Volume 06 (1987)

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3D Models in Computer-Assisted Chemistry
(Eurographics Association, 1987) Roch, Michel; Cretegny, Isabelle; Weber, Jacques
Novel and efficient algorithms have been developed in order to display on a raster scan device some basic 3D models used in computer-assisted chemistry. They allow, among other things, the construction and manipulation of the geometrical structure, or shape, of chemical species containing several hundreds of atoms, both as simple skeleted and sophisticated 3D space filling models with Gouraud shading and hiddensurface treatment. In addition, the technique of image storing is used in order to simultaneously display the molecular model and both 2D (colorfilled contour levels) and 3D (solid model) representations of chemical properties of the compound. The images thus generated allow an immediate perception of the major features of the species under study, which provides the chemist with an invaluable tool in computer-assisted chemistry. Some simple examples, which illustrate the potential of these 3D models for discussing chemical reactivity, are presented. Finally, the algorithms and procedures used for constructing the 3D images are briefly described and discussed. *Correspondence address: Dr J. Weber, Laboratory of Computational Chemistry, University of Geneva, 30 quai Ernest Ansermet, 1211 Geneva 4, Switzerland
6th EUROGRAPHICS UK Conference
(Blackwell Publishing Ltd and the Eurographics Association, 1987)
ACM SIGGRAPH 86, Dallas, Texas, 18-22 August
(Blackwell Publishing Ltd and the Eurographics Association, 1987) Robinson, K.
Active-Ray Tracing for 3D Medical Imaging
(Eurographics Association, 1987) Trousset, Yves; Schmitt, Francis
Large quantities of three-dimensional (3D) information are produced by 3D medical imaging techniques such as CT and MRI, in the form of digital volumes (DV). We propose a new approach to help a human observer to visualize these volumes. This approach is based on the idea that, in order to achieve true user-interaction, segmentation and visualization should not be treated separately. This is achieved by introducing active ray tracing, a method inspired by ray tracing but working directely on unsegmented digital volumes. Segmentation takes place as the active rays penetrate through the volume.
ADA? and NIL: Two Concurrent Languages for GKS
(Blackwell Publishing Ltd and the Eurographics Association, 1987) Milanese, V.
The Graphical Kernel System (GKS) has become an international standard in graphics programming and attempts are now being made to integrate it with multiprocessing, possibly in distributed systems. It is therefore necessary to consider new programming languages able to support distributed implementations of GKS. Among them, Ada and Nil are considered here, since they are particularly suitable for concurrent programming. They are compared and evaluated in those specific tools which may provide data safety, system reconfigurability, and availability to distributed programming. The structural philosophies of the two languages are emphasized and reconfigurable implementation schemata for GKS in both of them are then suggested.
An Algorithm for 3D Scan-Conversion of Polygons
(Eurographics Association, 1987) Kaufman, Arie
A three-dimensional (3D) scan-conversion algorithm, that scanconverts 3D planar polygons into their discrete voxel-map representation within a Cubic Frame Buffer (CFB), is presented. The algorithm, which is a variation of a 2D scan-line filling algorithm, is incremental and uses only simple operations like additions and testy inside the inner loops. The algorithm performs scan-conversion with computational complexity which is linear in the number of voxels written to the CFB. The paper also presents an algorithm that scan-converts polygons clipped to the CFB boundaries with no added time complexity. An all-integer decision mechanism which makes the inner-most loop of the algorithm more efficient is discussed too. All the algorithms guarantee lack of 6-connected "tunnels" in the converted polygons. The algorithms have been implemented as part of the 3D geometry processor of the CUBE Architecture, which is a voxel-based system for 3D graphics. These algorithms allow the' CUBE system to generate the essential primitive polygon within the CFB from a 3D geometric model.
Annual General Meeting of the Spanish Chapter of EUROGRAPHICS
(Blackwell Publishing Ltd and the Eurographics Association, 1987)
An Approach to the Formal Specification of Configurable Models of Graphics Systems
(Eurographics Association, 1987) Arnold, D.B.; Duce, D.A.; Reynolds, G.J
This paper describes a general framework for the formal specification of modular graphics systems. The approach is illustrated by an example taken from the Graphical Kernel System (GKS) and uses the Z specification notation.
