Since 2008, Peter Jackson has been trying to bring "Mortal Engines" to a theater near you. It's been a decade, but that dream is finally becoming a reality -- albeit in a different way than Jackson originally intended.

Unlike previous passion projects, Jackson didn't take the director's chair this time around, and last year, Moviefone and other reporters visited the New Zealand set to find out why. We also learned what drew Jackson to the book in the first place.

So, the film's director, Christian, was saying that one of the earlier plans was for you to direct the film. Can you talk about that evolution? And why did you decide to not direct?

Peter Jackson: It was probably one of the movies I would've done, you know, during the time that "The Hobbit" was being shot, but I ended up directing that and sort of took me out of commission for five years. And coming out of it, we were faced with a situation where the rights to the books -- which we've had for, you know, probably nearly a decade or so -- they were due to expire and we had to move fast.

Christian is a filmmaker I want to support. He's worked with me for 25 years and he needed to direct something soon. Also, Fran [Walsh] and I ended up, after five years on "The Hobbit," with so many other projects that we wanted to write and develop ourselves.

What was it about this story has kept you hooked for so long?

Peter Jackson: This is one movie where I hope it's successful enough that we get to do the other stories because the other books are really -- I mean, this story mushrooms in such unexpected ways in the future books. So, I really hope we get to make those films.

It's a love story. It's an unlikely love story. It's about a young woman who doesn't really think that she will ever find love and she finds it through a very unexpected way in the middle of this chaotic, strange world that we're in. And I also just like the idea of seeing big cities eat other. It's going to be pretty amazing.

Can you talk about some of the stuff that you've been shooting on the second unit?

Peter Jackson: I've just been doing odd bits and pieces. Just doing it a bit here, a bit there. I get told what to do. It's quite good. I mean, Christian gives me a list of things that he wants shot and I can shoot them.

It's actually, you know, it's fun to do! To shoot some of the stuff that, if I was a director, I wouldn't get to shoot. Plus, I get to use a camera, too, because I haven't been able to do any camera operating for years and I always loved doing that. So, if I ever am doing anything on the second unit, I usually get a third camera. I'm the third camera and I find myself a place to shoot and I get to shoot some stuff. Which is also fun.We've talked to a lot of the cast and they've all talked about the collaboration on making this film. You know, talking with everyone in developing the characters in their own way. What's that been like as producer/writer? And also, how has that shaped what you think things might go in the future?

Peter Jackson: Well, we always like to collaborate with the actors. I mean, we've always done that in a way, you know? We write a draft of a script -- or several drafts of a script. You want to write something that's good enough for a studio to see it and green light it.

But, when you're casting it, now [you are dealing] with actors who you didn't necessarily imagine, or you didn't even know would be playing these roles when you wrote the initial draft. So, we were able to then, write it with their voices in mind and sit down and talk with them. Because there's a point in time, too, where you realize that, as a filmmaker -- or as directors, writer, producer, whatever --you've got everything on your mind. Whereas an actor is focused on their role and their character. We've always found it really rewarding to sit and talk with them about their character. They sort of take ownership of the character in a way. And in a sense, you're sort of handing it over to them.

We often get emails from actors, saying: "Oh, we're shooting this scene next week and I thought I could say this, or we could change this line, or I have this idea." Sometimes the ideas are good, sometimes they're not. But, we're certainly always happy to encourage it and sit and meet with them.

And even if the idea isn't necessarily the right one, perhaps the thought behind it is great. So, we sit there and talk with them and figure out a way to achieve what they're trying to do with their character.

It seems a little bit, based on what Philip Reeve has kind of said in the past, that there are some things that he wanted to fit into "Mortal Engines." For example, more details on the hierarchy that goes on in the city. Did anything that didn't make it into the book make it into this movie just by virtue of your conversations?

Peter Jackson: We've changed the book a bit in places. But, not really for those reasons. We've aged it up. The book is written for quite a young audience, to some degree, you know? And I just don't think anybody wants to see another dystopian-teenage movie any time soon.

So, it's one of the reasons why we've aged it sort of up... We had to make it a little bit more adult. And so, in some respects, it differs from the book in quite a few places, but not really for those reasons. Although, Philip came out here and we always send him script revisions as we do them and he always seems to be very pleased with them.

You know, having written the four books that he did, he said that he wished he could go back to the first one again and revise some parts of it because you certainly you see his confidence in his storytelling kind of grow as these four books progress.

If you do more of them, would you want to have the same sort of level of involvement?

Peter Jackson: Yeah. I have to see if Christian wants to direct some. That will be up to him. He might go off and do other things. I mean, I'd like to direct. I thought I was going to direct. I'd love to direct the last one if we got that far. But, by then, if he's directing them, I'll let him decide. We'd produce them for sure, and obviously, Christian would have the first offer to direct and hopefully he would.

Mortal Engines hits theaters December 14, 2018. Watch the trailer here.