They picked one of the projects they'd talked about, and took it to Pixar's Co-op program, an internal professional development project that sets aside resources for employees who want to learn by creating their own films. Borrowed Time took five years to develop and animate, with Coats and Hamou-Lhadj working on it in their spare time, with an all-volunteer team. I recently talked to them by phone about how they got started, how they used the Unity game engine for a last-minute fix, and what their mourning main character has in common with the pastel-colored emotion characters from Inside Out.

Coats was a senior at NYU's Tisch School of the Arts when Hamou-Lhadj arrived as a freshman. "The department is pretty small," Coats says, "so anyone who was serious about animation found each other, even though there was a big divide in ages." They quickly became friends and collaborated on each others' projects. Coats went on to work at Blue Sky Studios, on Horton Hears a Who!, Ice Age 3, and Rio, while Hamou-Lhadj interned at Pixar and got a full-time job there, working on WALL-E, Toy Story 3, The Good Dinosaur, and various short films. They'd planned several collaborative projects, but they had to put them on hold: "There wasn't good cloud-sharing technology back then," Coats says. "There wasn't a good way to work online, and across 3,000 miles. But when I started at Pixar, we said, 'Okay, no excuses, we can do something now.'"

The short animated film Borrowed Time, made over the course of five years as a side project by two animators at Pixar Animation Studios, has been circulating at film festivals since 2015. But this week it was made publicly available on Vimeo , which marked the first time most of the public could see it. The internet response has been tremendous. Writer-directors Lou Hamou-Lhadj and Andrew Coats say that as artists working on a huge team at a large company, they're used to being out of the public eye, and they've been overwhelmed by the direct, personal positive attention their film has drawn.

This interview has been edited for clarity and length. Tasha Robinson: What did Borrowed Time look like when you first conceived it? Lou Hamou-Lhadj: Originally, it was much more of an action piece. We were looking at films that inspired us when we were students, where everything was 2D, hand-drawn, very action-oriented. But as we were starting to develop it, we realized it was going to take us a very long time, and doing animation for animation's sake wasn't really what we were hoping to get out of it. We also wanted to grow as storytellers, and take on something we were less comfortable with. So we came up with more of a drama. Andrew Coats: There's a lot of fun in physical or comedy-based animation, in coming up with poses and interesting in-betweens. But we were kind of burned out on that. We wanted to tackle something we didn't get to do at work. What was the pitch to Pixar's Co-op program like? AC: We just had to go through the legal department at Pixar. We just had to send a synopsis of what the film would be, and the main players, schedules, run times. That's pretty much it. Our synopsis was vague enough that it holds up even to the version we have now. But that's all that's involved. You don't actually have to pitch. It's basically just, "Legally, does this get in the way of anything coming down the pipe at Pixar? Does this infringe on anything we have going on here?" If they say, "No, it's yours," then it's yours to make. You make it however you can. Pixar production timelines are reportedly intense. How did you find time for this project, or find so many people who volunteered to help? LH-L: It was pretty challenging. [Laughs] Our schedules are really flexible here, but we work hard. There are periods of intensity when certain milestones in our films need to be met, and scheduling around those, and around the availability of people we were trying to get to help us, was no small feat. Our producer, Amanda Jones, was our saint. She navigated, better than we ever hoped, all the trickiness of encouraging people to help without burning themselves out. And Andrew was always a proponent of finding time to not work on the film. We started out, in the beginning, both doing too much, and working every night of the week on it. It quickly became just as important to schedule days off on it. "Andrew was always a proponent of finding time to not work on the film." AC: The first two-and-a-half years was just Lou and I designing, modeling, rigging, doing story reels and animatics. We thought we were gonna do it on our own, like another student film. We did everything we already knew how to do, and luckily, we got far enough along that we could use what we'd done to recruit people, and to show how serious we were about finishing the film. Our credit list is big, it's 80 people or so, but to be honest, we gave credit to anyone that did anything on the film, even for a day or two. The core of the movie was made by about 12 people. The rest were people who helped fill in the gaps to get us to the finish line.

