Walt Disney Animation Studios chief technical officer Andy Hendrickson, in a talk at the Siggraph conference Sunday, laid out the thinking behind the studio’s feature strategy. The bottom line: The average number of viewers per release is falling, and studios need to fight that trend with tentpoles.

The number of tickets sold domestically, Hendrickson said, is roughly flat since 2005. But with the exception of a drop after the 2008 financial crisis, the number of titles released has grown considerably. Even that dropoff only took the number of 2010 tiles back to 2006 levels. Therefore the average number of viewers per release is falling.

“Profit equals the ability to capture more than the average share of viewers,” Hendrickson told attendees at the confab in Vancouver.

Hendrickson also said that while the market for homevideo has not shrunk, revenues from each streaming purchase are the same as from VHS rentals. The high-revenue DVD era between VHS and streaming is looking like the aberration.

The equation for studios, according to Hendrickson, is: Declining home profit plus the need for more viewers equals a focus on tentpole films.

“A tentpole film is one where you can seed the desire to see the film to everyone in every distribution channel. It’s the only kind of film you can spend $100 million marketing,” he said.

Hendrickson’s talk was mainly focused on solving problems in digital production on tentpoles, but he began with an “Econ 101” presentation on the movie business.

“People say ‘It’s all about the story,'” Hendrickson said. “When you’re making tentpole films, bullshit.” Hendrickson showed a chart of the top 12 all-time domestic grossers, and noted every one is a spectacle film. Of his own studio’s “Alice in Wonderland,” which is on the list, he said: “The story isn’t very good, but visual spectacle brought people in droves. And Johnny Depp didn’t hurt.”

Visual spectacle, he said, drives attendance in a film’s first few weekends. And unlike years past when a movie like “The Lion King” might stay in theaters as long as a year, almost all movies are out of theaters quickly now. “Once you’re out of theaters your maximum profit potential is over,” he said.