How were the spectacular tornadoes in Twisters created?

Thirty years after working on Jan de Bont's film, Ben Snow, visual effects professional for ILM, deciphers his work in post-production of the blockbuster event.

Since its release in mid-July, Twisters is enjoying great success in theaters, both American and French. Critics agree that it is above all for its striking visual effects that the film is Lee Isaac Chung stands out from the crowd. Already, the original film of Jan de Bont, Twisterwas nominated for the Oscar for Best Special Effects in 1997. The main name that links the two films? It's Steven Spielberga big name in the field, who produced the two blockbusters, almost thirty years apart.

Alongside Spielberg, the company Industrial Light and Magic (ILM for short), and Ben Snowa VFX specialist. Thirty years later, he returned to tame tornadoes for this new disaster film with Daisy Edgar-Jones, Glen Powell And Anthony Ramos headliner. Things have changed a lot in three decades, as Ben tells IndieWire :

“For the original film, everything was more difficult. We were inventing a lot of the technology and we didn't really know what we were doing. That's why I think it's really good to be able to go back and revisit it with a modern set of tools.”

It was also necessary to adapt to Lee Isaac Chung's new vision of tornadoes, a naturist vision where tornadoes present singular characteristics. Each tornado has its own personality, in short.

“It was very important for the director to be able to identify them. We went through some images to see what each one would look like. We also looked at video clips of the different rhythms we wanted, because one of the advantages we have today is that there is a lot of footage available on YouTube. So we took the reference photos and clips that Isaac had given us and we talked about the character of each tornado. We had a fairly large animation team, and we started by figuring out what the tornado would look like, and then we tried to give it a sense of movement through animation.”

The entire plot of the film is based on the confrontation of an EF-5 tornado, which took away the relatives of Kate, a young PhD student who was working on a university project. Years later, due to climate change, tornadoes are multiplying and wreaking havoc in the Midwest, and Kate returns to test a new device that could help study them. In fact, Twisters features no less than six tornadoes that increase in intensity throughout its plot, ranging from EF-1 to EF-5.

Ben Snow has found the recipe for a perfect tornado: a funnel surrounded by a thin layer of dust or vapor, a dusty debris field, a hard debris field, a wall cloud to connect the funnel to the clouds, and a shelf cloud that connects it all to the sky in the background.

“These elements were determined by our visual studies of real tornado sequences, which we selected based on what science tells us about how they are formed.”

Of course, the technician did not create all the images from scratch, and found a workaround to save precious time, as well as money:

“In some cases, I was able to find footage of actual storm chasers. I would make compilations with raw cuts in editing software. We would review them with our ILM artists to make sure they would be a good fit for the VFX team, and creatively with Isaac Chung. Once Isaac approved them, that practical material was our starting point.”

The biggest challenge was the two EF-5 tornadoes that frame the narrative, one at the beginning of the film, the other at the end. Be careful, it's a bit technical:

“For the EF-5 tornadoes, we had essentially the same ingredients. But instead of a funnel, we used a gigantic wedge. To get the detail we needed in the simulation, we could break the corner of the tornado into 3D volumetric tiles, like large voxels (one pixel in volume, Editor’s note). This allowed for great accuracy in each simulation, and LFL's pyro tool (software that allows you to make flames, Editor's note) allowed us to pass velocities and directional vectors across the boundaries of the volumetric tiles, so that the end result is a coherent whole in terms of cloud and dust physics and behavior.”

While all of this assembly is done primarily on computer, the actors did not emerge unscathed from their encounters with the tornadoes on set. In an interview, Anthony Ramos, who plays Javi in ​​the film, told Première about the filming of these action sequences:

“The filming took place on location, with the idea that everything had to be as realistic as possible. To create the illusion of tornadoes, the special effects team used airplane engines. And we were more on a Boeing 707 than on a small model. Chasing the tornadoes in a car was no easier than in real life. Between the curtain of artificial rain, the blast of the engines and the earth that was thrown in our faces, we couldn't see two meters. In addition, the camera – which was sheltered, on a truck that was driving in front of us – was very tight on us, so we had to be careful with our facial expressions. It was really an experience like no other.”

Twisters is still available to discover at the cinema. Here is the trailer for the film, with storms in it: