In 2013 I participated in a developers camp. With a group of four people we made a program that created a 3D version of a key requiring only a picture of the key and a picture of the lock.
Within a week we were able to refine this process such that we could take the two pictures, print the key, and immediately open the lock. As far as we know we were the first people in the world to 3D print keys. A video of the process can be found here: