Methods and computer systems for methods, computer systems, and computer-readable memory media for determining a warp function. A first watertight spline model of a first object and a set of points and associated metadata from a second object are received. A second watertight spline model of the second object is constructed based on the set of points, the metadata, and the first watertight spline model. A warp function is determined based on a difference between the first watertight spline model and the second watertight spline model. The warp function is a continuous function approximating differences between the first object and the second object. The warp function is stored in a non-transitory computer-readable memory medium.