While exporting Creo files to .U3D format, hidden items are not captured. They are missing in newly saved(created) .U3D file. Currently, there are no options available in Creo while exporting to .U3D format.
Enhancement idea : Provide a pop-up Option window such that the user can decide whether to select "export all items in window" or "just visible/selected items" during .U3D conversion.
Business impact : Apparently, a lot of OEM companies are looking at Model Based Definition or 'drawing less future' where 3D models are directly exported to various formats instead of drafting them. Even though .U3D is an older format, many companies are not able to use file format effectively due to limited feature support from CAD development teams. It has many advantages over .stp format, primarily being lighter in size than .stp. format. It is a chance for PTC to dominate market in this field may be by a little promotion to use .U3D file formats.