triangleNeighbors method
Returns the neighbor triangles for triangle t.
Returns -1 for edges on the convex hull.
Implementation
List<int> triangleNeighbors(int t) {
return [
_triangleOfEdge(halfedges[t * 3]),
_triangleOfEdge(halfedges[t * 3 + 1]),
_triangleOfEdge(halfedges[t * 3 + 2]),
];
}