Patent ID: 7557803

Claim:
A storage medium readable by a computer or processor-controlled machine and having recorded thereon a computer program configured to instruct a computer to read and write a data structure into a memory, the data structure representing a graph of topological and geometrical information of a two- or three-dimensional object, said graph being composed of individual points and line segments connecting adjacent pairs of said points, respectively, comprising: a set of point data for each of said individual points of said graph representing said topological and geometrical information of said two- or three-dimensional object, said point data of each said point comprising i) an adjacency list written in a storage area of said memory individually allocated for each point, and ii) an information defining a log of alteration levels, wherein a plurality of adjacent points, associated with said point, with address pointers to storage areas allocated to each of said adjacent points, respectively, are written in said adjacency list, said adjacent points having a sequential order in said adjacency list according to a predetermined rule, wherein a storage location number is written for each address pointer of each adjacent point in said adjacency list, said storage location number indicating where, with respect to the sequential order of an adjacency list of the adjacent point indicated by the address pointer, an address pointer to said storage area allocated to said point is written, wherein information on a current alteration level of said graph is written in said data structure and incremented with each alteration to said graph, wherein information on the log of alteration levels of each of said points is written as an alteration history level in said point data for each point, and wherein a new alteration history level, having a value representing the current alteration level incremented by one with said alteration, assigned only to each of said individual points of said graph affected by said alteration.