We love it when things go boom on screen. These days, we expect to be blown away in action movies, and Hollywood goes ever more over the top to keep us entertained. There’s a lot of science that goes into making increasingly spectacular explosions look real.
Theodore Kim of the University of California, Santa Barbara explains what goes into making computer-generated explosions look so convincing in this video from University of California’s Fig. 1 series. It’s about the way smoke and debris behave, and it’s at least as thrilling as the last exploding car you saw fly across the screen.
Hollywood’s programmers used to create big bangs with large flowing swirls like you might draw coming out of a cup of coffee, and lots of smaller swirls on top. The problem with this system was that the number-crunching took hours, so getting just the right kaboom was prohibitively time consuming.
In 2008, UCSB published a paper on “wavelet turbulence,” an open-source technique that radically sped things up. They joined an existing algorithm for quickly drawing little swirls with another one that draws big ones. A “wavelet transform” algorithm positions the little guys convincingly, and “texture invection” makes them move along with the big ones. One final bit of mathemagic deletes any small swirls that get pulled too far out or jammed too close in. And boom.