Boundary Evaluation for a Cellular Model

Abstract

Feature modeling systems usually employ a boundary representation (b-rep) to store the shape information on a product. It has, however, been shown that a b-rep has a number of shortcomings, and that a cellular model can be a valuable alternative. A cellular model stores additional shape information on a feature, including the faces that are not on the boundary of the product. Such information can be profitably used for several purposes. A major operation in each feature modeling system is boundary evaluation, which computes the geometric model of a product, i.e. either the b-rep or the cellular model, from the features that have been specified by the user. Because it has to be executed each time a feature has been added, removed or modified, its efficiency is very important. In this paper, boundary evaluation for a cellular model is described. Subsequently, its efficiency is compared to the efficiency of boundary evaluation for a b-rep, on the basis of performance measurements and considerations for both. It turns out that boundary evaluation for a cellular model is in fact more efficient than for a b-rep, which makes cellular models even more attractive as an alternative for b-reps.