老师你好我在看相关例子的时候看到这么一段话：Note: Particle scattering with a substrate
The ‘box of monitor’ far field projection is frequently used when studying particle scattering. This is fine, but it’s important to remember the requirement that everything beyond the monitor box must be a single homogeneous material. When a substrate is present, this approach is not valid. Instead, the best way to calculate the far field scattering pattern is to use a single monitor, located above or below the particle (depending if you want scattering in the forward or backwards direction). You can then use the standard farfield3d function. When using a single monitor, it’s important to make the simulation span large enough that most of the scattered light will pass through the monitor before hitting the PML absorbing boundary conditions.