`perimeter`

Perimeter length of a polyshape or a 2-D alpha shape.

Category: Mathematics > Computational Geometry

Syntax

L = perimeter(pshape)

Total length of all boundaries, holes included.

L = perimeter(pshape, I)

Perimeter of only the boundaries selected by I.

L = perimeter(shp)

Perimeter of a 2-D alphaShape. For a 3-D one use surfaceArea.

Description

The perimeter is the sum of the edge lengths along every boundary. A hole contributes its own boundary length, since it is also an edge of the shape. A 4 by 3 rectangle has perimeter 14; carving a unit square hole raises it to 18.

Input arguments

pshape: A polyshape object.
shp: A 2-D alphaShape.

Output arguments

L: Scalar length, in the units of the coordinates. An empty shape has perimeter 0.

Example

Perimeter with and without a hole

P = polyshape([0 4 4 0], [0 0 3 3]);
H = polyshape([1 2 2 1], [1 1 2 2]);
D = subtract(P, H);
perimeter(P)
perimeter(D)

Output

ans = 14
ans = 18

perimeter