自由曲面特征模型中的数值和曲线参数*

成功的特征模型系统，在很大程度上取决于是否能给用户提供友好的方式来指定和改变特征模型，针对这一点，给出了两个新的功能：a）利用数值参数和曲线参数来指定和改变自由曲面特征模型；b）除了特征模型中现有的参数，其他参数可以添加到特征模型，包括特征之间的交叉曲线。为了提供这些功能，提出了一个新的三个层次的结构，最高层次为不可估计模型，最低层次为可评估的模型，中间层次为部分评估模型，后者链接最高层次的特征和最低层次的几何模型，并且也提供了最高层次和最低层次几何模型中的特征定义的交互。

Numeric and curve parameters for freeform surface feature models

A successful feature modeling system, largely depends on whether it can provide a user-friendly way to specify and change feature models. Aiming at this point, this paper introduced several new facilities. The first, presented numeric and curve parameters for specification and variation of freeform surface feature models. The second, other parameters could be added to a feature model, including intersection curves between features. To provide these facilities, introduced a new three-level structure, which included three parts, the highest level, called the unevaluated model, the lowest level of the feature model was the evaluated model, a new intermediate level, called the partially evaluated model. The latter linked the features at the highest level to the geometric model at the lowest level, but also intersectioned between features to both their definitions at the highest level and the geometric model at the lowest level.