With Disney/Marvel’s “Iron Man” clanking to a cool billion worldwide and Paramount’s “Star Trek Into Darkness” on a similar course, one thing has been notably absent: Complaints about 3D conversion.

Both pics were converted to 3D, as were Warner/Legendary’s upcoming “Man of Steel” and “Pacific Rim.” Gone, it seems, are the days when fans lit up Twitter and Facebook with complaints about ugly, distorted 3D. Today auds seem to be concerned about paying the premium for a 3D ticket and not feeling they got a 3D experience, rather feeling their eyes were assaulted by bad conversion.

William Sherak, president of StereoD, the conversion company that added stereo to “Iron Man 3,” “Star Trek Into Darkness and “Pacific Rim,” says he feels shooting and conversion have both matured to the point where filmmakers can choose whatever is best for their project. “One, your post schedule and two, your shooting schedule, those can be your determining factors,” Sherak says.

Barry Sandrew, founder and chief creative officer of Legend3D, says filmmakers are learning how and when to use each technique. For shots that use compositing to combine live-action and computer-generated elements, conversion is becoming the favored solution. “Having two eyes composited, it’s very difficult to do that,” says Sandrew. All-CG shots are best rendered in 3D by the visual effects company, Sandrew says.

But when the two are mixed, conversion is more efficient. Sandrew also sees a trend toward realism — that is, 3D rendered to more or less resemble the way the eye perceives real life. “We’ve done that type of work. And the response, really, has been ‘Classy.’ That’s the most common word we’ve seen. And that’s the kind of movie where you forget it’s in 3D over time. And that’s the ultimate goal. We want people to experience 3D in the entire movie but we want them to forget they’re in a 3D movie.”