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This moment from the DreamWorks picture “Monsters vs. Aliens” was made possible by a special simulation model developed by a computer science professor. Video screenshot by Danny Gallagher/CNET
A good explosion can take a terrible movie and turn it into something that wasn’t a complete waste of time, money and popcorn.
Theodore Kim, an associate professor of computer science at the University of California at Santa Barbara who also works as a senior research scientist at the Pixar Research Group, came up with an ingenious way for filmmakers to make explosions look more realistic without having to stuff a bunch of nitrocellulose under something and light it on fire. He explains his creation in a new video for the University of California’s video series Fig. 1.
Kim’s model for improving the look of smoke, fire and explosions on film is called “wavelet turbulence.” He first described his model in a paper published in 2008 in the journal ACM Transactions on Graphics.
The wavelet turbulence method improves on another method that uses “swirls” to make computer-generated images of smoke more realistic in movies like Pixar’s “The Incredibles.” However, the original method didn’t work as well when scenes called for blowing up bigger structures because it required more time for a computer to produce the image. And Jerry Bruckheimer can’t wait all night for a big explosion. He’s got “Teenage Mutant Ninja Turtles” sequels to make that nobody wants.

Kim’s wavelet turbulence method not only improves the look of smoke and fire on the screen by placing tiny swirls within bigger swirls, but it also speeds up the production process by giving these swirls a better sense of direction and organization. Kim explains in the embedded video below that his method contains algorithms for models such as a “wavelet transform” that organizes the smaller swirls instead of scattering them all over the scene where they don’t belong, and “texture advection” that pull the tiny swirls along with the flow of the bigger swirls.

Kim released his algorithm to the public along with his paper in 2008, and over the years, he’s seen it in films such as the final scene in “Monsters vs. Aliens,” the train explosion scene in “Super 8” and the Mandarin’s attack on Tony Stark’s mansion in “Iron Man 3.” The Academy of Motion Picture Arts and Sciences honored Kim for his special-effects innovation by giving him a special Oscar for technical achievement in 2012.
I hope Kim does another study that uses physics to explain why cool guys don’t look back at explosions.

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