Issue 4

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https://diglib.eg.org/handle/10.2312/63

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    Recovering a Smooth Boundary Representation from an Edge Quadtree and from a Face Octree
    (Blackwell Science Ltd and the Eurographics Association, 1994) Pla-Garcia, N.
    The Face Octrees are a representation scheme which is very suitable to represent both smooth free form surfaces and solids with smooth boundary, as well as, to perform operations among them. However, the Face Octree representation is non continuous, thus an algorithm to convert this model to a boundary representation can be necessary. The conversion algorithm makes the advantages of this scheme really significant. The current paper is involved in the conversion from the Face Octrees model to a smooth boundary representation. However, first the planar case is treated.
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    Animation using NURBS
    (Blackwell Science Ltd and the Eurographics Association, 1994) Preston, M.; Hewitt, W. T.
    All animation, whether generated by pen or processor, is concerned with the changing behaviour of synthetic actors through time. Computer animation has allowed an animator to regard different actors as functionally equivalent entities for the purpose of generating their behaviours. This has opened the door to visually impressive effects, such as actors changing their appearance, thereby becoming other actors.For NURBS to become a tool which is useful to the writer of animation packages, it is necessary to provide this ability to in-between objects of different appearances through time.This paper aims to present a technique for creating higher dimensional NURBS to model object deformation, as well as to illustrate its advantages.
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    Ray Traversal of Spatial Structures
    (Blackwell Science Ltd and the Eurographics Association, 1994) Kuzmin, Yevgeniy P.
    This article presents an efficient algorithm for ray traversal of uniform and hierarchical spatial structures. Only simple integer and logical operations are used. The problem of error accumulation during ray casting is considered. The algorithm is well suited for efficient software and hardware implementation.
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    Animations to Represent Multivariate Data
    (Blackwell Science Ltd and the Eurographics Association, 1994) Palamidese, P.; Crise, A.
    Building animations is a current practice to study problems in the computational and experimental sciences. There are several classes of applications which generate descriptions of complex phenomena, based on a large variety of variables. In this paper, we discuss the application of traditional animation techniques, such as interpolation and kinematics animation, and of visualization techniques, like mapping, to the production of animation of multivariate data. Some examples of animation are illustrated from simulated bio-physical models of a sea basin.
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    An All-integer Algorithm for Drawing Anti-aliased Straight Lines
    (Blackwell Science Ltd and the Eurographics Association, 1994) Kui, Liu Yong
    An algorithm for drawing anti-aliased straight lines based on Bresenharn sline algorithm is presented in this paper. Only integer calculations are required. Multiplications or divisions are not needed (only simple addition/subtraction and sign testing are used). The algorithm can be used to choose between 2n intermediate grey levels between black and white.
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    Deriving Spectral, Reflectance Functions of Computer-Simulated Object Colours
    (Blackwell Science Ltd and the Eurographics Association, 1994) Schettini, R.
    A method is presented which, given the RGB values of a colour stimulus displayed on a given cathode ray tube (to which a CIE XYZ triple corresponds), makes it possible to find a spectral reflectance function characterizing an object colour. Such an object when"illuminated" by a given illuminant produces a metameric spectral power distribution, that is, one with the same XYZ tristimulus values. The method is useful in the colorimetric matching of colours on different media or supports.
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    Computation of Offset Curves by the Huygens Principle
    (Blackwell Science Ltd and the Eurographics Association, 1994) Mikheev, A.; Nozik, M.; Rubinstein, J.
    A new algorithm for computing offset curves is proposed. The algorithm is based on the Huygens principle for propagating wave-fronts. It automatically avoids the topological singularities that appear in conventional methods. The algorithm is simple to implement and it does not require any multiplication or other floating number operations.
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    The Design and Specification of a Visual Language: An Example for Customising Geographic Information Systems Functionalities
    (Blackwell Science Ltd and the Eurographics Association, 1994) Paterna , F.; Campari, I.; Scopigno, R.
    In this paper the design of a visual program editor and its specification using formal grammars are discussed. We consider an environment to specify, analyse and execute visual programs for a Geographical Information System (GIS). The lack of sophisticated user interfaces is one of the major drawbacks to Geographical Information Systems, particularly for people without a sound background in computer science. The use of a visual language approach is useful in order to hide the plethora of basic GIS functions, while providing ready- to-use tools to solve users tasks. The visual environment provides users with higher level interfaces- it is based on the module concept, which is conceived as a software building block that implements a solution to a general basic task and is presented to the user through an interactive frame. Complex GIS queries can be carried out by interconnecting modules into flow networks, using a direct manipulation approach.