There’s definitely a strange and scary beauty to the Toxic Storm from "Mad Max: Fury Road," the movie’s biggest VFX sequence. The cataclysmic event goes beyond the random havoc George Miller wanted overall, sweeping up vehicles into the sky. It achieves an otherworldly spectacle, courtesy of the magnificent fluid sim work by Australia-based Iloura.
"It was the climax of the first act and had to be spectacular," admitted Miller, who wanted to magnify the size and intensity of the towering dust storms they occasionally get in Sydney that look like nuclear winters.
Production VFX supervisor Andrew Jackson ("300") worked with Iloura on the immense cloud-form sim build, referencing the biggest tornadoes and split it up into multiple twisters. "It was the first sequence George Miller passed to us, it occurs early in the film, and is pivotal to the story so he needed it resolved as soon as possible," recounted Tom Wood, Iloura’s VFX supervisor. "The sequence was delivered to us by production as an incomplete post-vis construction. The cut was solid and twisters were laid out represented by inverted cones with spinning textures."
Miller requested "a super cell type storm" and Wood had concept art produced by a team of artists at Method Studios in London. Included was igniting fuel rising into the twister as well as wide vistas of the storm exterior as a dark and dirty super cell cloud. "When I visited the set in Namibia, I showed the concepts to George and he loved them. As the sequences were cut, the artwork was used in editorial and the look pretty much stayed the same," said Wood.
"We sourced a huge amount of real twister footage to find visceral effects we liked and thought would work well for this sequence. The main, large core of the twisters were 3D volumes, almost entirely shader-based, allowing internal lighting. These were then wrapped in multiple, dense particle simulations that connected to the ground and sky. The sky was a 3D, animated matte painting created as numerous layers in Photoshop and assembled in Nuke. As the plates were shot in full sun, the vehicles were tracked and partially re-lit in CG to sit in the dark environment.
"The ground was often replaced to give greater speed and an un-driven, clean look. Onto this we added layer upon layer of individual dust simulations. Ground dust that looked like arctic ice racing close to the surface, rivers of dense dust up to window height, large, dense clouds of roiling dust the vehicles swept through and a huge volume that gives a modulation to visibility into the distance," he said.
"On top of these, we added CG and practical element grit and light variation to immerse the camera into the experience. Lightning strikes were added as light sources, casting shadows onto and lighting through the dust layers. These had a whole series of choreography passes reviewed by George to accent the action, building to the final crash-endo."
A twisting velocity field provided the base motion of a vortex with layers of turbulence and collisions adding details. "A particle system emitting from the ground was advected through the velocity grids and more layers of noise and turbulence were applied, Bethell explained. "The particles were then rendered through PRMan using particle instancing to increase the numbers, sometimes up to half a billion particles."
Simply put, this was not a good place to be.