Abstract: A plurality of representative points are selected from a group of points obtained as results of shape measurement of an object, respective principal curvatures are calculated at the representative points on the basis of positional relationships between the representative point and a plurality of points existing around the representative point, a line of curvature is created on the basis of the principal curvatures of the representative points and a curved surface is generated using this line of curvature.

Abstract: A computer aided design system and a computer aided design program which can greatly increase the utility of a computer aided design model, and can improve the efficiency of design and production processes, by adopting a curved surface theory which ensures the continuity of a free-form line or surface. A computer executes: a point sequence information extraction process for extracting a plurality of point sequences on a curved surface; a dividing process for generating a curved surface from the point sequences and dividing the curved surface into a predetermined number of mesh points; a first fundamental form computing process for computing coefficients of the first fundamental form; a second fundamental form computing process for computing coefficients of the second fundamental form; and a storage process for storing the point sequence information, the coefficients of the first fundamental form and the coefficients of the second fundamental form.

Abstract: A plurality of representative points are selected from a group of points obtained as results of shape measurement of an object, respective principal curvatures are calculated at the representative points on the basis of positional relationships between the representative point and a plurality of points existing around the representative point, a line of curvature is created on the basis of the principal curvatures of the representative points and a curved surface is generated using this line of curvature.