simplify

Simplify polyshape boundaries

Syntax

polyout = simplify(polyin)

polyout = simplify(polyin,'KeepCollinearPoints',TF)

Description

polyout = simplify(polyin) returns a polyshape object made up of the boundaries of the polygon polyin with all vertex duplicates removed, and all boundary intersections and improper nesting resolved.

polyout = simplify(polyin,'KeepCollinearPoints',TF) specifies whether to keep or remove collinear points in polyout.

Examples

Intersecting Boundary

Create and plot a polygon that contains a boundary intersection.

P = [0 0; 1 1; 1 0; 0.5 0.5; 0 1; 0 0];
polyin = polyshape(P,'Simplify',false)

polyin = 
  polyshape with properties:

      Vertices: [5×2 double]
    NumRegions: 1
      NumHoles: 0

plot(polyin)

Use the simplify function to remove the intersection, which produces a well-defined polygon. Simplifying the polygon maintains the boundary shape, but splits the polygon into two distinct regions.

polyout = simplify(polyin)

polyout = 
  polyshape with properties:

      Vertices: [7×2 double]
    NumRegions: 2
      NumHoles: 0

Input Arguments

polyin — Input polyshape

scalar | vector | matrix | multidimensional array

Input polyshape, specified as a scalar, vector, matrix, or multidimensional array.

Data Types: polyshape

TF — Collinear vertices indicator

false | true

Collinear vertices indicator, specified as false or true:

• false — Remove collinear points so that the output polyshape contains the fewest vertices necessary to define the boundaries.

• true — Keep all collinear points as vertices.

When the 'KeepCollinearPoints' parameter is not specified, its value is automatically set to the value used when creating the input polyshape.

Data Types: logical

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Dynamic memory allocation must be enabled for code generation.

• Name-value pair must be compile time constant.

Thread-Based Environment
Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

Version History

Introduced in R2017b

R2024b: Improved performance when simplifying polyshape objects with many boundaries

The simplify function shows improved performance when operating on polyshape objects with many boundaries. For example, this code simplifies a polyshape object with 11,100 vertices. The code is about 23x faster than in the previous release.

function t = timingTest
n = 300;
x = (1:n)'*[sind(0:10:360),NaN];
y = (1:n)'*[cosd(0:10:360),NaN];
p = polyshape(x(:),y(:),Simplify=false);

f = @() simplify(p);

t = timeit(f);
end

The approximate execution times are:

R2024a: 0.28 s

R2024b: 0.012 s

The code was timed on a Windows^® 11, AMD EPYC™ 74F3 24-Core Processor @ 3.19 GHz test system by calling the timingTest function.