As the trend of neutron guide designs points towards longer and more complex
guides, imperfections such as waviness becomes increasingly important.
Simulations of guide waviness has so far been limited by a lack of reasonable
waviness models. We here present a stochastic description of waviness and its
implementation in the McStas simulation package. The effect of this new
implementation is compared to the guide simulations without waviness and the
simple, yet unphysical, waviness model implemented in McStas 1.12c and 2.0