  Surface tension has a strong influence on the shape of fluid interfaces. We
propose a method to calculate the corresponding forces efficiently. In contrast
to several previous approaches, we discriminate to this end between surface and
non-surface SPH particles. Our method effectively smooths the fluid interface,
minimizing its curvature. We make use of an approach inspired by Monte Carlo
integration to estimate local normals as well as curvatures, based on which the
force can be calculated. The technique is applicable, but not limited to 2D and
3D simulations, and can be coupled with any common SPH formulation. It
outperforms prior approaches with regard to total computation time per time
step, while being stable and avoiding artifacts.
