Volume 07 (1988)
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Item 3D Images of Molecular Properties by Triangulation of Contour Lines(Blackwell Publishing Ltd and the Eurographics Association, 1988) Roch, Michel; Weber, Jacques; Pellegrini, ChristianComputer programs have been developed to display molecular properties on a raster scan device, both as 2D colour-filled contour maps and as 3D solid models. Starting from 2D contour values calculated in parallel molecular grids, a triangulation algorithm, based on the connection of contours lying in successive planes, is applied for generating 3D solid models displayed with Gouraud shading. These methods of presentation have proved to be very useful for demonstrating the main features of chemical bonding and molecular reactivity.Item 7th EUROGRAPHICS UK Conference(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Adding Name Sets and Workstation Filters to GKS a Future Extension(Blackwell Publishing Ltd and the Eurographics Association, 1988) Bakkert, MienteItem Animation of Stochastic Model-Based 3-D Textures(Eurographics Association, 1988) Gagalowicz, Andre; Ma, Song D.We have previously shown the validity of a statistical model proposed by us for realistic textures. We have also shown how to use this model to map realistic textures onto a still surface of any shape and extent, maintaining consistency and scaling without producing repeating patterns.The problem we have to solve in this paper is how to use this statistical model in order to produce animated objects while keeping temporal consistency. This problem a priori difficult to solve as our mapping technique is statistical.We propose two different techniques. The first method called the image space method creates texture directly on the image planes. The second one called the object space method performs the texture synthesis on the object surface itself which has to be sampled finelly beforehand.Item Application Profiles for Computer Graphics Standards - A Touch of Realism(Eurographics Association, 1988) Mumford, Anne M.Computer graphics standards have become widely used and are now a fact of life. We have reached the stage of reviewing and extending the current standards. There is an important move within the user community which needs to be taken into consideration in these processes. This is the development of application profiles within user groups to make their use of the graphics standards easier and to ensure portability. This paper suggests that this move is important and cannot be ignored by users of standards or those involved with the current standards work.Item Architectures for Mass Market 3D Displays(Eurographics Association, 1988) Winser, Paul; Bonnet, Thierry; Dumont, Dominique; Mathieu, YvesWe discuss the specific architecture requirements of real time 3D display systems intended for low cost mass market products of the near future. Vertex transformation and polygon rendering are two processing aspects where hardware acceleration must be used to achieve the performance target. The use of one or more DSP chips as vertex processors is discussed, and two efficient z-buffer implementations described. Antialiasing and texture mapping greatly improve the visual impression at some processing cost.Item Architectures of Graphic Processors for Interactive 2D Graphics(Blackwell Publishing Ltd and the Eurographics Association, 1988) Fontenier, Guy; Gros, PascalInteractive 2-D systems have benefited greatly from the improvements in 1C technology. Today, the trend is to relieve the host computer from low level tasks through increasing the graphic system s computational power. The introduction of video RAMs has solved the problem of contention for memory cycles between the display generator and the video refresh controller. The improvements in graphic controllers have led from the first fixed instructions controllers to today s third generation of programmable graphic processors, able to support computer graphic interface standards. This article will present this evolution, and focus on a 2-D graphic processor designed at the Imagery, Instrumentation and Systems Laboratory, based on the separation of graphic generation and memory management functions.Item Automatic Detection of Closed Parametric Surfaces without Interior(Eurographics Association, 1988) Seidel, Hans-PeterThis paper presents an algorithm for the automatic detection of closed piecewise parametric surfaces without any inside or outside, e.g. a Klein bottle. The algorithm is able to decide whether a given closed surface is orientable or not. If non-orientable, the surface will not divide Euclidean 3-space into two halves. Therefore a non-orientable surface can never serve as the boundary of a solid object. The algorithm is based on results from algebraic topology and thus avoids the computation of derivatives and normal vectors. Several applications of the algorithm to rational tensor product B-spline surfaces are given.Item Book Reviews(Blackwell Publishing Ltd and the Eurographics Association, 1988) Owen, J.F.R.A.Hopgood, D.A.Duce, J.R.Gallop, D. Csutcliffe Introduction to the Graphical Kernel System (GKS)G.Enderle, K.Kansy, G.Pfaff Computer Graphics Programming.Reviewer: Ken Brodlie Department of Computer Studies University of LeedsItem Book Reviews(Blackwell Publishing Ltd and the Eurographics Association, 1988) Owen, J.Title: CGM and CGI: Metafile and Interface Standards for Computer GraphicsTitle: Computer Graphics: Systems and ConceptsTitle: Computer Graphics and Geometric