Recently Collider took some time to talk with Stephane Ceretti about the visual effects that went into making Doctor Strange. Usually, this would seem like a bit of an odd interview. The artists who work on the post-production of a film tend not to be highly sought after interviews. But in the case of Marvel’s latest film, the special effects are one of the biggest draws of the movie. The process to bring those stunning visuals to life is an interesting one.

As most MCU fans know at this point, hiring Benedict Cumberbatch was a bit of a journey, and ultimately it delayed the film. That delay was a blessing in disguise for the team working on the visual aspects of the movie, because it gave them time to hone in on what they were creating.

The good thing on this film was that we had a lot of time, before we started to shoot, to try to figure it out. We pushed five months because Benedict [Cumberbatch] wasn’t available, so I started in September 2014, which is more than two years ago. Because of that, we had lots of time to figure things out and do some concepts and do a lot of pre-vis. We were lucky that Marvel said to keep going on pre-vis and concepts. It’s a difficult film and they knew that from the start, so they really gave us the tools to figure it out, from a script point of view and a visual point of view.

Director Scott Derrickson kept the VFX team in the loop throughout the process, including the ways the script was shifting in preparation for filming. This approach created a positive feedback loop that aided the film altogether. Even the actors’ performances were influenced by the “pre-vis” snippets that they saw. “Pre-vis” is a term for rough effects that are done even before filming begins. They are a sort of moving storyboard. Such a tool was vital as the team struggled to translate Ditko inspired 2D art into a 3D film.

The environments are never settled. They always move and change, they’re always dangerous, there’s always action in it, and there’s always camera moves. The storyboards were not conveying the ideas well enough, so we went into pre-vis very fast. That way, we could create the sequences and build them, from the start. The ideas are so out there, from the creative point of view, storytelling point of view, scripting point of view, and shooting point of view. Figuring out how to shoot everything was a big puzzle and a big nightmare. We had to work together and figure things out.

One of the hallmarks of the success of Marvel Studios is the ability of the various parts to work in concert. Since the movies are connected, each director has some responsibility to other directors and other upcoming films. Balancing individual artistry and the grander narrative is complicated, but Kevin Feige and team have done it well. That collaborative spirit trickles down as well, to all parts of the production.

There were so many different things, and everybody has a different opinion. You end up in the room with quite a few people – the director, the people from the studio and the editors. It was very challenging, in that sense, because there are so many questions that need an answer, on so many levels, that it’s very grueling. But, it’s exciting. That makes it interesting to do. And the nice thing is that everybody was really excited about the challenge. From the top of the studio, all the way to the artists in the facilities, everybody was trying to bring their best. Anything can work, as long as it tells a story. People were throwing ideas at us, even in post. We just wanted to push it. In that sense, Marvel is very collaborative and open to ideas from everywhere. If there’s a good idea, why not use it? Sometimes it’s like, “No, that’s not going to work,” but sometimes it’s like, “Yay!” We’re very excited about the whole process, so there’s cheering in the room. It’s pretty cool. You can’t complain. But, it was challenging.

If you asked the average Marvel viewer what film is the most special effects-heavy, many would think Doctor Strange. Certainly, the marketing for the movie pushed the eye-popping visuals more than that of any other movie. Still, that guess would be an incorrect answer. Instead, the most special effects filled MCU film is…

There’s 1,450 shots in the film, which is not a huge number. Guardians was 2,300 shots. But the complexity of the shots, in terms of design, was much bigger. It’s not so much about the sheer number of shots. It’s also about the complexity and variation of the shots. Every shot was a bit of a puzzle and a bit of, “Oh, my god, how are we going to do that?!” It was extensively difficult.

Ultimately that answer makes a lot of sense. One of the triumphs of Guardians of the Galaxy is that viewers forget that every second where Groot and Rocket appear on screen is a VFX shot. The differences between the effects on the two films show just how diverse the work of Ceretti and her team are. A talking raccoon is one kind of challenge, folding New York city into itself is another thing altogether.

For a lot more context and details, check out the excellent interview over at Collider. Doctor Strange is out in theaters now, but time is probably running out to see the movie in IMAX 3D. So, if you haven’t seen it that way yet, go do it now!