中文说明：在前面1维，2维的基础上继续推出3维的FDTD程序，可以帮助解决复杂的3维电磁散射问题，适用范围更广。这个程序给出计算要求的参数即可运行。
English Description：
On the basis of the previous 1-D and 2-D FDTD program, the 3D FDTD program can help solve the complex 3D electromagnetic scattering problems, and has a wider application range. This program can be run by giving the required parameters.