In 2005, Quantic Dream unveiled The Casting, a short tech demo that explored the possibilities of the then nascent PlayStation 3. A short performance by a single actor that slowly increased in intensity and darkened in tone, it hinted at the new, expressive power of Sony's console, of how this generation could enable the kind of human drama that's typically been the reserve of non-interactive medium.

It's a drama that, to an extent, 2010's Heavy Rain delivered upon, and it's a path that Quantic Dream has largely travelled alone. The digital theatre of Team Bondi's LA Noire was strangled by awkward performances, while Naughty Dog's Uncharted games, for all of their technical achievements, were more concerned with matinee thrills than raw, adult drama.

Not that Heavy Rain was perfect, of course - for all of its cinematic pretentions it often felt more like a straight-to-video thriller, while its stars found themselves at the foot of the uncanny valley.

Some seven years after The Casting Quantic Dream has again begun to explore, looking to find a solution to the problems raised by Heavy Rain, and to come another step closer to CEO and founder David Cage's own dream of providing interactive human drama.

"Our goal at the time with The Casting was to use the game engine to see how we could convey different emotions," Cage tells us prior to the GDC talk where he's unveiling a slice of what Quantic Dream has been up to since 2010. "We wanted to see what it would take in terms of the technology but also with the acting, and working with the actor on-stage to have this performance coming across in the game engine. We learned so much doing it for Heavy Rain, from the good things that worked very well but also from the mistakes that we made, and things we could have done differently.

Kara's played by Valorie Curry, most recently of Twilight: Breaking Dawn fame.

"When Heavy Rain was over, we thought why not do exactly the same thing and do a short sequence in real-time, in the game engine to see how our next game is going to benefit from what we're going to learn?"

"In Kara, you can't imagine the same scene having the same impact as someone who's not a talented actor. Technology becomes more precise and detailed and gives you more subtleties, so you need talent now. I'm not talking about getting a name in your game - I'm talking about getting talent in your game to improve the experience and get emotion in your game."

Welcome to Kara, the product of Quantic Dream's recent work on the PlayStation 3, and of its investment in new motion capture facilities. Again it's a one-woman show built around a slow tonal shift, again channelled through a strong and actorly central performance - but the distance between Kara and The Casting is as good a measure as any of the technical progress we've seen this generation, and of a shift in ambition and capability within Quantic Dream.

Kara's foundation is the studio's new engine, her purpose to reveal what it's capable of before the team embarked on its next game proper. "We really wanted to move forward and push the envelope on the new game," says Cage. "There were many things that we couldn't do on the old engine, so we decided to build a new one from scratch. Kara's the very first thing we've done with this brand new engine, so it's not optimized - it's got 50% of the features that we have right now, as Kara was done a year ago.

Kara's not just the product of new tech and a better understanding of the PlayStation 3's architecture - she's also the result of a new approach to motion capture at Quantic Dreams, and an investment in the more sophisticated techniques that have become the norm in Hollywood's CG industry as the studio moves across to using full-performance capture.

"What we call full-performance capture is shooting the body, the voice and face at the same time," explains Cage. "Most studios right now in the game industry use what we call split performance, which means you shoot the face and voice on one side and then you use the body, and not in one take.

"It works okay - there have been some great games made using this process, and Heavy Rain was done this way. But we felt that if we wanted more emotion, and more performance from the actor we needed to have everything from the same take, and we needed to shoot everything at the same time.

"So we invested a lot in our motion capture studio. Heavy Rain was shot with 28 cameras, and we've upgraded the studio to 65 cameras. Now we can shoot several actors - their body and their face - at the same time. It's not a small change, but at the same time this is how Avatar and Tintin were shot, and it's how the CG industry works because they know how much you gain from shooting face, voice and body at the same time."

Arriving in tandem with Quantic Dream's new full-performance capture facility is a new technical pipeline that allows performances captured in the morning to be viewed in-engine that afternoon. It allows for quick-fire iteration and brings the concept of working in a game studio a little closer to that of working on a film set, the director working through digital rushes after a day's virtual shoot.

Kara's played by Valorie Curry, formerly a regular on Veronica Mars and more recently a star of Twilight: Breaking Dawn, and she displays a remarkable range in her performance as Kara, moving from a robotic apathy through to a child's wonder and fear convincingly within six minutes. While Heavy Rain's female lead Jacqui Ainsley or The Casting's Aurélie Bancilhon were adequate, Curry's clearly an actor of a higher calibre - and it seems that tech that brings more fidelity to a performance demands performances of greater magnitude.

