The release of Rogue One has sparked an unexpected controversy. The film features Peter Cushing, a familiar face from the original Star Wars: IV A New Hope (1977), reprising his role as Grand Moff Tarkin. Cushing appears in new scenes and interacts with fresh characters, despite having died in 1994. More than 20 years later, an actor has been digitally resurrected.

Responses have been mixed, to say the least. Some hate the digital version of Cushing because they perceive it to be artificial and distracting. Others have ethical concerns about the use of a deceased actor's image (although Cushing's estate gave permission for this). Other viewers just assumed they were watching a live actor.

As a visual effects artist, I found the work in Rogue One impressive but not totally convincing. There is still, for me at least, that oddly disconcerting gap between the artificial and the real. If the computer generated (CG) version of Cushing had been used more sparingly the audience would have had less time to study every detail and search for flaws.

The CG version of young Princess Leia in Rogue One was altogether more successful with audiences, though I confess to finding her smooth-skinned youthful face less believably real than digital Cushing's craggy visage. The acceptance of CG Leia was likely due to the character's limited screen time.

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Carrie Fisher herself is said to have approved of the move. Since her death, however, Disney has emphasised that it will not be creating a digital Leia for future episodes.

Regardless of the success or otherwise of these examples, I suspect we are very close to a genuinely believable CG actor who will fool even experienced professionals. As an artist I find the prospect exciting, though as a human being I have twinges of concern that the technology may not always be used wisely.

Robert Zemeckis, with his trilogy of motion captured CG films, The Polar Express (2004), Beowulf (2007) and A Christmas Carol (2009), has arguably done more than any single director to push the boundaries of fully CG digital actors.

The characters from these films are oddly unnerving to watch and more than one commentator has called them "creepy". However, they represent key moments in the development of the technology.

A more common use for digital doubles is to portray living actors in situations of great danger. There are a couple of options in this scenario. One is an entirely digital character created from a full body scan of the actor. The other option is to digitally paste an actor's face onto the body of a stunt performer.

Disney has recently denied a rumour that for the next Avengers film it plans to paste Benedict Cumberbatch's face on to a body double to facilitate shooting around his busy schedule.

Extensive digital doubles were already used for Doctor Strange (2016) so there is no reason to assume Disney is about to change its working methodology.

Less well known is the use of this technology for "beautification". Body doubles for nude scenes have been used in Hollywood for decades. Now, an actor's face can be pasted right on top of the body double for a seamless effect, though no actor wants to admit to it and visual effects companies are required to sign non-disclosure agreements.

It is generally only when things go terribly wrong - such as when viewers noticed obvious signs that Lena Headey's nude Game of Thrones "Walk of Shame" involved Headey's face pasted on to another actress's body - that it's noticed.

Harrison Ford famously refused to dye his hair for Indiana Jones and the Kingdom of the Crystal Skull (2008) and again for Star Wars: the Force Awakens (2015).

However, not all actors may have the confidence or the industry clout to resist when there is a digitally perfect version of their 25 or 30-year-old self readily available to be used.

- The Conversation