Wire-frame modeling
Wire-frame modeling is direct transfer of 2D geometric approach to 3D cases. In such a modeling, geometric model is built from a limited set of graphic primitives – segments, arcs, or conic curves. However, a wire-frame model has only the body skeleton (frame), which generally cannot be used to restore the solid body, because there can be several topologically non-equivalent 3D bodies with the same wire-frame.