断层图象序列的层间插值是三维重建的关键技术之一。已有的断层插值方法主要使用灰度，灰度梯度，距离，方向等约束，重建的三维表面往往不平滑，本文引入有向距离概念，增加表面平滑约束，提出一种重建三维平滑表面的断层图象间形状插值方法。

Surface interpolation of cross-sectional images is one of the techniques of crucial importance in 3-D reconstruction. Gray scale value,gradiant of gray scale value,distance, oriantation are commonly used constraints in literatures. Using these methods, the 3-D reconstructed sufaces are often not smoothing. In this paper, the concept of directional distance and the constraint of smoothing surface are introduced. The method of smooth constrained 3-D surface interpotation of cross-sectional images and its experimental results are presented.