  As a generic example for crystals where the crystal-fluid interface tension
depends on the orientation of the interface relative to the crystal lattice
axes, the nearest neighbor Ising model on the simple cubic lattice is studied
over a wide temperature range, both above and below the roughening transition
temperature. Using a thin film geometry $L_x \times L_y \times L_z$ with
periodic boundary conditions along the z-axis and two free $L_x \times L_y$
surfaces at which opposing surface fields $\pm H_{1}$ act, under conditions of
partial wetting, a single planar interface inclined under a contact angle
$\theta < \pi/2$ relative to the yz-plane is stabilized. In the y-direction, a
generalization of the antiperiodic boundary condition is used that maintains
the translational invariance in y-direction despite the inhomogeneity of the
magnetization distribution in this system. This geometry allows a simultaneous
study of the angle-dependent interface tension, the contact angle, and the line
tension (which depends on the contact angle, and on temperature). All these
quantities are extracted from suitable thermodynamic integration procedures. In
order to keep finite size effects as well as statistical errors small enough,
rather large lattice sizes (of the order of 46 million sites) are found
necessary, availability of very efficient code implementation of graphics
processing units (GPUs) was crucial for the feasibility of this study.
