HANDS ON GUIDE

01 - Hardware Restrictions

The hardware for CG quality graphics is beyond the reach of most of us.

HARDWARE RESTRICTIONS

The primary difference between CG films and CG games, of course, is that games operate in real time, while companies can spend hours rendering a single 3D scene in a film. Simon Maddocks, a CG supervisor from British CG film company Cinesite, who worked as a digital effects artist on 'Star Wars: The Phantom Menace' and 'Charlie and the Chocolate Factory' thinks that this is unlikely to change. On the subject of achieving CG film effects in real-time, he comments, 'There will always be somebody who will say, "If we slow it down we can do something better".'

Hold on though - don't we have quad-core CPUs and masses of parallel computing power now? Yep, but while you might think that multicore workstations would help to speed up the process of rendering, the truth is that 3D effects in film are so complicated that even opening one frame can bring a top-end PC to its knees. 'You can't really do something on the workstation now where you get a WYSIWYG interface,' explains Maddocks. 'If you're working on a film like 'Transformers', you won't open a Maya file containing a robot with 600 joints. You'll have to look at a limited representation of that, because if you load the file, your machine will fall over, it will be too expensive or you'll wait all day for it to open.'

Maddocks isn't joking when he says limited representation either. He describes a typical crowd scene in which hundreds of people are represented on screen in the rendering program by a simple geometric shape, such as a cylinder or a rectangle. 'There will be 100 rectangles walking over a bridge,' he explains, 'but when we hit the Render button, the software will find a more complex representation of that and load it using a memory-efficient method. You can't load a billion polygons and render the scene, because everything will grind to a halt, the network will choke and people will ask what this guy is doing.

However, this is only the beginning. Having pushed the 'Render' button, you then need to wait for the software to render the scene. Cinesite uses an array of rack-mounted blade servers, but despite having rooms full of high-power PCs, a single frame still takes a long time to render. Cinesite's Sue Rowe, the visual effects supervisor on 'The Golden Compass', which won an Oscar and a BAFTA for its special effects, told us that an hour a frame isn't unusual, although simpler frames can be rendered more quickly. Maddocks offers the example of 3D work he's carrying out for the forthcoming film 'Beverly Hills Chihuahua', (sounds like one for the critics! - ed), which features talking dogs. His work involves taking film footage of the dogs and replacing the muzzle with CG to lip-sync with the voice track. A frame such as this, he says, can take ten minutes to render.

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