[rxm]

Amazing things can happen when cellular automata have symmetries. Conserve number and momentum and you're a few steps from the HPP gas [0]. Make the momentum flow a bit more isotropic, and you are on your way to the FHP gas [1]. The history I remember is that Hasslacher and Wolfram had overlapped at the IAS early 1980s. On the summer of 1985 Hasslacher visited Frisch in Nice. It was there that they guessed that the hexagonal lattice might brake the strange conservation laws of HPP. After that it was a few days until they had a set of rules for the lattice gas fluid in 2d. From France Hasslacher called Shimomura at Los Alamos and asked him if could implement them. In a few days Shimomura has a crowd staring at his screen watching a simulation of a fluid flow past an obstacle shedding vortices in real simulation time. We can do that today with our smartphones, but at the time it must have been a first.

[0]: Hardy, Pomeau, & Pazzis (1973) JMP: 10.1063/1.1666248

[1]: Frisch, Hasslacher, & Pomeau (1986) PRL: 10.1103/PhysRevLett.56.1505