surface expandedness

The characteristic of the algorithm is that distance between the edge points and the center points is changeless before or after surface expandedness, so It meets the request of putting metal wallboards together without gap.
算法具有曲面展开前后其边沿点到中心点的距离不变的特点,从而可以满足曲面整体拼装后的接缝整齐美观的要求。