As he was making “Minding the Gap,” Bing Liu had a history of films about skater culture somewhere in the back of his mind, usually at arm’s length since most had never felt all that true to his own experience and besides what was unfolding in front of him was fascinating enough. But he couldn’t ignore the legacy of films he was entering into when he walked in one night to find one of his two main subjects, Keire, lounging on the couch ready to watch Larry Clark’s “Kids.”

“[My] mind was blown,” recalls Liu, of experiencing some deja vu from his first time watching the ‘90s film set against the Manhattan skate scene nearly a decade earlier, kicking it at a friend’s house after a couple of beers. “I’m like, ‘Are they really about to put ‘Kids’ on right now?’”

The way history could repeat itself was already something Liu had been thinking about with “Minding the Gap,” as was the way that past depictions of the skate community seemed to only skim the surface of what drives someone to pick up the board in the first place, but perhaps most resonant for the filmmaker was that he had put the time in to simply be there when the moment happened, the result of five years spent in the company of the 16-year-old Keire and the 23-year-old Zack, two natives of Rockford, Illinois who he knew from the same skate park where he had been doing kickflips when he was a teen. A broken arm led Liu to take on the Spike Jonze role in the community rather than Tony Hawk, getting his mom Mengyue to loan him the money to buy a mini DV cam, but while he no longer had a board under his feet, he still found a way to glide with the camera, leading him towards a steady income in the camera departments of various Chicago-based productions including “Divergent” and “Jupiter Ascending.” It was in Chicago where he’d also come to the attention of Kartemquin Films, the venerable documentary production house behind such films as “Hoop Dreams,” known for longitudinal projects like the kind that Liu had stumbled into.

Yet if Liu wasn’t entirely aware of what he was taking on when he first embarked on the project, initially interviewing skateboarders around the country after a pattern developed amongst his old friends of destructive behavior that tended to be rooted in the tough lives at home that led them to the solitude of skating, he certainly wasn’t ill-equipped to handle the enormity of it, a project that grew larger in scope as he narrowed his focus to just Zack and Keire. A film that satisfies the first time you see it, “Minding the Gap” becomes deeper and richer over multiple viewings as Liu uses the parallel experience of the two young men on the cusp of starting their own lives, while still living in the shadow cast by their own fathers, with Zack soon to be a first-time dad with his girlfriend Nina and Keire beginning to take the steps to envision a life outside of Rockford, starting with a dishwashing job at a local restaurant. However, as much as their instinct as skaters is to live in the moment, Liu finds that Zack and Keire are heavily shaped by their past, both enduring abuse as children that has manifested itself in different ways into the young men they’ve become, and eventually comes to revisit painful moments that he and his mother and his half-brother had to endure.

“Minding the Gap” is a truly exceptional film, and remarkably one of two such projects Liu has coming out this month as he also serves as one of the segment directors on the Starz series “America to Me,” spending a year with the students at Oak Park and River Forest High School, premiering next week. In the midst of a very busy summer, the filmmaker spoke about leaving behind one version of “Minding the Gap” to pursue another, earning the trust of his subjects and how a random piece of footage he shot years earlier than he started on the film gives it one of its most dramatic moments.

Keire and Zack in "Minding the Gap"You’ve said that you started with an entirely different approach, interviewing skateboarders around the country. How did the version that focused on Zack and Keire come into focus? [SPOILERS BLURRED]

There were three main phases – the first one was very much a film that thematically wanted to explore things like family and childhood trauma and I went around the country and interviewed skateboarders I met over the years to try to do that. The patterns were very real, and when I met Keire a year in and it was like, “Oh no, we’re going to make a longitudinal character film.” It helped that when I met Keire, I found out Zack was about to become a father, so here’s the story of a guy who’s processing all this for the first time.

