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It was a muggy summer night in one of Santa Monica’sseedier neighborhoods. I was on assignment. My job wasto capture the Shadow 代写英语毕业论文Lady. I didn’t expect it to be easy.But I guess that’s why I get the big bucks.I loitered in a dark doorway, watching and waiting. As Ifinished my Lucky Strike, I saw her. The Shadow Lady pulledup in her little red sports car and, without looking around,walked through an unmarked door into a big warehouse.She was wearing an overcoat and a beret. Odd, that overcoat.This July night in Santa Monica, the evening temperaturewas still in the 80s. I took one last drag, threw down
the butt, and followed her in. It was time for some action.I’m a motion capture technician. I handle the hard stuff—set-up, calibration, cleaning up data—all the stuff nobodyelse wants to do. We need lots of room, lots of electrical power,and the freedom to work any hours we need to. That’s whywe work in what looks like a run-down warehouse. Inside,
we have nearly a million dollars worth of gear.The Shadow Lady is a professional dancer and actress.
She’s lithe, graceful, expressive, and perhaps most importantly,reallypatient. She gave herself the name: “All youkeep is my shadow,” she said at the end of a session onemorning. Basically, she was right.Catching shadows
Motion capture houses throw away the person andkeep the shadow—the essence of their motion—andapply that motion to animate all kinds of characters.Perhaps you saw those dancing cars and credit cards inthe Shell ad on TV. That was done with MoCap. Or youmay have admired those folks strolling on the sun deckin Titanic. That was MoCap, too. In the past few years,as the technology has become less expensive and at thesame time more accurate, MoCap has helped lessen the
rigors of traditional cell animation—especially in highlycost-conscious projects like TV commercials.A MoCap studio can use both magnetic and Opticalcapture systems. Each has certain advantages. The magneticsystem handles shoots that don’t need really highaccuracy, and the director wants to be able to apply thedata to his character in real time. Magnetic systems generallyare faster at providing data to use in animation,though optical systems are generally more accurate andcan track more points. That may be changing, though.The first real-time optical system was shown at Siggraph98 by Motion Analysis (Santa Rosa, California).When I walked onto the capture stage, the Shadow Ladywas ready to “suit up.” She’d dropped the overcoat to reveala formfitting pink leotard. The color didn’t matter, ofcourse. It was her moves we wanted. Our magnetic systemincluded 13 receivers/sensors, each with 6 degrees of freedom.We attached them to the Shadow Lady’s leotard withVelcro straps (see Figure 1). This gave us pretty good coverage—good enough for this assignment, anyway, an animatedcommercial.
Magnetic systems work by generating three orthogonalelectro-magnetic fields from each transmitter. TheBen Delaney
CyberEdge
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0272-1716/98/$10.00 © 1998 IEEE
On the Trail of the Shadow Woman:
The Mystery of Motion Capture ______________________
Applications
Editor: Michael J. Potel
https://www.wildcrest.com
14 September/October 1998
1 The Shadow
Lady strikes a
pose. She’s
wearing the
Ascension
MotionStar
Wireless magnetic
tracking
system. Each
small cube is a
receiver. Her
waist pack holds
a battery, data
collection unit,
and radio