EG 1992 Conference Proceedings

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/13891

Browse

Now showing 1 - 20 of 39

The Visualization Input Pipeline - Enabling Semantic Interaction in Scientific Visualization
(Blackwell Science Ltd and the Eurographics Association, 1992) Felger, W.; Schroder, F.
Scientific Visualization systems are primarily output-oriented, Users can specify and change parameters that are controlling the visualization process, which will result in different data representations or images respectively. But no mechanism is provided to really interact with the application data (semantic interaction) that has been changed step by step by the process of visualization.In this paper general concepts are elaborated and presented to achieve semantic interaction in dataflow environments for Scientific Visualization.
Pandora: An Experiment in Distributed Multimedia
(Blackwell Science Ltd and the Eurographics Association, 1992) King, Tony
An experimental workstation is described which supports digital video and audio in a distributed environment, and which presents this functionality to the user through the medium of a video-extended implementation of the X Window System. The Pandora Workstation is built out of two quite separate parts. A standard UNIX machine (the Pandora Host) brings standard hardware and software computing resources to the system- a highly-specialised processing engine (Pandora s Box) handles the high-bandwidth, time-critical, and device-dependent processing. A 50 Mbit/second ATM network provides for real-time data communication within the system. Nineteen Pandora Workstations have been deployed within Olivetti Research Ltd and the Cambridge University Computer Laboratory, and are used routinely to run distributed applications including video mail, video conferencing, and real-time media delivery services.
SX/Tools - An Open Design Environment for Adaptable Multimedia User Interfaces
(Blackwell Science Ltd and the Eurographics Association, 1992) Kuhme, Thomas; Schneider-Hufschmidt, Matthias
In this paper a brief review of user interface management systems (UIMSs) and their advantages is given. Shortcomings of current UIMSs and open requirements imposed by industrial application areas are outlined. Among the most important requirements are uniform design mechanisms independent of interaction media, techniques, and styles as well as a straight forward end-user adaptability of user interfaces.A new approach to interactive interface construction, called"direct composition", is introduced. In this approach all interface objects contain the means for their own modification and design and therefore offer consistent interaction techniques for both the construction and usage of user interfaces. Moreover, end-user adaptability is an inherent feature of direct composition interfaces.The user interface design environment SX/Tools is described to exemplify specific properties of user interface management systems following the principle of direct composition. The impacts of direct composition on user interface design include a uniform interface development process covering tool development, interface development, and"on-usage" interface adaptation. It is argued that the direct composition approach can overcome many of the problems with traditional UIMSs.
Computing Dynamic Changes to BSP Trees
(Blackwell Science Ltd and the Eurographics Association, 1992) Chrysanthou, Y.; Slater, M.
This paper investigates a new method for dynamically changing Binary Space Partition (BSP) trees. A BSP tree representation of a 3D polygonal scene provides an ideal data structure for rapidly performing the hidden surface computations involved in changing the viewpoint. However, BSP trees have generally been thought to be unsuitable for applications where the geometry of objects in the scene changes dynamically. The purpose of this paper is to introduce a dynamic BSP tree algorithm which does allow for such changes, and which maintains the simplicity and integrity of the BSP tree representation. The algorithm is extended to include dynamic changes to shadows. We calibrate the algorithms by transforming a range of objects in a scene, and reporting on the observed timing results.
Visual Composition and Multimedia
(Blackwell Science Ltd and the Eurographics Association, 1992) de Mey, Vicki; Breiteneder, Christian; Dami, Laurent; Gibbs, Simon and Tsichritzis, Dennis
Multimedia applications can be seen as sets of autonomous parts, independent yet capable of working together. This assumption allows for the construction of multimedia applications in a"connectionist" fashion. In this paper we describe mechanisms for the visual composition of multimedia applications. These mechanisms allow for quick and flexible application construction by direct manipulation with reference to multiple composition models. An object-oriented framework for multimedia systems will be introduced throughout the paper.
The Parametric Differential Method: An Alternative to the Calculation of Form Factors
(Blackwell Science Ltd and the Eurographics Association, 1992) Baranoski, Gladimir V. Guimaraes
The parametric differential method calculates the form factors without using approximations by polygons. Because of this it contributes to the improvement of the realism of the images synthesised through the radiosity method. This paper presents the most important characteristics of the parametric differential method as well as the results concerning its accuracy. Comparison of the form factors found using the new algorithm has been made with those analytically found.
Realistic Generation and Real Time Animation of Images of the Human Colon
(Blackwell Science Ltd and the Eurographics Association, 1992) Haritsis, Angelo; Gillies, Duncan; Williams, Christopher
