An Improved Shooting and Bouncing Ray Method based on Blend-Tree for EM Scattering of Multiple Moving Targets and Echo Analysis

An improved shooting and bouncing ray (SBR) method based on the Blend-Tree structure is presented for solving the scattering from multiple complex movement targets. Since the positions and attitudes of targets change with time, the spatial distribution of facets is variable. Hence, quickly finding illuminated areas and tracing high-order rays are two main bottlenecks. A Blend-Tree structure consisting of the ray aggregation transport layer (RATL) and the multiple octree layer (MOL) is proposed for the above problems. RATL assigns a conversion interface (CI) and target-seeking interface (TSI) to each target. MOL stores each octree which is built at the initial moment and connected to CI. In shadow elimination, targets are rotated and translated for virtual display by CIs, and the scanline algorithm is used for acceleration. In high-order raytracing, the ray which enters and exits the target is transformed quickly by quaternions in CIs. The TSI determines the next target for the exiting ray. Therefore, the raytracing area is extremely limited within each bounding box and time-invariant. Furthermore, the ray marching algorithm is improved to accelerate ray tracing in octrees. Numerical results demonstrate the computational accuracy and efficiency of this method. Moreover, echo characteristics of multiple moving targets are analyzed.