Cameron, a fervent believer in 3D, said a lack of high-quality content was also a barrier to wider adoption, but a poor technology to accommodate groups of people watching from different angles without glasses was the main obstacle.

"The biggest hurdle right now is the experience in the home. While it's quite good, it requires committing to wearing glasses," Cameron told Reuters in a telephone interview.

"It's a family phenomenon so it has to be seen from different angles. High-quality, full HD-resolution, glasses-free displays are two to four years away," he said. "In the next few years, I think the market will explode."

Three-dimensional films, which enhance the perception of depth by being shot from two perspectives, gained in popularity during the 2000s and achieved a breakthrough with Cameron's Avatar in 2009, which became the top box-office earner ever.

Films shot in 3D are still few and far between, but many studios are converting their back catalogues of traditional films into 3D - with mixed results.

"One of the things that I think has hurt the business are quick and shabby versions in 3D," said Cameron. "It's not worth it if you can't do it right."

Cameron's own Titanic was re-released in a 3D version in cinemas last month, after a year of work on the conversion personally supervised by Cameron, it will be released on high-definition Blu-ray for home viewing in 2D and 3D on September 14.

The disc will include extra footage including world experts on the Titanic disaster trying to solve the mystery of how the "unsinkable" ship sank a century ago.

But few fans will be in a position to enjoy the 3D version: according to media analysis firm Screen Digest, just 18 million households globally will have the television set, player and glasses necessary to play Blu-ray 3D at home this year.

"We're talking about a really small market. It's a luxury product within a luxury segment of video," says Screen Digest video analyst Tony Gunnarsson.

The dual perspective creates challenges for viewing: without glasses, the image has to be focused for the audience in another way, which is easier for single viewers with a fixed perspective than for groups of people, each in a different place.

For that reason, Cameron said, 3D was likely to catch on faster on tablets and laptop computers, where viewers typically watch on their own, than on large screens in the home.

The cinematic 3D re-release of Titanic was a huge commercial success for Twentieth Century Fox and Paramount Pictures, taking about $345 million at the box office since its April 4 release.

The 3D version, which cost $18 million to convert from 2D, has been especially popular outside the United States, notably in China, where most people had no chance to see the original film in 1997.

Elsewhere, Cameron said, audiences were returning to the film out of nostalgia or a desire for the big-screen experience.

"It's maybe women in their 30s who were in their teens at the time, wanting to share it with their daughters for example, or a lot of younger audiences who knew it only from video and wanted to share it as a group."

(Reporting by Georgina Prodhan, editing by Paul Casciato)

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