An Improved Z-Buffer Accelerated PO Method for EM Scattering from Electrically Large Targets

The physical optics (PO) method is widely used to solve the electromagnetic (EM) scattering problems involving electrically large structures, in which each surface element is required to determine whether it is blocked by others. It may suffer from the computational efficiency issue due to elementwise shadowing testing. In this paper, an efficient Z-buffer based shadowing testing method is proposed to accelerate this procedure. In this method, all triangular facets are first mapped to a grid plane using the Z-buffer method, and for each grid cell, all projected triangles that intersect it are recorded. Then, rigorous shadowing testing is made for all facets recorded in the grid where the centroid of each triangle is projected. It can avoid a large number of redundant operations for pairs of triangles with no occlusion relation, which leads to the same accuracy as the traditional rigorous shadowing testing method while significantly inproving efficiency. Four numerical examples are carried out to validate its accuracy and efficiency.