Automatic recognition and representation of shape-based features in geometric modeling system

A method is presented for the automatic identification and extraction of feature information from the solid model of an object. The procedure consists in recognizing shape features, extracting these features as solid volumes, and arranging them in a hierarchical structure. This hierarchical model, described in this article, represents the main shape of the object at the highest levels of abstraction and its form features at lower levels of specification. The system is divided into three modules: feature recognition, feature extraction and feature organization. The recognitition step works on a face-based representation of solid objects, called a face adjacency hypergraph and it takes advantage of Kyprianou's method (Shape Classification in Computer-Aided-Design, Ph.D. thesis, Computer Laboratory, University of Cambridge, England, July 1980). In the extraction phase each recognized form feature is completed by dummy entities in order to form a feasible object and in the organization step the completed features are arranged into a hierarchical graph, called Structured Face Adjacency Hypergraph.