[Then] when Nina told me Zack was being abusive, [I thought] I have to rethink this film [because] it was mostly like, I still want to keep exploring this [relationship], but what gives me the right to do that? That’s what led me to interviewing my mom. I didn’t want to make a personal doc because what’s the reason for putting myself in? But then I had a reason once Nina told me Zack was being abusive because it’s like, “Okay, I can both explain why the filmmaker thinks he has a right to go there and also show parallels between how this affects women and why they stay in these relationships. If Nina wouldn’t have revealed that – if that relationship didn’t become abusive, I don’t think I would’ve gone and interviewed my mom.

Was Nina immediately onboard to continue filming when that happened?

It started out [with Nina where] she was like, “Oh, Zack’s doing his project and I’m in the background.” But at one point, I was like, “How do you feel about being a main character in the film?” And she was like, “I didn’t realize I was a main character.” This scene isn’t in the film, but I went to the hospital with them because she had to get induced into pregnancy and they botched the epidural – it was super-traumatizing, and she had to have an emergency C-section. I did a long interview with her about that experience, so it was pretty early on that we built up that relationship and after she revealed the abuse to me, I heavily followed her and I think that really cemented in her mind that this is really my story too.

Bing Liu in "Minding the Gap"Did the initial incarnation of this – interviewing skateboarders around the country – influence how you approached these stories with Keire and Zack, even if you were ultimately discarding that footage?

It just made me more confident that I’m on to something bigger than these guys’ stories. Just about everyone talked about abuse in some form or another growing up, whether it was emotional or physical or domestic or sexual. So when Keire talked about his father abusing him, I knew this was part of a larger pattern, and making the film with Kartemquin, they make verite films where issues come out of character’s stories and their lives lead the actual film, so I was confident that Keire’s story could do that. But a lot of people talked about abuse and it helped them to talk about it, but no one had quite processed it yet in the way that Keire hadn’t. Zack [dismissively] says later, “Yeah, my dad whupped my ass.” Most people were like that. They’d brush it off. It didn’t matter anymore. They had hardened their softness around it. Keire hadn’t yet and that reminded me of myself.

Would you find that they didn’t yet have the words to articulate it?

That’s such a microcosm for the whole film, which is [that] most young people feel the feelings that the young people in “Minding the Gap” feel, but because adolescent emotions are so written off in our society — “Just grow up, kid” or “Stop being so emo” — there’s so many epithets for it, that we never get the chance to articulate it, so that’s why I had to literally over the years ask Zack and Keire the same questions over and over again and they slowly articulated it more and more. Over time, there was growth in that.

You’ve said you hadn’t approached this as a verite film until Kartemquin came on – was that an easy choice for you or a comfortable one?

Absolutely, because the way Gordon [Quinn, the founder of Kartemquin] explained verite during the fellowship was, you let your characters’ lives lead and if you follow them long enough, every social issue will come out of that. He explained it that [in the past], they used to shoot film and it was really expensive, so you’d hang out with the camera all the time, but you’re not shooting all the time. You’re building relationships and picking up sound because it’s a lot cheaper to record on tape and then when something happens, then you start filming. And I was like, “Wait a minute. That’s what I did on skate videos.” You always have the camera with you and you just film when you film, so there were some parallels that meshed really well. Then [when] I watched their films, I was like, “Ohh…this is powerful,” so I bought into it pretty quickly.

I played soccer in elementary school, and a little football, and there was a structure there and a lack of freedom, but in skateboarding, you make up the rules. You could do this because you can emulate something you see in a skate video, but then you realize, all the rules are just constructed, so I brought that to making skate videos and later to filmmaking. What was nice about [initially] not having funding was that I didn’t have to please anybody. I was just experimenting and I tried different things. It was a time in my life where I could really develop my voice. As a teenager, I had learned so much on my own on the Internet, emulating films that I looked up to and then in my twenties what got laid on top of that was this formal way of lighting and cinematography that all added to who I became as a visual storyteller.

Keire in "Minding the Gap"At Sundance, I remember you also saying that you were building sequences before you even got to editing. What did you mean by that?

