The eye icon is both loved and hated by our users, but I believe there is a confusing behavior for the folder eye icon. When I close the folder’s eye and have both 2D and 3D renderings, only the 3D hides:
To confuse even more the users, the 2D slice is kept on the 3D view. I’ve personally spent 10 minutes fiddling with the volume rendering sliders only to discover that the folder eye was closed. I was seeing the 2D slice at the 3D view and at the slicewidgets but the 3D rendering was not showing, so I thought the visibility was fine.