It's a public holiday and raining and the Tuesday 5pm session of 3D Sex and Zen: Extreme Ecstasy at Hoyts Broadway is sold out but for a few spots in the first two rows.

Hoyts Broadway is one of three Sydney cinemas screening the film which broke the opening day ticket sale record in Hong Kong, taking the title from the $US237 million 3D blockbuster Avatar.

3D Sex and Zen, made in Hong Kong, cost just a fraction of James Cameron's epic — about one seventy-fifth as much — and is shown in Cantonese with English subtitles.

Like Avatar, its goal is to take the viewer on a trip to "a world they've never seen before", says director Christopher Sun.

So, does it succeed? During the two-hour-plus screening, news.com.au learned quite a few things.

For example, that subtitles are really hard to read while wearing 3D glasses. Also, that the women of 15th Century China enjoyed spectacularly powerful orgasms.

But perhaps the most important revelation — and the one you are here to read about — is that "3D porn" is still a long way from a must-see.

Most of the 3D effects in Sex and Zen are reserved for computer-generated graphics, rather than the wonders of nature.

3D is only occasionally applied to the movie's many — many — sex scenes, and when it is the results are hit and miss.

In one instance, when the entire screen is filled with a close-up shot of gigantic, jiggling body parts, it just looks ridiculous.

In others it makes the scene appear more "real" than usual, but also rather blurry.

In fact, Sex and Zen is a bit of a tease — it hints at the potential of porn in 3D without actually giving you much of it.

Viewers who only want to go for the sex scenes without worrying how many dimensions they have won't be disappointed.

But be warned — the sex comes with quite a lot of blood and guts as well.

Sex and Zen is a film in two halves. The first half is a light-hearted erotic comedy with plenty of softcore porn.