I am using an array in conjunction with a curve modifier to make a stone wall along a path. But the problem is that it is easily noticeable that all the stones have the exact same mapping (i.e. the exact same cracks in the exact same place) which looks terrible. This problem is easy to eradicate for just the displace modifier by basing the texture coordinates on an empty. I would like to be able to do something like this for the material mapping as well, altering the position of the UV pelt on the UV grid. Though I am open to any suggestions on how to fix this problem.
Edit:
As a clarification, I need to use UV coordinates, not generated.