Problem 45219. Find edges from a vertex

Created by Nicolas Douillet

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First input is T, a triplet list of indices. Second input is i, a single index (positive integer). The goal of this function is to find and return all the edges [e1 e2] this vertex belong to.For example if inputs are<pre class="language-matlab">T = [1 2 3 ;...
 1 3 4 ;...
 1 4 2 ;...
 2 3 4]
</pre>and<pre class="language-matlab">i = 4
</pre>then the output is the 3 x 2<pre class="language-matlab">matrix edg_list= [1 4;...
 3 4;...
 2 4]
</pre>since vertex number 4 is linked with vertices number 1, 2, and 3 and then part of edges [1 4], [2 4], and [3 4]. Format of the output must be the following :<ul><li>size(edg_list) = [number of edges, 2]</li><li>Every row of it is an edge at the format [e1, e2], sorted in ascending order, i.e. e1 &lt; e2, and e1, e2 positive integers.</li><li>Each edge is present once and only once, no duplicated edge admitted</li><li>Order of rows / edges in the output doesn't matter .</li></ul>If the vertex is not in the list, the function must of course return the empty set.

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Last Solution submitted on Oct 14, 2020

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1 Comment

Nicolas Douillet on 3 Dec 2019

Info : T is actually a triangulation -list of triangles-, in which each index corresponding to the row index of a vertex in another list -a vertices list-, it is a widely used technique used to store and write triangular meshes in mesh processing. Here below the example is a tetrahedron -4 facets-.

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3d edge face facet find geometry index indices mathematics mesh mesh processing surface triangle triangulation trimesh vertex vertices

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Problem 45219. Find edges from a vertex

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