  We construct scattering diagrams for generalized cluster algebras,
generalizing the cluster scattering diagrams of Gross, Hacking, Keel and
Kontsevich. They turn out to be natural objects arising in Fock and Goncharov's
cluster duality. Analogous features and structures (such as positivity and the
cluster complex structure) in the ordinary case also appear in the generalized
situation. With the help of these scattering diagrams, we show that generalized
cluster variables are theta functions and hence have certain positivity
property.
