Parametric Representation and Implementation of Freeform Surface Feature Based on Layered Parameters

To solve the problem of parametric representation of freeform surface feature,a framework for multi-level parametric definition and implementation of freeform surface feature is proposed.The method parameterizes freeform surface feature step by step from global to local shape and from high to low level.A framework of three-level parameters and two-grade mappings is put forward to define freeform surface feature,that is,three-level parameters including high semantics parameters,middlelevel characteristic curve and low-level shape data.Furthermore,mappings and constraints are built up between three levels.Last,it supports users to instantiate the feature by Scheme command.The method avoids the traditional complex mapping relation directly between the high-level feature parameters and the bottom data.Experiments show that the above method is convenient for users to intuitively edit and modify freeform surface feature with high-level parameters.It can effectively express freeform surface feature.