Geometric modeling: a survey

Computer programs are being developed to aid the design of physical systems ranging from individual mechanical parts to entire buildings or ships. These efforts highlight the importance of computer models of three dimensional objects. Issues and alternatives in geometric modelling are discussed and illustrated with comparisons of 11 existing modelling systems, in particular coherently-structured models of polyhedral solids where the faces may be either planar or curved. Four categories of representation are distinguished: data representations that store full, explicit shape information, definition languages with which the user can enter descriptions of shapes into the system, and which can constitute procedural representations, special subsets of the information produced by application programs, and conceptual models that define the logical structure of the data representation and/or definition language.