What do you mean by "resource"?
The Resources you can add to a 3D annot. There was another question that was more specific in the 3D forum.
Ahh, I haven't done any 3D scripting in a while, but when I did, I had to add a resource the hard way, with PDF CanOpener. If you remember the robot arm model, the coin the arm grabbed was a resource. I think things have changed a great deal since then. The 3D forum is the right place for this question.