A simulator has been built to teach doctors the skill of handling a flexible endoscope for gastrointestinal investigations. Trainees use a dummy endoscope in which the control actions are transduced into voltages and sensed by the computer. The simulator computes the position and viewing direction of the endoscope within an internal model of the human colon. Then a renderer draws the view, reproducing as far as possible what would be seen during a real colonoscopy. Since the system must generate at least ten frames per second for realistic animation, standard rendering techniques, such as ray tracing, could not be used. Consequently a new method was devised, based on identifying coherent regions along each scan line which can be rendered by table lookup. The method allows shaded Lambertian surfaces to be drawn at a frame rate of 15 per second, using modest computing resources. Although several approximations were required in the analysis, the computer images of the internal surfaces of the human colon present a high degree of visual realism.
A line clipping algorithm and its analysis
(Blackwell Science Ltd and the Eurographics Association, 1992) Krammer, Gergely
One of the classical problems of Computer Graphics: line clipping against a rectangle is revisited. Coordinate raster refinement and some unusual forms of the parametric equation of the line are used to develop formulae for a line clipping algorithm. The algorithm is first presented in a form, where clarity of presentation is the prime concern. It is then transformed into one big nested branch, which after optimisation is assumed to be the most efficient form with a heavy cost on size. It is assumed that any mathematical consideration of the clipping problem would after a similar optimisation lead to a branching structure of equal complexity and speed. Line clipping thus belongs to the class of problems for which after a proper mathematical and logical analysis automatic program transformations may do the rest.This work has been supported by a grant from the Hungarian Academy of Sciences, Project No. OTKA 2572/1991
Fractals and Solid Modeling
(Blackwell Science Ltd and the Eurographics Association, 1992) Groller, Eduard
Trying to combine fractal geometry and solid modeling seems to be a contradiction in itself, In this paper a new type of 3D objects is presented that accomplishes this combination in a specific way. Objects with a fractal macro structure and a 3D solid micro structure can be specified and rendered efficiently by using context free, attribute, geometric grammars. This new object type can be incorporated into the CSG-modeling technique (Constructive Solid Geometry) in two ways: a) using CSG for the specification of the micro structure of the new object type, b) using these fractal like objects as a new type of primitive in the CSG model. Ray tracing is used for generating high quality images of these geometrically complex objects.
A Unified Approach for Physical and Geometric Modeling for Graphics and Animation
(Blackwell Science Ltd and the Eurographics Association, 1992) Essa, Irfan A.; Sclaroff, Stan; Pentland, Alex
We present a unified approach for geometric and physical modeling using implicit functions, for application to graphics and animation. This method extends previously proposed techniques, and allows the standard finite element method to be directly combined with geometric modeling, resulting in quick calculation of an object s mass and stiffness matrices, and its vibration modes and frequencies. Because the approach is based on an implicitfunction representation, it allows very fast collision detection and characterization. Examples of complex physical and geometric modeling are presented.
An Object-Oriented View of the User Interface
(Blackwell Science Ltd and the Eurographics Association, 1992) Zhou, Tom Z.-Y.; Kubitz, William J.
The object-oriented view of the user interface presented here is a model of object responsibilities-sharing and cooperation for a typical user interface. The model regards the user interface as a three-layer architecture, with the application contributing to one of the layers called the application exposure, The model seeks to promote user interface software reuse by coupling the user interface and the application with well-defined message protocols, by properly allocating user interfacefunctions to the layers so as to reduce and discipline their dependencies, and byfactoring complex abstractions into reusable secondary components.
Adaptive Sampling of Area Light Sources in Ray Tracing Including Diffuse Interreflection
(Blackwell Science Ltd and the Eurographics Association, 1992) Kok, Arjan J. F.; Jansen, Frederik W.
Ray tracing algorithms that sample both the light received directly from light sources and the light received indirectly by diffuse reflection from other patches, can accurately render the global illumination in a scene and can display complex scenes with accurate shadowing. A drawback of these algorithms, however, is the high cost for sampling the direct light which is done by shadow ray testing. Although several strategies are available to reduce the number of shadow rays, still a large number of rays will be needed, in particular to sample large area light sources. An adaptive sampling strategy is proposed that reduces the number of shadow rays by using statistical information from the sampling process and by applying information from a radiosity preprocessing. A further reduction in shadow rays is obtained by applying shadow pattern coherence, i.e. reusing the adaptive sampling pattern for neighboring sampling points.
Composing Hierarchically Structured Images
(Blackwell Science Ltd and the Eurographics Association, 1992) Patterson, John W.; Cockton, Gilbert
This paper begins by examining the classical raster-based composition model, establishing its weakness, and developing a new composition algebra based on line drawing. It then examines the role of composition in the Hierarchical Display Model, demonstrates that the forms of composition assumed in this model are inadequate to deal correctly with the interactions of two-dimensional representations of three-dimensional objects, and shows that our composition algebra resolves this difficulty. The composition steps required can be packaged with the use of a single attribute which constrains the apparent order of composition. This attribute is associated with the object which is to be taken out of order , obviating any needsfor layers.
A Simple Description of Complex Curves
(Blackwell Science Ltd and the Eurographics Association, 1992) Bouras, A.; Shariat, B.; Vandorpe, D.
