DCM - Data Channel Modifier
Produces a map for dust that settles on top of whatever faces that are top facing (world).
Extract preset to:
C:\Users\xxx\AppData\Local\Autodesk\3dsMax\2017 - 64bit\ENU\en-US\plugcfg\DataChannelPresets
Then in your DCM, load it as a Preset.
Of course, if you want your Dust 'fixed', simply change the Vector to Local instead of World...or if dust
is coming from a direction (rickety door in an old ghost town) then use Node Look At
(Snow, bird droppings...anything goes...)
(Thought maybe I should rename it to DCP instead, = DataChannelPreset)