EG1985 Proceedings (Technical Papers)

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GENERALIZATION OF CONTOUR TRACKING IN IMAGE SYNTHESIS, AND APPLICATION
(The Eurographics Association, 1985) Hegron, Gerard; C.E. Vandoni
In this report, we propose to present most of the treatments about convex and nonconvex colored shapes from a data structure of their contour which is the general approach of contour tracking . Contour filling and oblique cross-hatching take advantage of the coherence between adjacent scan lines and adjacent hatching lines. The position of a point with respect to a nonconvex polygon is solved from filling logic, and the clipping of a line segment by a nonconvex polygon uses the slant cross-hatching idea. We present the clipping of the two nonconvex polygon set. From the area filling of non polygonal blobs, contour tracking is generalized to three geometric problems : position of a point, clipping of a line segment and of a circular arc by a non-polygonal contour, Finally, we discuss the general advantages of contour tracking and application in the writing of a text in a nonconvex polygon.
TOWARDS OBJECT-ORIENTED GRAPHICS STANDARDS
(The Eurographics Association, 1985) Wisskirchen, Peter; C.E. Vandoni
The introduction of powerful object-oriented systems such as Smalltalk-80 and ZetaLisp Flavors offers a number of potential benefits to the field of computer graphics. This paper examines the potential for marrying object-oriented programming languages to emerging graphics kernel standards definitions. Examples of object-oriented hierarchies of graphics structures are provided, and modifications and extensions to kernel standards are suggested in order to both simplify the standards and more readily embrace the objectoriented approach.
NEM: A LANGUAGE FOR ANIMATION OF ACTORS AND OBJECTS
(The Eurographics Association, 1985) Marino, Giuseppe; Morasso, Pietro; Zaccaria, Renato; C.E. Vandoni
The animation of actors and objects is considered in the framework of knowledge representation, with particular regard to motor knowledge. In our opinion, a formal model for motor knowledge should fill a gap between action planning and low level computer animation graphics; such model should be able to "virtualize" the actor and the interaction with the environment so that the planner could produce (and rely on) high level abstract actions, characterized by high autonomy and naturality. The paper discusses some general aspects about actions, actors, and scenes, and finally describes the NEM language, for the representation and animation of humanoids in a scene, which is meant to provide a software laboratory for experimenting with action schemas.
TABLE LOOK-UP GRAPHlC INTERPOLAT ION
(The Eurographics Association, 1985) Alia, G.; Barsi, F.; Martinelli, E.; Tani, N.; C.E. Vandoni
In this paper a fast procedure is presented to fairly interpolate a given set of points, which is mainly based on the use of table look-up techniques. Storage amounts required can be easily supplied by present memories technology. Though our procedure can be applied to any interpolation method, it is well suited for a spline, using an angle as a parameter, which was defined by the authors in a previous paper. Benefits and limits of the procedure are discussed and several examples of its behaviour are given.
INTEGRATED GRAPHICS ENIVRONMENT EASES AVIONIC DISPLAY SOFTWARE DEVELOPMENT
(The Eurographics Association, 1985) BRATEL, Alain; CLAPIER, Christian; ETTER, Michel; C.E. Vandoni
An original methodology to develop real-time graphics software is presented. It will supply efficient software production for avionic display systems. The purpose is a complete specification, simulation and programming environment. The first available tool is ODISSEE, a computer aided design software for avionic symbologies including a graphics editor and a database manager. Although it is part of the avionic display integrated environment, ODISSEE is a portable graphics device independent and highly interactive general purpose software.
A CSG LIST PRIORITY HIDDEN SURFACE ALGORITHM
(The Eurographics Association, 1985) Jansen, F.W.; C.E. Vandoni
Several algorithms exist for visualizing geometric models defined by constructive solid geometry (CSG). Each of these algorithms is based on standard hidden surface methods, such as ray tracing, scan-line and z-buffer algorithms. In this paper a CSG list priority algorithm is described that is combined with a ray tracing algorithm in the use of a spatial subdivision technique and a CSG list structure to exploit CSG coherence. The combined algorithm is designed for interactive viewing and high quality rendering of CSG models with faceted primitives.
VIEWING SOLID MODELS BY BINTREE CONVERSION
(The Eurographics Association, 1985) Koistinen, Petri; Tamminen, Markku; Samet, Hanan; C.E. Vandoni
A hidden surface algorithm is presented for viewing constructive solid geometry representations of solids (CSG trees) by converting them implicitly into a 3-d recursive spatial subdivision (bintree). The algorithm prunes the CSG tree to its minimal representation within each bintree block and does not evaluate it in regions of space (bintree nodes) that are totally hidden to the observer.
A NORMAL-BUFFER VECTORIZED SURFACE SHADING MODEL
(The Eurographics Association, 1985) Curington, Ian J.; C.E. Vandoni
A surface rendering implementation is described that separates visibility operations from surface shading operations with a Normal-Buffer data structure. This allows for scene complexity independent shading operations at a fixed computational cost per frame. The Normal-Buffer approach also allows the implementation of a fully vectorized surface-shading algorithm when the shading model is applied to each pixel in the scene. The vectorized shader is described using an array processor with a directly attatched frame store in a high performance scene-generation system.
TOUCHSCREEN AND COMPUTER GRAPHICS IN A SCIENCE MUSEUM
(The Eurographics Association, 1985) Clerget, Yves; Cottrell, Vincent; Raoust, Michel; Withnell, Jean; C.E. Vandoni
Scientific information presented by a Science Museum must be both easily understood and easily memorized. Public interest must be maintained at a very high level during the presentation: interaction of the public with the message is greatly desirable. Computer techniques which mix user-friendly software, colour graphics and a touch-screen as the input device satisfy these requirements. This paper describes a scientific "game" designed to teach the player the sensitivity of architecture and climate in indoor comfort and energy consumption. It is based on a micro-computer, the IBM-PC, and a touch-screen and it uses colour graphics to convey information. The software benefits from a three-year experience at La Villette in the design of scientific exhibits for a large public. In this article the cost of software and hardware are mentioned.
