1. A method of producing a three dimensional representation of an undeformed object, the method comprising: using a computer to perform steps including: combining information from two 2D images taken from different viewpoints of the object under deformation, estimating the volume of the deformed object, and constraining the three dimensional representation of the object to have substantially the same volume, wherein the information from each of the two images is combined by the steps of: (a) detecting the outline of the object in each of the two images, (b) reducing area of the outlined areas by a predetermined amount, and (c) using the outlines of the reduced areas as profiles from different directions of the three dimensional representation of the object.