Explained: What is 4D Aromascope

New Delhi: The latest movie in the Spy Kids series Spy Kids: All the time in the World is adding a fourth dimension to the film - smell.

The producers are promoting the film as Spy Kids 4 in 4D presented with Aroma-scope. While the audience watches the movie in 3D with stereoscopic glasses they have scratch and sniff cards to smell at different points during the film. "Families are going to love the interactivity of this new addition to the movie going experience," says director Robert Rodriguez.

There will be eight opportunities in the movie where viewers can access the action interactively through smell. The Aroma-scope cards will be distributed for free with the tickets and will have different numbered regions that viewers are supposed to rub and smell a corresponding number flashes on the screen. Movie viewers can experience the scent of Spy Kids 4 even if they watch the movie in conventional 2D.

One of the first films to add of smell to the movie viewing experience was Scent of Mystery (1960) that used a technology called Smell-O-Vision that released an odour into the theatre during the screening of a film. Another similar technique was AromaRama that sent the scents through the air-conditioning system.

In the early versions of the technology the act of smelling was involuntary for the audience. In 1982 director John Waters gave the viewers more control with the 'Odorama' version of his film Polyester that had scratch and sniff cards with 10 different smells. The 2003 movie Rugrats Go Wild also used Odorama cards and the cards were also included in the DVD release. But idea of adding the sense of smell to cinema never caught on and only a handful of films used the technique.

Spy Kids: All the time in the World releases on August 19, 2011.