Volume 07 (1988)
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Item Offers to EUROGRAPHICS Members(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Fourth Eurographics Workshop on Graphics Hardware(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Tools for Efficient Photo-Realistic Computer Animation(Eurographics Association, 1988) Stößer, Achim; Schmitt, Alfred; Neidecker, Burkhard; Müller, Heinrich; Maus, Thomas; Leister, WolfgangThe goal of the project “Occursus Cum Novo” was to generate a complex photo-realistic animation of nontrivial length in reasonable time at reasonable cost. Photographic realism comprises complex geometric models as well as the implementation of several optical effects. Both can be achieved by simulation. Simulations guaranteeing high quality, as ray tracing does for rendering, are known to be very time consuming. They require the design of powerful data structures and algorithms taking the abilities of todays hardware into account. The first part of this paper is devoted to rendering, here carried out by the raytracing method. An organizing scheme for a network of work stations is described which enabled us to generate 5-minutes of raytraced animation within 2 months without affecting any regular user of the work stations. The second part is devoted to the simulative modeling tools applied in “Occursus Cum Novo”. The recursive generator WAXI and a motion simulator METAMORPHOSIS are described to some detail. The results of the project are of general interest since they show a way leading to efficient high quality photo-realistic animation synthesis in the future.Item 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 HCI International 89 Third International Conference on Human-Computer Interaction(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item EUROGRAPHICS General Assembly(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item 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 7th EUROGRAPHICS UK Conference(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Offers to EUROGRAPHICS Members(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Fast Algorithm for Polygon Clipping with 3D Windows(Eurographics Association, 1988) Burkert, Andreas; Noll, StefanMany applications which use 3D graphics, need 3D geometric modeling and hence polygon clipping against 3D Windows or general volumes. The disadvantages of existing clipping algorithms are that they are 2D, slow or produce incorrect results. This paper describes a new 3D clipping algorithm for concave polygons with one contour. The new algorithm is an extension to the algorithm of Liang and Barsky: The necessary condition for the appearance of a corner of the clipping rectangle in the output polygon is replaced by a necessary and sufficient condition and then extended to the three dimensional case. Another advantage of the presented algorithm is the the removal of degenerated edges. The algorithm is useful for implementing the draft international standards GKS-3D and PHIGS and also for 3D Window Systems.Item Guidelines for Determining When to Use GKS and When to Use PHIGS(Blackwell Publishing Ltd and the Eurographics Association, 1988) Bettels, Jurgen; Bono, Peter R.; McGinnis, Eileen; Rix, JoachimGKS, GKS-3D, and PHIGS are all approved ISO standards for the application programmer interface. How does a system analyst or programmer decide which standard to use for his application? This paper discusses the range of application requirements likely to be encountered, explores the suitability of GKS and PHIGS for satisfying these requirements, and offers guidelines to aid in the decision process.Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item IXPHIGS: A Portable Implementation of the International PHIGS Standard(Eurographics Association, 1988) Gorog, Jenö; Krammer, Gergely; Vincze, ArpadThis paper describes a "portable" object-oriented implementation of the international standard PHIGS. A rapid prototype has been achieved by making use of earlier developments : the IX-CGI module for graphical input, output and interaction and IX-TAM for the creation of and access to objects of different classes, and thus the creation, manipulation and traversal of graph structures with different classes of leaf objects, The “post” function of PHIGS by definition is applied to structure node objects. For each node, it goes. through the element list of the node and, for each element in the list, it invoker the post function of the appropriate element class. Standard extensions are incorporated into this IX-POST module. The limited capabilities provided by the PHIGS input functions are enhanced by an additional interaction interface module IX-IF. A STRUCture e d i TOR program built on top of the PHIGS application interface serves not only as a demonstration of PHIGS capabilities but also as a turnkey program for the wide class of applicaticans with the task of creating and editing symbolic drawings. IXPHIGS is written in the language C and it is a "full software implementation" of all PHIGS capabilities, even for parts which may he enhanced later by using advanced hardware on some target configurations.Item Conic Beta-Splines with Local Tension Control for Interactive Curve Fitting(Eurographics Association, 1988) Pham, BinhPolynomial Beta-splines were introduced by Barsky as an extension of polynomial B-splines with bias and tension parameters which allow more flexibility in controlling shape in curve fitting. It is possible to show that a quadratic Beta-spline segment is equivalent to a quadratic B-spline segment with suitably modified control vertices. This provides a simple method for evaluating quadratic Beta-splines using De Boor's algorithm for calculating polynomial B-splines. A representation for conic Beta-splines with one tension parameter is introduced and some properties are derived. They form a basis for an efficient algorithm for interactive curve fitting with conic Beta-splines. The results are extended further to cover the case of conic Beta-splines with varying tension where the tension parameter is an interpolating function between the tension values at each end of a segment.Item Continuous Processing of Images through User Sketched Functional Blocks(Blackwell Publishing Ltd and the Eurographics Association, 1988) Kaya, Aydin; Ozguc, BulentItem Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1988)Item Construction of Interactive Programs in Computer Graphics(Blackwell Publishing Ltd and the Eurographics Association, 1988) Dufourd, Jean-FrancoisIn interactive computer graphics, one often finds a gap between sophisticated algorithms, using very high level data structures, and poor methods of program and object construction. Particular programming languages are too readily adopted for solving problems, before a precise specification of the problem to be solved has been formulated.This paper shows that progress can be made by using modern engineering methods to specify and develop graphical software. Two programming techniques are studied here: the algebraic specification of data types and a functional static modular method of problem statement.The paper also discusses these proposals in the context of other modes of computer graphics specification and programming.Item Generation of High-Quality Curve and Surface with Smoothly Varying Curvature(Eurographics Association, 1988) Higashi, Masatake; Kaneko, Kohji; Hosaka, MamoruA method for generating curves and surfaces which satisfy constraints of tangent directions and curvature at arbitrary points and which have smoothly varying curvature is introduced. The method is geometrical determination of a Bezier polygon, and quite different from conventional methods such as minimizing the integral of the square of curvature value or the second derivative. This method enables following things : generation of smooth curves by explicitly indicating the characteristic properties of the curves generation of smooth surfaces having not only smooth boundaries but also cross tangent and curvature which change smoothly along the boundary curve, high accurate approximation of intersection curves of surfaces, by satisfying a tangent direction, an osculating plane. and curvature constrained by the surface equations.Item Pseudo Ordering of CSG-Trees(Eurographics Association, 1988) Cottingham, Marion S.Using Constructive Solid Geometry (CSG) methods, it is usual for primitive object representations to be stored at the leaf nodes of binary trees. The major part of the work involved in generating an image of the object is finding what surface is visible at each pixel in the screen. Using conventional rendering methods this can be simplified by ordering the primitives by their screen positions and by their depths. Using ray tracing techniques this can be achieved by testing if rays intersect with primitives, the number of these intersection tests can be reduced by ordering. However it is not generally possible to order data (in any one direction) in CSG-trees where intersection or difference operators are involved. This paper describes a method that enables 'local' three-way ordering of the data contained in CSG-trees that can be used with either conventional scan-line rendering methods or ray tracing techniques. This is achieved by the introduction of underlying data structures that dynamically change throughout the image generation step. Using this method, the primitive/polygon visible at a particular pixel can usually be accessed directly via pointers.Item Report on the Third Eurographics Workshop on Graphics Hardware(Blackwell Publishing Ltd and the Eurographics Association, 1988) Blake, E.H.