Method and system to compare and search polyhedral shape
View Patent ↗Polyhedral data is compared with limited information while keeping accuracy. A comparison of two polyhedrons is accomplished as follows. (1) A squared-sum of the difference of primary moment functions and a squared-sum of the difference of secondary moment functions are separately sought at sample points of polyhedron Ma, Mb, normalize them and compute the sum of both, or seek sum functions of the primary moment functions and the secondary moment functions to compute the squared-sum of the difference of the sum functions, the primary moment function all the sample points of polyhedral data that occupy central symmetry directions are blended in the same sign, which is the different sign in the case of the secondary moment function, the functions having variables representing points on a surface of a sphere of which center is the center of gravity of the polyhedron and a value which is an axial moment value, the axis defined as a line through the points and the center, and (2) in the case that the value of the sum is a certain threshold or less, it is determined that the polyhedrons are similar in shape.
1. A 3D-model display and search system, comprising
a display for displaying a 3D-model;
a 3D-model database storing a plurality of polyhedrons; and
one or more computers configured to perform for each of said plurality of polyhedrons
comparing directions of radial vectors from a center of gravity of the polyhedron to sample points on a surface thereof and a normal vector of the sample points thereon,
based on the comparison, dividing the sample points into a first set of sample points of the same directions and a second set of sample points of different directions, and
based on a coordinate value of each sample point and a weight value given in advance to each sample point, converting the first and second sets into numbers, and
storing the numbers on said 3D-model database as a plurality of values for each polyhedron,
said display, 3D-model database, and one or more computers being configured to perform for an input that is a 3D-model used as a search query, performing the steps of comparing, dividing, and converting to produce a plurality of search values,
comparing said plural values stored on said 3D-model database with said plurality of search values, and
displaying on said display a polyhedron from the 3D-model database having stored values closest to the search values.
2. The system according to claim 1 wherein said display is configured to display a plurality of polyhedrons from the 3D-model database in an order of best to worst match from the comparison step.