1. A method for using a haptic device as an input device, comprising: receiving information identifying a virtual haptic object which is modifiable by said haptic device, said virtual haptic object being associated with a processor of a computer-assisted surgery system; receiving with the processor an input from said haptic device; modifying at least one of a position, a size, a shape, and an orientation of said virtual haptic object in the processor in response to receiving the input from said haptic device; and restricting movement of said haptic device relative to at least two directions in accordance with the virtual haptic object, wherein the directions are defined relative to at least a portion of an anatomy of a patient.