METHOD FOR GENERATING THREE-DIMENSIONAL ORTHOGONAL GRATING DATA

PURPOSE: To provide a three-dimensional(3D) orthogonal grating generating method simple in calculation procedure and capable of automatically generating a diffraction grating of culculus of finite difference corresponding to a complicated 3D shape from shape data (including shape data whose shape area is not completely closed) such as CAD data. CONSTITUTION: In a block 1, facet (fine polygon) data for existing CAD data relating to a shape model are read out, an area surrounding the whole model is calculated and a VOXEL is generated, and in a block 2, numerical data are stored in VOXEL intersecting with all facet data to generate surface VOXELs corresponding to the surfaces of the shape model. Finally in a block 3, a prescribed area having the surface VOXELs as a boundary is inverted to obtain the 3D orthogonal grating of the shape model. In the case of inverting the prescribed area, one of VOXELs on the outermost layer of the object area is selected and numeric data are successively and recursively stored in all VOXELs started from the selected VOXEL to invert values in the whole area. The facet data constitute a numerical group consisting of the number of points of a polygon and the coordinate values of respective points.