Issue 2

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    Survey of Continuities of Curves and Surfaces
    (Blackwell Science Ltd and the Eurographics Association, 1992) Veltkamp, Remco C.
    This survey presents an overview to various types of continuity of curves and surfaces, in particular parametric (Cn), visual or geometric (Cn, Gn), Frenet frame (Fn), and tangent surface continuity (Tn), and discusses the relation with curve and surface modeling, visibility of (dis) continuities, and graphics rendering algorithms. It is the purpose of this paper to provide an overview of types of continuity, and to put many terms and definitions on a common footing in order to give an understanding of the subject.1991 Computing Reviews Classification:I.3.5 [Computer Graphics] Computational geometry and object modeling.I.3.7 [Computer Graphics] Three-Dimensional Graphics and Realism.
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    Ray Coherence Between a Sphere and a Convex Polyhedron
    (Blackwell Science Ltd and the Eurographics Association, 1992) Horvath, Tamas; Marton, Gabor; Risztics, Peter; Szirmay-Kalos, Laszlo
    Using the two ray coherence theorems of Ohta and Maekawa the computation time of ray tracing algorithms for scenes of spheres and convex polyhedra can be reduced considerably. This paper presents further theorems which, together with the first two, may enable further reduction in computation time.
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    User Interface Management Systems for Engineering Applications
    (Blackwell Science Ltd and the Eurographics Association, 1992) Sastry, Lakshmi
    Essential features of a User Interface Management System (UIMS) from the perspective of engineering applications user interface development are described. Three commercially available UIMS are validated against this set of essential features and the results of such a categorised evaluation are reported. The proliferation of user interface design tools necessitated an initialfiltering to select these tools on the basis of their availability on a wide range of platforms currently used by engineers, supplier support for the product and the prototyping tools the UIMS offer. Graphic Modelling System (GMS), TeleUSE and USEIT were selected for their potential utility to engineering applications.An earlier version of this paper was presented at the 1991 European X User Group Annual Conference held at Queens College, Cambridge, UK.This comparative evaluation is compiled on behalf of the UK Science and Engineering Research Council, for the benefit of the UK academic engineering research community.
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    Integer de Casteljau Algorithm for Rasterizing NURBS Curves
    (Blackwell Science Ltd and the Eurographics Association, 1992) Anantakrishnan, Narayanan; Piegl, Les A.
    An integer version of the well-known de Casteljau algorithm of NURBS curves is presented here. The algorithm is used to render NURBS curves of any degree on a raster device by turning on pixels that are closest to the curve. The approximation is independent of the parametrization, that is, it is independent of the weights used. The algorithm works entirely in the screen coordinate system and produces smooth rendering of curves without oversampling. Because of the integer arithmetic used, the algorithm is easily cast in hardware.
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    PHIFI: A PHIGS Interactive System for the Visualization of Scalar and Vector Fields
    (Blackwell Science Ltd and the Eurographics Association, 1992) Ascani, Fabrizio; Moltedo, Laura
    This paper describes the characteristics of PHIFI, an interactive system for the visualization of scalar and vector fields. PHIFI has been developed at the IAC where applications of the system have also been investigated.
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    A Statistical Comparison of Two Hidden Surface Techniques: the Scan-line and Z-buffer Algorithms
    (Blackwell Science Ltd and the Eurographics Association, 1992) Slater, Mel; Drake, Kieron; Davison, Allan; Kordakis, Emmanouell and Billyard, Adam and Miranda, Eliot
    This paper compares two image space hidden surface removal algorithms for polygonal scenes. These are the z-buffer and scan-line algorithms. There is first an overview of each algorithm, followed by a simulation experiment, designed to compare the number of polygons per second which can be rendered by each algorithm. The simulation varies the number of polygons in the scene, and the size and distribution of polygons over the display. The results suggest that the z-buffer is preferred for a large enough number of polygons, however, smaller polygons and uniform distribution of polygons favour the scan-line approach. The analysis does not take into account the complexity of the shading rule, which is likely also to favour the scan-line method.