I'm working with historical mining maps and trying to visualize mine shafts below the surface in a 3d WebScene. The process in ArcScene is to just apply a negative extrusion to a flat polygon layer relative to an elevation surface. This same process works for positive extrusions in the web scene, but as soon as a negative value is used the polygon disappears. Underground navigation is on and the base map is set to [none] with the default ground set to partially transparent.
Is the My Scene app not able to visualize underground or subsurface features?