AN IMPROVEMENT OF THE RAY-TRACING ALGORITHM
(The Eurographics Association, 1985) COQUILLART, Sabine; C.E. Vandoni
This paper describes an improvement of the ray-tracing algorithm. The new method takes advantage of a data structure which allows us to consider only the closest objects to the path of the ray. This technique can be applied to primary and secondary rays. Using this method, the run-time depends more on the complexity of the generated picture than on the complexity of the scene.
MULTI-DIMENSIONAL GRAPHICS
(The Eurographics Association, 1985) Inselberg, Alfred; C.E. Vandoni
DETERMINATION OF LOCAL COORDINATE SYSTEMS FOR TEXTURE SYNTHESIS ON 3-D SURFACES
(The Eurographics Association, 1985) MA, SONG DE; GAGALOWICZ, ANDRE; C.E. Vandoni
We propose and compare three types of local coordinate systems and describe their geometric properties Several results of texture synthesis on 3-D surfaces using these local coordinate systems are presented The synthesis procedure is driven by a texture model including only a small amount of statistical parameters
CREATING CSG MODELLED PICTURES FOR RAY-CASTING DISPLAY
(The Eurographics Association, 1985) CORDONNIER, E.; BOUVILLE, C.; DUBOIS, J.L.; MARCHAL, I.; C.E. Vandoni
30-picture synthesis systems used for instance in the audiovisual field or networked services require the implementation of easy-to-use aids to composition. This particular composition software realizes the sizing and locating of even complex CSG objects in a simple and direct manner. The Ray-casting method is used for display and designation.
BICEPS - THE INTERACTIVE GRAPHICS AIDED SYSTEM FOR BI-DIMENSIONAL GEOMETRY YODELING, NESTING AND FLAME CUTTING TECHNOLOGY
(The Eurographics Association, 1985) Kobvlinski, Wiktor J.; C.E. Vandoni
An essential condition for effective usage of numerically controlled devices is their correct and efficient programming. Especially in cutting applications every nesting layout requires a new control program tape. The BICEPS system referred here has been implemented in work shops with both: batch production - very stable one and simple part cutting in repair shops where every day new parts are manufactured. In both cases significant material savings (by narrow nesting) and reduction of production preparation time are obtained. The present paper deals with the very first step of production preparation process: modeling of the geometry of Bi-dimensional (2D) contours of Darts manufactured.
Graphics Programming with "Archetypes" - A Preliminary Study -
(The Eurographics Association, 1985) Martins, Fernando Mar io; Oliveira, Jose Nuno; C.E. Vandoni
This paper is a brief report on the initial phase of the formal development of a graphics programming system. At this stage of the specification, the system architecture is just outlined and attention is focussed on the conceptual level. The abstract notion of a graphic 'archetype' is introduced and proposed as a basis for the style of graphics programming to be implemented. The formal description of this meta-concept of the system is sketched.
AN INTERACTIVE RENDERING TECHNIQUE FOR 3-D SHAPES
(The Eurographics Association, 1985) KONDO, Kunio; KIMURA, Fumihiko; TAJIMA, Taro; C.E. Vandoni
This paper describes an interactive rendering technique for giving an impression of 3-D shapes. The following points are discussed : 1) The classification of continuous tone patterns 2) Methods of drawing pictures to enhance 3-D shapes 3) Rules of rendering for the representation of 3-D shapes. The following results are obtained: The use of the rendering rules and CARP facilitates the clear representation of these characteristics and is proved to be effective in creating a picture in which the shapes of bodies are clearly defined,
An illumination model for ray-tracing
(The Eurographics Association, 1985) MONTCEL, Bruno TEZENAS DU; NICOLAS, Alain; C.E. Vandoni
GKS Inquiry Functions within Prolog
(The Eurographics Association, 1985) Sykes, Pete; Krishnamurti, Ramesh; C.E. Vandoni
This paper discusses the semantics of the GKS inquiry functions within a Prolog environment and illustrates the flexibility built into a proposed Prolog binding.
GEOMETRIC MODELLING USING EXACT OCTREE REPRESENTATION OF POLYHEDRAL OBJECTS
(The Eurographics Association, 1985) Brunet, Pere; Navazo, Isabel; C.E. Vandoni
In the last few years, octrees have been proposed for the representation of solids in Geometric Modelling systems. Using them, boolean operations are simple; however, they use a great amount of memory and it is very difficult to obtain smooth graphical outputs from them or to recompute the boundary model. In the present paper, a new class of Octtrees is introduced, which allows face, edge and vertex nodes as well as the classical white, black and grey nodes. The required amount of storage is less than in the case of classical Octtrees, and boolean operations are also simple. Futhermore, there exists an algorithm for the exact recomputation of the boundary model.
PIPEMATIC: A DISTRIBUTED SYSTEM FOR THE DESIGN OF GEOMETRICALLY TIGHT PIPING STRUCTURES
(The Eurographics Association, 1985) Sulonen, Reijo; Tikkanen, Matti; C.E. Vandoni
The main principles of an interactive design system intended for the solution of 3D geometric placement problems are described. The first applications for the system will be related to the design of machine rooms in ships where a large number of geometric objects must be placed and connected together with appropriate piping structures. However, the system is application independent. The emphasis of this paper is on the systems structure, algorithmic problems are not dealt with. Implementation of the system is currently underway.

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