  The effects caused by nonresonant nonlinear interaction between noncollinear
self-focusing beams are considered in 2D optical samples using multi-scale
analysis. The analytical expression for the beams trajectories shift due to the
mutual interaction is derived, and the range of parameters is given beyond
which the mentioned consideration fails. We compare our results with the naive
geometrical optics model. It is shown that these two approaches give the same
results. This justifies the use of geometrical optics approach for description
of elastic and almost-elastic collision processes both in Kerr and saturable
nonlinear media.
