ILM’s Ben Snow has come full circle. After serving as a young artist on Jan de Bont’s “Twister during the early days of digital in 1996, the VFX vet returned as production supervisor on Lee Isaac Chung’s “Twisters” with a full CG arsenal at his disposal. “The original film was a tough show,” he told IndieWire. “We were inventing a lot of the technology and didn’t really know what we were doing. And so I think it’s really good to be able to come back and revisit it with a modern toolset.”
What director Chung envisioned for his update, which concerns the rivalry between tornado chasers Kate (Daisy Edgar-Jones) and Tyler (Glen Powell) during Oklahoma’s most destructive season, was making the CG tornadoes terrifying forces of nature with individual characteristics. This impressionistic approach was important in charting Kate’s emotional arc during her redemptive mission to tame these monsters through a combination of intuition and science.
“It was really important for Isaac Chung to identify them,” Snow said. “We went through some hero frames for what each one would look like. Also some video clips of different beats that we wanted because one of the advantages that we have today is so much footage on YouTube. So we took the stills and the reference clips that Isaac had given us and talked about what the character of each tornado would be. We had a pretty big animation team on the show, and we started with what the tornado would look like, and then trying in animation to give it a feeling of the way it moved.”
“Twisters” features six tornado scenes for which ILM built 10 models. They used their LFL pyro simulation program that interfaces with Houdini to generate the surfaces, many containing multiple layers. On a meteorological scale, the tornadoes ranged in magnitude from EF-1 to EF-5.
Each tornado was made up of a funnel, a dust shroud (thin layer of dust or vapor surrounding the funnel), a debris field (dust picked up from the ground), rigid debris objects, a wall cloud (where the funnel connects to the clouds), and a shelf cloud, which connects to background sky. “Those components were determined by our visual studies of real tornado footage we selected to match for each of the sequences,” Snow added, “and based on what science tells us about how these storms are made up.”
For most shots, once the VFX team had a cut from editorial, Snow would go through it, identify skies they could keep from the plates, and then choose a matching set of high-resolution still panoramas from their still photography gathered by storm chasers. They would assign a panorama for each shot or group of shots that needed sky replacements and select a viewpoint that matched the lighting direction of the plate.
“In some cases,” I was able to find moving footage from the storm chasers,” Snow said. “I’d make bash comps with crude extractions in editing software. We’d review that with our ILM artists to make sure they’d work for the VFX team, and creatively with Issac Chung. Once Isaac approved them, that practical material would be our starting point.”
The first tornado in the prologue is an EF-5, with a wind speed exceeding 200 miles per hour, capable of blowing homes off their slabs. It hides behind a rain curtain, assaulting Kate and her college crew of storm chasers with hail and precipitation, allowing only glimpses of its terrifying structure in a “Jaws”-like maneuver. This becomes the bogeyman that haunts her after the tragic failure of the science project.
“For the EF-5 tornadoes, we had basically the same ingredients,” Snow continued. “But instead of a funnel, we had a large wedge. To get the detail we needed in the simulation, we had a way that we could break the wedge of the tornado up into 3D volumetric tiles, like big voxels. This allowed a lot of precision with each simulation, and the LFL pyro tool allowed us to have the velocities and directional vectors carry across the boundaries of the volumetric tiles so that the final result was a cohesive whole in terms of the physics and cloud/dust behavior.”
Kate encounters the second tornado on her return to Oklahoma five years after the prologue. This EF-1 is a classic funnel-cloud twister, but it’s enough to trigger her PTSD, and she freezes under pressure. With the third tornado, she reconnects with the thrill of storm chasing and her mission to tame tornadoes. However, this one offers the rare phenomenon of a single twister splitting into two: one weak (EF-2), one strong (EF-3). Kate pursues the strong one, which rolls through the nearby town of Crystal Springs.
Meanwhile, the fourth tornado (EF-4) blows through the town of Stillwater and turns into a nightmare, reminding Kate of the monstrous first one, with the interplay of practical effects, digital effects, stunts, and long shots. Kate then returns to her childhood home, where she teams up with Tyler to chase the fifth tornado (EF-1) to test a new taming approach.
The sixth and final tornado is the sum of all fears, which Kate courageously confronts with everything she’s learned. A minor whirlwind grows into a full-blown EF-5 thanks to a massive supercell thunderstorm that produces multiple tornadoes at once. After rumbling through an oil refinery and catching fire, the tornado ravages the town of El Reno, toppling a water tower, shredding a farmer’s market, and obliterating a movie theater playing “Frankenstein.” (Snow worked on the tornado in “Twister” that hit a drive-in playing “The Shining.”)
“This one’s bigger, in fact, than the first one,” he said. “What happens is it smashes into some electrical stuff in the refinery, and there’s a chain reaction that’s not apparent in the film. But it gave us a backstory to work out. All of this heat and everything else causes a vortex [a firenado] that you usually see in wildfires. Isaac very much wanted to anchor this in reality, and the truth is that firenadoes don’t travel. So there’s a moment where it sort of gets extinguished. But what comes up in its place is an EF-5, and that’s when it starts heading off towards El Reno.”
