`subtract`

Boolean difference of two polyshapes: the first with the second cut out.

Category: Mathematics > Computational Geometry

Syntax

P = subtract(P1, P2)

Returns the part of P1 that is not in P2.

Description

If P2 lies fully inside P1, the result is P1 with a hole. If it cuts across an edge, a notch is removed. If they do not overlap, P1 is returned unchanged. The order of arguments matters: subtract(P1, P2) and subtract(P2, P1) are different shapes.

The companion operations are union, intersect and xor.

Input arguments

P1: The polyshape to cut from.
P2: The polyshape to remove.

Output arguments

P: The difference, as a new polyshape. It can have holes or several regions.

Example

Punching 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);
D.NumHoles
area(D)

Output

ans = 1
ans = 11

subtract