How Moonfall’s VFX used real physics to bring the moon down

It’s not every day you get to bring the Earth to the brink of destruction, but that’s exactly what director Roland Emmerich set out to do in his latest film, Moonfall.

Directed and co-written by Emmerich, the film follows a pair of former astronauts and a conspiracy theorist forced to undertake a dangerous journey to the moon in order to stop it from crashing into Earth. Why the moon was suddenly knocked out of its orbit — and how to get it back there — are mysteries faced by the characters in the film, but they were also a problem to solve for the team tasked with grounding the film’s cosmic calamity in plenty of very-real physics.

“Visual effects supervisor Peter Travers, who previously worked with Emmerich on 2019’s Midway and served a similar role on Guardians of the Galaxy, Watchmen, and other films, soon found himself taking a deep dive into astrophysics and conceptual mathematics in order to make Moonfall live up to its title. He spoke to Pro Well Tech about the process of creating a realistic, cataclysmic meeting between Earth and the moon, as well as developing the look and design of the mysterious entities responsible for the disastrous scenario.

(Note: The following interview includes a discussion of plot points from the film.)

Pro Well Tech: What goes through your head when you’re initially asked how a project can depict the moon flying out of orbit and potentially crashing into Earth?

Peter Travers: That really is, ultimately, the very first discussion, too — because where do you even put your camera with something that big? If you put it out in space, it will be comprehensive, but that’s not a camera [perspective] we’re accustomed to, so it could take you out of the moment. That’s why, every chance we got, we tried to put the camera at eye level on the Earth, because that’s the most impactful camera.

Early on, we did some simulations and setup, and one thing we realized is that if the moon is just a mile or two up in space, it’s going to fill the entire sky. So scale and accuracy were very important, too, in order to figure out what it would look like and how foreign it would look to the audience. There’s always a balance you have to find because if it looks too abstract and weird, it’s hard for the audience and the artists working on it to maintain any grounding in reality. If every pixel is foreign to you, it’s going to be hard to feel the impact of what you’re seeing.

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You mentioned grounding it in reality, and the film had a bunch of scientists and astronauts who were credited as consulting on it. What form did their input take?

Well, we actually did our own simulations initially and kept in close touch with NASA. I used Maya, which is the standard CG software for most of the effects we do. Most people don’t realize that Maya is actually a physics simulator at its core. I started by asking Roland a few questions like, “How long do you want the movie to last?” and “How long does it take for the moon to fall?” or “How many orbits does it make before it actually hits the Earth?” That way, we had some basic constraints. He wanted the moon to revolve around the Earth four times before it finally hits, and he wanted it to happen within a month.

So in Maya, I created an accurate, volume-scale-speed model of a mini solar system of the Earth, the moon, and the sun. There are a lot of weird things about the moon — its density, its orbital speed, and that it’s actually five degrees tilted, for example. So I just started plugging in all of this stuff, and, using Newtonian physics, I got a simulated moon to spin at the correct speed around the Earth. Then we started messing with it, trying things to get the moon to fall the way we need it to.

You were really tapping into any astrophysics knowledge you’ve accumulated! 

Exactly! And we eventually discovered that the answer was to inject the moon with quite a bit more mass than what it currently has. We started by cranking up the mass of the moon in the simulation and watching it fall towards the Earth. It was an iterative process, because initially the moon just kind of launched out of orbit, and then on the other side of the tinkering we did, it thudded into Earth in just one day. I eventually injected just enough mass into the moon that it collided with the Earth after four revolutions, over about three weeks, from a set point in its initial orbit. It ended up taking an additional mass equivalent to about a third of the mass of Earth.

And you felt the satisfaction that comes with creating an extinction event.

Right? What was really great about it is that Roland also wanted a lot of gravitational effects on the Earth for all the people running around, and by injecting the moon with mass, it actually did create those gravitational distortions. At that point in the simulation, when the moon is at its absolute closest, it was creating 3G [aka three times the force of gravity on Earth] of gravitational pull towards the moon. There’s a whole car chase at the end of the movie where they’re driving and the moon is rising, and at that exact point, based on the mathematics in our model, the moon really would be pulling the characters in the story and all the objects around them sideways with 3G of force.

