1. An apparatus for automatically assessing radiation therapy segmentations comprising an electronic computer executing a stored program to: (a) receive a first and second electronic file each providing data points describing different three-dimensional surfaces circumscribing a structure in a human or animal patient intended for radiation therapy; (b) generate a first and second volume model defined by the different three-dimensional surfaces of the first and second electronic file respectively; (c) compare the first and second volume model to identify: (i) common volume elements in common to both of the first and second volume models; (ii) missing volume elements of the first volume model that are not in the second volume model; (iii) extra volume elements of the second volume model that are not in the first volume model; (d) output an indication of a conformance between the three-dimensional surfaces circumscribing the structure defined by the first and second electronic files based on a metric method of measuring volumes of the missing volume elements and extra volume elements; whereby segmentation represented by the second electronic file may be evaluated.