INCREMENTAL AND LOCALIZED UPDATE OF CONVEX DECOMPOSITION FOR FORM FEATURE DECOMPOSITION

摘要

Alternating Sum of Volumes with Partitioning (ASVP) decomposition is a volumetric representation of a part obtained from its boundary representation, organizing the faces of the part in an outside-in hierarchy. A Form Feature Decomposition (FFD) which can serve as a central feature representation for various applications is obtained from ASVP decomposition. In a typical design procedure, part designs are analyzed for a given application context and redesign suggestions are made; design changes are then propagated from one context to another through the FFD. Thus, incremental update capability is crucial to support design refinement. FFD incremental update can be achieved by incrementally updating the corresponding ASVP decomposition. This paper describes how ASVP incremental update is achieved by exploiting the hierarchical structure of the decomposition. ASVP incremental update seeks to determine the new decomposition tree of a part, after its boundary representation is changed, without computing it from scratch. Based on local face alteration and extremality considerations, we look for active components that need to be updated. For a connected delta volume, defined as the volumetric difference between the old and new parts, active components are localized in a subtree of the decomposition tree, called active subtree. Then, the new decomposition is obtained by only updating the active subtree using localized ASVP decomposition operations.