Abstract: A method is provided for rapid prototyping of complex structures, such as complex bone structures and internal neural and cardiovascular pathways. The method involves loading the triangles from a polygonal mesh computer model of a 3D object having one or more internal void spaces, converting the triangles to voxels, separating the voxels of the model into watertight pieces, and printing the pieces using a 3D printer such as a ZPrinter™. The method allows realistic internal void space representation through removal of excess powder from printing which would otherwise be trapped in the whole object and also allows the application of a resin to internal surfaces which may provide realistic internal object density useful for medical and other applications. Pegs and holes may also be added to and subtracted from the pieces to allow for assembly of the printed object. A system and computer program product is also provided.