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Readers who have grown up with gaming will remember how 3DFX’s Voodoo 3D graphics card changed forever our perception of video games (with help frthom Quake). Well, dedicated physics processors, like Ageia’s, could rival that impact and even make stunning worlds in Far Cry and Half-Life 2 feel flat.

Physics made cool
What the PhysX does is calculate the physics-influenced motion that we see on screen. At present, the best example of interacting with your world arguably comes from Half-Life 2 and the Source engine. This lets you pick up an object, like a chair, and throw it at something else. If you’re lucky the object that takes the impact might move a bit.

Now take a look at the screenshots from CellFactor, the first game to make decent use of the PhysX card. Here you can create an explosion whereupon dozens of boxes, pipes and any other debris are affected, all at once, by the force of the bang and fly into the air. The most heavily affected objects will disintegrate into tiny particles which will all fly off in directions dependant on the force that acted upon them. When anything collides with anything else, the motion will be affected according to the force and direction of the object that hit it, relative to the speed and direction in which it was already travelling. In short, rather than a big bang ‘sprite’ being generated, a real explosion is calculated in real time meaning that the debris flying everywhere will look as you’d expect it to in a real life ‘bang’.

Fabric
The other jaw dropping effect is the behaviour of fabric. The CellFactor demo features a vast banner flapping in the wind. Try shooting it or throwing an object through it and the banner shreds exactly as you’d expect it to in real life. If you tear the top, it will start to tear under gravity and flap down, breaking into smaller pieces which then float away. Stunning.

Fabric tears, rends and disintegrates thanks to PhysX's maths prowess.

So basically the PhysX card aims to bring far more complex and realistic effects to gaming. It processes everything from collision calculations to the dynamics of rigid bodies, particles, fabrics, fluids and every state in between. Consequently we’ll see solid objects, sparks, smoke, rain, cloth, water and even light moving and acting more impressively and realistically than ever before and in greater volumes.

Most physics calculations were previously been done by the CPU which also had to tell the GPU what to render and display and also deal with any Artificial Intelligence from characters and situations.

Applications
At present, games that make use of the PhysX card are near non-existent. CellFactor is only a demo and Ghost Recon uses it for some fancy grenade effects, but that’s about it. Patches for existing games may appear soon but speculation suggests that compatible bonus levels in the much-awaited Unreal Tournament 2007 might be the killer application which makes or breaks it.

Boom! An enormous amount of collision calculations are made in real time to spectacular effect.

With so much grunt it’s not surprising that graphics industry folk are making use of the PhysX already, with both Maya and 3D Studio Max having announced plugins to make certain rendering work faster.

Specs
Ageia isn’t quite ready to tell the world how its revolutionary new card works, so details are sketchy. What we do know is that it’s multi-core and based on 130nm fabrication and has a memory bandwidth of 2.1 terabits per second on a 128-bit bus. It has 125 million transistors and 128MB of GDDR3 RAM and requires a standard PCI slot and a molex power connector. In traditional graphics card terms it’s elderly in some respects, but has a suped-up rocket pack attached.

Competition
CPU companies, Intel and AMD have said for a while that their multicore chips don’t have to use identical cores. As such future CPUs could sport dedicated physics processors. However, both NVIDIA and ATI are closer to offering direct competition. NVIDIA has been working in partnership with Ageia’s rival, Havok to produce Havok FX which turns a second graphics card running in SLI into the physics processor. While this might put off very high end gamers who would prefer to keep SLI graphics processing and use it with a separate physics processor card, it might just be a killer reason for the masses to buy into SLI.

ATI, on the other hand, is more focused on its General Purpose GPUs (GPGPU). These will speed up applications as diverse as protein folding, database searching and, potentially, physics.

Conclusion
At $499 it’s certainly not cheap and there’s practically no reason to buy one yet. However, if CellFactor turns out to be as good as it looks we could be raving about it as early as next month or as late as Christmas. Quite simply, we won’t know until applications arrive and make the best of it.