I often need to model lenses or diffuser plate with some texture grains applied on some part of it. Normally it’s called out as Mold-tech or VDI texture grain, which are commonly used for surface diffusing optical elements.

The question is how do I apply that correctly in the Zemax optical model. Is there any DLL library for that or should I use Gaussian or AGg to approximate that? Problem is there is no available data to correlate such scatter model to Mold-tech definitions.