A 4-clique. Here we know the (x,y) coordinates of points A,B,C,D in the image plane, so we can find the equation of straight lines . We take the pair of straight line equations and and find the intersecting points between the pairs. Only one pair intersect within the convex hull of points (A,B,C,D) while others pairs are either parallel or will intersect outside the convex hull. By using this we understand that A pairs with C and B pairs with D. Accordingly we assign (X,Z) (The segments containing points A and C) and (W,Y) (The segments containing points B and D) pair with weight from Equation 7 (Blue curve in Figure 8-D) and for other pairs we assign from Equation 8 (Red curve in Figure 8-D).