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vertexAttachments - Class: TriRep

Return simplices attached to specified vertices

Syntax

SI = vertexAttachments(TR, VI)

Description

SI = vertexAttachments(TR, VI) returns the vertex-to-simplex information for the specified vertices VI. In relation to 2-D triangulations, if the triangulation has a consistent orientation the triangles in each cell will be ordered consistently around each vertex.

Inputs

`TR`	Triangulation representation
`VI`	`VI` is a column vector of indices into the array of points representing the vertex coordinates, `TR.X`. The simplices associated with vertex `i` are the `i`'th entry in the cell array. If `VI` is not specified the vertex-simplex information for the entire triangulation is returned.

Outputs

`SI`	Cell array of indices of the simplices attached to a vertex. A cell array is used to store the information because the number of simplices associated with each vertex can vary. The simplices associated with vertex `i` are in the `i`'th entry in the cell array `SI`.

Definitions

A simplex is a triangle/tetrahedron or higher dimensional equivalent.

Examples

Example 1

Load a 2-D triangulation and use TriRep to compute the vertex-to-triangle relations.

load trimesh2d

Find the indices of the tetrahedra attached to the first vertex:

Tv = vertexAttachments(trep, 1)
Tv{:}

Example 2

Perform a direct query of a 2-D triangulation created using DelaunayTri.

x = rand(20,1);
y = rand(20,1);
dt = DelaunayTri(x,y);

Find the triangles attached to vertex 5:

t = vertexAttachments(dt,5);

Plot the triangulation:

triplot(dt);
hold on;

Plot the triangles attached to vertex 5 (in red):

triplot(dt(t{:},:),x,y,'Color','r'); 
hold off;