Using the locally compact abelian group \BT \times \BZ, we assign a
meromorphic function to each ideal triangulation of a 3-manifold with torus
boundary components. The function is invariant under all 2--3 Pachner moves,
and thus is a topological invariant of the underlying manifold. If the ideal
triangulation has a strict angle structure, our meromorphic function can be
expanded into a Laurent power series whose coefficients are formal power series
in q with integer coefficients that coincide with the 3D index of
\cite{DGG2}. Our meromorphic function can be computed explicitly from the
matrix of the gluing equations of a triangulation, and we illustrate this with
several examples.Comment: 34 pages, 4 figure