First input T is a triangulation (triplet list of indices -positive integers-, each index refering to a vertex number in a corresponding vertices list).
Given a second input t (a certain triangle row index), one would like to query the list L of all its triangle neighbor indices. A triangle is neighbor to another triangle if they share exactly one edge.
For instance if
T = [1 2 4;...
2 3 4;...
5 6 8;...
6 7 8;...
1 2 5;...
2 5 6;...
2 3 6;...
3 6 7;...
3 4 7;...
4 7 8;...
4 1 8;...
1 8 5]
and t = 3, then the function should return
L = [4, 6, 12]'
since rows / (triangles of T) 4, 6, and 12 contain an edge in common with triangle / row 3.edge [6 8] for the first, edge [5 6] for the second, and edge [8 5] for the third.
Hypothesis :
- Since a triangle is not considered neighbor of itself, t should not be part of L.
- Order doesn't matter, but T must be a column vector containing all the neighbor triangle -row- indices (except itself then) once only. No duplicata is admitted.
- Edges are symmetric : [e1, e2] is the same edge as [e2, e1]
- Every indices are positive, distinct integers.
See also
Solve

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Last Solution submitted on May 24, 2026

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Chris Cleveland Mehdi Dehghan Shane Coffey Lorenzo

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