`addboundary`

Adds a new polygonal boundary to a polyshape and returns the combined shape.

Category: Mathematics > Computational Geometry

Syntax

pshape = addboundary(pshape, x, y)

Adds the polygon with vertices (x, y) as a new boundary of pshape.

Description

addboundary is the way to put a second polygon, such as a separate island, into an existing polyshape without taking a union. The result is normalized: a new boundary lying inside an existing one becomes a hole, while a separate one becomes another region.

The original object is not changed; the function returns a new polyshape.

Input arguments

pshape: A polyshape object.
x, y: Vectors with the x and y coordinates of the new boundary's vertices, in order around the polygon.

Output arguments

pshape: A polyshape with the original boundaries plus the new one.

Example

Two separate squares

P = polyshape([0 4 4 0], [0 0 3 3]);
B = addboundary(P, [5 6 6 5], [0 0 1 1]);
disp(B.NumRegions)
disp(area(B))

Output

     2
    13

addboundary