由于特征线在反求工程 CAD建模中具有非常重要的作用,因此利用图形图象处理中的多分辨率模型概念,通过研究三角曲面模型的特征线,提出了一种三角曲面特征线的计算方法.将计算得到的初始特征线通过编辑、修改等手段进行处理,得到清晰的特征线,并将其作为进一步划分重构 B样条曲面边界的依据和参考,从而为实现基于三角曲面模型的B样条曲面重构奠定了基础.实验结果证明,该算法能够在三角曲面上提取出令人满意的特征线 ,并据此重构出拓扑划分合理的B样条曲面.

Feature plays an important role in reverse CAD modeling. Based on the multiresolution modeling, a series of approximation models and algorithms for feature curves extraction from the triangular Bézier patch is studied. First, a near coplanar merging algorithm based on Gauss sphere is used to generate superfaces. Then the outer and inner boundaries of every superfaces are extracted, which are original or coarse feature curves. Taking account of the complexity and arbitrary of triangular Bézier patches model, editing operation applying on feature curve is inevitable during practical application. The feature curves are the important reference fo rectangular boundaries definition. This research has laid a good fundamental for fulfilling the local B-spline surface reconstruction from triangular Bézier patches. Some experimental results show that the above method is feasible and satisfying, and reasonable rectangular topological B-spline surfaces can be reconstructed according to the feature curves extracted from the triangular Bézier patches.