1. A method for segmenting a region on a display using an input device, the region composed of a bounded area or volume, the display including one or more regions within a larger area or volume, the input device capable of converting user input into a two or three-dimensional position, the method comprising: a) entering an interactive segmenting mode, then b) interactively specifying a segmentation of the region with the input device, then c) leaving the interactive segmenting mode