"In the past I was the main actor," says Cage. "In Fahrenheit I was Lucas Kane - I did the motion capture myself, but I'm not a very good actor. In Heavy Rain the quality in what we were trying made that impossible. We needed real actors, because we needed people with talent because the technology's reached the point where you can tell if someone's an actor and someone's not an actor.

It's an all-new engine, rendered entirely on the PlayStation 3 and relying on full-performance capture for its impressive results.

"In Heavy Rain that was definitely the case. In Kara, you can't imagine the same scene having the same impact as someone who's not a talented actor. Technology becomes more precise and detailed and gives you more subtleties, so you need talent now. I'm not talking about getting a name in your game - I'm talking about getting talent in your game to improve the experience and get emotion in your game."

Valorie herself was picked from 100 hopefuls auditioning for Cage in Los Angeles - although the decision, in the end, was an easy one. "When Valorie entered the room - well, she looked like an android already. We didn't change her face, didn't change her haircut - and the performance that she delivered was so impressive in the casting session that it was truly obvious that it was her."

It's more than a performance, though. Kara's the focus of a touching sci-fi fable whose power comes not only from Curry but also from a script that suggests Cage has re-kindled his love for the fantastical. It's a love that was richly evident in Omikron and Fahrenheit, yet almost entirely absent in the misery-core of Heavy Rain, and with its pondering upon what humanity is Kara plays out like a Philip K. Dick story told by way of Chris Cunningham's video for All is Full of Love.

A key influence, Cage reveals, was Ray Kurzweil's The Singularity is Near, itself an extension of the idea popularized by Kurzweil's of an imminent moment when technology races outside of humanity's grasp. "My idea was thinking of the first machine that would be self-conscious, and that would feel something and believe that it's living and human," says Cage.

"For me I imagine that it'll happen like a bug in a factory, and it's something that should never happen - but it happened. It's the beginning of something, and you can easily imagine how more Karas can be built having this emotional sense and how the world could change based on that."

It's tempting to think that, as The Casting introduced a more domestic threat that was later the foundation for Heavy Rain, so Kara could introduce a science-fiction element that could be explore by Quantic Dream's as-yet-unannounced new game.

"I'm interested in exploring anything that's human," comes Cage's enigmatic reply, "Whether that's in the past, the present or the future, it doesn't matter. It's all about human beings and emotions and relationships, how we feel how we love and how we hate. That's what I want to explore - everything else is just a background."

"What we're trying to create is really interactive entertainment for an adult audience. We don't pretend that we're cleverer than anyone else - but there are so many games out there that provide limited entertainment, and we try to make something for a more mature audience."

So whatever shape Quantic Dream's next game takes, it's likely to explore territory that's familiar to fans of the studio's work - and it's likely again to be a game that's uniquely adult in its themes and drama, and serving an audience that few others are willing to cater for.

"There are people doing more interesting things or different things, perhaps, but I feel we're pretty alone in what we're trying to explore," says Cage of Quantic Dream's particular pursuit. "What we're trying to create is really interactive entertainment for an adult audience. We don't pretend that we're cleverer than anyone else - but there are so many games out there that provide limited entertainment, and we try to make something for a more mature audience.

It's an interesting problem that games face as an audience that grew up with them slowly outgrows them, the medium often seemingly trapped in an infinite teen twilight of guns and fast cars, and one that Cage hopes to be able to solve.

The Casting, a 2006 tech demo, set the tone for Heavy Rain. It's perfectly possible that Kara will do the same for Quantic Dream's next game.

"Being older, when I ask people around me what games they play they say they don't play them anymore," Cage says. "They still watch TV, they still go to the movies - and the fact that they don't play games anymore isn't because they don't have time, it's because there are no games for them any more. To get this massive audience back, you can give them casual games - look at what Angry Birds did, it's very exciting. Or you can have family entertainment - look at the Wii, and how it introduced people who wouldn't have played games otherwise. It's great.

"You can reach this mass of people who don't play, or who play less through casual gaming or family gaming. What we try do is convince them to play again by giving them some adult content, some adult experiences and saying this is for you guys. It's for people expecting something else from gaming than just fun and adrenaline."