  The diagnosis of new high-resolution spectropolarimetric observations of
solar prominences made in the visible and near-infrared mainly, requires a
radiative modelling taking into account for both multi-dimensional geometry and
complex atomic models. Hereafter we contribute to the improvement of the
diagnosis based on the observation of He I multiplets, by considering 2D
non-LTE unpolarized radiation transfer, and taking also into account the atomic
fine structure of helium. It is an improvement and a direct application of the
multi-grid Gauss-Seidel/SOR iterative scheme in 2D cartesian geometry developed
by us. It allows us to compute realistic emergent intensity profiles for the He
I 10830 A and D3 multiplets, which can be directly compared to the simultaneous
and high-resolution observations made at THeMIS. A preliminary 2D multi-thread
modelling is also discussed.
