  The motion of three-dimensional (3D) solitary waves and solitons in nonlinear
crystal-like structures, such as photonic materials, is studied. It is
demonstrated that collective excitations in these systems can be tailored to
move in particular directions of the 3D system. The effect of modulation
instability is studied showing that in some cases it can be delayed by using a
lensing factor. Analytical results supported by numerical simulations are
presented.
