FREE SURFACE DATA PREPARATION METHOD.

摘要

In a free surface data preparation method for generating a free surface by spreading three-sided patches expressed by predetermined vector functions in a frame space, the method of the invention connects first and second three-sided patches by changing a common boundary arbitrarily with surface shapes maintained when changing of the common boundary is designated, and when changing of the common boundary is not designated, the method of the invention maintains the curved line shape of the common boundary, changes arbitrarily the surface shapes of the first and second three-sided patches and connects the first and second three-sided patches. Therefore, the surface shapes of the first and second three-sided patches after the connection can be selected according to a designation as to whether or not the common boundary is to be changed. The present invention satisfies only the condition where a first tangential vector extending along the common boundary at an arbitrary point on the common boundary and second and third tangential vectors crossing transversely the common boundary and extending in the direction of the first and second three-sided patches exist always on the same plane. Accordingly, the present invention can always connect the first and second three-sided patches reliably and smoothly. In a free surface preparation method, the present invention generates control points expressing the boundary curve of three-sided patches by using, as a frame, a plurality of triangles formed by connecting in proper quantities a plurality of points in three-dimensional data expressing a predetermined object by a plurality of groups of points existing on a plurality of parallel planes. Therefore, free surface data consisting of the aggregate of three-sided patches can be prepared easily from the three-dimensional data.