What was the most useful thing you got from other people? LH-L: There were skillsets Andrew and I had almost no experience in at the time. By the end of the film, we had to touch a little bit of everything. On the back end of the pipeline — shading work, lighting, effects, rendering — we needed key players to help us out. But I think outside of that, we relied on outside people for objectivity. After three years of toiling on a film late at night, you can quickly lose sight of what you're making. We'd grab people and say "Can you give us a fresh pair of eyes on this?" We relied on that as much as feet on the ground. AC: We were too close to a lot of it, honestly. We were too involved. So it was really helpful to step back. Just screening it in front of a fresh audience changes your perspective of what the movie feels like. You almost don't need their notes. The day before, you're like, "Totally nailed it! This is going to be awesome." And as soon as you see it with the audience, you're like, "Oh my God, this is not working." And it was amazing to realize how helpful it is to be in front of an audience, and feel it through them, and get that objectivity back, even just for a second. Over the five years you were working on this, a lot of Pixar's processes changed, and they came up with new technology for things like the hyper-realistic water in The Good Dinosaur. How did that affect your film? "when a file changed, it could suddenly blow up what we were doing." AC: The reality is that when things evolved, technology-wise, we had to scramble to not fall apart. It wasn't like, "Oh, let's get this new technology to do this thing we couldn't do in the previous version," it was more like, "Oh my God, we can't render anymore, the characters are not building," and then scrambling to figure out what broke and why. We had live links to different things on different pipelines, so when a file changed on a different movie in progress, it could suddenly blow up what we were doing. But it's funny you brought up the water! LH-L: We had drawn, as one of our explorations of the space, a canyon carved out by a river. But we ignored it until the end of production, because there were bigger fish to fry. Then we realized shots were being held up because we didn't have a river. The work you're speaking to in The Good Dinosaur requires a large team and a lot of time. It wasn't going to be feasible to do it the "right" way. There was a point where Andrew and I lamented that we would have to give up the river, and just make it a dried-up riverbed. Then we were reflecting on video games we'd played recently, and how real-time game rendering has come so far that certain effects can look really cinematic. And we said, "What if we took a page out of that and tried to do the water in a game engine?" A couple of days later, we had proof-of-concepts with the river comped into our final film frames. It was completely created in the Unity game engine. It wasn't until the end of the process that we started looking at those kinds of efficiencies, to get across the finish line. We had said "We're not going to take any shortcuts. We're going to do this as true to Pixar as possible, within the pipeline." AC: Our producer equates using the Pixar pipeline for Borrowed Time as using the Titanic as a tugboat, or to go island-hopping. It sounds awesome, but then you're like, "Oh shit, I need 50 people to make this machine run. Oh God, I just need to go to this island. Can't we just do it? Can't we just go here?" "No, first we have to warm up the engines, then we have to back out over here, because it's too shallow." It's an obstacle just because the machine is so big. So finding ways to go around the systems was actually really helpful. What was it like getting the Unity engine talking to the software you were already using? LH-L: That was was something we were dabbling in as part of a research project. We're getting some of our tools to talk to game engines. But all we cared about at the end of the day was being able to match the camera movement in both engines. That wasn't difficult. It took us maybe half a day of deep thinking. AC: We used the canyon render from the Pixar pipeline and matched it with the Unity camera, and comped them together in Nuke. It was just about figuring out how to bring the camera information out of our system.

In the first shot of your protagonist, the fuzzy texture on his shirt seems so similar to the fuzzy, effervescent skins of the Inside Out emotion characters. Is that a case where you were able to work a new Pixar tool into your film? LH-L: Yeah, that is actually very similar technology that's responsible for those two things. All that stuff is happening at render-time. It's a procedural shader for cloth that generates flyaway curves to generate an organic quality. AC: And we really pushed for getting the gritty reality into our characters. We wanted a groundability. It's a short where you have to emotionally understand this character, even though he's a caricature, not a realistic-looking person. But we wanted to ground the details, and get some of that grit of a Western, getting more dirt on their faces. Finding more detail, and making a statement about it, helped keep people invested in the characters. Emotionally, this is a really tough story. By the end, your protagonist has come back from the edge, literally and figuratively, but his situation isn't resolved at all. Why did you want to leave people on that specific moment in the story? "There is no real answer to how you deal with grief." AC: We wanted people to find out what that moment means for themselves. We didn't want to be too explicit. There is no real answer to how you deal with grief. A lot of people hold guilt about losing someone: "I wish I'd talked to them one more time, I wish I'd gone to see them. Why didn't I XYZ." This was a dramatization of that feeling. We wanted to end in a way that's not about him being fixed. He's not a fixed man now, he's a man who decided to keep going, to continue with his memories, and the good side of what his father was to him. What's been great about seeing the responses online is that a lot of people bring a lot of different emotions to what it means for them. That was the goal for us in the end. It's about asking questions for yourself, and finding the answer for yourself, not being spoon-fed an answer. LH-L: We wanted to end on a hopeful upturn, but not have it solved. He's just on the path toward being able to deal with this in a more healthy way. Were there personal reasons why you wanted to spend this much time exploring grief? AC: Well, it wasn't what we set out to do initially, honestly. The film evolved as we honed in on the story we were trying to tell. In the beginning, it was a much bigger story, and it was more about forgiveness and betrayal. And we very quickly learned that we couldn't do that film. We had to simplify and bring the story down to something we could do in six-and-a-half minutes. And what we were left with was this guy standing on the edge of a cliff. We tried to stay true as much as we could to what we'd learned about him in developing the story, and what it would have taken for him to be there, and what it would take for him to get what he needs. He's there to be closer to his dad. Getting to the bottom of the cliff is a positive thing for him, because he wants to reconnect with his father. Finding the strength to keep living was where we ended up, and it was through him more than through us. It's weird to say, but stories take on their own energy, unless you manhandle it into whatever you want it to be. We let the story tell itself after a certain point. The short leaves viewers with a lot of questions about this man's life, both between the time periods we see, and where he's going next. Do you have an interest in telling that larger story? LH-L: Over the course of five years of development, we had seven or eight whole versions of the film that explored different aspects of who he was. We had moments where we were time-lapsing through the years we don't see, catching a glimpses of what changed. So we thought a lot about that, and we have a lot of material for it. I think it's just a matter of deciding whether we want to spend however many years living in this world, or whether there are other stories out there that we're interested in telling.