Modeling Using Beta-splinesItem Boundary to Constructive Solid Geometry: A Step Towards 3D Conversion(Eurographics Association, 1988) Juan, R.Several solid representation schemes exist today in solid modeling. As none of them has properties that are uniformly better than any other, the need for modeling systems working on two or more different schemes which perform every operation in the most suitable scheme, became evident. Then it is necessary to provide geometric modeling systems with the ability of converting from one scheme into another scheme. As most solid modellers use either, a boundary representation (BR) or a constructive solid geometry representation (CSG), conversion from one into the other appears to be of capital importance. Conversion from CSG into BR has been carefully studied but a few attention has been deserved to the conversion from BR to CSG. This paper presents an algorithm which generates CSG binary trees from BR representations over a restricted class of polyhedra. The tree is optimal in the output size. Unfortunately, the algorithm does not in general warrant a correct conversion and, consequently some open questions and ideas for further research are presented.Item The Calculus of the Non-Exact Perspective Projection - Scene-Shifting for Computer Animation(Eurographics Association, 1988) Hofmann, Georg RainerThis paper shows the principle way to apply the, scene-shiftin technique of the classical film to computer animation. calculus is presented which is a modification of the well-known classical calculus of the perspective projection. However,, a given perspective view (which may be a frame in a computer animated film) of a three-dunensiona! scene does not change homogenous1 when the position of the viewer (i.e. the eyepoint, the location of the camera ... ) changes. So the subject of this paper is to ask for these parts of the frame with only little changes within a tolerance E. Based on the theorems of the presented calculus, a computer animated film as a sequence of single frames may no longer be computed frame by frame, one frame independent from another, and every frame passing through the whole visualization pipeline of the rendering system. In any frame, parts of the preceeding frame may be inserted, if necessary with two-dimensional modifications: scaling, shifting. This will decrease the computing costs for that frame significantly, since for these arts of the frame no new perspective transformahon and rendering is required. It is a shortening of the visualization pipeline. For the sake of the compactness of this paper we will give no detailed proofs of the theorems presented in here. The interested readers may obtain these information directly from the author.Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item CALL FOR PAPERS AND EARLY REGISTRATION(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Colour Raster Operations(Blackwell Publishing Ltd and the Eurographics Association, 1988) Willis, P. J.; Walters, G. W.We propose a form of three-input BitBlt/RasterOp which is useful for pictures constructed in a colour-mapped form as well as in true colour. The model used for this is that of a piece of potentially multicoloured paper on which the picture appears as ink marks. Computationally simple range testing operations can be applied to the source and destination regions to produce many useful effects, some of which we demonstrate. The resulting operations are primitives which can be used to construct more complex operations.Item COLOUR SECTION(Eurographics Association, 1988) VariousItem A Compositional Semantics for Graphics(Eurographics Association, 1988) Pineda, Luis A.In this paper a theory for developing "intelligent" interactive graphic systems is detailed. The Fregean compositionality principle is enunciated for graphical representations. Geometrical symbols and relations receive semantic interpretations which are expressed as first order relations in the first order logical language. These interpretations are introduced with the help of deictic expressions. Deictic expressions constitute one associative mechanism between analogical representational systems used in graphics, and functional representational systems commonly used in AI applications. Interpretations of graphical symbols and geometrical relations between them constitute an ontology upon which complex linguistic interpretations are assigned to graphics. A concept of graphical grammar is introduced. Frege's compositionality principle, and the notion of graphical grammar lead to a concept of meaningful drawing. The graphical grammar constitutes a second associative mechanism between the two representational systems that have been mentioned. The truth conditions for relations in the graphical grammar are computed through geometrical knowledge. Computational geometry algorithms are associated with the high level representational system by means of the graphical grammar. Semantic interpretations of graphics are useful in carrying out natural language-like dialogue about graphical representations. Dialogues refer to true facts in particular interactive states, A notion of interactive state as a function of time and situation is then developed. One example of how this theory can be used in linking interactive graphics with AI applications is given. In the example, the semantic interpretation of a geographical map is constructed. This theory has been tested with an experimental program called GRAFLOG. The program is implemented in PROLOG and GKS.