1. A method for generating boundary surface information using a computer, the method comprising the steps of: (a) performing an input step comprising inputting information on a boundary surface of an object to the computer; (b) performing a grid sampling step comprising determining cutting points and normal vectors of the boundary surface at the cutting points, wherein the cutting points are points at which the boundary surface cuts across edges of a predetermined rectangular parallelepiped grid, and storing the cutting points and the normal vectors in a storage unit as primary data, and wherein, in the case where a rate of change in the normal vectors of the primary data exceeds a predetermined threshold value, a size of the rectangular parallelepiped grid is divided by octree division, and generation of primary data, and the storage of the primary data, are repeated so that cutting points and normal vectors are stored in a hierarchized manner; (c) performing a D-polyhedron data generation step comprising connecting adjacent cutting points with a line segment to form a triangle one by one for generating D-polyhedron data constituted of triangles only; and (d) performing a V-polyhedron data generation step comprising generating V-polyhedron data constituted of intersections of a plurality of infinite planes passing through the cutting points and whose normals coincide with the normal vectors; wherein when the D-polyhedron data is generated from the primary data, the V-polyhedron data is generated as a dual of the D-polyhedron data, and when the V-polyhedron data is generated from the primary data, the D-polyhedron data is generated as a dual of the V-polyhedron data.