How Real Storm Footage Was Blended With VFX Magic

Snow worked as a digital effects artist on Twister, he found himself hoping to have another go at crafting the violent air clouds that unleashed devastation across Oklahoma in the 1996 film.

“The tool set was evolving so quickly back then that I’d wished we could go back and do it over because technology advanced so quickly,” Snow (yes, that is his real name) tells The Hollywood Reporter.

Nearly 30 years later, Snow got his chance as the visual effects supervisor for this year’s stand-alone sequel Twisters, starring Daisy Edgar-Jones and Glen Powell. The challenge this time was not technological limitations but rather viewer expectations. “Ultimately, it does have to convince an audience that is much more visually aware of what tornadoes look like now than when they saw the original film,” says Snow of the special effects. “That was something we set out to do.” 

Officially, six tornadoes were created for the film, though the simulation of the final storm, which catches fire after hitting an oil refinery, was so complex that it had to be broken down into smaller iterations, bringing the total to 10. Grounding the tornadoes in reality amid the heightened action of the movie and giving each its own individual character was the primary mandate from director Lee Isaac Chung, says Snow. The VFX team consulted with meteorologists to make sure their simulation tools were both scientifically accurate and powerful enough to capture the complexity of different types of storms, from wide wedge tornadoes to narrow cones. Using the 3D animation application Houdini, computational fluid dynamics software and a proprietary tool from VFX studio Industrial Light & Magic, the team was able to mimic air movement, temperature, buoyancy, gravity, moisture density, vapor dissipation and other elements that determine a storm’s appearance.

The VFX team also did research on the ground. “We sent a team of storm chasers out with motion picture cameras to photograph storms. They actually got a couple of tornadoes on film. Unfortunately, nothing’s in the movie, but some of the storm clouds we were able to use as footage,” says Snow. “It was a great thing for our visual effects team because you could study the detail with high-quality, high-resolution material — a lot better than what you might see on YouTube, for example. It allowed us to make [the tornadoes] very realistic. That was our watchword.”

Shooting in Oklahoma, a state within the area known as Tornado Alley (and where the film takes place), was a “mixed blessing,” says Snow, recounting how the frequency of storms of all kinds often caused shooting to be shut down. “At one point, we were filming a scene in a farmers market toward the end of the film, and a big storm came and demolished the set. The irony was we were going to demolish the set in the movie, so we had to rebuild this demolished set that the hailstorm had taken out and then demolish it again.”

On the other hand, the location allowed for some meaningful practical effects. “The good thing was that everyone got to feel what the weather was like,” says Snow. “The electricity in the air that you get in those severe storms — it was good for the actors as well. Scott Fisher’s special effects team on set would have jet engines, rainmakers, hail-makers, everything imaginable [to replicate the environment].”

Much like the unpredictability of the weather, even the best storm calculations couldn’t guarantee an accurate result. “There’s also the element of chance because you’re simulating things with math and you don’t really know how it’s going to turn out. So there’s this crazy piece of magic when you’re working with these tools to get that spark,” says Snow. “There are happy accidents just like there are when we film live action.”

The need for the storms’ behavior to be guided in the same way as actors are in a film is why, even as technology continues to advance rapidly, Snow doesn’t see a world where AI replaces the human touch in franchises like this one. 

“One thing that hasn’t changed between the original film and this film is you need to be able to artistically direct things,” says Snow. “[The technology] has to serve the story, and what helps make things look real and beautiful and what makes it compelling to the audience is the artistry. And that aspect, I think, will be there even in another 30 years’ time. If it’s not, I don’t know that you want to go and see the movie.” 

This story first appeared in a January stand-alone issue of The Hollywood Reporter magazine. To receive the magazine, click here to subscribe.