Eurogamer: I'm very interested in the process of creating the game's vehicles. It's easy to imagine a number of scenarios, but most people I've spoken to about it seem to assume one of two things: that you adopt a real-world vehicle as your model and subtract and distort until you have a GTA car, or that you decide on a range of characteristics that fit the requirements of a particular area on the game's curve, and prototype something before sliding it in the direction of an existing archetype, like a Porsche or Lambo.
Aaron Garbut: It's a little of both actually. We make some basic decisions early on about the spread of vehicles. This is based on generally what we want from the game - the basic number of sports cars, the general percentage split of luxury cars, four-doors, four-doors, vans, lorries etc. Then the vehicle department start putting images to the percentages. We don't specifically go for one particular car but take elements of many cars and put them together into something new. I think if you know a lot about cars you could break the vehicles in the game down into the real world inspirations. But you would find many for each vehicle and you'd find a lot of our own ideas in there too.
I think if our guys actually designed real cars I'd be driving one. Some of the things they have come up with are beautiful.
Eurogamer: As an entertainment series, with humorous and fantastical elements, do you have clearly defined structural, narrative and interactive parameters - a kind of GTA World Bible - or do you employ more of an organic approach informed by your experience of what worked in past titles?
Aaron Garbut: Every part of our process is pretty organic as I was saying earlier. We know what we are doing, we've been doing it for a while. We split up the responsibilities for the various elements between departments and have a fair amount of crossover. With a project of this scale it's increasingly difficult to have an overview of every element so we just have to have people take control of certain aspects and drive this.
A lot of this works because of the iterative process we use. Since things are "blurrier" to begin with - less well-defined - we are able to tighten and cross-reference more and more as elements come into focus. So we end up with something cohesive and working as a whole because the smaller elements that really pull things together happen later once the bigger picture is more defined. The more time we have, the more interconnected and defined the experience becomes as layers of complexity are added.
Eurogamer: How do you go about creating the fictional brands and adverts that you use in the game?
Aaron Garbut: These things come from all over the place. We have a design department that heads this stuff up, organises it, dishes it out to the artists, and works with everyone and anyone to produce it. A lot of it they come up with themselves, a lot comes from the radio ads and shows, every so often an email will be sent out looking for ideas for businesses or slogans which always ends up degenerating into pictures of cats and diarrhoea for some reason. But ideas come from all those places.
Eurogamer: One of GTA IV's most written-about additions is the Euphoria physics, and we've seen plenty of examples of how that can be used to capture things like drunkenness, and compliment the game's freeform structure and emergent gameplay with humour. Was including Euphoria a hard decision to take? Did you perhaps feel you were - and was there perhaps any resistance to the idea of - ceding artistic control of certain aspects of physical behaviour to procedural animation?
Aaron Garbut: No, the decision to use Euphoria was pretty straightforward. I don't think we ever felt we had to compromise to achieve what we wanted. It is more a layer that happens on top of other animation whenever we decide we want it to. Basically we are always in control of it. In that respect we aren't losing any artistic control at all and what we gain is huge. We gain another level of interaction with the world and that adds a lot to its believability and solidity.
I think the basic fact is it's almost impossible to create predefined animation that deals with physical interaction with a world in as many possible varieties as we would need. It makes much more sense to let physics do what it does and just make things happen correctly. At its simplest that would have been adding a ragdoll, but Euphoria is so much more than this even at its most basic level.
Eurogamer: Finally, do you have a favourite character in GTA IV, and what is it about he or she that you particularly adore?
Aaron Garbut: For me it has to be Niko. He's just a breath of fresh air in what can be such a dull, clich-ridden industry. He's got real depth and soul, and just seems so unique. He's likeable and he's got a pretty dark history. He has done some pretty bad things in his past, but he still feels like a good guy.
Grand Theft Auto IV is due out on PS3 and 360 and will be released on 29th April.