The Secret to Some of Lucasfilm's Magic: Nvidia's GPU Chips
Like the visual effects you’ve been seeing in movies these days? Of course, you already know that in most cases they’re computer-generated. And as you’ve seen over the last few days during my visit to Lucasfilm’s Industrial Light and Magic, the computing power used to render the visual effects isn’t exactly consumer grade.
But as I learned, the effects wizards at ILM have a secret weapon that shares a lot in common with your PC at home. If you play any graphics-heavy games, your PC probably has a graphics processing unit in it, and chances are pretty good that GPU card came from Nvidia. As you might expect, displaying ever-more realistic scenes in a PC game is similar in many respects to what you need to make a wicked cool effect in a movie. And in certain cases they’re better than even the most powerful traditional CPU chips from the likes of Intel or Advanced Micro Devices.
The story goes that when he was working on a scene for “Harry Potter and the Half-Blood Prince,” Chris Horvath was asked to create a “tornado of fire” (the picture above is borrowed from that scene). At the time, the conventional way of doing it just didn’t produce a satisfying result. “We needed to do this very complicated fire simulation and we just didn’t have a solution to do it,” said Craig Hammack, an ILM visual effects supervisor who was sitting near Horvath at the time.
Someone suggested to Horvath that he try working with GPUs, and not only that but writing an effects program to take advantage of their unique computing capabilities. (Horvath tells the story in the video below.) The result was a piece of internal ILM software called Verté that reduced the desired fire effects to a series of flat two-dimensional images linked together to look like they were 3-D.
Next came a new tool called Plume, used to simulate the movements of fluids. It’s written to take advantage of a newer Nvidia parallel computing technology called CUDA. Suddenly, the work required to create deeply complex visual effects involving images of fire or water sped up considerably because the software written for Plume could talk directly to the graphics chip itself.
“We used to have a smoke simulation engine that we had been using for I don’t know how long, and it rendered on CPUs, and the turnaround time was about a day,” Kirk Haller, ILM’s director of research and development told me. “You’d have to set things up and feel pretty confident that you were doing the right things,” because you wouldn’t see the result until the day after.
Plume changed the game in a big way. Developed first for use on “The Last Airbender,”, it allowed artists working on simulations to mess around with them on the fly, literally changing settings on software dials. “It’s a very friendly system. People who aren’t experts and don’t know exactly what numbers and settings to put in on the old system could tweak the settings and learn how it behaves, and get the artistic refinement and the look that they want,” Haller told me.
Plume sped things up so much on “Airbender” that effects artists were able to work with director M. Night Shyamalan in near real-time, allowing him to have input on how the simulated fire and water and air would look in each shot and how it would affect the characters on the screen, Olivier Maury, a research and development engineer at ILM, told me. Instead of waiting a day to see the results of each day’s work, an artist could work up as many as several versions of a complex simulation every day.
That’s why Plume–which is a proprietary tool–is now being used on every film currently in the works at ILM. And that’s a lengthy list, including “Cowboys and Aliens,” “Pirates of the Caribbean 4” and “Transformers 3,” to name but a few.
Plume simulation renders are run on a rack of 12 Nvidia Quadroplex 2200′s. Each machine in the rack contains two GPU chips, but each chip has 240 cores, the central computing brain of the chip. That means this rack has 5,760 computing brains jamming on simulations and effects shots at any time. That’s some serious horsepower. The rack is situated only steps away from the “Death Star” rack I showed you last week, though, silly me, I didn’t have the presence of mind to shoot any footage of it.
I wasn’t able to shoot any video to demonstrate any of this. But the folks from ILM like the results they’re getting from the Nvidia GPUs so much they appeared in a video about it last year that coincided with the release of “Airbender,” and it shows a good bit of the evolution of the process from “Potter 6″ to “Airbender.” Chances are you’ll be seeing a lot of shots first created in Plume in movies coming this summer.