Setting up ground meshes for export

Ground meshes must be Maya polygonal objects, and must be manually triangulated before export.
You can do this with Polygons Menu -> Triangulate (in modelling mode).

Ground meshes must also be assigned names with a 'ground_' prefix.
(Specifically, the relevant name here is the name of object transform node.)
Objects without this name prefix will be ignored on export.

Refer to the Maya documentation for information about creating and editing polygon objects.
Refer to this page for information about limitations that apply specifically to building PathEngine ground meshes.