Particle Effects, Rigid Body Dynamics and Planet-Busting in the Film's CG-Heavy Third Act

To say that director J. J. Abrams’ film Star Wars: Episode VII — The Force Awakens is a success is an understatement. The film has earned more than $2 billion to date and now ranks third behind Avatar and Titanic for the all-time worldwide box-office record. It has received the AFI Award for movie of the year, a BAFTA award for best visual effects, four BAFTA nominations, four VES awards (outstanding visual effects, created environment, virtual cinematography, and models), seven VES nominations, and five Oscar nominations including a nomination for best visual effects.

Artists at Industrial Light & Magic’s four studios created visual effects for the Disney/Lucasfilm production with help from partner studios Base, Hybride, and Virtuous, and Abrams’ Kelvin Optical. Overall visual effects supervisor and second unit director Roger Guyett and visual effects supervisor Patrick Tubach of ILM received the Oscar nominations along with creature effects supervisor Neal Scanlan and special effects supervisor Chris Corbould. Guyett and Tubach previously worked together on two films directed by J. J. Abrams, Star Trek Into Darkness, for which both received visual effects Oscar nominations, and Mission: Impossible III, as well as several other projects including two Pirates of the Caribbean films and Star Wars: Episode III — Revenge of the Sith.

We spoke with Guyett previously about the careful and, to some, surprising use of digital effects in The Force Awakens. In this interview, Pat Tubach carries the conversation further with details about the application of CG effects in the film's dramatic and destructive third act.

StudioDaily: We’ve heard about some of the digital effects in the film, especially during the desert chase sequence, the CG characters, the models, and the environments, but not much about the third act. How much of the crew’s effort centered on sequences for the finale?

Pat Tubach: Well, it all overlaps, but the third act occupied a good amount of our overall time. There was so much destruction. If you consider our schedule to be a little over a year, the third act was probably a good nine months. 

All images © 2014 Lucasfilm Ltd. & TM. All Rights Reserved.

It sounds like there was a lot of CG in the third act.

There was quite a bit. We had the lightsaber fight between Kylo Ren and Rey in the forest, and for that we did forest extensions. The forest was a set that needed to be built out on several sides. We have the X-wings and Po flying an X-wing into the trench, on into the oscillator, flying around inside, and then destroying the inside. We created the crevasse between Rey and Kylo, which was a huge deal, and the planet exploding.

What was most difficult?

That’s like choosing a favorite child. They’re difficult for different reasons, but I might tag the shot when the crevasse opens. It’s a large overhead three-quarters shot. You see the ground crack open and separate Rey on one side and Kylo on the other. We had to come up with an entire system based on that one shot. We had to figure out how the rocks and snow would interact [and] what is beneath. The interior structure is always visible. You don’t see much of it, but we put it down there and then layered things in. Once we came up with a system for that shot, we could use it for other shots. We had to get the whole team on the same page: effects artists, generalists (the environment artists), and the rigid sim guys working in tandem. We had to pass things from one group to another and have it all flow properly.

You have two simulation groups?

It’s a multi-layered approach. The rigid effects simulation group does hard surface destruction [rigid body dynamics]. They shake the trees, break the large chunks of rocks. We sometimes have traditional animators do that as well, but it takes more time and runs the risk of not being physically correct. And when we have large amounts of that kind of destruction we call in the rigid simulation artists.

The hard surface simulation affects the large pieces — the large assets — and that drives the particle effects. The particle effects artists do their magic on top. They handle anything that generates or spawns particles. The rocks emit snow and the snow reacts to the falling rock. For this film, we developed a new engine for particle effects. 

All images © 2014 Lucasfilm Ltd. & TM. All Rights Reserved.

Tell us about the new particle effects engine and why it was necessary.

Rick Hankins, an effects TD and R&D engineer, worked with Dan Pearson [effects TD supervisor] on building a version of our Zeno-based effects engine to handle more complex simulations and to mix materials together. We have been able to have a mix of materials before, but there was a limitation on how many particles we could run at once. And you can always detect when you layer things together that don’t interact. For example, if you want sand to interact with rocks and snow, you want to do that all at once to get more realistic results. But you hit limits. Rick’s focus was on how to put more materials into each simulation so the collisions happen more realistically. Each material has its own physical properties. When the ground splits apart and the crevasse opens up, you see rocks crumbling, snow sloughing off the rocks, the trees wavering, and snow coming off the trees. All those materials are interacting in one simulation.

There was a small version of the oscillator on set with the wall texture and a little of the bay with stairways and pipes. This is where Han Solo and Kylo Ren have their confrontation so there was a long process of deciding what the oscillator looked like. J.J. [Abrams] wanted that space to look really large, reminiscent of the Imperial structures before the Death Star, with large expanses and edges with no railings. He gave us a lot of freedom to create that interior space. We didn’t build all of it for destruction, but when we knew Po would fly inside, we made parts destructible. Getting the right amount of debris was a challenge. We couldn’t end up with debris obscuring the scene, so we had artists go in and tweak it to keep the focus on what the shot should be about. We tried hard to make sure you could track Po’s ship. Because it was dark inside, we often kept his ship in front of fire to see the silhouette of the X-wing.

