Fig. 1. One-dimensional Morton code generation for planar triangular patches.

Fig. 2. BVH tree and spatial construction of the tire model’s mesh.

Fig. 3. Three steps of shadow judgment between patches in the IPO-BVH method: (a) The process begins with the incident plane wave facing the aperture surface; (b) the patches on the aperture surface are directed towards the patches on the inner wall; (c) the judgment is made between inner wall patches.

Fig. 4. shadow relationship judgment between the field triangle and the source triangle.

Fig. 5. Comparison of the CPU time of the shadow judgment process under different numbers of patches.

Fig. 6. Monostatic RCS of the COBRA model at as a function of in the horizontal plane: (a) H-H polarization and (b) V-V polarization.

Fig. 7. Distribution of the induced current convergence of the IPO-BVH method in the COBRA cavity: (a) incident angles involving azimuth angle = 90° and pitch angle = 90°; (b) incident angles involving azimuth angle = 130° and pitch angle = 90°.

Fig. 8. Monostatic RCS of the SLICY model at as a function of in the vertical plane: (a) horizontal polarization and (b) vertical polarization.

Fig. 9. PO and IPO-BVH methods induced current distribution with incident angles involving azimuth angle = 90° and pitch angle = 45°: (a) PO method and (b) IPO-BVH method.

Fig. 10. Monostatic RCS of the ship-sea model at as a function of in the vertical plane: (a) the incident azimuth angle is = 0° and (b) the incident azimuth angle is = 90°.

Fig. 11. Ship-sea model induces current distribution under the incident azimuth angle = 0° and = 70° with different methods: (a) PO method and (b) IPO-BVH method.