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Computer Graphics and Applications, IEEE

Issue 5 • Date Sept. 1989

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Displaying Results 1 - 7 of 7
  • Optimal tubes [spacecraft modelling]

    Publication Year: 1989 , Page(s): 8 - 13
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    A technique devised to cut down the number of polygons required to model and render the Voyager spacecraft is presented. It requires the solution of a simple geometric problem: find the tangent lines from a point to a circle. He describes two ways of solving this problem, one using conventional analytical geometry and the other using homogeneous coordinates. The latter provides some useful generality.<> View full abstract»

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  • Computer graphics for cellular reconstruction

    Publication Year: 1989 , Page(s): 16 - 23
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (750 KB)  

    The use of computer graphics to study the three-dimensional structure of tissues within an organism such as a human is considered. A system called Sterecon, which uses stereo views of thick sections of tissues and a high-voltage electron microscope, is described. Contours of structures are traced in stereo and entered into a graphics database. Using thick sections decreases the work by ten- to twenty-fold. The database can be manipulated to display cellular organization using various graphics representations.<> View full abstract»

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  • An object-oriented approach to the solid modeling of empirical data

    Publication Year: 1989 , Page(s): 24 - 35
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (998 KB)  

    An object-oriented approach to the construction, manipulation, and display of complex geometric models of oil reservoirs is described. The authors have extended the traditional constructive solid geometry modeling techniques to accommodate the requirements for reservoir models. Both the user interface and the model building are implemented in Strobe, an object-oriented extension to Interlisp. The geometric model is specified through a CSG-graph editor built using an object-oriented toolkit for graphical interfaces. This editor proves to be an invaluable tool with which to build, maintain and manipulate large, complicated geometric models.<> View full abstract»

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  • Cartographic name placement with Prolog

    Publication Year: 1989 , Page(s): 36 - 47
    Cited by:  Papers (1)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (972 KB)  

    A major problem in computer cartography is how to place names on maps so they are clearly associated with the features they annotate, while avoiding overlap with other names and features. The logic programming language, Prolog, can be used to express the name-placement problem as a set of rules, referring primarily to the identification of free space, the generation of trial label positions, and the resolution of conflict between these positions. Cartographic features can be specified either explicitly as facts in the Prolog database or implicitly by presenting Prolog with the results of a prior analysis of potential label positions. The Prolog inference mechanism can then determine whether there is a combination of label positions that satisfies the rules of placement.<> View full abstract»

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  • A menagerie of rational B-spline circles

    Publication Year: 1989 , Page(s): 48 - 56
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (519 KB)  

    The article was motivated by J. Blinn's column on the many ways to draw a circle (see ibid., vol.7, no.8, p.39-44, 1987). The authors have found several other ways to represent the circle as a nonuniform rational B-spline curve, which they present. Square-based methods, infinite control points, triangle-based methods, general circular arcs and rational cubic circles are some of the methods and types of circle discussed.<> View full abstract»

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  • Geometric data transfer between CAD systems: solid models

    Publication Year: 1989 , Page(s): 57 - 71
    Cited by:  Papers (1)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1312 KB)  

    The first phase of the ESPRIT project CAD*I resulted in a specification for the exchange of solid models as well as in some pilot implementations of processors based on this specification. The authors summarize the CAD*I approach, addressing the structure of neutral files for solids, entities, and attributes supporting three kinds of representations: facilities for the transfer of parametric designs; referencing library components; and other general mechanisms. They also describe the current state of the specification and processor implementations and include an example of a CAD*I neutral file. Results from cycle and intersystem solid model transfer tests are presented, showing the practicality of the CAD*I proposal. B-rep model transfer results are discussed in some detail. The relationship of this work to standardization efforts is outlined.<> View full abstract»

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  • Architectural issues in solid modelers

    Publication Year: 1989 , Page(s): 72 - 87
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1310 KB)  

    Several issues related to solid modeling are examined. Fundamental background definitions and concepts are presented, concentrating especially on dual-representation solid-modeling environments. An ideal architecture is hypothesized and it is shown that the current state of the art leads to one of two compromise architectures in practice. Also studied are lower level development strategies, including schemes that trade-off, to varying extents, the goal of minimizing flexibility in geometric forms as provided to the designer. The need for software architectures that promote development of application functions has led to the development of standard modeling-system interfaces at the procedure call level. Several open issues are identified. Some prevent the complete realization of the ideal architectures, whereas others arise as areas potentially benefiting from a flexible dual-representation environment.<> View full abstract»

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IEEE Computer Graphics and Applications bridges the theory and practice of computer graphics.

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Editor-in-Chief
L. Miguel Encarnação
University of Iowa