Using Imported Geometry Surfaces to Create Zone Groups

Creating a numerical mesh for a large zoned embankment dam. For a mesh created from building blocks, is it possible or advisable to assign group names (e.g., core, shell, filter, etc.) to numerical zones using only the upper surface of the layers for a CAD program (e.g., DXF program of the upper surface of the core, upper surface of the filter, etc.)? For background, I have had limited success with the zone group s range geometry-space count i or the zone group s range geometry-space direction v commands. Creating a topologically closed volume (i.e., **zone group s range geometry-space inside) works perfectly but requires that I produce topologically closed volume now in the CAD program. Any suggestion on better use of imported geometric surfaces that are not topologically closed volumes to assign zone groups?

Using an open geometric surface typically works well, when the surface is rather flat and the provided direction for the geometry-space range is along the normal of this surface. When your surface is rather undulated, then the “test ray” from each zone along the direction vector may intersect the surface multiple times and mess with your zone assignment.

I would always prefer closed volumes, but maybe a helpful hint for you could be, that these closed volumes for each group must not necessarily be so complex. For example, you could make a rough bounding box as a closing boundary around one of your surfaces and assign material “A” and then hide it. Then you can do the same with another rough closing of your boundary “B”. This could theoretically also include areas of region “A”, but since you’ve hidden it, it will not mess with your assignment.