# Bounding Volume Hierarchy-Assisted Fast SAR Image Simulation Based on Spatial Segmentation
## 4 Discussion of Simulation Results
### Test Parameters  
Table 1 gives the basic SAR system parameters of the test. The CUDA configuration parameters are as follows: CUDA version 10.0. The shared memory size is 49,152 bytes. The number of registers per block is 65,536. The dimensions of the block are 1024, 1024, and 64. The dimensions of the Grid are 2147, 483,647, 65,535, and 65,535. The GPU clock rate is 1.70 GHz, see Table 2 for details.  
The property parameters of the main components of the materials used in the test are shown in Table 3, which can be flexibly changed according to different application requirements. Usually, it is necessary to sample the materials on the surfaces of the target components and conduct comprehensive physical tests to obtain the material property parameters. Since the selected test target is non-cooperative, we set the material property parameters of the main material composition of the target surface reasonably based on objective experience. These material property parameters can be flexibly changed according to the actual situation, and the closer the material properties of the parameter are to the  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**System Parameters** & **No. I** & **No. II** \\ \hline Bandwidth & 180 MHz & 180 MHz \\ Pulse duration & 1.0 μs & 1.0 μs \\ Range sample space & 0.68 nm & 0.75 nm \\ Incidence angle & 60\({}^{\circ}\) & 45\({}^{\circ}\) \\ Center frequency & 15 GHz & 15 GHz \\ Platform height & 2.0 km & 2.0 km \\ Effective radar velocity & 300 m/s & 300 m/s \\ Doppler bandwidth & 400 Hz & 200 Hz \\ PRF & 450 Hz & 250 Hz \\ Azimuth sample space & 0.66 m & 1.20 m \\ \hline \hline \end{tabular}
\end{table}
Table 1: System parameters.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**GPU** & **CUDA** & **Graphics** & **Compiler** & **CPU** & **Total Memory** & **Operation** \\
**Version** & **Version** & **Memory** & **Environment** & **Version** & **System** \\ \hline NVIDIA & & & & 11 th Gen Intel(R) & & \\ GeForce & 10.0 & 6G & VS2019 & Core (TM) & 16 G & Windows 10 \\ RTX3060 & & & & i7-11800H & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Configuration parameters.  
actual value, the more realistic the simulation results. The vacuum relative permittivity usually set to 1, and the relative permittivity of metal materials is larger than that of the vacuum, which is used to quantify the influence of different materials on the polarimetric scatter intensity. the reflection coefficient is related to the anisotropy of the material microfacet normal vector distribution: when the diffuse coefficient is 1, and it indicates that the distribution of the microfacet normal vectors is completely anisotropic in all aspects. When the specular reflection coefficient is 1, it indicates that the distribution of the microfacet normal vectors is completely homogeneous in all aspects. The reflection index is used to constrain the specular surface distribution. The reflectance index is used to constrain the projection range of specular reflected energy in the receiving direction. The surface of a natural object is usually complex with a certain degree of roughness and gloss, and the diffuse coefficient and specular reflection coefficient are between 0 and 1, which are used to regulate the proportion of the normal vector distribution of the microfacet. When EM waves are incident with the surface, some of the energy will be absorbed, and the energy decay coefficient is used to quantify the wave-absorbing capacity of different materials, thus controlling the number of recurrences of multiple scatterings of EM waves.