐D effects on photographs or in general on any image created by rendering a 3‐D world The artist interacts with the image using a set of intuitive direct manipulation interface objects These objects let the user define a 3‐D model, display at, and manipulate it in a 3‐D space which is correlated with that of the input image.The generated model can be an arbitrarily complex 3‐D polyhedron Any texture, including texture taken from the input photograph, can be mapped into any of its faces arid used for special effects We discuss and show examples for effects such as copy and paste, motion blur, model editing and deformations lighting effects, and shadows.