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Stephane Ceretti Talks ‘Guardians of the Galaxy’

The overall VFX supervisor on James Gunn’s new Marvel action hit discusses the film’s main visual effects sequences.

Marvel’s hilarious new sci-fi film Guardians of the Galaxy, which opened to a stellar $94 million, is probably their most critically acclaimed movie since The Avengers. This feat is all the more impressive when you consider that Guardians is based on a relatively unknown Marvel comic book. The studio took a risk by investing so heavily in a lesser known property, but it’s a risk that paid off. A film featuring a walking tree and a talking racoon could easily have gone horribly wrong, but Marvel managed to deliver a movie of superior quality to many of the other big superhero outings we’ve seen this summer (I’m talking about you, Spiderman). This movie feels fresh and original when compared with many other Marvel films, but it still has a definite strand of the studios DNA running through it. There’s no doubt that director James Gunn has put his mark on this movie, kicking off the franchise with a difficult act to follow.

In order to bring its rich, vibrant worlds and unique characters to life, Guardians relies more heavily on visual effects than any other Marvel film. Heading up the huge VFX effort on the movie was Stephane Ceretti. A veteran of French VFX powerhouse BUF, Ceretti’s recent credits include Cloud Atlas, X-Men: First Class, Captain America: The First Avenger and Thor: The Dark World. He was kind enough to take the time to speak with me about the some of the challenges he and his team faced in bringing the movie’s extraordinary worlds to life.

'Guardians of the Galaxy.' All images © Marvel 2014.

Paul Younghusband: So this is probably Marvel’s most ambitious film to date in terms of visual effects?

Stephane Ceretti: Yes, I think so. Around 90% of the movie is visual effects. Overall I think there were 2,400 shots in the film, of which 2,200 were effects shots.

PY: And how do you start planning for such a huge volume of work?

SC: Well, my VFX Producer Susan Pickett started on the show before I did, because I was finishing up on Thor: The Dark World. She started going through the script with the director and breaking it down. I think the initial VFX shot count was around 1,700, but when we started working through thumbnails, storyboards and previs, that number just kept growing and growing! At the beginning, you know you’ve got this big mountain in front of you that you’re going to have to climb, and you just need to prepare as much as you can for it.

PY: How did you go about dividing up the work between the different vendors?

SC: We started with two main vendors who shared the bulk of the work…MPC and Framestore. Initially we were thinking that maybe we should have one vendor doing all the character animation, and another doing all the backgrounds and set extensions. But that wouldn’t have worked because there was too much overlap. What we ended up doing with the characters was having MPC build Groot, and Framestore build Rocket, and then share the assets. So that means that MPC could do shots with Framestore’s Rocket, and Framestore could do shots using MPC’s Groot. We couldn’t have one vendor doing all Groot, and another vendor doing all Rocket, because they are almost always in shots together. It would have been way too complicated.

Then for the environments and the battle sequences, we gave Morag, which is the opening sequence, and Xandar, which is where the final battle takes place, to MPC. They also handled the ships which included Peter Quill’s ship the Milano, Ronan’s ship the Dark Aster, the Necocraft and the Nova Corps ships that take part in the final battle. And then we had Framestore handling Knowhere, which was quite a contained sequence in the film that featured a lot of Rocket animation, so it made sense for them to take that sequence because they were initially building that character. And Framestore also handled the The Kyln, which is the space prison sequence. That also had quite a lot of Rocket in it. So that’s pretty much how we broke it up.

PY: This was James Gunn’s first big visual effects movie. Is it a challenge to work with a director who doesn’t have experience working with visual effects on this scale?

SC: I don’t think there are many directors who have worked on visual effects movies of this scale! But James is very savvy actually. When he worked on the Scooby Doo movie, even though he was the writer on that show, he was very involved throughout the production and that film had quite a lot of visual effects work. And then on a smaller level when he directed Slither, that movie contained quite a few visual effects shots too. So he had some experience, and more importantly, James was very prepared. He had co-written the script and he was doing all the thumbnails for the pre-storyboard stuff. He was also excellent when it came to working with previs. James is very precise when it comes to choreographing action; he has a very good visual sense. He really jumped in and became very involved with the visual effects process.

PY: Let’s dig in and talk about Rocket and Groot. How did you go about bringing those characters to the screen?

SC: Well, it all starts with the script. One of the things that James was very adamant about was making sure that these characters were written in a way that felt real, that they were just as fleshed out as the other three characters in the group. And in a lot of ways that makes the job of bringing them to life easier, because we have a very clear grasp of who these characters are. Charlie Wen [head of visual development] and his team at Marvel’s internal design group produced all of the character designs. By the time I came on board Groot had already been fully designed, and Rocket had been fleshed out quite significantly.

One of the first things we did for Rocket was to start looking at real racoons. We had a racoon in our office in London for a day, and our vendors came along to interact with it, and get an idea of how it looked and moved. So we started doing some animation study, and one of the things we were really focusing on was how to get a lot of expression in Rocket’s face. He talks quite a lot during the movie and he has quite a lot of attitude. James really didn’t want him to look like a human talking on top of a racoon face. So we had to do a lot of testing and tweaking early on to figure out what kind of expressions we could pull off. It was a lot of work both at the design stage and in animation tests in order to make sure we could get the right amount of range.

PY: How were you shooting him on set?

SC: We actually got James’ brother, Sean Gunn, who is a very talented actor, to play Rocket on set so that we could get a real interaction with the other actors. We also had a stand-in for Groot. And we’d actually shoot a take with the stand-ins and the actors, which would be used as reference for editorial. Then we’d shoot another take, which we would consider to be the master that would be without the stand-ins. So for this take the actors would be looking at ping pong balls, or whatever we used to give them an eyeline on set, and the stand-ins would still be off camera delivering their lines. This way we didn’t need to paint out Sean or Krystian [Godlewski, the stand in for Groot]. Doing it this way made a big difference, because we could really refine the performance with the real actors.