There were also lots of digital stunts and complex rigid simulations. We had pipes affecting walkways and walkways pushing storm troopers over railings and throwing them around. You set all this up, start the simulation, and whatever happens happens. We had a lot of fun watching the stormtroopers flying around. We could sort of move things around after, but as long as it looked OK and not too distracting, we didn’t change it. If you watch the film again, you might see a couple stormtroopers fly 100 feet through the air when the stairways buckle.

All images © 2014 Lucasfilm Ltd. & TM. All Rights Reserved.

There were two main shots. In one, Chewie and Rey are back on the Falcon. The Falcon turns toward camera and takes off. The ground crumbles beneath. You see the interaction of the crumbling ground with the snow in the lights of the Falcon. It was a massive simulation. And then the planet rips apart [and] the top of the mountain comes off. These were very big, expensive sims. It was one of those shots that you knew you had to art-direct and didn’t want to limit, but that would take so long you had to be careful about iterations. We spent a lot of time running tests before rendering.

The big shot is the one you watch from space. People might not realize that this was a hacked planet, a natural environment they hacked into and built inside. So there is an interior skeleton inside. We designed that interior skeleton to give resistance to the explosion. You can see parts collapse, suck inward, and blow out. It wasn’t one giant boom. It was a much more complicated, multi-stage, multi-tiered explosion with arcs of energy and sinkholes. 

We did it stage by stage. First we built the structure. We asked Vinh Lee, our lead effects artist, to come up with what the explosion might look like using the cage of a skeleton. Then we introduced the idea of arcs coming out. At first they were rings, but they covered too much of the circumference and sent too much debris out. The arcs looked cool. They pushed out debris in sections and left other sections scarred. 

How long did it take to destroy the planet?

We spent a good eight weeks on that shot alone. It was one of those shots you know you cannot run every night. At the end, our turnaround on getting all the stages of the sim done was probably three days. You know when you do sims, everything is dependent on the frame before, and the planet shots were probably 1600 to 1700 frames. If you wanted to make a change you’d have to start the process over again. And it was a large, large rendering job.

How long were you on the film?

Almost two years.

VFX crews often feel like they are crunched for time. Did you feel like you had a luxury of time for this film?

People ask that and I try to think of the best way to answer. On this movie more than any other, I felt like we were actually helping to create the film. It wasn’t like it was decided and then you have a certain amount of time to finish and do or do not feel rushed. We all had the job of making this film and making it as good as it could be. There was pressure, of course, to get done on time, but at the same time we were invited by J.J. to create the film together. So we always felt under the gun to make the best version of the film we could, to make the scene in the way that was best for the film. We had a lot of late nights, jamming as hard as we could. But at the same time, we felt like we were part of the creative process. It was awesome.

All images © 2014 Lucasfilm Ltd. & TM. All Rights Reserved.

I think it was just because of J.J. The X factor is that we are all, him included, big fans of Star Wars and the legacy of ILM, so there was that added bit of pressure. Here we go: This is Star Wars. But the great thing none of us could have anticipated is that we’ve all worked together a lot now. We’ve done movies together before. J.J. trusts Roger [Guyett] to be the second-unit director, and J.J. has a level of comfort with ILM. There are a lot of familiar faces from previous projects. Also, he has an extraordinary knowledge of digital effects. He enjoys it, he likes learning about it, [and] he wants us to tell him about it. That helps him get the best out of us and helps us communicate with him. So it was a great coming together. That level of trust and confidence that we could deliver allowed him to open up and let us in on the process.

Why do you think your colleagues voted for Star Wars to receive an Oscar nomination?

I think people really connected with the philosophy that J.J. had, and we had, in making the film. It isn’t showing off what effects can do, but using them in the most beneficial way for the film. I think they saw there is a certain amount of restraint. There is, of course, a lot of CG in the film, but we didn’t try to create a heavy CGI film. We tried to respect the legacy. There are practical creatures, sets, characters on set for the actors. It felt like a true sequel to Star Wars IV, V, and VI, the same kind of movie we saw in the 70s and 80s, but one that acknowledges new filmmaking techniques and digital effects. I’m proud that audiences didn’t dissect the visual effects as they watched the film. That they got lost in the moment. 

Does receiving two wins for best visual effects — BAFTA and VES — make you feel more nervous or more confident going into the Oscars?

The competition is too stiff to feel like you can predict anything. All the films nominated deserve recognition and then some. It’s been an awesome feeling to know people are as accepting of the work as they are. The best reward is to be recognized and have people discuss your work. That’s all you can ask for.

Read our earlier interview with ILM's Roger Guyett.