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Über dieses Buch

This fourth volume of Advances in Computer Graphics gathers together a selection of the tutorials presented at the EUROGRAPHICS annual conference in Nice, France, Septem­ ber 1988. The six contributions cover various disciplines in Computer Graphics, giving either an in-depth view of a specific topic or an updated overview of a large area. Chapter 1, Object-oriented Computer Graphics, introduces the concepts of object ori­ ented programming and shows how they can be applied in different fields of Computer Graphics, such as modelling, animation and user interface design. Finally, it provides an extensive bibliography for those who want to know more about this fast growing subject. Chapter 2, Projective Geometry and Computer Graphics, is a detailed presentation of the mathematics of projective geometry, which serves as the mathematical background for all graphic packages, including GKS, GKS-3D and PRIGS. This useful paper gives in a single document information formerly scattered throughout the literature and can be used as a reference for those who have to implement graphics and CAD systems. Chapter 3, GKS-3D and PHIGS: Theory and Practice, describes both standards for 3D graphics, and shows how each of them is better adapted in different typical applications. It provides answers to those who have to choose a basic 3D graphics library for their developments, or to people who have to define their future policy for graphics.



1. Object-Oriented Computer Graphics

Object-orientation and computer graphics from a natural, if occasionally uneasy alliance. Tenets of object-orientation, such as data abstraction, instantiation, inheritance, and concurrency, also appear in the design and implementation of graphics design. We explore the relationship between object-orientation and computer graphics, and consider the structuring of various kinds of graphics systems in an object-oriented manner.
Eugene Fiume

2. Projective Geometry and Computer Graphics

Projective geometry is the basic mathematical tool to visualize three dimensional objects on a two dimensional surface. As a consequence, it is also the mathematical background for the output pipeline of all three dimensional graphics packages, whether this is explicitly stated or not (usually not). This chapter tries to present some of these mathematical tools to give a deeper insight into these systems, and, at the same time, to assist in the creation of new algorithms and methods to improve them or to elaborate new ones.
Ivan Herman

3. GKS-3D and PHIGS — Theory and Practice

Since this tutorial was presented both GKS-3D and PHIGS have become international standards. PHIGS PLUS extends PHIGS to include lighting and shading capabilities. This chapter examines these systems and looks at some simple applications. In practice, PHIGS can be quite difficult to use — a fact which is not apparent until one actually tries to do something with it. For many applications, GKS-3D would be a better choice, unless lighting and shading are necessary. It seems, however, that many manufacturers are ignoring GKS-3D and are only supporting PHIGS for 3D applications. The chapter concludes with advice and information about implementations.
Roger Hubbold, Terry Hewitt

4. Special Modelling

Texture modelling and synthesis are first studied in a general framework. Models for planar black and white textures are extensively studied. This work is then generalized to the colour case and to textures lying on 3D surfaces.
Graftals may simulate various plants and trees. They are based upon the use of parallel rewriting grammars. Various fractal synthesis techniques are described next. A particular interest is given to Barnsley’s IFS (integrated function system) model. Particle systems of W Reeves simulate beautifully fires, plants and trees. Solid texturing is a new possibility to produce textured objects. A solid texture block is sculptured in order to obtain the desired object contour. We present the most striking applications of this technique by Perlin to the design of marble, glass objects, fires and bubbles, and for clouds by Gardner. Botanistic models of the French botanist De Reffye who discovered a model available for most types of trees and for their growth, are implemented by various French researchers from the AMAP group. Planar graphs of Lienhardt and Françon are used to model leaves and flowers grown more geometrically.
This tutorial is dedicated mainly to advanced users and developers, and presents some non-standard techniques tractable to present particular objects (trees, plants etc...) and the texture of their surface.
André Gagalowicz

5. Developments in Ray-Tracing

After a brief recall of the basic principles of ray-tracing, the traditional and distributed approaches will be presented with the related illumination models. This will include an introduction to relevant topics such as photometry and optics, Monte-Carlo integration, stochastic sampling and a discussion on implementation issues. Then, the fundamental problem of ray object intersection will be tackled. First, intersection algorithms for various type of objects will be described including simple objects (solid primitives, polygons,...) as well as more complex objects (bicubic patches, fractals, CSG modelled object,...). Then, after a discussion on bounding volumes, the case of large and complex collections of primitives is considered by examining the two basic classes of organizing structure (i.e. hierarchical data structure and space-partitioning) and their related traversal algorithms. Eventually, the parallel processing issue will be discussed.
Christian Bouville, Kadi Bouatouch

6. Rendering Techniques

This tutorial will provide a general overview of the traditional rendering process and both the theory and application of the most common techniques in use today. We will describe the basic stages of traditional rendering along with techniques commonly used to obtain more realistic images. Topics covered will include geometric transformations, visible surface determination, sampling and filtering, shading, mapping techniques, shadow generation, motion blur and atmospheric and other special effects. In addition, a number of examples and case studies will be used to illustrate specific problems and their solutions. Finally, methods and systems which allow the user to obtain maximal rendering capabilities will be discussed and illustrated.
Tom Nadas, Armand Fellous


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