 The straight skeleton is the set of curves traced out by the moving vertices in this process.In the illustration the top figure shows the shrinking process and the middle figure depicts the straight skeleton in blue.The straight skeleton may be computed by simulating the shrinking process by which it is defined; a number of variant algorithms for computing it have been proposed, differing in the assumptions they make on the input and in the data structures they use for detecting combinatorial changes in the input polygon as it shrinks.