Aspects of the present disclosure relate generally to preparing models of three-dimensional structures. In particular, a model of a three-dimensional structure constructed of porous geometries is prepared. A component file including a porous CAD volume having a boundary is prepared. A space including the porous CAD volume is populated with unit cells. The unit cells are populated with porous geometries having a plurality of struts having nodes on each end. The space is populated with at least one elongated fixation element extending beyond the boundary to produce an interlocking feature enabling assembly or engagement with a mating structure.