RSVP: a geometric toolkit for controlled repair of solid models

摘要

The paper presents a system and the associated algorithms for repairing the boundary representation of CAD models. Two types of errors are considered: topological errors, i.e., aggregate errors, like zero volume parts, duplicate or missing parts, inconsistent surface orientation, etc., and geometric errors, i.e., numerical imprecision errors, like cracks or overlaps of geometry. The output of our system describes a set of clean and consistent two-manifolds (possibly with boundaries) with derived adjacencies. Such solid representation enables the application of a variety of rendering and analysis algorithms, e.g., finite element analysis, radiosity computation, model simplification, and solid free form fabrication. The algorithms described were originally designed to correct errors in polygonal B-Reps. We also present an extension for spline surfaces. Central to our system is a procedure for inferring local adjacencies of edges. The geometric representation of topologically adjacent edges are merged to evolve a set of two-manifolds. Aggregate errors are discovered during the merging step. Unfortunately, there are many ambiguous situations where errors admit more than one valid solution. Our system proposes an object repairing process based on a set of user tunable heuristics. The system also allows the user to override the algorithm's decisions in a repair visualization step. In essence, this visualization step presents an organized and intuitive way for the user to explore the space of valid solutions and to select the correct one.