boundaryshape

Create polyshape from 2-D triangulation

Syntax

polyout = boundaryshape(TR)

[polyout,vertexID] = boundaryshape(TR)

Description

polyout = boundaryshape(TR) creates a polyshape object from the boundary of a 2-D triangulation. TR can be either a triangulation object or a delaunayTriangulation object.

Once you create the polyshape object polyout, you can analyze its properties or perform additional computations using polyshape functions. For example, you can access the vertices that define the boundary with the property polyout.Vertices, and you can plot the shape using the command plot(polyout).

[polyout,vertexID] = boundaryshape(TR) also returns a vector vertexID that maps the vertices of the polyshape to the vertices of the triangulation.

Examples

Simple Boundary

Create and plot a simple triangulation object.

P = [2.5 8.0; 6.5 8.0; 2.5 5.0; 6.5 5.0; 1.0 6.5; 8.0 6.5];
T = [5 3 1; 3 2 1; 3 4 2; 4 6 2];
TR = triangulation(T,P);
triplot(TR)
xlim([0 9])
ylim([4.5 8.5])

Create and plot a polyshape object whose boundary is equal to the boundary of the triangulation.

polyout = boundaryshape(TR);
plot(polyout)

Solid and Hole Boundaries

Create and plot a triangulation object.

T = [5 1 3; 6 1 4; 5 4 1; 2 6 3; 3 6 5; 2 1 6];
P = [3 0.5; 3.5 1.5; 4 0.5; 3.25 0.6; 3.75 0.6; 3.5 1];
TR = triangulation(T,P);
triplot(TR)
xlim([2.8 4.2])
ylim([0.4 1.8])

Create and plot a polyshape object whose boundaries are equal to the boundaries of the triangulation. Due to the inner and outer closed boundaries of the triangulation, polyout contains both a hole boundary and a solid boundary.

polyout = boundaryshape(TR)

polyout = 
  polyshape with properties:

      Vertices: [7x2 double]
    NumRegions: 1
      NumHoles: 1

plot(polyout)

Input Arguments

TR — Triangulation

2-D triangulation object | 2-D delaunayTriangulation object

Triangulation, specified as a 2-D triangulation object or a 2-D delaunayTriangulation object.

Output Arguments

polyout — Output polyshape

polyshape object

Output polyshape, returned as a polyshape object.

vertexID — Vertex identification

vector

Vertex identification, returned as a vector of integers. Each element in vertexID corresponds to the row number of the triangulation vertex in the Points property. The length of vertexID is equal to the number of rows in the Vertices property of the polyshape object.

Data Types: double

Version History

Introduced in R2018b