[Crazywater]

This is the latter. There are a lot of reasons you would not want this for accurate simulation, one being that you basically prime your simulation on your training data. The other one being that SPH is already quite an approximation of Navier Stokes.

But for real-time animation, this is very nice. The problem with particle fluid simulations is that everything scales linearly, but only in the number of operations per particle per simulation timestep. But the more particles you have, the smaller the timestep needs to be in order to not let the simulation explode. And this is a real problem, because you want multi-million particle simulations for realistic water, but then the number of steps you need to compute per frame increases.

They managed to do a single simulation step per frame.