23 August 2010 Last updated at 08:04 GMT

Can technology replace human actors?

By Zoe Kleinman Technology reporter, BBC News

Click's Spencer Kelly goes to the world famous Industrial Light and Magic in July 2007 to find out how computer generated characters are created

Some of the biggest movies of the last few years haven't actually featured any actors in the flesh. Is technology stealing their limelight?

British actor Andy Serkis attracted great acclaim for his portrayal of the creepy, tormented creature Gollum, in director Peter Jackson's adaptation of the Lord of the Rings trilogy.

And yet he was never seen on screen. Gollum was created using a combination of digital animation techniques of which motion capture, or mocap as it is known, was a fundamental part.

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It would be understandable for actors to feel nervous of the way in which technology can literally overwrite them, but when it comes to motion capture, it is the animated film producers rather than the performers who seem to be holding back.

Dreamworks is a major animation studio with credits including the Shrek films, Madagascar and Kung Fu Panda.

Chief Technology Officer Ed Leonard told BBC News that the studio has no intention of using motion capture beyond the initial stages of storyboarding and scene mapping.

"We can look down a ten year roadmap at Dreamworks and there is nothing in the pipeline involving mocap," said Mr Leonard.

"I don't see it happening for a real long time, if ever. It's not the end goal for us."

Andy Serkis, on the other hand, is a self confessed "performance captureaholic".

In April 2010 he called for the establishment of a UK studio dedicated to producing motion capture content and teaching the necessary skills.

Animation film giant Dreamworks, the studio behind the Shrek films, does not use motion capture in its films

"It is one of the most exciting and liberating tools to do with technology that has come out of recent times," he gushed during a speech at the British Screen Advisory Council (BSAC UK).

But through using motion capture a screen character and the world in which it lives can be completely digitally created. So might he be talking himself out of a job?

Move on demand

Alan Lewis is a lecturer in computer animation at the Met Film School in London, which has just launched a motion capture course for actors and animators.

While exaggerated movements are easy for a non-actor to simulate, a more expressive performance still requires a professional, said Mr Lewis - although there may be room for both.

"There's performance capture and motion capture," he said.

"Performance capture is more about capturing the emotional performance of a character. Performance capture as a phrase arrived with (James Cameron's film) Avatar. Before that it was more about fighting warriors in games - very physical."

What is motion capture?

A digital way of recording movement, motion capture (mocap) performers wear suits covered with motion sensors.

Lights around the studio pick up the movements of the performer. The resulting sequence is recorded by computers and can then be used as a base for a digitally drawn character by animators.

Mocap has applications outside of the film industry. Researchers at MIT are developing a portable version called Prakash which works in natural light and could be used to monitor elderly people at home.

It is not uncommon for such fighter sequences to be re-used, he added.

"In the games industry martial artists will be hired to record a series of predictable movements.

"There's no point in hiring new people for a similar game or re-release when you can map them onto a different character. There's always a bit of re-scaling or re-adjustment but you can tweak."

In fact there are already several mocap libraries who offer standard packages covering a wide range of generic movement sequences from sports to common office behaviour.

Pascal Langdale, who played one of the lead characters in the game Heavy Rain, has recently set up a service, Motives in Movement, which specialises in creating libraries for individual actors.

Mr Langdale claims that a production can save up to 30% of its budget by using such libraries but he still thinks the actors need to perform their own motion capture in order to create a personal catalogue of their stock moves.

"I believe in the idiosyncrasies that an actor brings to a role," he said. "It's crazy to think that you could get away with mixing it up... you pull the life out of it."

Actor art

Andy Serkis has directed two video games, Heavenly Sword and Enslaved.

Traditional motion capture tracks only movement

He is also adamant that when it comes to performance capture, the skill of the actor is fundamentally unchanged by the technology.

"There is absolutely no difference in terms of the acting process, the getting into character, the research," he told BSAC UK.

"I think it's a real shame that people are still writing 'actor lends his voice to blue tall creature in Avatar' - these are actors who have worked on a set for upwards of nine months playing a role."

Ed Leonard at Dreamworks, does not see mocap as a threat to the actor's craft either.

"If you wanted to recreate and make an actor photo-real digitally, we have the technology to do that," he said.

"But it will never replace actors - that doesn't make any sense. Talent is about the expression of that performance."

For Dreamworks, traditional key frame, a form of hand drawn animation, is still the preferred method of animated film production, with a team of 35- 45 artists working for 18 months on a particular project.

The reason is that generally the results of motion capture just aren't good enough, said Mr Leonard.

"Even if you look at the guys looking at loads of mocap there's a whole bunch of tweaking and key framing," he claimed.

"You want expressiveness, you don't want literal translation. It's come a long way but in terms of using it for animated films it's not what we're looking for."

This pursuit of perfection is expensive, however.

"It's easy to be a little elitist about it," admitted Mr Leonard. "We spent $150m making a film, not everyone has that kind of money.

"But if you're showing a blockbuster it had better be compelling, that's what sells so everybody's after that goal. The big guys are spending lots of money to make sure their quality stands above the pack."