Using rather difficult test problems, we have shown that our 3D long-characteristics method gives very good results when compared to our well-tested 1D code. The main differences are due to poorer spatial resolution close to the center of the grid in the 3D case. The code has also been parallelized and scales to very large numbers of processors. Future work will examine a short-characteristics method of solution which should enable higher resolution grids with the same memory requirements and an extension to full multi-level NLTE modeling.
