The practical photographic element shoots and the digital compositing work done to bring the subatomic and large scale explosive effects of ‘Oppenheimer’ to the screen.
Oppenheimer visual effects supervisor Andrew Jackson remembers the first call Christopher Nolan made to him regarding the director’s film about the American scientist’s role in building the first atomic bomb.
“Chris rang me and said he had a new script he wanted me to read,” Jackson told befores & afters. “He said, it’s got some quite big effects, but I really don’t want to use CG on this one in particular because it’s so important for the style of the film and the way that he wanted it to feel. He wanted it to have that raw, gritty feel.”
Almost immediately, Jackson began pulling together an animated grid of looped videos of various practical effects tests he had carried out himself over the years. These came from Jackson’s time running his own practical special effects and miniatures company, as well as explorations done for films where he was the visual effects supervisor (his most recent credits include Nolan’s Dunkirk and Tenet).
“These things were often little tiny tests that I’d done to inspire the final visual effects work,” says Jackson. “Sometimes they were not even usable elements. But one of the main things that you get from shooting stuff for real is not necessarily just the way that it looks, it’s that idea of bringing in ideas that you could never think up. There are things that just happen when you create a practical event and film it. In a CG world, someone would have to actually think of that thing and make it happen rather than it just happening at random.”
Jackson showed Nolan his collection of tests and received a very positive response from the director. “There were all sorts of things on there–liquids and particles and sand. That fit the ideas in the script about subatomic particles, electrons and waves. Chris was very open to it, and he wasn’t actually very rigid about exactly what he wanted. He said, just go away and come up with whatever you can.”
‘Coming up’ with the visual effects
Ultimately, Jackson’s task, and one he shared very closely with special effects supervisor Scott Fisher, would be to visualize several kinds of physical phenomena for Oppenheimer. Many shots included close-up views of subatomic particles, while others involved re-creating the nuclear blast of the Trinity Test that took place in New Mexico in 1945. The overall approach would be to capture real photographic elements–largely with IMAX cameras–and then incorporate those into the film, either directly as shot plates, or by compositing different elements together digitally, a task handled by DNEG.
Jackson began that process by, he says, “hanging out in Scott Fisher’s workshop for the first two months, building little things and filming them on digital stills cameras and iPhones at high speed and just testing ideas as fast as we could.”
“When we had a little collection of things, I would go and see Chris and show him what we were doing. He was very open and collaborative and encouraging. We would take the ones that he thought were really successful and develop them further. Chris also treats all of the effects as really one department. We get together and we discuss how to approach all of the effects. I absolutely love that approach. I think it’s a really sensible way of dealing with the effects, rather than dividing it into two different camps.”
Those explorations later included an early IMAX camera test day. Some elements filmed that day actually made it into the final film, notes Jackson, who also points out the close interaction he and Fisher would have with director of photography Hoyte Van Hoytema on the film.
The final effects elements were generally captured on IMAX at up to 48 fps, although a 35mm film camera was also used for shooting elements since it was able to capture at 150 fps. “For times when we really had to slow things down, we relied on re-timing in post,” explains Jackson. “A lot of the miniature things we shot were done at very slow frame rates in order to get really long exposures, say for the electrons spinning, which were essentially long streaks from long exposures.”
“By the end of the shoot,” continues Jackson, “we had an enormous library of footage. That process of experimenting continued into post once we knew exactly what lines in the script they related to.”
No computer-generated rendered elements were realized for the film. Indeed, as DNEG visual effects supervisor Giacomo Mineo related to befores & afters, “a significant proportion of the shots that might seem like post-production constructs were, in reality, captured in-camera or underwent minimal compositing adjustments. Our task after the shoot was to create the visuals still missing and to improve what was already in the cut. It was a very fluid process where we were constantly exploring new ideas and that went on until the last available day.”
During filming of the elements, Jackson regularly mocked-up shots in After Effects using QuickTime files from the rushes. “I would show Chris those quick mock-ups and for the ones that he liked, we would develop them further and take them into Nuke at DNEG. There were some cases where he never liked the Nuke comps quite as much as the original After Effects take, so some of those original After Effects comps from QuickTimes went into the movie.”
DNEG delivered just over 100 final visual effects shots for Oppenheimer. Jackson comments that the film contains only around 200 ‘effects shots’. “There were a lot of shots that just went straight into the film without any digital work at all,” he says. “These are ones that never got scanned. They never got sent to DNEG to do any post work.”
The shots that DNEG did work on ranged from, Jackson discusses, “tiny bits of tweaking and adjusting with maybe a couple of layers, to the other extreme where we did a lot of work of twisting and deforming and retiming and layering hundreds of layers together. The big explosions were the most extreme case of that, especially some of the really long slow full screen, big roiling fireball shots. There were also a few environment shots and modern artefact removal shots.”
“The primary aim,” states Mineo, “was to maintain a high degree of minimalism and uphold the raw essence of the original footage. However, for certain instances like the chain reactions or the implosion/explosion shots, a diverse array of elements were combined. This approach was pivotal to preserving the authentic photography feel, captured on film.”
