A Coding Mechanism for Topological Entities in Form Features

In feature-based parametric modeling system，designer usually define models by a sequential history of modeling steps．Each step is a feature operation．Models can be changed by modifying some parameters and regenerated according to the recorded construction history．In order to maintain the design intent while changing the topology of the part，a topological IDs system is presented，that can easily assign a unique code to every topological entities such as faces and edges