Monday, 18th May 2009 at 2:14 pm
A film is instantly recognisable. You can immediately tell the difference between a summer blockbuster and a TV documentary, and you’re never going to mistake a scene from Gone In 60 Seconds for an outside broadcast on South Today.
It’s not just the content that’s different; it’s the whole look of the film that makes it unmistakably cinematic.
The art direction of our game – the recently announced Split/Second – is cinematic realism. We don’t want our game to be a movie, but we want to use the tricks of cinema so that it feels cinematic. We want it to look like it has high production values. Think Transformers rather than Panorama.
So what is it that filmmakers do to their summer blockbusters to make them so unmistakable? One of the first things to note is that viewers expect film to exhibit certain characteristics, and those expectations were formed in the movie heyday of the 1940s and 1950s.
Firstly, they expect the film to run at 24fps, with heavy motion blur making up for the slow speed. These days there is no technical reason why films must run at 24fps – with modern digital film cameras it would be possible to have films run at 60 or even 100fps, which would give much greater visual fidelity and would require much less motion blur.
However, viewers associate the slow shutter speed and motion blur with films, and they associate films with high production values. Not that I’m advocating slow frame rates here – it’s good motion blur that is important.
Another artefact of earlier film making technology is the vignette. This is the darkening down and loss of saturation of the film at the corners of the screen. Old multiple element lenses caused this, where the rear lenses got shaded by the front lenses. Again, this isn’t a problem with modern machinery, but it’s one of the cues we all use to differentiate film from TV, and so modern films artificially apply it as a post process.
It's also important to simulate when an old fashioned lens would flare and bloom. Modern lenses are built to more exacting specifications than older lenses, and so have fewer of the imperfections that cause bloom and flare. Again, though, there is an association that needs to be maintained if the product is to thought of as having high production values. After all, Lawrence of Arabia would hardly be the same without the sun effects.
Of course, developers have tried putting crude lens flare effects in their game since the ‘90s, but only recently are we starting to see some convincing examples of internal reflection in the lens.
But by far the most important difference between movie and cheap TV is colour correction. Originally colour correction was used to compensate for variations in the lighting conditions and white balance of the film to achieve colour continuity. But these days it’s increasingly used to establish a desired look and to set a mood. It’s this modern usage of digital colour correction (increasingly called colour enhancement to reflect it’s current usage) that we’re interested in, and that sets films like Transformers apart from TV and games. It’s this that brings a boring outdoor scene to life and makes it look like a movie.
We use a colour correction technique described in GPU Gems that involves an artist bringing a screenshot of the game into Photoshop and treating it until they get the desired look. Because we know there exists a one-to-one mapping between the input colour and output colour we can represent the conversion as a 1D texture. Essentially it's a palette that we use in-game during the tone-mapping phase to convert each pixel to achieve the look we're after. We also blend between these textures to change the look at different points in the game, for example, a crash state will convey a different mood to a winning state.
We take post-processing seriously and, as I described in last month’s column, we spend 50 per cent of our render time in that phase. A lot of our post-processing is down to our deferred shading system, but the techniques described above can be equally achieved with a forward renderer. Having said that, if you’ve got a deferred shader then per- pixel motion blur becomes somewhat easier because it already manages the multiple render targets for you.
Of course, this isn’t the whole story; the lighting, camera work and animation play an equally important role in conveying the production values of the game, and I’ll go into more details on these in a future column. But this is a good start to making your game more Nicolas Cage than Fred Dinenage.
David Jefferies started in the industry at Psygnosis in Liverpool in 1995, eventually working on Global Domination and WipEout 3. He later moved to Rare where he worked on the Perfect Dark and Donkey Kong franchises. Next came a move down to Brighton to join Black Rock Studio (which was then known as Climax Racing) in 2003. On this generation of consoles he’s been the technical director of MotoGP’06 and MotoGP’07 before starting work on new racer Split/Second.
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