License: This is licensed for commercial or non-commercial use.
The fog is a cube, with corners at -0.5 and +0.5 Poser units. It has all the usual 6 faces of a cube, and that cube contains 63 evenly spaced square faces at 90deg to the z-axis, spaced at 0.015625 (= 1/64) Poser units apart. Those 63 faces are alternately reversed-normal and not, so they can be seen from both sides in display mode. In Poser materials room, set its transparencies to 0.9 to 0.95 according to opaqueness needed.