Arbitrary Rotation of Raster Images with SIMD Machine Architectures
(Blackwell Publishing Ltd and the Eurographics Association, 1987) Arabnia, H.R.; Oliver, M.A.
An algorithm for the rotation of a raster image by an arbitrary angle is described. The image data structure is closely related to runlength code. The algorithm has been designed to exploit SIMD parallel architectures. It has been implemented on an ICL DAP on which non trivial images can be rotated in times very close to real time.
An Automatic Interpolation Method of Grayvalued Images Utilizing Density Contour Lines
(Eurographics Association, 1987) Agui, Takeshi; Saito, Minoru; Nakajima, Masayuki; Arai, Yukihiro
This paper presents an automatic method of interpolation or inbetweening for gray valued images, which have been difficult to be processed automatically. The method consists of three parts. The first i s the extraction of density contour lines from a pair of gray valued key frame images, the second i s the interpolation of the contour lines and the l a s t is the generation of in-between gray valued images. In the second part, the correlation of corresponding contour lines of the key frames i s carried out automatically utilizing some kinds of similarity functions. The method is applied to a pair of pictures of a plaster head photographed slightly different directions and generates a very smooth rotating animation picture of the p l a s t e r head. This method has much applicability to computer animation and motion picture analysis. Stereo pair images are available from key frame pictures of objects photographed from any direction. Interpolation of color images is also possible.
Bezier Patches with Local Shape Control Parameters
(Eurographics Association, 1987) Schmitt, Francis J. M.; Du, Wen-Hui
In this paper, we introduce three types of shape control parmeters (tension, bias, and continuity) into the modelling of free-form surfaces composed of bicubic Bernstein-Bezier patches. This is an extension to surfaces of the three control parameters introduced in the local interpolatory spline curves by Kochanck and Bartels [12]. We first analyze the general conditions for guaranteeing the G' continuity of the surface at corners where three, four, or five patches meet. The analysis of the continuity constraints reveals the remaining degrees of freedom which can be exploited for the control of the surface shape. The shape control parameters arc then introduced. Experimental results are provided. They show the efficiency of these parameters for an easy and intuitive control of the surface shape.
Book Reviews
(Blackwell Publishing Ltd and the Eurographics Association, 1987)
Book reviewed in this article:Author:EncarncaTao, J.L. Title: CAD-Handbuch, Auswahl d Einsatz von CAD-Systemen (CAD manual, selection and introduction of CAD systems)Author. EncarncaTo, J., Schuster, R. and Voge, E. (eds.) Title: Product data interfaces in CAD/CAM applicatoonsAuthor htt, M.J., Goult, RJ. and Chinnery, M J. Title: Comparison and translation of surface representations within CADCAM systems
Calendar of Events
(Blackwell Publishing Ltd and the Eurographics Association, 1987)
Calendar of Events
(Blackwell Publishing Ltd and the Eurographics Association, 1987)
Calendar of Events
(Blackwell Publishing Ltd and the Eurographics Association, 1987)
Calendar of Events
(Blackwell Publishing Ltd and the Eurographics Association, 1987)
Call for participation
(Blackwell Publishing Ltd and the Eurographics Association, 1987)
THE CGM - A METAFILE FOR GKS?
(Blackwell Publishing Ltd and the Eurographics Association, 1987) Brodlie, Ken; Henderson, Lofton; Mumford, Anne
The Clockworks: An Object-Oriented Computer Animation System
(Eurographics Association, 1987) Breen, David E.; Getto, Phillip H.; Apodaca, Anthony A.; Schmidt, Daniel G.; Sarachan, Brion D.
The Clockworks is an object-oriented computer animation system developed at RPl's Center for Interactive Computer Graphics (CICG). The Clockworks has the ability to model and graphically simulate complex 3-D engineering processes, Its interactive capabilities also allow it be used as a design tool. Object-oriented concepts have been utilized in developing its high level architecture and its low level implementation. The Clockworks is defined as a collection of objects which communicate with the user and each other via messages. The actual implementation involved the creation of an object-oriented programming methodology using C and Unix. The complete system provides a rich research environment for exploring modelling, scripting and rendering. It also provides an interactive environment for design and a simulation environment for visual analysis of complex interacting structures.
COLOUR SECTION
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