‘Twisters’ Needed to Create Tornado-Force Winds and Rainstorms on Set for Action Scenes

[Editor’s Note: IndieWire will cover VFX contributions to “Twisters” next week.]

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One key to the success of “ Twisters ” is how well the CGI tornados are integrated with the action of characters running away from — or, in the case of the storm trackers, driving toward — these terrible forces of nature. Director Lee Isaac Chung recently told IndieWire about how he thought he designed action scenes in terms of layers.

“The ultimate layer, the background layer is going to be the tornado within any frame,” said Chung. “And that I knew had to be CGI because there was no way to actually capture one in the moment.”

What visual effects supervisor Ben Snow’s team achieved in creating six distinct, realistic tornados for each of the film’s big action set pieces is remarkable, but that alone is not enough to sell the movie magic.

“Ultimately what makes that background layer feel real is that [the tornado] is doing to very tangible things in the foreground.” said Chung. “Really what creates drama and tension is when we don’t see [the tornado], and when we’re focusing on its effects.”

Between the camera and CGI background, Chung relied largely on what special effects supervisor Scott Fisher could do practically on set. This applied not only to things like a Coke machine being blown across an empty swimming pool but also to creating wind and rain on set. While Fisher scooped up all the wind-producing machines he could find, “Twisters” required more than the standard Hollywood moviemaking tools. The SFX supervisor purchased two jet engines capable, according to the film’s press notes, to create 170- to 180-mph winds, which, when kept a good distance from the set, could simulate the desired effects.

“Scott had such huge fans, we had to make sure everybody’s wearing earplugs, because they were deafening, especially that jet engine,” said Chung, who said on-set winds maxed out at 110 mph. “An EF1 tornado is right in that 100 mph range, so these were tornado wind speeds that we’re putting the actors through. They’re not acting at those moments. They’re just reacting to the weather, and it comes off as very realistic.”

To simulate a tornado’s rain effects, Fisher’s team had 10,000-gallon “dump tanks” and high-pressure pneumatic water cannons. For hail, they used a rubbery water-soluble polymer that resembles ice, but which is softer, causing less pain when it hits the actors.

Beyond the whipping precipitation, it’s the swirling debris and dirt that makes the wind’s power visible on screen. A veteran of Christopher Nolan’s productions, Fisher came equipped with a number of tricks up his sleeve.

“He had also developed a type of debris and dust that he had used on ‘Interstellar,’ because there’s this wonderful storm sequence in [that film], a dust storm, and he had concocted this mix to do that,” said Chung. “He brought that on to this set because it’s nontoxic, it’s not going to hurt our actors, and it really reads the wind very well.”

Cinematographer Dan Mindel did early camera tests on the practical effects, which he told IndieWire combined nicely with the film grain of the 35mm stock they shot on.

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“We did a proof-of-process test very early on with the physical effects, the rain, the ice, the smoke, dust, all those things,” said Mindel. “And the more of that we have, the more texturization you get in the film because we’re shooting analog, real film.”

In a story about storm trackers, a great deal of the exterior tornado scenes involve vehicles, as characters are often driving in and out of the storms.

“The fact that the cameras are mounted on moving vehicles, and there’s real wind and noise and bumps , gives you another layer of tactile involvement for the viewer,” said Mindel. “And you’re not just sitting there looking at a CGI-created frame going, ‘Oh, this is horseshit.’ You become more involved in the story.”

Mindel has been shooting big action films since the 1990s, including films in major visual effects-heavy franchises like “Mission: Impossible,” “Spider-Man,” “Star Wars,” and “Star Trek.” He’s used to a close collaboration with VFX teams. He strongly believes that the combination of analog film and digital effects is the best way to marry CGI and practical layers.

“ Shooting on film gives you so much more control because of the lack of absolute clarity that you have,” said Mindel. “The fact that the resolution at its best is going to be 4K or 2.9K is low compared to most digital cameras. That allows us a lot of wiggle room in how these effects sit in the film frame. It allows us to dumb down, to a certain extent, the visual effects because they don’t have to resolve so well. There’s sort of a meeting halfway.”

Chung agrees. While doing his sound mix at George Lucus’ Skywalker Ranch, he saw some of the original matte paintings (the original effect background layer, before CGI) from the first “Star Wars” films. What struck him about seeing the old matte paintings was they looked more like “pointillist art” — and less fleshed-out in terms of detail.

“That stuff just still holds up today, and it’s because it’s not very detailed. I feel [like] what they found is that if they made that detailed, it would throw the eye, and so what film grain, to my eye, does is add that layer, creating a little bit more of that pointillism within the image,” said Chung. “It helps us to let the VFX sit within that grain and marries it really well. And I felt like J.J. [Abrams’] ‘Star Wars’ films with Dan [ Mindel, who shot ‘The Force Awakens’ and ‘The Rise of Skywalker’ on celluloid], both of those look so impeccable. The VFX looks so incredibly real, and I think Dan had learned that lesson on all of the giant films that he’s done.”

Ryan Lattanzio contributed reporting.

Look for IndieWire’s Toolkit episode with Lee Isaac Chung on Spotify , Apple , and other major podcast platforms this weekend.