Complete Shape from Imperfect Contour: A Rule-Based Approach

摘要

Two important issues of shape from contour research are addressed in this paper. The first is the imperfection of input data and the second is the completeness of output 3D object models. We present a solution that is based on: (1) the analysis of imperfect line drawing configurations, especially the properties of L junctions and (2) the implementation of a rule based system. Constraints imposed by line labeling, 2D and 3D geometry, and Gestalt principles of human visual perception are formulated into production rules, and the system control mechanism is designed so that these rules can work interactively. Perfect line drawings are treated as special cases in this system. Complete 3D object models, including invisible faces, that are consistent with human perception can be reconstructed.A nonmonotonic forward reasoning mechanism is realized by using the truth maintenance system (TMS). The TMS is used to maintain a dependency network of currently active facts for reasoning in hypothetical situations. It also leads to an effective way to backtrack an assumption to resolve contradictions which is called dependency directed backtracking (DDB).