Reply To: Precise volume average for Import Surface geometry

[Guilin Sun]

Are the two screenshots from the same structure with the same material, source bandwidth and mesh?

Have you compared the grating results if they are the same structure? 

You may also use Conformal Variant 0 instead of precise volume average. When precise volume average is used, it uses finer mesh than the FDTD mesh to average the permittivity, and it should not change anything for uniform material, eg, away from material interface. It may need more memory. the Conformal Variant 0 is always recommended, except that you find it is not accurate or cause other issues.

Anyway, there are many different methods to treat the effective material property at the material interfaces. While they all work well in many cases they can lead to some differences in results. But the difference from your screnshots seem too large if they are from the same simulation file.