Amongst animation fans, Ralph Eggleston is something of a legend.

Pixar hired Eggleston in 1992, when the studio was in full swing on the first "Toy Story" and he has served as a production designer, storyboard artist, writer and director. (In 2000, his short film, "For the Birds," won an Academy Award.) He has contributed substantially to every Pixar film and this week's "Inside Out" is no different.

For the brilliant new film that takes place inside the head of an 11-year-old girl, Eggleston served as Production Designer. And it's a pretty unbelievable task, conjuring forth worlds as vast as the human mind (including the subconscious, Dreamland Studios, where dreams are made, the Train of Thought, and, of course, Headquarters).

We sat down with Eggleston and talked about the film's lengthy development and production process, being part of the fabric of Pixar, and what he's got coming up next.

Moviefone: You talked about working on "Inside Out" for a long time and just realizing that it wasn't working. What was the breaking point where you said, "We have to do something else?"

Ralph Eggleston: Well, that was every day almost. The idea was always there. It was always about Riley and her emotions. Variations on that were what took place. The real world component of the film, for example, ... Riley's grandmother died and they moved to New York City and Riley's grandmother was a hoofer in the follies in the 1920's and Riley wanted to be like her grandmother. The idea was a big fish in a small pond moves to a big pond and she's a small fish. And the whole mind world was based on the catwalks, all the way to the sublevels of a theater. That was a take. And that lasted for a couple of weeks, I'm sure. But the idea was always Riley and her emotions. Pete [Docter] didn't want to spend too much time with Riley initially. And of course, the film has come back around to that, which is totally cool. The problem, for a little while, was that you didn't care about the emotions or the journey they went on unless you cared about Riley and understood enough about her.
What was the hardest thing to lose?

Oooh, that's a hard one. This didn't go very far, but there was an idea for a concept of what the mind was that was much more based on a fractal. It was the idea that the further you zoomed in, the further you zoom in. It was never ending. There is this thing called a Mandelbrot cube fractal, which is a three-dimensional fractal. And they always look weird and hippy dippy ... But it looks like a cube and you zoom in and it looks like an H.R. Giger painting, except in 3D.

But the idea was interesting – the further you zoomed in, it was infinity. But also that if you were on one set, say you were outside headquarters, which is in the middle of everything, and you got on the Train of Thought, it could go like this [he starts contorting himself] and then you're looking like this, and these little dots are there and up is there. It was so intriguing. I remember having lunch with Brad Bird somewhere in this process and I pitched him that and he stared at me and said, "That would be awesome." If the story had been much more advanced in terms of the push and pull of the elements, maybe we could have done it.

Where did the design of Headquarters come from?

To be honest, a lot of it had to do with the brain, finding elements of the physicality of a brain or a body – cellular structures, elements of hypothalamus, DNA. We would sit there and draw. We got macro-photography books of cells and body parts and we would just sit and doodle and abstract. And it was also a bonding experience for us.
And you've been here for a long time.

Well, Pixar started in 1985. I got here at the tail end of 1992.

You've worked on all of these things. Do you have any ambition to do a project of your own?

Well I have, it's called "For the Birds."

What about a feature?

I've pitched several things here. I'll go wherever they want me to go. That's always been the truth. So many people here go home and do their own thing. That's not me. I am somebody who likes to do the work with groups. I don't care where I fit in. It's such a collaborative effort. That's the most fun part of this job. So directing, I don't know that I would want that pressure. I would rather fit in with a particular director and I've been lucky enough to fit with each one of the directors I've worked with... My job is to make their job easier.

Do you look in on other productions?

We always do. We share a lot here. The only stuff they keep away, not from people in the company but anybody else, in the most general sense, is the stuff in the early stages of development. If there's something in production, and we have several things in varying states of production, any technical person or staff person from any phase in production can go in and do whatever they want.

And you said "Inside Out" was the most difficult thing you've ever worked on?

It was. Mainly because of the enormity of the possibilities -- It was incredibly daunting.

Can you talk about what you're working on next?

Yes -- Driving home!

"Inside Out" is in theaters now.