Making a Marvel movie like "Spider-Man: Homecoming" can be "maddening or exhilarating", according to visual effects expert Lou Pecora. And the toughest shots in this effects extravaganza might not be the ones you think.

Like most modern blockbusters, the effects in "Homecoming" were divided among different VFX companies, including Sony Pictures Imageworks, Iloura and Trixter. But the big-ticket action sequence, in which Spider-Man and the villainous Vulture clash on New York's Staten Island ferry, was contracted to Digital Domain, the Oscar-winning effects outfit originally founded by James Cameron and Stan Winston in 1993.

Pecora, Digital Domain's visual effects supervisor, oversaw a team of 280 people to create the sequence. We chatted to him on the phone from Los Angeles about the effects of the "Homecoming" ferry sequence.

Q: Our first glimpse of "Homecoming" was in the trailers starting late last year. But look closely and you'll see the clips of the action scenes are actually different to the finished movie.

Lou Pecora: We redid them for the films. We did them as temps essentially. We only had a few weeks to pull those off. You end up doing them twice.

In the trailer, we make it look like you think you're seeing a moving camera, but you're not. If you move a camera around you get parallax between things in the foreground and things in the background -- things sliding against each other. You have to do that "for real", so [instead] we did a little sneaky trick called a "nodal camera move". That was really the only way we could have pulled those shots off in the time that we had.

Creating the actual ferry sequence for the movie began with shooting the "real" elements, such as the human actors.

Lou Pecora: We had a partial set built in Atlanta, with a little bit of interior space just so you could see it. The set split in half and 40,000 pounds of water could get in there in 10 seconds -- it had all the bells and whistles.

If you've ever been on the ferry, it's a symmetrical boat -- both sides are the same. You call it the Manhattan side and the Staten Island side. So we had a set that was the back or the front depending on how we dressed it.

Columbia Pictures via Digital Domain

We had a real ferry docked for a few days and we went and scanned the heck out of it. We photographed it top-to-bottom, front-to-back. We scanned it with LIDAR scanners so that we were able to recreate the model of the actual ferry.

Then we stitched the front of the Atlanta set on to the model of the real one, so that we ended up with something of a patchwork of ferries.

Chuck Zlotnick

Front and centre during shooting was Tom Holland, the actor and dancer who played Spider-Man.

Lou Pecora: Most of his own stunts, he did. And when we ended up getting into post, freed from the confines of having to shoot for real, we came up with a lot of new ideas that required new actions from Tom. So he cheerily -- and I couldn't accentuate that word more, he's a very cheery guy who is very happy to do this stuff -- we got him back out on the motion capture stage and did a bunch of mo-cap shooting with him.

We're between takes watching the monitor and you look over and Tom's doing somersaults, climbing up the wall, pretending to shoot webs, doing backflips. He's like a little kid out there jumping around just having the time of his life.

A Marvel movie is a collaboration with an interesting -- and challenging -- process.

Lou Pecora: Marvel's done this a few times, so they know exactly what they're doing. Their process can either be maddening or exhilarating. For me, I love their approach to making films. They're trying to make the best movie they can right up until the very last moment. It's a very ego-free environment. Hollywood has a lot of egos in film, but these people are not like that.

Columbia Pictures via Digital Domain

If you treat filmmaking as a job, you're going to be miserable. When a curveball comes your way, it's going to throw you. But if you treat this business as a passion, then when they come to you with four or five weeks to go with a new cut that involves a whole bunch of new stuff, and a whole bunch of old stuff you've been working on is out….that would be maddening to someone who is rigid in their thinking.

But to someone who's looking at this as a realization of a childhood dream, when you hear an idea like, "We should get Spider-Man off the boat and get him over the water somehow", some people will go, "Oh god, we're gonna have to figure all this stuff out, we're going to have to kick it up to 20 hour days, 7 days a week".

Other people like me and my animation director, Jan Philip Cramer, look at it like, "Cool, we get to figure out how to get him off the boat and over the water!" Some people find it maddening. For us, it's awesome.

We were working on shots right up until the last second. You can always make something better so we were still beating on some shots when they finally told us that's it, the reel's locked, we're done. We sent the shots over anyway. Maybe they'll end up on the Blu-ray, I don't know.

After all the spectacle of the ferry sequence, one of the most challenging shots came after the action was over, when Peter and Tony meet for a tough talk atop the Governor's Island vent shaft.

Lou Pecora: Those shots were brutal. The way they were shot, it was lit to be a certain time of day, and afterwards it was decided to change that time of day. Relighting practical photography on human skin, that's a tall order.

Chuck Zlotnick

There was a lot that had to go into reworking those shots: Peter's hair blowing, Tony Stark's fabulous coif dancing in the breeze, and you're having to get each one of those hairs to ensure what was shot hair-wise is there in the final comp. The hair is flopping in the breeze and you want to keep that to get that sense of wind. It was having to retain that performance and actually, as funny as this sounds, to retain the performance of their hair.

You and I walking around, we don't see a lot of explosions and a lot of guys jumping around from building to building and spinning webs and such. But we see faces and hair in the breeze all the time, so you're gonna know if it's wrong.

Tech Culture: From film and television to social media and games, here's your place for the lighter side of tech.

Star Wars at 40: Join us in celebrating the many ways the Force-filled sci-fi saga has impacted our lives.