Jill the babysitter is walking across the kitchen when she notices someone sitting at the counter. “Oh my god!” she says, clutching the towel wrapped around her body. “Mr. Johnson! I hope you don’t mind I used the shower.”

Mr. Johnson, like the babysitter, is a character in an adult video, and the actor who plays him doesn’t have any lines. The audience will never hear his voice or see his face, even though he does have a big part in the movie. This is virtual-reality pornography, and every scene is shot from his point of...