1. A method for constructing a model of an object to fit a set of surface point data associated with adjacent layers of the object, said surface point data including an indication of a direction away from an interior of the object in each layer, comprising the steps of: (a) for each layer of the object, constructing an implicit function defining an isosurface extending generally through the surface point data associated with the layer, thereby producing a plurality of implicit functions defining the layers; (b) producing an object implicit function having an isosurface that generally extends through the surface point data for the object by blending implicit functions defining adjacent layers from the plurality of implicit functions; and (c) using the object implicit function to produce the model of the object, said model corresponding to the object.