`turningdist`

Turning-function distance between two polyshape boundaries.

Category: Mathematics > Computational Geometry

Syntax

d = turningdist(PG1, PG2)

Returns a dissimilarity measure between the shapes of PG1 and PG2.

Description

The distance compares the turning functions of the two polygons: the direction of the edge as a function of the arc length along the boundary, with lengths normalized by the perimeter. The measure is intended to ignore translation and uniform scaling, so it focuses on shape rather than position or size.

Both polyshapes must have exactly one boundary; otherwise an error is raised.

Input arguments

PG1, PG2: polyshape objects, each with a single boundary.

Output arguments

d: Non-negative scalar. It is 0 for identical shapes and grows as the shapes differ.

Example

Square versus rectangle

P = polyshape([0 1 1 0], [0 0 1 1]);
Q = polyshape([0 2 2 0], [0 0 1 1]);
d1 = turningdist(P, P)
d2 = turningdist(P, Q)

Output

d1 = 0
d2 = 0.5854

turningdist