In this paper, we propose a method of complex curves description, based on the use of standard primitives (curve arcs), inscribed in including boxes. This method simplifies the creation steps (curves are not defined with the help of control points), and the manipulation steps (using including boxes).This study constitutes an extension to our descriptive universal language, named"G", which is used in a general desig n environment, permitting the integration of various models (solids1, polyhedrons2, surfaces3 and fractals), in order to offer the adequate tools adapted to the problems to be solved, in a unique modeller.
Radiosity in Flatland
(Blackwell Science Ltd and the Eurographics Association, 1992) Heckhert, Paul S.
The radiosity method for the simulation of interreflection of light between diffuse surfaces is such a common image synthesis technique that its derivation is worthy of study. We here examine the radiosity method in a two dimensional, flatland world. It is shown that the radiosity method is a simple finite element method for the solution of the integral equation governing global illumination. These two-dimensional studies help explain the radiosity method in general and suggest a number of improvements to existing algorithms. In particular, radiosity solutions can be improved using a priori discontinuity meshing, placing mesh boundaries on discontinuities such as shadow edges. When discontinuity meshing is used along with piecewise-linear approximations instead of the current piecewise-constant approximations, the accuracy of radiosity simulations can be greatly increased.
Rendering NURB Regions For 2D Animation
(Blackwell Science Ltd and the Eurographics Association, 1992) Willis, Philip; Oddy, Robert
We describe an accurate method of rendering by scan-conversion of closed regions bounded by NURBs, with particular comments on its application to computer-based 2D animation. It is shown that the method is fast, analytically accurate, and can be readily extended to include anti-aliasing and clipping.
Affine Texture Mapping and Antialiasing Using Integer Arithmetic
(Blackwell Science Ltd and the Eurographics Association, 1992) Nehlig, P.; Ghazanfarpour, D.
Texture mapping techniques are very useful for generating more realistic images. However, texture compression, generally induced by geometric transformations, is at the origin of aliasing artifacts especially the well-known"moire" patterns. Two discrete affine texture mapping methods based exclusively on integer arithmetic are presented here. This original approach of discrete affine mapping is adequate for antialiasing in the case of compressed textures.
The Input Model of Standard Graphics Systems Revisited by Formal Specification
(Blackwell Science Ltd and the Eurographics Association, 1992) Faconti, Giorgio P.; Zani, Nicola; Paterno , Fabio
This paper describes the specification of an input model for graphics systems. The initial aim of the work reported in this paper was to revise the input model adopted by graphics standards by means of formal specification techniques in order to acquire a deep knowledge of its capabilities, to eventually discover errors and to develop improvements. Taking into account similar works done in this area by others and considering a number of major issues related to input recently discussed within the graphics community, a new model is being proposed that addresses the very key concepts of parallelism, extensibility and reconfigurability. The model is based upon composition operations defined over basic components specified as a set of concurrent processes. Composition operations and process definitions have been formally specified by using the LOTOS notation and investigated by means of the LOTOS Interactive Tools Environment. In the first part of the paper, the input model of graphics standards is shortly examined in the light of the results so far achieved by related works on formal specification of computer graphics systems. Subsequently, an improved model is presented. Finally, its capability of simulating the traditional operating modes of logical input devices and a methodology for defining new operating modes is demonstrated.
A CAD System for Color Design of a Car
(Blackwell Science Ltd and the Eurographics Association, 1992) Oshima, Tetsuya; Yuasa, Shinji; Sakanoshita, Ken-ichi; Ogata, Yoshinori
We have developed a color CAD system which enables a color designer to evaluate and create body colors of a car on a graphic display and put this system into practical use. The system has three features- generating realistic images comparable to photography to satisfy the car designer s needs, through close analysis of the physical phenomena taking place in the real environment, reproducing the desired colors very accurately on a CRT monitor, through analysis of the CRT colorimetric characteristics of reproducing the specified colors in response to the input signals, and utilizing a parallel computer to generate realistic images at a high speed and to control colors through interactive operation. Application of the CAD system reported here to the field of color design made it possible to fully evaluate and create body colors by means of computer graphics, replacing the conventional method which requires the painting of clay models or prototype cars.
An adaptive Discretization Method For Radiosity
(Blackwell Science Ltd and the Eurographics Association, 1992) Languenou, Eric; Bouatouch, Kadi; Tellier, Pierre
When using radiosiiy, the visual quality of the rendered images strongly depends on the method employed for discretizing the scene into patches. A too fine discretization may give rise to artifacts, while with a coarse discretization areas with high radiosity gradient may appear. To overcome these problems, the discretization must adapt to the scene. That is, the interaction between two patches must account for the distance between them as well as their surface area. In other words, surfaces far away are discretized less finely than nearby surfaces. These aspects are considered by the new adaptive discretiration method described in this paper. It performs both discretization and system resolution at each iteration of the shooting process, allowing then interactivity.

Browse

Browsing EG 1992 Conference Proceedings by Issue Date

Results Per Page

Sort Options