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.