  The modern Doppler Imaging (DI) technique allows the reconstruction of
different stellar surface structures based on accurate calculation of spectra
of specific intensity. New applications like the mapping of the magnetic field
vector put very stringent requirements on the radiative transfer (RT) solver
which should be accurate, fast, and robust against numerical errors. We
describe the evaluation of three different algorithms for our new magnetic DI
code INVERS10. We also show the first results of numerical experiments made
with the new code.
