PURPOSE: To generate accurate pry pattern by calculating the distance from an outer surface to an intermediate surface and decomposing a parts model into fitting-in shells.

CONSTITUTION: Composite parts 20 generate a ply pattern by a computerizing method and has airfoil parts 21 and curve end parts 22 and 23. An uniform thickness outline on parts 21 is calculated to determine the boundary of ply in a three-dimensional space. It is calculated by calculating the distance from the outer surface to the intermediate surface. A series of points 37 are sampled from the outer surface to calculate the shortest distance 38 from each point to the intermediate surface 36. An outline or a shell boundary is generated by interpolation along the sampled distance 38 and is shown like a chart by a short line 39. In the same procedures, both of parts 22 and 23 are decomposed into many fitting-in shells.