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Creating Unreality from Reality

Using Real-Life Motion Capture in Computer Animations


You've seen it more than once: computer generated images moving across your screen with eerie fluidity, peopling your movies, your video games, with motion and inflection so detailed that it's almost unreal. It can seem like magic, a sort of digital wizardry too far beyond anything man-made. The idea of animators working to impart that level of minute detail and realism to an animated humanoid figure is almost staggering, and can look like an impossible amount of effort.

Realistic Motion is a Lot of Work. How Do They Do It?
While there is, in fact, a great deal of work involved, there's less magic, mystery, and painstaking effort than you might think. Those unreal motions are actually, all too real, and are accomplished through the use of motion-capture technology. Many movies and video games make use of this technology to animate their digital models; it's been seen in games like Square-Enix's Final Fantasy X, movies like New Line Cinema's The Lord of the Rings Trilogy, Dreamworks' Shrek and Shrek 2, and Warner's The Polar Express--to name only a few examples from the past few years. Motion-capture technology has been in use in digital animation for quite some time, but many of its secrets are only now coming into light.

So Just How Does Motion-Capture Work, Exactly?
The simplest rundown is that live actors' motions are digitally recorded and then applied to 3D models. The physical recording itself can be done through one of two methods: the actor can wear a cumbersome bodysuit wired with complex sensors that detect their movements, or they can attach smaller singular sensors at pivotal points to capture the motion of those particular joints and interpret it into full-limb motion.

Where Does the Captured Data Go from the Live Capture?
Either way, these digital readings are fed into linked computers, where they are recorded and interpreted into motion sequences by programs like MetaMotion's Kaydara. From there the recorded sequences can be imported into 3D animation programs such as 3D Studio Max, and then applied to character models by mapping recorded motion data onto key points defined on the 3D models. There is still a great deal of work involved in interpreting the data correctly, and if even one mistake is made in recording the motions, sometimes the entire scene must be re-shot.

Where is Motion Capture the Most Useful?
This technique is highly effective when animating humanoid or otherwise bipedal characters and can create a captivating illusion of reality, or even simulate animated characters interacting with real actors. The technology for motion-capture is constantly undergoing refinement and improvement, and the process grows in leaps and bounds; however, no doubt it's a long way away from being able to capture the motions of quadrupeds or other members of the animal and insect kingdoms. I don't know about your pets, but I know that my cat wouldn't be particularly pleased about being wrapped in a bulky blue sensor suit; forget about getting him to follow the script, or even stay in one place.

Come to think of it, it might be a little difficult to get me to behave in that situation, as well; I'd much rather watch the fascinating fruits of said labor, or better yet, be involved in the digital aspect of production. To be able to produce such dazzling effects by pairing the world of the real with the world of the make-believe is a difficult and complex task; but somehow, knowing the technical details behind the final product doesn't remove the magic or enjoyment from these 3D-animated wonders. So the next time you're seated in the movie theaters watching the latest animated blockbuster play its way across the screen, don't be afraid to speak up when the awed whisper of "How'd they do that?" reaches your ears.

Though...you might want to wait until after the movie to clue them in.

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