You've spent hours to create the perfect 3D model in your favorite 3D tool. Do you own this digital property? Probably, but can you prove it?
Exactly. That's the problem that's solved by third party intellectual property registration services, such as ProtectRite. They'll accept (for a fee) your digital file and timestamp it within their secure storage system. You'll then be more able to prove ownership as their is third party documentation providing evidence of your works and the date they were registered.
How does a service like this work? You "register" a work by uploading it and paying a fee. ProtectRite's fee, for example, is USD$18.95 for a ten-year period. Only you will be able to pull the file from their servers. A side benefit is that you could use their copy as your backup in case of total personal digital disaster.
Is this service for you? Maybe, if your work is of such value you feel it warrants special protection.
On the other hand, there's always the Creative Commons License if you want others to make use of your work.