Yes, I want to replace farfieldvector3d with farfieldexact from the full metalens simulation. I want to use the farfieldexact with summing method. Essentially, I want to use the summing method for a very large metasurface to calculate it's farfield at an exact location described by the user. How could we use Lumerical script commands to achieve this? Also, can you explain why we can use farfieldvector3d with summing method and why we can not use farfieldexact?