I. Introduction
Undulating terrain synthetic aperture radar (SAR) raw data and image simulation play an important role in SAR system parameter design, imaging algorithm verification, and SAR image postprocessing [1], [2]. Shadow simulation is the most critical part of undulating terrain SAR raw data and image simulation, and the accuracy of shadow simulation which will directly determine the accuracy of simulated SAR images and will also affect the accuracy of subsequent shadow-based SAR image processing applications [3], [4], [5].