1. A method for producing a visual representation of a three dimensional body, the method comprising: providing a computer having a memory; generating a three dimensional signal pattern that represents the values of a physical property associated with a three dimensional body at spaced apart locations within the body; generating a threshold value of the physical property, the threshold value and the three dimensional signal pattern defining a three dimensional isosurface that partitions the three dimensional signal pattern into pattern groupings; converting the three dimensional signal pattern into a set of data vectors, each data vector having a physical property component and a location component corresponding to a respective one of the spaced apart locations; storing the data vectors in the memory of the computer using the computer to sort the data vectors, so as to create a first and second group of data vectors, the first group including data vectors having a physical property component less than the threshold value, the second group including data vectors having a physical property component greater than the threshold value; using the computer to generate coordinates of a set of polygon vertex points approximately lying on the three dimensional isosurface, coordinates of each member of the set of polygon vertex points being interpolated using a respective data vector belonging to the first group and a respective data vector belonging to the second group; using the computer to generate a body saddle value from data vectors having location components that are spatially coadjacent with one another; using the computer to compare the threshold value to the body saddle value; linking two members of the set of polygon vertex points if the body saddle value and values associated with the two members are all greater than the threshold value; linking two members of the set of polygon vertex points if the body saddle value and values associated with the two members are all less than the threshold value; using the linked members of the set of polygon vertex points to generate a piecewise polygonal approximation that is topologically consistent with the isosurface, in that the polygonal approximation partitions the signal pattern into the same pattern groupings as does the isosurface; and using the polygonal approximation to generate an image representative of the body.