Ray-Based Simulation of Scattering from Discretized Curved Bodies for Vehicular and ISAC Applications

Realistic modeling of scattering from curved metallic bodies - such as vehicles and roadside structures - is essential for cellular and vehicular channel modeling as well as radar applications. A practical approach is to approximate curved surfaces with planar facets and apply ray-tracing with diffraction methods; however, accuracy depends critically on both geometric discretization and diffraction modeling. This work investigates ray-tracing-based modeling of near-field scattering from curved bodies, including the forward (shadow) region, using the Uniform Theory of Diffraction (UTD), extended with vertex diffraction and double-bounce interactions. A discretization strategy linking facet size to local curvature and wavelength is proposed to balance geometric fidelity, computational accuracy and efficiency. Validation is performed against analytical solutions and full-wave simulations for canonical geometries (sphere and circular cylinder), as well as a realistic vehicle model to demonstrate the method's practical relevance. Results show that appropriate discretization combined with extended diffraction modeling significantly improves scattering prediction from curved bodies, providing a computationally efficient framework for vehicular propagation and integrated sensing and communication (ISAC) channel modeling.