Effects at the subatomic level
The subatomic world of electrons, protons and neutrons is featured in several shots during the film, often somewhat in the ‘mind’ of Oppenheimer as he contemplates nuclear research and the building of an atomic bomb. Jackson relied on a range of methods to film practical elements, ranging from beads on wires, to miniature elements and water tanks, to burning thermite.
Spinning electrons
To communicate the idea of an electron spinning around the nucleus of an atom, Jackson shot spinning beads on wires that were vibrating with long exposures. “I was trying to achieve this idea of vibration combining vibrations in particles, in waves. There’s still a debate, I think, about whether electrons in that really minute subatomic world are actually particles or waves and they kind of behave as both. But, that was the inspiration. We were looking for things that moved in a wavy pattern, but also looked like a particle.”
Rigs were made that, owing to their complicated structure, introduced various arcs into the movement of the beads so that they intertwined with each other, rather than just having one simple rotating arc. The spinning was enabled via a motor on a shaft, with the shafts removed in post so that only the beads or points of light remained.
“We also sometimes combined it with a starfield effect to conjure up the idea of things happening in space,” says Jackson. “We also used them on set in front of Cillian and filmed past it, that is, filmed him through these spinning beads of light.”
The final effect came after several trial and error attempts. “We tried spinning with pieces of string and varying the length of the string, trying to get it to vibrate on a horizontal path, but that didn’t really read. We ended up going for much more of a vertical vibration on its arc with a more erratic shape. It was a long thin wire that was quite springy, and so it sort of wobbled as it went around.”
The life and death of stars
To depict how stars and suns are born and die, and to also realize several ‘explosion-like’ small-scale events, Jackson filmed separate elements that would often be composited with multiple layers. For one of these moments, for example, an element that was filmed was fire and smoke going vertically that would then be unwrapped, turned inside out and wrapped up the other way to produce a circular pattern. “Then for the middle bright spot area,” explains Jackson, “that was a miniature of liquid and particles with light behind it. The background is a big tank of water with tiny metal flake particles in it.”
In fact, several of the elements made use of a water tank, which necessitated filming ‘underwater’. The production made a bespoke probe lens for the IMAX camera for this purpose that was waterproof, and so could go into the tank for filming. “We were pushing the lens right in through a waterproof membrane into the tank so that it really felt like you were in and amongst this big universe of stars,” says Jackson.
For moments where interstellar explosions reached massive levels–almost filling frame–Jackson filmed a crucible of thermite. “We took these two different powders–aluminum powder and iron oxide–and mixed them together and set fire to it. It burns at something like 2000 degrees centigrade and turns into molten iron. It’s so hot and incredibly bright. We had to expose right down to get into the detail that’s there. The white hot metal illuminates the smoke that’s coming from it as well, so it looked amazing.”
Another approach that also employed thermite produced more spark-like effects. “We shot some things in a flower pot up high for this,” elaborates Jackson. “We put some metal under it so that once it melted through, it would drip through the hole in the flower pot. The sparks came from the drops of molten iron hitting something else and exploding.”
A shot that seemed to depict the surface of a star or sun came, again, from multiple elements. “We used cloud tanks with falling particles,” says Jackson. “We had an edge for pouring particles into water which made up the flares at the back of the frame. Then the surface itself was actually the molten metal texture from the crucible of molten iron from the thermite mix, used in a completely different way.”
Some other particle-filled effects moments were also made up of multiple elements. A few involved, as Jackson describes, “quite a lot of 2D work simulating the depth of field with a 2D pass. Quite often the particles weren’t as blurred as we wanted them, so we got some nice bokeh generated out of Nuke.”
How to fake a nuclear explosion
The Trinity Test brought the effects requirements into the large-scale pyro world–”as big as we could do with lots and lots of fuel to naturally get that mushroom cloud shape,” notes Jackson. Explosion elements were orchestrated by Scott Fisher’s team in New Mexico and filmed with multiple cameras with different lenses and at different distances.
“That meant we had really close-up detail and it meant we could slow them down even more to make them feel much bigger and layered,” outlines Jackson. “There’d be multiple takes stitched together where we’d put more detail into some areas where we needed it. We also combined that with shockwave elements, which were shot as smaller miniature effects that we used for the ground.”
“At times,” details DNEG’s Mineo, “a practical large-scale explosion was cleaned-up, re-timed and augmented. While in other instances, a blend of massive explosions and micro elements captured in IMAX came into play. Examples include underwater ink churning, minute shockwaves of dust, and various tiny underwater explosions, all meticulously composited together while drawing inspiration from archived footage of the Trinity Test for reference. That was an exciting but complex task, achievable thanks to the great team of highly skilled compositing artists on the show.”
An early hint of the Trinity Test seen right after the opening credits includes several explosive moments that were crafted with different large-scale and small-scale techniques. One of these shows a tendril of fire emanating from a spherical core.
The final shot began as an underwater element. Then, says Jackson, “the spiky flame was actually the top of a really huge explosion that wasn’t like the classic mushroom that we were aiming for–for some reason, the jet of fuel went up really high in the center and made that shape. So we just ‘stole’ that and comp’ed it here for this shot.”
The complete methodology behind that particular shot is one that Jackson does not wish to fully reveal. “It’s one of my favorite shots. Sometimes it’s good not to completely show behind the curtain, so I want some of them to stay a mystery.”