So that was just a happy coincidence that the math worked out? Did that inform what happened in the film, or were those scenes always part of the plan?

Well, that was a stipulation at the beginning, and it just happened to be something the simulation reinforced, so they took it and ran with it. The directionality of the gravity was interesting because when the moon is rising, the gravity is not straight up, it’s pulling sideways. So you were getting this weird shearing effect on Earth. That physics element of Maya and the model we created really came into play. Cars were sliding, then floating upward at an angle, and all that kind of stuff. There was an initial hope we would have these kinds of gravitational effects to play with, and the simulation delivered this added bonus of telling us, “Yeah, the physics in this supernatural condition do create these gravitational effects,” which is what Roland was hoping we would have in the story.

How did the consulting scientists respond to the work you did in creating these simulations and models? Was there some pressure to get their approval?

I know this sounds kind of strange, but this sort of Newtonian physics is actually simple calculations when you have a small number of gravitational objects. When you get into a large number of gravitational objects, it gets really complicated. The terms for it are the “Two-Body Problem” and “Three-Body Problem,” based on how many objects you’re dealing with. I only had to do it with the moon and the Earth, so I could keep it pared down, but NASA looked at the model and said, “Yup, that’s about right!”

And then the trick with the movie becomes, “So how does all of this actually happen?”

So how did it happen? Did the nanoswarm and its look evolve based on the model, or was its design planned all along?

Well, it all happens together. It’s this mad jumble as we get started. But the nanoswarm — or The Anomaly, as we call it — was always the mechanism that caused the moon to do what it does. How it looked started with Roland showing me a Mandelbulb — a 3D plot of a Mandelbrot equation. Roland saw this thing that looked like, as it was evolving and the equation kept running, it was kind of swallowing itself. It was very mathematical, very fractal, in a repeating pattern. Roland was like, “I like this. How do we do something like this?”

So that’s when we activated both of our VFX vendors that were working on the anomaly in conjunction. They were working in parallel: Framestore and DNEG. Framestore handled all of the attack sequences of the anomaly outside the moon, and DNEG was all inside the moon. They built the anomaly in parallel, with everybody working together and hoping we can just get this all done before the movie comes out, as is usually the case.

At its core, there’s so much mathematical engineering that goes on when we do CG. Effects animators are probably some of the most brilliant artists in the industry. It’s like a black-box kind of a thing, in that you basically say, “Here, go do your genius stuff, and come back with the stuff we need,” and it always feels painful at the time, but in the end, the reward is that much greater because the anomaly just looks so odd. It’s so foreign-looking, just the way it was meant to be.

In a film with so much spectacle, it’s easy to overlook invisible effects. Is there anything in the film people would be surprised to learn is a visual effect?

There are a ton of invisible effects in the movie. There are around 1,700 shots in the movie that have some form of visual effects. Sometimes it’s as simple as doing wire removals. One great example is, in all the space sequences — like the spacewalks and stuff in the opening sequence — the visors and a good portion of all the helmets are CG. Typically, we’re struggling to paint out any reflections when we have glass in a scene, but in this case, because we didn’t have oxygen going into the spacesuits, the helmets had to be open. So we had to paint in everything that is supposed to seen be in that reflection.

In the opening scene, when you’re looking at Brian (Patrick Wilson), you can see the other astronaut, Marcus (Frank Fiola), reflected in his helmet. That is all pure CG. We have to build a full digital double of all of the astronauts, just so you can see them in any of the reflections. Framestore did that work and it looks so good you don’t even register it. To be perfectly honest, sometimes I forget about it. It’s like, “Oh, that’s right, we did a visor in that shot!” It just looks so good you’re able to look past it.

There’s so much going on in Moonfall from the visual effects side and it’s been such a crazy few years to get it all done. How does it feel to have the film out there? What’s the element you’re most proud of?

I’m excited about all of it. I love all my children, so to speak, you know? And every little shot matters. […] I love the satisfaction of well-made plans. You always have a certain amount of chaos, especially in a movie like this, where there’s chaos everywhere. But I love the long-term planning and payoff that comes down the road. […] I have one of the coolest jobs in the world.

Roland Emmerich’s Moonfall is in theaters now.

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