1. A computer-implemented method of generating 3-dimensional model data of a 3-dimensional object, the method comprising: obtaining a first set of hexahedron data representing first hexahedron models, each of the first set of hexahedron data associated with a corresponding hexahedron model from the first hexahedron models at a corresponding coordinate of a first cross-sectional image of the 3-dimensional object; obtaining a second set of hexahedron data representing second hexahedron models, each of the second set of hexahedron data associated with a corresponding hexahedron model from the second hexahedron models at a corresponding coordinate of a second cross-sectional image of the 3-dimensional object; adjoining adjacent hexahedron models among the first hexahedron models and the second hexahedron models; generating surface data including coordinates of closed surfaces of the adjoined hexahedron models, the adjoined hexahedron models surrounded by the closed surfaces, each of the closed surfaces of the hexahedron models including at least two triangles; and generating the 3-dimensional model data based on the surface data.