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Constraint based solid modelling with geometric features3. J. Zhang A. E. Middleditch R. S. LathamDepartment of Computer Science, Brunel UniversityUxbridge, Middlesex UB8 3PH, UKABSTRACTEngineering design practice usually follows a design hierarchy. Constraints more or less reflect engineeringrequirements. But constraints are practically useful only when they are correctly embedded into design hierarchies.The concept of geometric features is introduced to serve the following purposes: to allow a designer to work withthe conventional design hierarchy; to control the effect of constraints; and to decompose a complicated constraintbased geometric modelling problem into simpler ones. Geometric features are constructed hierarchically. Althoughconstraints are applied to low level geometric entities (points, lines, etc.), the impact on a design model is usuallyimposed on higher level features. In terms of constraints processing, each feature is viewed as an independentproblem and its constraints are solved independently. All constraints in a design model are therefore solvedhierarchically bottom up.Key words: Solid modelling, geometric feature, constraint based modelling1. INTRODUCTION |
