Method for planning a process of cutting human or animal bone tissue. The method includes: obtaining initial data of an initial situation of the bone tissue； defining target data of a target situation of the bone tissue； and computing a cut geometry using the initial data and the target data for cutting the bone tissue apart. The cut geometry includes a structure such that the bone tissue is reassemblable in an at least in one degree of freedom in the target situation after being cut apart along the cut geometry. By shaping the structure of the cut geometry according to the target situation the planned cut can be provided with a particular function. Such a functional cut can geometrically define and restrict possible movements of cut apart bone portions. The functional cut can allow for comparably precisely repositioning the bone into the target position and any movement therefrom can be prevented.