Then we would send off the reference takes to editorial so they could start the editing process. The master takes would head off to postvis, where they would be combined with the audio from the reference takes. Once we had that, the actors could work with James to record the voices using the postvis as reference. Then once we’d selected the lines we were going to use, the shots would go off to Framestore or MPC for them to get to work on the animation.

PY: Was there any particular reason to go hand animated over performance capture?

SC: We did think about doing performance capture, but we wouldn’t have been able to have Bradley Cooper or Vin Diesel on set with us. In addition to this there were proportion issues. Rocket’s face doesn’t have the same proportions as a human face, so we wouldn’t be able to retarget it very well. And Groot, although he had a lot expressions, he didn’t really have too many lines. We also felt having all the clunky equipment that goes with doing performance capture on set wasn’t really going to work for us. James likes to shoot very quickly, so we didn’t need the complication of all that stuff. It just wasn’t viable for this project. And also, from my point of view, I really wanted the animators to have their go at it, to bring an extra dimension to the performance. And I think they did a really good job.

PY: What about Groot? Were there any unique challenges with this character?

SC: A lot of the techniques we used were the same for Rocket and Groot. But in terms of the character himself and what we wanted to get out of him there were some distinct differences. Obviously Groot is a tree, and we really wanted to make sure that when we animated him, he still looked like a tree. We didn’t want him to be too bendy. So we came up with a pretty complex rig, where the branches themselves stay straight, and the vines are pushing and pulling like muscles within the structure. Also, throughout the film, Groot grows. He’s growing arms, growing upwards and outwards and all these things had to be taken into account when building the rig. It was a big challenge.

The other thing about Groot is that he doesn’t talk much. He only says “I am Groot.” MPC did a lot of work making sure that we could get enough expression out of his face, especially around the eyes and the eyebrows, but again, making sure he still looked like a tree. There are actually two sides to Groot in terms of his behaviour. On the one side he’s very child like, very sweet, shy and innocent. When he goes into a new place he’s always looking around wide-eyed, trying to take it all in like a child would. And then on the flip side of that we have the more aggressive Groot, who we see during the battle sequences, where he becomes this huge beast. We had this thing happen we called “hulking,” where Groot bulked up, became bigger and grew all these branches. So that was another challenge, to make sure we could accommodate these two different sides to his character.

PY: There were a number of worlds that needed to be realized for this movie…

SC: Well there are four main environments. We have Morag at the beginning, which is a very wet and windy planet. There were a lot of concepts for what Morag should look like, but they ended up basing the look on a place in Egypt called the White Desert. We actually went there, even though it wasn’t really the best time to be visiting Egypt, because we wanted to get some reference photographs. Then Charlie Wood [the production designer] built a 120 feet square set surrounded by green screens at Longcross, outside the back of Shepperton Studios in London. We used the set in different ways and moved it around, and then we had MPC extend it. It’s a very wet, windy and volatile planet, so we had some practical geysers on set, and fans for wind and big rain machines. And as part of the CG set extension we added even more geysers, more CG rain, smoke and multiple layers of atmospheric stuff.

The there was Xandar, which is actually a full CG city. For the sequence near the beginning of the movie where the group is arrested, we built a small section of the mall at Longcross, but everything else was CG. The city was based on buildings from modern cities such as Singapore, Dubai and Shanghai, and we also based some of it on a train station in Belgium which is quite modern. So MPC created a huge CG asset for the city of Xandar, but they also had to create the sky and upper atmosphere too, because this is where the final battle takes place. So that was a huge environment effort for them, but it represented a significant portion of the movie.

Then we also had The Kyln, which is the space prison. This was actually a very impressive set. It was 3 levels, 360 degrees, and very detailed. We extended it up, to add more levels, and we also built a CG exterior for when they fly into the watch tower, and cross the bridge into the prison. This was all handled by Framestore, who also did all the work on Knowhere, which is the mining planet. Knowhere is actually the severed head of a Celestial being, which has been mined out from the inside. So the design of it was very much a mixture of organic matter, and these big mechanical structures. It was a pretty cool environment.

PY: How did you approach the final battle sequence?

SC: James was very precise in how he wanted the final battle to play out. Every beat was written and clear in his mind. So after thumbnailing and storyboarding we went through an extensive previs phase with this sequence. One of the things we decided to do was to get the film editors in before we started shooting to edit together the previs. This worked really well because we had all these different camera angles and variations and we had real editors putting it all together. And the more they worked the more refined it became.

Once we’d put everything together we realised that it was way too long. I think it ran about 50 minutes! So we started the process of compressing it and combining things to bring the run time down. Then in March or April, just as we were about to film additional photography, we came to the conclusion that the Novo Corps were not very well represented in the battle. It was their planet being attacked, but they weren’t really a big part of the fight. So James came up with the idea of them joining together to create the net to stop the Dark Aster from reaching the ground. So we did another round of previs for that, which ended up changing things quite a lot but I think it made the whole sequence much better.

PY: What would you say you’re most proud of when you look back at the project?

SC: Well the thing I’m most happy with is the way Rocket and Groot turned out. James said very early on that we need to believe in them as real parts of the Guardians. And I think you really do. After a few minutes on screen you completely forget that these characters are CG. You buy them as being part of the group and don’t even question it. Our vendors did a really great job of bringing them to life. I honestly feel that if that didn’t work, everything else would have fallen apart. Because it’s all about the characters in the end.


Paul Younghusband is a producer and writer based in Los Angeles. He has currently served as editor of Visual Magic Magazine, and has contributed to publications such as VFX World and Animation World Magazine.