WEST HOLLYWOOD, Calif. — In January 2017, the director Jon M. Chu announced an open casting call for Asian and Asian-American actors for his movie adaptation of “Crazy Rich Asians.” Recorded in the kitchen of his West Hollywood home (you can see his fridge in the background), the online plea instructed anyone interested in joining his all-Asian cast, from aspiring actors to “cool personalities with hidden talents,” to post a two-minute video of themselves on social media. “We are looking for you,” he beamed.

The call was an enticing one. The romantic comedy was going to be a major feature film, with a reported budget of $30 million; its inspiration, the best-selling novel by Kevin Kwan, had already sold millions of copies. And then there was the sheer singularity of it all. How often did a Hollywood filmmaker go looking for a whole bunch of Asians for anything? The last time a major Hollywood film set in the present day showcased a majority Asian cast was a whopping 25 years ago, with “The Joy Luck Club” in 1993. Many of the folks Mr. Chu was seeking now weren’t even alive then.

For Asian and Asian-American viewers, the film, which opens on Aug. 15, is important not just as something of a cinematic Halley’s comet — before “Joy Luck Club,” there was “Flower Drum Song” in 1961, and then, what? There’s also an eager hope that if this movie succeeds, it just might stave off another quarter-century drought. Producers use something called “comps” — recent films similar to the ones they’re pitching — to help sell studios on their ideas and budgets. For the producers of “Crazy Rich Asians,” there weren’t any. For scores of Asian-themed films to come, the hope goes, “Crazy Rich Asians” could be that comp.

When Mr. Chu made his online pitch, the film seemed a godsend for Asian actors, aspiring or otherwise. Forget a few token parts here and there; in this one film, Asian actors would play everything: the romantic leads and sympathetic sidekicks, the comic foils and cads, the faces in the crowd. With more than 4 billion Asians on the planet, how hard could it be to cast this thing?