Hi Daniel,

At this time, there aren't any Bulk Scattering DLLs which support a changing particle density for a single bulk scattering object -- the closest definition we have to modeling a particle density input for bulk scattering is through the Mie Scattering DLL. However, you could potentially approximate the desired change in particle density by defining a series of volumes adjacent to each other, each with a different particle density depending on your needs. The 'resolution' in the change in particle density would depend on how many volume 'slices' you define, but this could at least be a way to start modeling your setup.

Otherwise, for a single volume object, you will need to define a DLL yourself which models a change in the particle density depending on some inputs for the DLL. As a starting point, you could take a look at the Knowledgebase article here which gives a brief discussion on what the Bulk Scattering DLL wants to take in from OpticStudio and compute for the output scatter ray. Of course, you can take a look at the .C code for some of our Bulk Scatter models at 'C:\ ... \Zemax\DLL\BulkScatter' (note: this is the default install location, so it could be different if you've changed your directory!).

Please let us know how these thoughts work out for you!

~ Angel