Fig. 2.

Illustration of the computation of FHs between two objects A (green) and B (orange). a Both objects and the parallel lines sweeping across the image oriented by a specific angle θ°. b The final FH (with angles between 0° and 360°) describing the spatial relationships between A and B. In this example, the maximum value of the FH is obtained for an angle of approximately 18° and is empty for values between 50° and 350°, since no line meets both objects A and B along these orientations. FH forces histogram