A new method for classification and parametric representation of freeform surface feature

摘要

Representation and parameterization of freeform feature is one key issue in CAD. Based on the idea of layering freeform feature and feature global shape (FGS), a novel method for classification and parametric representation of freeform feature is proposed. Firstly, freeform features are classified in use of a multi-side method which combines FGS, approaches for surface generation, types of characteristic curves and their topological structures. Secondly, freeform feature is parameterized step by step from global to local shape, from basic to fine characteristic, and from high to low level, thus its representation can be unified. Lastly, the framework of three-level structures and two-grade mappings is put forward to define freeform feature so that parametric semantics can be clearer and it is convenient for users to edit and modify surface by intuitive parameters. It is shown in the examples that the method can effectively improve classification and parameterization of freeform feature. It can be applied to surface feature-based design and other domains as well.