Comparing the experience of shooting his first fiction feature “Rocket Science” with making his popular documentary “Spellbound,” writer-director Jeffrey Blitz, in Dallas for a festival screening of his new film, observed, “The funny thing is, I feel like they’re actually much more similar than people want to believe they are.

“In a documentary, you control things much more than people think you’re controlling them. Your choice of how to shoot something creates the tone of the piece you’re going for, the sensibility behind it. You exert a lot of creative control in a documentary that people don’t think about.

“The flip side to it is that in a feature film, you’re exerting much less control than people think. Even on the most tightly controlled set, in both cases you’re kind of hoping for the happy accident. In a documentary you want the real world to unfold in a way that helps you tell your tale. And in a fiction film you’re hoping that all these variables that are beyond your control suddenly work in your favor. But they’re both fun to do.”

Blitz added that “Rocket Science,” about a stuttering high-school kid who’s pressured by an ambitious classmate into joining the debate team, followed naturally from “Spellbound.”

“When you work on a documentary project,” he said, “there are all of these loose ends, all these things that could have happened but didn’t, characters I could have encountered but didn’t. So at the end of it [‘Spellbound’] I was left feeling, ‘Wouldn’t it have been great if we had found this kind of kid, and if we had found this kind of drama?’ So I was left with a desire to work with imagining what all of these potential other stories would have been. And when HBO Films offered me the opportunity to write a screenplay for this high-school movie, I had all these loose ends from ‘Spellbound’ that I wanted to follow through on.”

There’s an autobiographical element to “Rocket Science”—Blitz suffered from a pronounced stutter as a youth, too, and participated in debate in high school. But one shouldn’t take the various plot threads—an infatuation, a twist that gives the protagonist a new partner—as being part of his own life.

“Autobiographical movies tend to give me the heebie-jeebies,” he explained. “They tend to be overly earnest. So I really wanted the autobiographical element just to be the bare bones of it, and then let myself get into the dark comedy of it, get away from my own life and let this absurdist comic world come out. I was not that kid at all in high school.”

Blitz did strive, though, to be true to the strange world of debate that he remembered so well—a world that will seem alien to most viewers. “I wanted to make a movie that feels authentic to that world, to the world that I knew in high school when I was debating and in public speaking,” he said. “It’s a whole subculture, and I felt an obligation to try to get that subculture right. I had to make some compromises in order to let the movie be understood by people who don’t know that world”—like actually slowing down the speed with which participants rattle off their arguments. “But I wanted to do right by high-school debaters.”

Of course Blitz also wanted to be true to the characters he was creating, especially the young hero, played by newcomer Reece Daniel Thompson, whom he discovered through general auditions, success in which he described as “like the weirdness of falling in love with someone. It’s hard to explain the chemistry, but in my experience you know it as soon as it happens.” And Thompson, he added, eventually got the stuttering down exactly as he’d intended. “The way I had scripted it and patterned it,” he explained, “I kind of had to find a balance where you could get the pain of the lead kid’s stuttering without it getting in the way of the comic timing of the lines. But [Thompson, who’d rehearsed with his mother, a speech therapist] came ready to do an authentic stutter that didn’t have any awareness of the comedy of the lines, and it was awful. Reece and I had a few weeks of rehearsal, and we worked on the speech patterns. And very soon in the shooting he got so good at it that he would be able to tell me the way I would have stuttered on a line as a kid. And he was right.”

Blitz hopes that people will find his new picture, like “Spellbound,” a story of particular characters that takes on a more general resonance. “I love movies that seem like they’re going to be small and end up being big, or that try to illuminate something bigger by looking at something small,” he said. And that’s what he hopes “Rocket Science” will do.