I did so much of this in my free time until we got funding in late 2016. I’d be really excited by, for example, that interview with Keire and I’d just go home and maybe have a call time [for another movie] the next day and go on a shoot, then that night, I’d just start editing. Then over time, I had scenes built, I’d assemble it together, I’d try to form it into an arc, and have a feedback screening, and the edit got shaped over and over and over again. Mostly, it was because I kept filming and things kept happening.

There was [also] a lot of reverse engineering. I didn’t really know Keire until my mid-twenties. He’s seven or eight years younger than me. I caught him getting into a fight once. The other footage I sourced from Zack and Keire’s friends who filmed them after I left Rockford. I did know Zack a little bit better than Keire, but I didn’t really get to become friends with them until we were making the film and we talked to each other more than just about skating at the skate park.

Wait, so that scene where you see Keire after a fight when he was 13 where you’re asking him what happened was just sitting around in a closet somewhere?

Yeah, I think I had already moved to Chicago and I just happened to come back and I was filming at the skate park. I had seen that everyone had run over to a grassy field and was like, “Oh, there’s two kids getting into a fight” and then years later when I was doing “Minding the Gap,” I was going through my old footage and in the back of my head, I was like, “I wonder if that kid was Keire.” I found the clip and I sent a screengrab to one of Keire’s friends [asking], “Hey, is this Keire?” And he was like, “LOL, yeah.” And I was like, “Oh my God, I wonder if I can build around this?”

I went back and got someone who’s Keire’s age who’s a filmer and got a bunch of footage from him, so it made it feel like you got to know him growing up as well. But that montage towards the beginning where it [looks] like we’re building relationships of who Zack, Keire and I were as kids – I was the main filmer in Rockford. Zack was the charismatic guy and Keire was the young goofy kid, but it was more like Zack and Keire were really good friends and they just [happened to be] in the footage together growing up. I didn’t realize people were going to take it away like, “Oh, we were like ‘Stand By Me’ best friends.” Really, we were part of the skate community, which is like the music industry where you meet with hundreds of people because you jam with them, but you’re not really [close] friends.

Keire and Zack in "Minding the Gap"Every time I’ve seen the film, it’s played differently for me because there’s so much there. Was it difficult for you to figure out where to place emphasis in the edit, if you ever even felt that way?

It was a game of just really not being emotionally attached to one thing too much. I’m still really surprised we made it work. There’s so many themes in the film – domestic violence, child abuse, masculinity, gender relations, intergenerational trauma, race, class…and skateboarding. [laughs] What was required of that is you can’t go too deep. If you look at the mechanics of how it works, it’s either one-two punches on a theme or one-two-three punches — like for Keire, [in the] first act, he jokes about [race] and brushes it off, second act, it’s like he gets pulled over and no matter how he feels about it, the world feels a different way and the third act, it’s like oh no, he realizes even amongst his friends there’s this divide of experience. So what I took away from the experience is you can do a lot with a little.

You showed Keire and Zack a rough cut of the film before it was locked – what was that screening like?

It was hard, mostly for Zack and Nina. Zack thought he was going to be portrayed worse, so I think he was relieved. At the end of the film, he was crying and [told me], “Wow, you got it. You captured it.” Nina relived her relationship with Zack… and it opened up these old wounds. She fell in love with how charismatic he was and then she was hurt again by what he had done. So we had to have a long conversation with her and process her feelings. And with Keire, that was probably the easiest. He was very emotional and every time he cried onscreen, he’d cry in person and every time he laughed onscreen, he’d laugh in person. Then I sent a link to my mom and my brother and my mom said, “I understand why you’re making the film now. I’m really proud of you” and my brother said he’s really proud of me too.

“Minding the Gap” opens on August 17th in Los Angeles at the Monica Film Center, in San Francisco at the Roxie Theater and in New York at the Metrograph. A full list of theaters and dates is here. It is also now streaming on Hulu.