  We present SMART, a new 3D implementation of the Schwarzschild Method and its
application to a triaxial N-body merger simulation. SMART fits full
line-of-sight velocity distributions (LOSVDs) to determine the viewing angles,
black hole, stellar and dark matter (DM) masses and the stellar orbit
distribution of galaxies. Our model uses a 5D orbital starting space to ensure
a representative set of stellar trajectories adaptable to the
integrals-of-motion space and it is designed to deal with non-parametric
stellar and DM densities. SMART's efficiency is demonstrated by application to
a realistic N-body merger simulation including supermassive black holes which
we model from five different projections. When providing the true viewing
angles, 3D stellar luminosity profile and normalized DM halo, we can (i)
reproduce the intrinsic velocity moments and anisotropy profile with a
precision of ~1% and (ii) recover the black hole mass, stellar mass-to-light
ratio and DM normalization to better than a few percent accuracy. This
precision is smaller than the currently discussed differences between
initial-stellar-mass functions and scatter in black hole scaling relations.
Further tests with toy models suggest that the recovery of the anisotropy in
triaxial galaxies is almost unique when the potential is known and full LOSVDs
are fitted. We show that orbit models even allow the reconstruction of full
intrinsic velocity distributions, which contain more information than the
classical anisotropy parameter. Surprisingly, the orbit library for the
analysed N-body simulation's gravitational potential contains orbits with net
rotation around the intermediate axis that is stable over some Gyrs.
