Fluid Simulation

This evening I went with my coworkers to a lecture at the Boston Museum of Science given by Doug Roble, editor of A K Peters’ JGT.

Don’t worry: this was much more lively than it sounds.

Doug Roble has won two Scientific and Technical Academy Awards for his work with Digital Domain, which does CG effects for movies.

He’s got a PhD in computers and has developed all sorts of software—this is one smart guy. But rather than abstract and complex his presentation (which focused on fluid simulation) was clear, engaging, and hilarious.

The basic facts I came away with:

In the eighteenth century Leonhard Euler developed equations to describe the motion of moving water, which we now use to help us generate computer models of water. CG water is much cooler (though less thirst-quenching) than real water because it can do things (like pile up or form shapes) that you could never do with real water, even in a model. Even if you just want a regular flood, it’s often better to use CG water because sets with water can be no smaller than 1/3 scale of actual before it looks cheesy. Artists can make things look like water, but they can’t make it move like water, and vice versa for computer engineers, so the two team up.

Doug took us through a series of movies: from Dante’s Peak, which used a 680,000-gallon tank of water to model a flood (the biggest—and last—dump tank in film history); to Lord of the Rings, where the Ford of Rivendell used his fluid simulator to flush out the black riders; to The Day after Tomorrow, where his fluid simulator created the director’s impossible vision of a plough-shaped wall of water hurtling through New York; to Pirates of the Caribbean, where his fluid simulator sent the ship over the edge of the world while a smoothed particle hydrodynamics function sent mist swirling up to greet it; to 2012, where his fluid simulator created wave, fire, smoke, and dust effects and tossed his own company into the ocean with the rest of LA; to Percy Jackson and the Lightning Thief, where the latest in fluid simulation created both the hydra’s flames and the towering wall of water Percy used to fight them.

Of course the modeling was even more interesting because those are all movies I love, partly because they shamelessly, as Doug said, “throw reality to the winds and make something really cool.” My favorite moment of the night: Speaking of the destruction of LA in 2012, an incredible scene in a really silly movie: “If only we worked on better movies . . . but can you a imagine a good movie with that scene in it?”